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Yuan, Fan

Overview:

Dr. Yuan's research interests include drug and gene delivery, mechanisms of molecular transport in cells and tissues, and tumor pathophysiology.

Cure of cancer through chemotherapy requires drug molecules to reach all tumor cells at an adequately high concentration. At present, such a requirement cannot be satisfied in most patients. This is because (a) amount of drugs that can be administered into patients is limited by normal tissue tolerance and (b) drug distribution and cellular response to drugs in tumors are heterogeneous. Therefore, cells in regions with drug concentration below the therapeutic level will cause tumor recurrence and they may also develop resistance to future treatment.

The goal of our research is two-fold. One is to improve delivery of therapeutic agents in solid tumors; and the second is to understand mechanisms of drug resistance in tumors caused by intrinsic cellular heterogeneity and physiological barriers. These studies may provide useful information on how to improve clinical treatment of cancer based on currently available drugs or molecular medicines in the future.

Research projects in our lab include quantification of transport parameters, delivery of drugs encapsulated in temperature sensitive liposomes, physical interventions of drugs, electric field-mediated gene delivery, mathematical modeling of drug and gene delivery.

Positions:

Professor of Biomedical Engineering

Biomedical Engineering
Pratt School of Engineering

Professor in Ophthalmology

Ophthalmology
School of Medicine

Member of the Duke Cancer Institute

Duke Cancer Institute
School of Medicine

Education:

B.S. 1983

B.S. — Beijing University (China)

M.S. 1985

M.S. — Beijing University (China)

Ph.D. 1990

Ph.D. — City University of New York

Grants:

Investigation of Endocytosis Involved in Electrotransfection

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
September 03, 2013
End Date
May 31, 2018

OCT measurement of TM/SC stiffness in living mice

Administered By
Ophthalmology
AwardedBy
BrightFocus Foundation
Role
Collaborator
Start Date
July 01, 2015
End Date
December 30, 2017

Analysis of DNA transport in electrotransfected cells

Administered By
Biomedical Engineering
AwardedBy
National Science Foundation
Role
Principal Investigator
Start Date
July 15, 2013
End Date
June 30, 2017

University Training Program in Biomolecular and Tissue Engineering

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
July 01, 1994
End Date
June 30, 2017

Shear stress regulation of barrier function in Schlemm's canal

Administered By
Ophthalmology
AwardedBy
National Institutes of Health
Role
Co-Sponsor
Start Date
April 01, 2014
End Date
March 31, 2016

Biosensor Biocompatibility

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Investigator
Start Date
February 15, 1999
End Date
May 31, 2015

Delivery of Bacterial Therapeutics to Solid Tumors

Administered By
Biomedical Engineering
AwardedBy
National Science Foundation
Role
Principal Investigator
Start Date
February 01, 2009
End Date
January 31, 2013

Electric Field-Mediated Gene Delivery in MCL Tumor Model

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
October 01, 2006
End Date
June 29, 2010

Training in Biomolecular and Tissue Engineering

Administered By
Orthopaedics
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
September 20, 2003
End Date
June 30, 2009

Electric Field-Forced Gene Transfer in Solid Tumors

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
September 11, 2002
End Date
February 28, 2009

Electric Field-Forced Gene Transfer in Solid Tumors

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
September 11, 2002
End Date
August 31, 2007

CAREER: Improving Convective Transport of Drugs and Genes in Solid Tumors

Administered By
Biomedical Engineering
AwardedBy
National Science Foundation
Role
Principal Investigator
Start Date
September 01, 2000
End Date
June 30, 2006

Upgrade of a Shared Instrumentation Resource in the PSOE: The Laser Scanning Confocal Microscope

Administered By
Biomedical Engineering
AwardedBy
Lord Foundation of North Carolina
Role
Co-Principal Investigator
Start Date
May 31, 2002
End Date
June 30, 2005
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Awards:

Fellows. American Institute for Medical and Biological Engineering.

Type
National
Awarded By
American Institute for Medical and Biological Engineering
Date
January 01, 2007

CAREER Award. National Science Foundation.

Type
National
Awarded By
National Science Foundation
Date
January 01, 2000

SPORE in Breast Cancer Career Development Award. Duke University Medical Center.

Type
University
Awarded By
Duke University Medical Center
Date
January 01, 1996

IPM Innovative Instrumentation Award. The Microcirculatory Society.

Type
National
Awarded By
The Microcirculatory Society
Date
January 01, 1994

IPM Innovative Instrumentation Award. The Microcirculatory Society.

Type
National
Awarded By
The Microcirculatory Society
Date
January 01, 1993

Publications:

The brain interstitial system: Anatomy, modeling, in vivo measurement, and applications.

Although neurons attract the most attention in neurobiology, our current knowledge of neural circuit can only partially explain the neurological and psychiatric conditions of the brain. Thus, it is also important to consider the influence of brain interstitial system (ISS), which refers to the space among neural cells and capillaries. The ISS is the major compartment of the brain microenvironment that provides the immediate accommodation space for neural cells, and it occupies 15% to 20% of the total brain volume. The brain ISS is a dynamic and complex space connecting the vascular system and neural networks and it plays crucial roles in substance transport and signal transmission among neurons. Investigation of the brain ISS can provide new perspectives for understanding brain architecture and function and for exploring new strategies to treat brain disorders. This review discussed the anatomy of the brain ISS under both physiological and pathological conditions, biophysical modeling of the brain ISS and in vivo measurement and imaging techniques, including recent findings on brain ISS divisions. Moreover, the implications of ISS knowledge for basic neuroscience and clinical applications are addressed.

Authors
Lei, Y; Han, H; Yuan, F; Javeed, A; Zhao, Y
MLA Citation
Lei, Y, Han, H, Yuan, F, Javeed, A, and Zhao, Y. "The brain interstitial system: Anatomy, modeling, in vivo measurement, and applications." Progress in neurobiology 157 (October 2017): 230-246. (Review)
PMID
26837044
Source
epmc
Published In
Progress in Neurobiology
Volume
157
Publish Date
2017
Start Page
230
End Page
246
DOI
10.1016/j.pneurobio.2015.12.007

Stiffness characterization of anisotropic trabecular meshwork.

Elevation of intraocular pressure has been correlated to changes in stiffness of trabecular meshwork (TM) in glaucomatous eyes although mechanical properties of the TM remain to be quantitatively determined. Data in the literature suggest that the TM cannot be considered mechanically as a uniform layer of isotropic elastic material, because the value of its Young's modulus depends on the methods of measurements and can vary up to five orders of magnitude. To this end, we proposed a new theoretical framework for mechanical analysis of the TM, in which the inner wall of Schlemm's canal and the juxtacanalicular tissue in the TM were treated as a uniform layer of isotropic elastic material, and the rest of the TM, i.e., the uveal and corneoscleral meshworks, were modeled as a uniform layer of transversely isotropic material. Using the model, we demonstrated that the large discrepancy in the apparent Young's modulus reported in the literature could be caused by the anisotropy of the meshwork that was significantly stiffer in the longitudinal direction than in the transverse direction. The theoretical framework could be used to integrate existing data of the stiffness, investigate anisotropic behaviors of the tissues, and develop new methods to measure mechanical properties of the TM.

Authors
Chang, J; Huang, J; Li, L; Liu, Z; Yuan, F
MLA Citation
Chang, J, Huang, J, Li, L, Liu, Z, and Yuan, F. "Stiffness characterization of anisotropic trabecular meshwork." Journal of biomechanics 61 (August 2017): 144-150.
PMID
28784463
Source
epmc
Published In
Journal of Biomechanics
Volume
61
Publish Date
2017
Start Page
144
End Page
150
DOI
10.1016/j.jbiomech.2017.07.021

Characterization of jet formation and flow field produced by tandem bubbles

© 2017 Author(s). Tandem bubble (TB) interactions have been shown to produce directional jets that can be used to create membrane poration on single cells. Jet speed and associated flow field produced around the TB have been postulated to play an important role in TB-induced bioeffects. In this study, dynamics of tandem bubble interaction in a microfluidic channel (25 μm in height) was analyzed by high-speed imaging and simulated using 3DYNAFS-BEM © (DYNAFLOW, INC.). The results suggest that jet size and geometry are primarily controlled by the maximum diameter of the first bubble (D 1 ) while jet speed is about linearly correlated with maximum diameter of the second bubble (D 2 ).

Authors
Yang, C; Koff, AS; Yuan, F; Zhong, P; Hsiao, CT; Chahine, GL
MLA Citation
Yang, C, Koff, AS, Yuan, F, Zhong, P, Hsiao, CT, and Chahine, GL. "Characterization of jet formation and flow field produced by tandem bubbles." March 17, 2017.
Source
scopus
Published In
AIP Conference Proceedings
Volume
1821
Publish Date
2017
DOI
10.1063/1.4977637

Involvement of a Rac1-Dependent Macropinocytosis Pathway in Plasmid DNA Delivery by Electrotransfection.

Electrotransfection is a widely used method for delivering genes into cells with electric pulses. Although different hypotheses have been proposed, the mechanism of electrotransfection remains controversial. Previous studies have indicated that uptake and intracellular trafficking of plasmid DNA (pDNA) are mediated by endocytic pathways, but it is still unclear which pathways are directly involved in the delivery. To this end, the present study investigated the dependence of electrotransfection on macropinocytosis. Data from the study demonstrated that electric pulses induced cell membrane ruffling and actin cytoskeleton remodeling. Using fluorescently labeled pDNA and a macropinocytosis marker (i.e., dextran), the study showed that electrotransfected pDNA co-localized with dextran in intracellular vesicles. Furthermore, electrotransfection efficiency could be decreased significantly by reducing temperature or treatment of cells with a pharmacological inhibitor of Rac1 and could be altered by changing Rac1 activity. Taken together, the findings suggested that electrotransfection of pDNA involved Rac1-dependent macropinocytosis.

Authors
Mao, M; Wang, L; Chang, C-C; Rothenberg, KE; Huang, J; Wang, Y; Hoffman, BD; Liton, PB; Yuan, F
MLA Citation
Mao, M, Wang, L, Chang, C-C, Rothenberg, KE, Huang, J, Wang, Y, Hoffman, BD, Liton, PB, and Yuan, F. "Involvement of a Rac1-Dependent Macropinocytosis Pathway in Plasmid DNA Delivery by Electrotransfection." Molecular Therapy 25.3 (March 2017): 803-815.
PMID
28129959
Source
epmc
Published In
Molecular Therapy
Volume
25
Issue
3
Publish Date
2017
Start Page
803
End Page
815
DOI
10.1016/j.ymthe.2016.12.009

Distinct Effects of Endosomal Escape and Endosomal Trafficking on Gene Delivery via Electrotransfection

Authors
Cervia, LD; Chang, C-C; Wang, L; Yuan, F
MLA Citation
Cervia, LD, Chang, C-C, Wang, L, and Yuan, F. "Distinct Effects of Endosomal Escape and Endosomal Trafficking on Gene Delivery via Electrotransfection." February 3, 2017.
Source
wos-lite
Published In
Biophysical Journal
Volume
112
Issue
3
Publish Date
2017
Start Page
473A
End Page
473A

Distinct effects of endosomal escape and inhibition of endosomal trafficking on gene delivery via electrotransfection.

A recent theory suggests that endocytosis is involved in uptake and intracellular transport of electrotransfected plasmid DNA (pDNA). The goal of the current study was to understand if approaches used previously to improve endocytosis of gene delivery vectors could be applied to enhancing electrotransfection efficiency (eTE). Results from the study showed that photochemically induced endosomal escape, which could increase poly-L-lysine (PLL)-mediated gene delivery, decreased eTE. The decrease could not be blocked by treatment of cells with endonuclease inhibitors (aurintricarboxylic acid and zinc ion) or antioxidants (L-glutamine and ascorbic acid). Chemical treatment of cells with an endosomal trafficking inhibitor that blocks endosome progression, bafilomycin A1, resulted in a significant decrease in eTE. However, treatment of cells with lysosomotropic agents (chloroquine and ammonium chloride) had little effects on eTE. These data suggested that endosomes played important roles in protecting and intracellular trafficking of electrotransfected pDNA.

Authors
Cervia, LD; Chang, C-C; Wang, L; Yuan, F
MLA Citation
Cervia, LD, Chang, C-C, Wang, L, and Yuan, F. "Distinct effects of endosomal escape and inhibition of endosomal trafficking on gene delivery via electrotransfection." PloS one 12.2 (January 2017): e0171699-.
PMID
28182739
Source
epmc
Published In
PloS one
Volume
12
Issue
2
Publish Date
2017
Start Page
e0171699
DOI
10.1371/journal.pone.0171699

Improvement in Electrotransfection of Cells Using Carbon-Based Electrodes.

Electrotransfection has been widely used as a versatile, non-viral method for gene delivery. However, electrotransfection efficiency (eTE) is still low and unstable, compared to viral methods. To understand potential mechanisms of the unstable eTE, we investigated effects of electrode materials on eTE and viability of mammalian cells. Data from the study showed that commonly used metal electrodes generated a significant amount of particles during application of pulsed electric field, which could cause precipitation of plasmid DNA from solutions, thereby reducing eTE. For aluminum electrodes, the particles were composed of aluminum hydroxide and/or aluminum oxide, and their median sizes were 300 to 400 nm after the buffer being pulsed 4 to 8 times at 400 V cm-1, 5 ms duration and 1 Hz frequency. The precipitation could be prevented by using carbon (graphite) electrodes in electrotransfection experiments. The use of carbon electrodes also increased cell viability. Taken together, the study suggested that electrodes made of inner materials were desirable for electrotransfection of cells in vitro.

Authors
Chang, C-C; Mao, M; Liu, Y; Wu, M; Vo-Dinh, T; Yuan, F
MLA Citation
Chang, C-C, Mao, M, Liu, Y, Wu, M, Vo-Dinh, T, and Yuan, F. "Improvement in Electrotransfection of Cells Using Carbon-Based Electrodes." Cellular and molecular bioengineering 9.4 (December 2016): 538-545.
PMID
28239428
Source
epmc
Published In
Cellular and Molecular Bioengineering
Volume
9
Issue
4
Publish Date
2016
Start Page
538
End Page
545
DOI
10.1007/s12195-016-0452-9

Visualization of conventional outflow tissue responses to netarsudil in living mouse eyes.

Visual impairment due to glaucoma currently impacts 70 million people worldwide. While disease progression can be slowed or stopped with effective lowering of intraocular pressure, current medical treatments are often inadequate. Fortunately, three new classes of therapeutics that target the diseased conventional outflow tissue responsible for ocular hypertension are in the final stages of human testing. The rho kinase inhibitors have proven particularly efficacious and additive to current therapies. Unfortunately, non-contact technology that monitors the health of outflow tissue and its response to conventional outflow therapy is not available clinically. Using optical coherence tomographic (OCT) imaging and novel segmentation software, we present the first demonstration of drug effects on conventional outflow tissues in living eyes. Topical netarsudil (formerly AR-13324), a rho kinase/ norepinephrine transporter inhibitor, affected both proximal (trabecular meshwork and Schlemm's Canal) and distal portions (intrascleral vessels) of the mouse conventional outflow tract. Hence, increased perfusion of outflow tissues was reliably resolved by OCT as widening of the trabecular meshwork and significant increases in cross-sectional area of Schlemm's canal following netarsudil treatment. These changes occurred in conjunction with increased outflow facility, increased speckle variance intensity of outflow vessels, increased tracer deposition in conventional outflow tissues and decreased intraocular pressure. This is the first report using live imaging to show real-time drug effects on conventional outflow tissues and specifically the mechanism of action of netarsudil in mouse eyes. Advancements here pave the way for development of a clinic-friendly OCT platform for monitoring glaucoma therapy.

Authors
Li, G; Mukherjee, D; Navarro, I; Ashpole, NE; Sherwood, JM; Chang, J; Overby, DR; Yuan, F; Gonzalez, P; Kopczynski, CC; Farsiu, S; Stamer, WD
MLA Citation
Li, G, Mukherjee, D, Navarro, I, Ashpole, NE, Sherwood, JM, Chang, J, Overby, DR, Yuan, F, Gonzalez, P, Kopczynski, CC, Farsiu, S, and Stamer, WD. "Visualization of conventional outflow tissue responses to netarsudil in living mouse eyes." European journal of pharmacology 787 (September 2016): 20-31.
PMID
27085895
Source
epmc
Published In
European Journal of Pharmacology
Volume
787
Publish Date
2016
Start Page
20
End Page
31
DOI
10.1016/j.ejphar.2016.04.002

Elastic hydrogel as a sensor for detection of mechanical stress generated by single cells grown in three-dimensional environment.

Cell volume growth occurs in all living tissues. The growth exerts mechanical stresses on surrounding tissues that may alter tissue microenvironment, and have significant implications in health and diseases. However, the level of growth stress generated by single cells in three-dimensional (3D) environment remains to be determined. To this end, we developed a growth force microscopy technique to determine 3D distribution of the stress. The technique was based on encapsulation of cells in elastic hydrogels, and involved 3D particle tracking and mechanical analysis of gel deformation. Data from the study demonstrated that the growth stress was dynamic, and the stress distribution at the gel-cell interface was correlated inversely to the mean surface curvature or the distance to the geometric center of the cell. The stress averaged over the cell surface increased with increasing gel stiffness, suggesting that cells could alter growth stress in response to stiffness change in microenvironment. These findings suggested that the elastic hydrogel-based microscopy technique had a potential to provide new insights into mechanisms of mechanical interactions between cell and its microenvironment.

Authors
Huang, J; Wang, L; Xiong, C; Yuan, F
MLA Citation
Huang, J, Wang, L, Xiong, C, and Yuan, F. "Elastic hydrogel as a sensor for detection of mechanical stress generated by single cells grown in three-dimensional environment." Biomaterials 98 (August 2016): 103-112.
PMID
27182812
Source
epmc
Published In
Biomaterials
Volume
98
Publish Date
2016
Start Page
103
End Page
112
DOI
10.1016/j.biomaterials.2016.04.024

Mathematical Modeling of Outflow Facility Increase With Trabecular Meshwork Bypass and Schlemm Canal Dilation.

To mathematically model the conventional aqueous humor outflow system with trabecular meshwork (TM) bypass and Schlemm canal (SC) dilation.The SC was modeled as a rectangular channel with the TM modeled as a permeable membrane. The collector channels (CCs) were modeled as fluid sinks distributed along the outer wall of SC. Two different implants were investigated in this study. The Hydrus Microstent (scaffold) was modeled with a TM bypass and a dilated region in SC that was 7 or 15 mm long and approximately 5-fold larger than the normal height of SC (h0). The iStent trabecular microbypass was modeled with a similar structure except that the dilated region in SC was 1 mm long and 25% larger than h0.Creation of a TM bypass structure would increase the pressure in the surrounding regions inside the SC and make it close to the intraocular pressure. SC dilation would increase the pressure more uniformly in the dilated region. The pressure increase led to higher flow rates in SC and CCs, and subsequently increased outflow facility (C). If CCs were uniformly distributed, the increase in C was the smallest after implantation of 1 microbypass, compared with that after implantation of 2 microbypasses or 1 scaffold. If CCs were nonuniformly distributed, the magnitude of increase in C was sensitive to the location of implant, and the sensitivity was higher for the microbypass than the scaffold.The study showed that creation of TM bypass and SC dilation significantly increased outflow facility, and the amount of increase correlated with the length of dilated regions in SC.

Authors
Yuan, F; Schieber, AT; Camras, LJ; Harasymowycz, PJ; Herndon, LW; Allingham, RR
MLA Citation
Yuan, F, Schieber, AT, Camras, LJ, Harasymowycz, PJ, Herndon, LW, and Allingham, RR. "Mathematical Modeling of Outflow Facility Increase With Trabecular Meshwork Bypass and Schlemm Canal Dilation." Journal of glaucoma 25.4 (April 2016): 355-364.
PMID
25836658
Source
epmc
Published In
Journal of Glaucoma
Volume
25
Issue
4
Publish Date
2016
Start Page
355
End Page
364
DOI
10.1097/ijg.0000000000000248

Signaling Pathways that mediate endoMT of Human Trabecular meshwork cells exposed to Cyclic Mechanical Stress

Authors
Liang, J; Yuan, F; Gonzalez, P; Stamer, W
MLA Citation
Liang, J, Yuan, F, Gonzalez, P, and Stamer, W. "Signaling Pathways that mediate endoMT of Human Trabecular meshwork cells exposed to Cyclic Mechanical Stress." June 2015.
Source
wos-lite
Published In
Investigative Ophthalmology and Visual Science
Volume
56
Issue
7
Publish Date
2015

A power-law dependence of bacterial invasion on mammalian host receptors.

Pathogenic bacteria such as Listeria and Yersinia gain initial entry by binding to host target cells and stimulating their internalization. Bacterial uptake entails successive, increasingly strong associations between receptors on the surface of bacteria and hosts. Even with genetically identical cells grown in the same environment, there are vast differences in the number of bacteria entering any given cell. To gain insight into this variability, we examined uptake dynamics of Escherichia coli engineered to express the invasin surface receptor from Yersinia, which enables uptake via mammalian host β1-integrins. Surprisingly, we found that the uptake probability of a single bacterium follows a simple power-law dependence on the concentration of integrins. Furthermore, the value of a power-law parameter depends on the particular host-bacterium pair but not on bacterial concentration. This power-law captures the complex, variable processes underlying bacterial invasion while also enabling differentiation of cell lines.

Authors
Lee, TJ; Wong, J; Bae, S; Lee, AJ; Lopatkin, A; Yuan, F; You, L
MLA Citation
Lee, TJ, Wong, J, Bae, S, Lee, AJ, Lopatkin, A, Yuan, F, and You, L. "A power-law dependence of bacterial invasion on mammalian host receptors." PLoS Computational Biology 11.4 (April 16, 2015): e1004203-.
PMID
25879937
Source
epmc
Published In
PLoS computational biology
Volume
11
Issue
4
Publish Date
2015
Start Page
e1004203
DOI
10.1371/journal.pcbi.1004203

Mechanical analysis of rat trabecular meshwork.

Stiffness of trabecular meshwork (TM) may play an important role in regulating outflow resistance in healthy and glaucomatous eyes. However, the current techniques for stiffness measurement can only be applied to TM dissected from human donor or large animal eyes. It is a challenge to measure TM stiffness in mouse/rat eyes because of their smaller sizes and the delicate nature of TM dissection. To this end, a new technique was developed to determine the stiffness of rat TM using atomic force microscopy (AFM). In the study, rat eyes were enucleated immediately after death and perfused with a tracer (Evans blue) for 40 min. Then, the anterior segment was dissected and flat-mounted on a Petri dish with TM facing upwards. An AFM probe with a gold-coated colloid tip was used to sequentially indent the corneal, TM, and uveoscleral tissues. Assuming these tissues to be neo-Hookean materials, the indentation data were analyzed with a newly developed mathematical model to calculate the apparent initial Young's moduli (E0)(app). The geometric mean & SE of (E0)(app) were 162 Pa & 1.2 (n = 13) for TM and 6189 Pa & 1.4 (n = 11) for cornea; and the difference was statistically significant (p < 0.01). The technique established in this study allows the use of rat eye as a potential model for investigation of TM stiffness and its influences on outflow resistance. Future studies may also utilize this technique to evaluate mechanisms of TM stiffness change caused by aging, outflow dysfunction, pathogenesis of glaucoma, and drug treatment.

Authors
Huang, J; Camras, LJ; Yuan, F
MLA Citation
Huang, J, Camras, LJ, and Yuan, F. "Mechanical analysis of rat trabecular meshwork." Soft matter 11.14 (April 2015): 2857-2865.
PMID
25710888
Source
epmc
Published In
Soft Matter
Volume
11
Issue
14
Publish Date
2015
Start Page
2857
End Page
2865
DOI
10.1039/c4sm01949k

Endothelial Cell Senescence Increases Traction Forces due to Age-Associated Changes in the Glycocalyx and SIRT1.

Endothelial cell (EC) aging and senescence are key events in atherogenesis and cardiovascular disease development. Age-associated changes in the local mechanical environment of blood vessels have also been linked to atherosclerosis. However, the extent to which cell senescence affects mechanical forces generated by the cell is unclear. In this study, we sought to determine whether EC senescence increases traction forces through age-associated changes in the glycocalyx and antioxidant regulator deacetylase Sirtuin1 (SIRT1), which is downregulated during aging. Traction forces were higher in cells that had undergone more population doublings and changes in traction force were associated with altered actin localization. Older cells also had increased actin filament thickness. Depletion of heparan sulfate in young ECs elevated traction forces and actin filament thickness, while addition of heparan sulfate to the surface of aged ECs by treatment with angiopoietin-1 had the opposite effect. While inhibition of SIRT1 had no significant effect on traction forces or actin organization for young cells, activation of SIRT1 did reduce traction forces and increase peripheral actin in aged ECs. These results show that EC senescence increases traction forces and alters actin localization through changes to SIRT1 and the glycocalyx.

Authors
Cheung, TM; Yan, JB; Fu, JJ; Huang, J; Yuan, F; Truskey, GA
MLA Citation
Cheung, TM, Yan, JB, Fu, JJ, Huang, J, Yuan, F, and Truskey, GA. "Endothelial Cell Senescence Increases Traction Forces due to Age-Associated Changes in the Glycocalyx and SIRT1." Cellular and molecular bioengineering 8.1 (March 2015): 63-75.
PMID
25914755
Source
epmc
Published In
Cellular and Molecular Bioengineering
Volume
8
Issue
1
Publish Date
2015
Start Page
63
End Page
75
DOI
10.1007/s12195-014-0371-6

A self-adaptive sampling digital image correlation algorithm for accurate displacement measurement

Authors
Yuan, Y; Huang, J; Fang, J; Yuan, F; Xiong, C
MLA Citation
Yuan, Y, Huang, J, Fang, J, Yuan, F, and Xiong, C. "A self-adaptive sampling digital image correlation algorithm for accurate displacement measurement." Optics and Lasers in Engineering 65 (February 2015): 57-63.
Source
crossref
Published In
Optics and Lasers in Engineering
Volume
65
Publish Date
2015
Start Page
57
End Page
63
DOI
10.1016/j.optlaseng.2014.05.006

Macrophage embedded fibrin gels: an in vitro platform for assessing inflammation effects on implantable glucose sensors.

The erroneous and unpredictable behavior of percutaneous glucose sensors just days following implantation has limited their clinical utility for diabetes management. Recent research has implicated the presence of adherent inflammatory cells as the key mitigating factor limiting sensor functionality in this period of days post-implantation. Here we present a novel in vitro platform to mimic the cell-embedded provisional matrix that forms adjacent to the sensor immediately after implantation for the focused investigation of the effects of early stage tissue response on sensor function. This biomimetic surrogate is formed by imbibing fibrin-based gels with physiological densities of inflammatory RAW 264.7 macrophages. When surrounding functional sensors, macrophage-embedded fibrin gels contribute to sensor signal declines that are similar in both shape and magnitude to those observed in previous whole blood and small animal studies. Signal decline in the presence of gels is both metabolically-mediated and sensitive to cell type and activation. Computational modeling of the experimental setup is also presented to validate the design by showing that the cellular glucose uptake parameters necessary to achieve such experimental declines align well with literature values. Together, these data suggest this in vitro provisional matrix surrogate may serve as an effective screening tool for testing the biocompatibility of future glucose sensor designs.

Authors
Novak, MT; Yuan, F; Reichert, WM
MLA Citation
Novak, MT, Yuan, F, and Reichert, WM. "Macrophage embedded fibrin gels: an in vitro platform for assessing inflammation effects on implantable glucose sensors." Biomaterials 35.36 (December 2014): 9563-9572.
PMID
25175597
Source
epmc
Published In
Biomaterials
Volume
35
Issue
36
Publish Date
2014
Start Page
9563
End Page
9572
DOI
10.1016/j.biomaterials.2014.08.002

Circumferential tensile stiffness of glaucomatous trabecular meshwork.

PURPOSE: Our previous work indicated that a larger circumferential Young's modulus (E) of trabecular meshwork (TM) correlated with a higher outflow facility (C) in normal human donor eyes. The current study investigated the influence of glaucomatous TM stiffness and cellularity on C. METHODS: Eight left eyes from glaucomatous human donors were perfused within 48 hours post mortem. Values of C were determined at pressures of 10, 20, 30, and 40 mm Hg. The TM was then dissected and imaged with optical coherence tomography to determine its cross-sectional area. Uniaxial tensile stress was applied longitudinally to TM segments to determine stress-strain curves. E was calculated at zero strain, representing the circumferential stiffness of the TM at a relaxed state. Confocal images of DAPI-stained TM segments were used to determine cellularity after mechanical stretching. RESULTS: C (μL/min/mm Hg) of glaucomatous eyes was 0.18 ± 0.02 (mean ± SE) at 10 mm Hg and decreased to 0.11 ± 0.02 when the pressure was increased to 40 mm Hg. C measured at 30 and 40 mm Hg correlated with TM cellularity. E was 12.5 MPa and 1.4 (geometric mean and SE) and did not statistically correlate with postmortem time, age, C, or cellularity. CONCLUSIONS: Compared with data of normal eyes observed in a previous study, C in glaucomatous eyes was reduced significantly, and the amount of reduction increased with increasing the pressure. E of glaucomatous TM was approximately one-fifth that of normal TM. Prospective studies are needed to further investigate the influence of TM tensile stiffness on outflow regulation.

Authors
Camras, LJ; Stamer, WD; Epstein, D; Gonzalez, P; Yuan, F
MLA Citation
Camras, LJ, Stamer, WD, Epstein, D, Gonzalez, P, and Yuan, F. "Circumferential tensile stiffness of glaucomatous trabecular meshwork. (Published online)" Invest Ophthalmol Vis Sci 55.2 (February 10, 2014): 814-823.
PMID
24408980
Source
pubmed
Published In
Investigative Ophthalmology and Visual Science
Volume
55
Issue
2
Publish Date
2014
Start Page
814
End Page
823
DOI
10.1167/iovs.13-13091

Mathematical modeling of the Phoenix Rising pathway.

Apoptosis is a tightly controlled process in mammalian cells. It is important for embryogenesis, tissue homoeostasis, and cancer treatment. Apoptosis not only induces cell death, but also leads to the release of signals that promote rapid proliferation of surrounding cells through the Phoenix Rising (PR) pathway. To quantitatively understand the kinetics of interactions of different molecules in this pathway, we developed a mathematical model to simulate the effects of various changes in the PR pathway on the secretion of prostaglandin E2 (PGE2), a key factor for promoting cell proliferation. These changes include activation of caspase 3 (C3), caspase 7 (C7), and nuclear factor κB (NFκB). In addition, we simulated the effects of cyclooxygenase-2 (COX2) inhibition and C3 knockout on the level of secreted PGE2. The model predictions on PGE2 in MEF and 4T1 cells at 48 hours after 10-Gray radiation were quantitatively consistent with the experimental data in the literature. Compared to C7, the model predicted that C3 activation was more critical for PGE2 production. The model also predicted that PGE2 production could be significantly reduced when COX2 expression was blocked via either NFκB inactivation or treatment of cells with exogenous COX2 inhibitors, which led to a decrease in the rate of conversion from arachidonic acid to prostaglandin H2 in the PR pathway. In conclusion, the mathematical model developed in this study yielded new insights into the process of tissue regrowth stimulated by signals from apoptotic cells. In future studies, the model can be used for experimental data analysis and assisting development of novel strategies/drugs for improving cancer treatment or normal tissue regeneration.

Authors
Liu, C; Li, C-Y; Yuan, F
MLA Citation
Liu, C, Li, C-Y, and Yuan, F. "Mathematical modeling of the Phoenix Rising pathway." PLoS computational biology 10.2 (February 6, 2014): e1003461-.
PMID
24516373
Source
epmc
Published In
PLoS computational biology
Volume
10
Issue
2
Publish Date
2014
Start Page
e1003461
DOI
10.1371/journal.pcbi.1003461

A self-adaptive sampling digital image correlation algorithm for accurate displacement measurement

© 2014 Elsevier Ltd. All rights reserved. Digital image correlation (DIC) is nowadays widely applied to many engineering areas as an effective optical displacement measurement technique. To minimize the potential effect of spatial sampling locations on full-field displacement measurement, this paper develops a self-adaptive sampling DIC algorithm for accurate and reliable displacement computation over entire specimen surfaces. Depending on local deformation states, the algorithm can automatically optimize spatial distribution of sampling points over specimen surfaces in a self-adaptive manner in combination with the well-developed DIC algorithm with Gaussian windows. Both a series of well-designed computer-simulated speckle images and actual cell-substrate deformation ones are employed to verify the feasibility and effectiveness of the proposed algorithm, which demonstrates that the set of self-adaptive sampling algorithm is capable of recovering more accurate and precise full-field displacements compared to the conventional DIC algorithm with equidistant sampling.

Authors
Yuan, Y; Huang, J; Fang, J; Yuan, F; Xiong, C
MLA Citation
Yuan, Y, Huang, J, Fang, J, Yuan, F, and Xiong, C. "A self-adaptive sampling digital image correlation algorithm for accurate displacement measurement." Optics and Lasers in Engineering 65 (January 1, 2014): 57-63.
Source
scopus
Published In
Optics and Lasers in Engineering
Volume
65
Publish Date
2014
Start Page
57
End Page
63
DOI
10.1016/j.optlaseng.2014.05.006

Macrophage embedded fibrin gels: An invitro platform for assessing inflammation effects on implantable glucose sensors

© 2014 Elsevier Ltd. The erroneous and unpredictable behavior of percutaneous glucose sensors just days following implantation has limited their clinical utility for diabetes management. Recent research has implicated the presence of adherent inflammatory cells as the key mitigating factor limiting sensor functionality in this period of days post-implantation. Here we present a novel invitro platform to mimic the cell-embedded provisional matrix that forms adjacent to the sensor immediately after implantation for the focused investigation of the effects of early stage tissue response on sensor function. This biomimetic surrogate is formed by imbibing fibrin-based gels with physiological densities of inflammatory RAW 264.7 macrophages. When surrounding functional sensors, macrophage-embedded fibrin gels contribute to sensor signal declines that are similar in both shape and magnitude to those observed in previous whole blood and small animal studies. Signal decline in the presence of gels is both metabolically-mediated and sensitive to cell type and activation. Computational modeling of the experimental setup is also presented to validate the design by showing that the cellular glucose uptake parameters necessary to achieve such experimental declines align well with literature values. Together, these data suggest this invitro provisional matrix surrogate may serve as an effective screening tool for testing the biocompatibility of future glucose sensor designs.

Authors
Novak, MT; Yuan, F; Reichert, WM
MLA Citation
Novak, MT, Yuan, F, and Reichert, WM. "Macrophage embedded fibrin gels: An invitro platform for assessing inflammation effects on implantable glucose sensors." Biomaterials 35.36 (January 1, 2014): 9563-9572.
Source
scopus
Published In
Biomaterials
Volume
35
Issue
36
Publish Date
2014
Start Page
9563
End Page
9572
DOI
10.1016/j.biomaterials.2014.08.002

Disease progression in iridocorneal angle tissues of BMP2-induced ocular hypertensive mice with optical coherence tomography.

The goal of the present study was to test for the first time whether glaucomatous-like disease progression in a mouse can be assessed morphologically and functionally with spectral domain optical coherence tomography (SD-OCT).We monitored progressive changes in conventional outflow tissues of living mice overexpressing human bone morphogenetic protein 2 (BMP2), a model for glaucoma. Intraocular pressure (IOP) and outflow tissue morphology/Young's modulus were followed in mice for 36 days with rebound tonometry and SD-OCT, respectively. Results were compared to standard histological methods. Outflow facility was calculated from flow measurements with direct cannulation of anterior chambers subjected to three sequential pressure steps.Overexpression of BMP2 significantly elevated IOP in a biphasic manner over time compared to mice that overexpressed green fluorescent protein in outflow cells and naïve controls. SD-OCT revealed changes in outflow tissues overexpressing BMP2 that corresponded with the timing of the IOP phases and decreased outflow facility. In the first phase, the angle was open, but the trabecular meshwork and the cornea were thickened. OCT detected increased trabecular meshwork stiffness after provocative IOP challenges of the BMP2 eyes, which corresponded to increased collagen deposition with transmission electron microscopy. In contrast, the angle was closed in the second phase. IOP elevation over 36 days due to BMP2 overexpression resulted in significant retinal ganglion cell and axon loss.Although not a feasible open-angle glaucoma model, the BMP2 mice were useful for demonstrating the utility of SD-OCT in following disease progression and differentiating between two forms of ocular pathology over time that resulted in ocular hypertension.

Authors
Li, G; Farsiu, S; Qiu, J; Dixon, A; Song, C; McKinnon, SJ; Yuan, F; Gonzalez, P; Stamer, WD
MLA Citation
Li, G, Farsiu, S, Qiu, J, Dixon, A, Song, C, McKinnon, SJ, Yuan, F, Gonzalez, P, and Stamer, WD. "Disease progression in iridocorneal angle tissues of BMP2-induced ocular hypertensive mice with optical coherence tomography." Molecular vision 20 (January 2014): 1695-1709.
PMID
25558173
Source
epmc
Published In
Molecular vision
Volume
20
Publish Date
2014
Start Page
1695
End Page
1709

Role of specific endocytic pathways in electrotransfection of cells.

Electrotransfection is a technique utilized for gene delivery in both preclinical and clinical studies. However, its mechanisms are not fully understood. The goal of this study was to investigate specific pathways of endocytosis involved in electrotransfection. In the study, three different human cell lines (HEK293, HCT116, and HT29) were either treated with ice cold medium postelectrotransfection or endocytic inhibitors prior to electrotransfection. The inhibitors were pharmacological agents (chlorpromazine, genistein, and amiloride) or different small interfering RNA (siRNA) molecules that could knockdown expression of clathrin heavy chain (CLTC), caveolin-1, and Rab34, respectively. The reduction in gene expressions was confirmed with western blot analysis at 48-72h post-siRNA treatment. It was observed that treatments with either ice cold medium, chlorpromazine, or genistein resulted in significant reductions in electrotransfection efficiency (eTE) in all three cell lines, compared to the matched controls, but amiloride treatment had insignificant effects on eTE. For cells treated with siRNA, only CLTC knockdown resulted in eTE reduction for all three cell lines. Together, these data demonstrated that the clathrin-mediated endocytosis played an important role in electrotransfection.

Authors
Chang, C-C; Wu, M; Yuan, F
MLA Citation
Chang, C-C, Wu, M, and Yuan, F. "Role of specific endocytic pathways in electrotransfection of cells." Molecular therapy. Methods & clinical development 1 (January 2014): 14058-.
PMID
26052524
Source
epmc
Published In
Molecular Therapy - Methods and Clinical Development
Volume
1
Publish Date
2014
Start Page
14058
DOI
10.1038/mtm.2014.58

Accurate displacement measurement via a self-adaptive digital image correlation method based on a weighted ZNSSD criterion

Digital image correlation (DIC) technique has been increasingly employed to implement surface deformation measurements in many engineering fields. Practically, it has been demonstrated that the choice of subset sizes exerts a strong influence on measurement results of DIC, especially when there exists locally larger deformation over the subsets involved. This paper proposes a novel subpixel registration algorithm with Gaussian windows to implicitly optimize the subset sizes by adjusting the shape of Gaussian windows in a self-adaptive fashion with the aid of a so-called weighted zero-normalized sum-of-squared difference correlation criterion. The feasibility and effectiveness of the self-adaptive algorithm are carefully verified through a set of well-designed synthetic speckle images, which indicates that the presented algorithm is able to greatly enhance the accuracy and precision of displacement measurements as compared with the traditional subpixel registration methods. © 2013 Elsevier Ltd.

Authors
Yuan, Y; Huang, J; Peng, X; Xiong, C; Fang, J; Yuan, F
MLA Citation
Yuan, Y, Huang, J, Peng, X, Xiong, C, Fang, J, and Yuan, F. "Accurate displacement measurement via a self-adaptive digital image correlation method based on a weighted ZNSSD criterion." Optics and Lasers in Engineering 52.1 (2014): 75-85.
Source
scival
Published In
Optics and Lasers in Engineering
Volume
52
Issue
1
Publish Date
2014
Start Page
75
End Page
85
DOI
10.1016/j.optlaseng.2013.07.016

Predicting glucose sensor behavior in blood using transport modeling: relative impacts of protein biofouling and cellular metabolic effects.

BACKGROUND: Tissue response to indwelling glucose sensors remains a confounding barrier to clinical application. While the effects of fully formed capsular tissue on sensor response have been studied, little has been done to understand how tissue interactions occurring before capsule formation hinder sensor performance. Upon insertion in subcutaneous tissue, the sensor is initially exposed to blood, blood borne constituents, and interstitial fluid. Using human whole blood as a simple ex vivo experimental system, the effects of protein accumulation at the sensor surface (biofouling effects) and cellular consumption of glucose in both the biofouling layer and in the bulk (metabolic effects) on sensor response were assessed. METHODS: Medtronic MiniMed SofSensor glucose sensors were incubated in whole blood, plasma-diluted whole blood, and cell-free platelet-poor plasma (PPP) to analyze the impact of different blood constituents on sensor function. Experimental conditions were then simulated using MATLAB to predict the relative impacts of biofouling and metabolic effects on the observed sensor responses. RESULTS: Protein biofouling in PPP in both the experiments and the simulations was found to have no interfering effect upon sensor response. Experimental results obtained with whole and dilute blood showed that the sensor response was markedly affected by blood borne glucose-consuming cells accumulated in the biofouling layer and in the surrounding bulk. CONCLUSIONS: The physical barrier to glucose transport presented by protein biofouling does not hinder glucose movement to the sensor surface, and the consumption of glucose by inflammatory cells, and not erythrocytes, proximal to the sensor surface has a substantial effect on sensor response and may be the main culprit for anomalous sensor behavior immediately following implantation.

Authors
Novak, MT; Yuan, F; Reichert, WM
MLA Citation
Novak, MT, Yuan, F, and Reichert, WM. "Predicting glucose sensor behavior in blood using transport modeling: relative impacts of protein biofouling and cellular metabolic effects. (Published online)" J Diabetes Sci Technol 7.6 (November 1, 2013): 1547-1560.
PMID
24351181
Source
pubmed
Published In
Journal of Diabetes Science and Technology
Volume
7
Issue
6
Publish Date
2013
Start Page
1547
End Page
1560
DOI
10.1177/193229681300700615

Digital Image Correlation with Self-Adaptive Gaussian Windows

Authors
Huang, J; Pan, X; Peng, X; Yuan, Y; Xiong, C; Fang, J; Yuan, F
MLA Citation
Huang, J, Pan, X, Peng, X, Yuan, Y, Xiong, C, Fang, J, and Yuan, F. "Digital Image Correlation with Self-Adaptive Gaussian Windows." EXPERIMENTAL MECHANICS 53.3 (March 2013): 505-512.
Source
wos-lite
Published In
Experimental Mechanics
Volume
53
Issue
3
Publish Date
2013
Start Page
505
End Page
512
DOI
10.1007/s11340-012-9639-8

Improving interstitial transport of macromolecules through reduction in cell volume fraction in tumor tissues.

UNLABELLED: Interstitial transport of large molecules and nanoparticles is an important concern in nanomedicine-mediated cancer treatment. To that end, the current study was proposed to improve the transport through enlargement of extracellular space by treating tumors with hypertonic solution of mannitol and cytotoxic agents (e.g., ethacrynic acid [ECA]), which could effectively shrink and kill cells, respectively. In the study, the improvement in interstitial penetration of dextran was investigated ex vivo using rat fibrosarcoma tissues sectioned into 600 μm slices. Experimental data showed that the hypertonic solution was more effective than ECA for improving interstitial penetration of dextran with molecular weights ranging from 4000 to 2,000,000. The extent of improvement depended on the size of dextran molecules and the time when the treatment was applied. Results from the study suggested that increases in both size and connectedness of interstitial pathways were important for improvement of interstitial transport of large molecules and nanoparticles. FROM THE CLINICAL EDITOR: This study reports on the optimization of interstitial transport both for large molecules and nanoparticles in nanomedicine-mediated cancer treatment. The study demonstrates that hypertonic solutions could efficiently lead to cancer cell shrinkage and more so than the applied cytotoxic agent thereby improving transport of chemotherapeutic entities.

Authors
McGuire, S; Yuan, F
MLA Citation
McGuire, S, and Yuan, F. "Improving interstitial transport of macromolecules through reduction in cell volume fraction in tumor tissues." Nanomedicine 8.7 (October 2012): 1088-1095.
PMID
22248816
Source
pubmed
Published In
Nanomedicine: Nanotechnology, Biology and Medicine
Volume
8
Issue
7
Publish Date
2012
Start Page
1088
End Page
1095
DOI
10.1016/j.nano.2011.12.009

A Novel Schlemm's Canal Scaffold Increases Outflow Facility in a Human Anterior Segment Perfusion Model

Authors
Camras, LJ; Yuan, F; Fan, S; Samuelson, TW; Ahmed, IK; Schieber, AT; Toris, CB
MLA Citation
Camras, LJ, Yuan, F, Fan, S, Samuelson, TW, Ahmed, IK, Schieber, AT, and Toris, CB. "A Novel Schlemm's Canal Scaffold Increases Outflow Facility in a Human Anterior Segment Perfusion Model." INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE 53.10 (September 2012): 6115-6121.
PMID
22893672
Source
wos-lite
Published In
Investigative Ophthalmology and Visual Science
Volume
53
Issue
10
Publish Date
2012
Start Page
6115
End Page
6121
DOI
10.1167/iovs.12-9570

Differential effects of trabecular meshwork stiffness on outflow facility in normal human and porcine eyes.

PURPOSE: The study was designed to determine trabecular meshwork (TM) stiffness and its relationship to outflow facility (C) in perfused normal human and porcine eyes. METHODS: Human and porcine eyes were perfused at pressures of 10, 20, 30, and 40 mm Hg to determine C and how outflow resistance (R = 1/C) varied with the pressure. Following perfusions, TM tissue segments were dissected and stretched uniaxially to determine the circumferential bulk Young's modulus (E). The statistical significance of difference between different groups was evaluated using a two-tailed Student's t-test or Mann-Whitney U test. RESULTS: A larger E correlated with a higher C measured at 10 and 20 mm Hg (P < 0.05), and a similar trend was observed at 30 and 40 mm Hg in human eyes (n = 7). Additionally, a higher C correlated to a lower variance of R, and a stiffer TM correlated to a lower variance of R in human eyes (P < 0.05). For porcine TM, E was inversely correlated to a cross-sectional area (P < 0.003, n = 11), and its value (24.9 and 1.5 kPa; geometric mean and geometric SE) was lower than E of human TM (515 ± 136 kPa; mean ± SE) (P < 0.01). C and variance of R were not significantly different between the species. CONCLUSIONS: A higher circumferential stiffness of the TM correlated with a higher outflow facility and less IOP elevation-induced variation in outflow resistance in normal human eyes, but not in porcine eyes. For future studies, these correlations need to be evaluated in glaucomatous eyes to better understand normal and abnormal TM functions.

Authors
Camras, LJ; Stamer, WD; Epstein, D; Gonzalez, P; Yuan, F
MLA Citation
Camras, LJ, Stamer, WD, Epstein, D, Gonzalez, P, and Yuan, F. "Differential effects of trabecular meshwork stiffness on outflow facility in normal human and porcine eyes. (Published online)" Invest Ophthalmol Vis Sci 53.9 (August 9, 2012): 5242-5250.
PMID
22786899
Source
pubmed
Published In
Investigative Ophthalmology and Visual Science
Volume
53
Issue
9
Publish Date
2012
Start Page
5242
End Page
5250
DOI
10.1167/iovs.12-9825

Critical issues in delivery of RNAi therapeutics in vivo.

RNA interference (RNAi) is a fundamental mechanism of gene regulation and has been harnessed to produce a new class of drugs for treatment of various diseases. A key issue in these applications is how to effectively deliver RNAi therapeutics into target cells. This review is focused on advances in RNA delivery in vivo. To achieve it, novel strategies have been developed to enhance stability of RNA in cells and tissues, overcome barriers to transport of RNA or its carriers in the body, and reduce immunogenicity and cytotoxicity of treatment. Approaches to RNA delivery are divided into three categories in this review: biological, chemical, and physical. Advantages and disadvantages of each method are discussed. At present, effective delivery of RNAi therapeutics in vivo is still a challenge although significant advances have been made in this field.

Authors
Rivera, S; Yuan, F
MLA Citation
Rivera, S, and Yuan, F. "Critical issues in delivery of RNAi therapeutics in vivo." Curr Pharm Biotechnol 13.7 (June 2012): 1279-1291. (Review)
PMID
22201583
Source
pubmed
Published In
Current Pharmaceutical Biotechnology
Volume
13
Issue
7
Publish Date
2012
Start Page
1279
End Page
1291

A microfluidic system for investigation of extravascular transport and cellular uptake of drugs in tumors.

Three-dimensional (3D) tumor models have been established in various microfluidic systems for drug delivery and resistance studies in vitro. However, one of the main drawbacks of these models is non-uniform distribution of cells, leaving regions with very low cell density within the 3D structures. As a result, molecular diffusion in the cell compartments is faster than that observed in solid tumors. To solve this problem, we developed a new technique for preparation of 3D tumor models in vitro. It was based on a microfluidic device containing three parallel channels separated by narrowly spaced posts. Tumor cells were loaded into the central channel at high density. To test the system, B16.F10 melanoma cells were perfusion-cultured overnight and the resulting 3D structure was characterized in terms of viability, density, and morphology of cells as well as transport properties of small fluorescent molecules. Immediately upon loading of tumor cells, the cell density was comparable to those observed in B16.F10 tumor tissues in vivo; and the viability of tumor cells was maintained through the overnight culture. The tumor model displayed low extracellular space and high resistance to diffusion of small molecules. For membrane-permeant molecules (e.g., Hoechst 33342), the rate of interstitial penetration was extremely slow, compared to membrane-impermeant molecules (e.g., sodium fluorescein). This versatile tumor model could be applied to in vitro studies of transport and cellular uptake of drugs and genes.

Authors
Elliott, NT; Yuan, F
MLA Citation
Elliott, NT, and Yuan, F. "A microfluidic system for investigation of extravascular transport and cellular uptake of drugs in tumors." Biotechnol Bioeng 109.5 (May 2012): 1326-1335.
PMID
22124930
Source
pubmed
Published In
Biotechnology & Bioengineering
Volume
109
Issue
5
Publish Date
2012
Start Page
1326
End Page
1335
DOI
10.1002/bit.24397

Regulation of trabecular meshwork cell contraction and intraocular pressure by miR-200c.

Lowering intraocular pressure (IOP) delays or prevents the loss of vision in primary open-angle glaucoma (POAG) patients with high IOP and in those with normal tension glaucoma showing progression. Abundant evidence demonstrates that inhibition of contractile machinery of the trabecular meshwork cells is an effective method to lower IOP. However, the mechanisms involved in the regulation of trabecular contraction are not well understood. Although microRNAs have been shown to play important roles in the regulation of multiple cellular functions, little is known about their potential involvement in the regulation of IOP. Here, we showed that miR-200c is a direct postranscriptional inhibitor of genes relevant to the physiologic regulation of TM cell contraction including the validated targets Zinc finger E-box binding homeobox 1 and 2 (ZEB1 and ZEB2), and formin homology 2 domain containing 1 (FHOD1), as well as three novel targets: lysophosphatidic acid receptor 1 (LPAR1/EDG2), endothelin A receptor (ETAR), and RhoA kinase (RHOA). Consistently, transfection of TM cells with miR-200c resulted in strong inhibition of contraction in collagen populated gels as well as decreased cell traction forces exerted by individual TM cells. Finally, delivery of miR-200c to the anterior chamber of living rat eyes resulted in a significant decrease in IOP, while inhibition of miR-200c using an adenoviral vector expressing a molecular sponge led to a significant increase in IOP. These results demonstrate for the first time the ability of a miRNA to regulate trabecular contraction and modulate IOP in vivo, making miR-200c a worthy candidate for exploring ways to alter trabecular contractility with therapeutic purposes in glaucoma.

Authors
Luna, C; Li, G; Huang, J; Qiu, J; Wu, J; Yuan, F; Epstein, DL; Gonzalez, P
MLA Citation
Luna, C, Li, G, Huang, J, Qiu, J, Wu, J, Yuan, F, Epstein, DL, and Gonzalez, P. "Regulation of trabecular meshwork cell contraction and intraocular pressure by miR-200c." PLoS One 7.12 (2012): e51688-.
PMID
23272142
Source
pubmed
Published In
PloS one
Volume
7
Issue
12
Publish Date
2012
Start Page
e51688
DOI
10.1371/journal.pone.0051688

Proliferation behavior of E. coli in a three-dimensional in vitro tumor model.

Advances in genetic engineering of non-pathogenic Escherichia coli (E. coli) have made this organism an attractive candidate for gene delivery vehicle. However, proliferation and transport behaviors of E. coli in three-dimensional (3D) tumor environment are still unclear. To this end, we developed a novel microfluidics-based tumor model that permitted direct in situ visualization of E. coli in a 3D environment with densely packed tumor cells (B16.F10 or EMT6). The E. coli was engineered to co-express two proteins invasin and mCherry (inv(+)) so that they had the ability to enter mammalian cells and could be visualized via fluorescence microscopy. E. coli expressing mCherry alone (inv(-)) was used as the control counterpart. The inv(-) bacteria proliferated to a higher extent than inv(+) bacteria in both the 3D tumor model and a 2D monolayer culture model. Meanwhile, the proliferation appeared to be tumor cell type dependent since bacteria did not proliferate as well in the EMT6 model compared to the B16.F10 model. These differences in bacterial proliferation were likely to be caused by inhibitors secreted by tumor cells, as suggested by our data from the bacterial-tumor cell monolayer co-culture experiment. The bacterial proliferation provided a driving force for E. coli spreading in the 3D interstitial space of tumors. These findings are useful for researchers to develop novel strategies for improvement of bacteria-mediated oncolysis or gene delivery in cancer treatment.

Authors
Elliott, N; Lee, T; You, L; Yuan, F
MLA Citation
Elliott, N, Lee, T, You, L, and Yuan, F. "Proliferation behavior of E. coli in a three-dimensional in vitro tumor model." Integr Biol (Camb) 3.6 (June 2011): 696-705.
PMID
21556399
Source
pubmed
Published In
Integrative Biology
Volume
3
Issue
6
Publish Date
2011
Start Page
696
End Page
705
DOI
10.1039/c0ib00137f

A review of three-dimensional in vitro tissue models for drug discovery and transport studies.

The use of animal models in drug discovery studies presents issues with feasibility and ethical concerns. To address these limitations, in vitro tissue models have been developed to provide a means for systematic, repetitive, and quantitative investigation of drugs. By eliminating or reducing the need for animal subjects, these models can serve as platforms for more tightly controlled, high-throughput screening of drugs and for pharmacokinetic and pharmacodynamic analyses of drugs. The focus of this review is three-dimensional (3D) tissue models that can capture cell-cell and cell-matrix interactions. Compared to the 2D culture of cell monolayers, 3D models more closely mimic native tissues since the cellular microenvironment established in the 3D models often plays a significant role in disease progression and cellular responses to drugs. A growing body of research has been published in the literature, which highlights the benefits of the 3D in vitro models of various tissues. This review provides an overview of some successful 3D in vitro models that have been developed to mimic liver, breast, cardiac, muscle, bone, and corneal tissues as well as malignant tissues in solid tumors.

Authors
Elliott, NT; Yuan, F
MLA Citation
Elliott, NT, and Yuan, F. "A review of three-dimensional in vitro tissue models for drug discovery and transport studies." J Pharm Sci 100.1 (January 2011): 59-74. (Review)
PMID
20533556
Source
pubmed
Published In
Journal of Pharmaceutical Sciences
Volume
100
Issue
1
Publish Date
2011
Start Page
59
End Page
74
DOI
10.1002/jps.22257

Enhancement of electric field-mediated gene delivery through pretreatment of tumors with a hyperosmotic mannitol solution.

Pulsed electric fields can enhance interstitial transport of plasmid DNA (pDNA) in solid tumors. However, the extent of enhancement is still limited. To this end, the effects of cellular resistance to electric field-mediated gene delivery were investigated. The investigation used two tumor cell lines (4T1 (a murine mammary carcinoma) and B16.F10 (a metastatic subline of B16 murine melanoma)) either in suspensions or implanted in two in vivo models (dorsal skin-fold chamber (DSC) and hind leg). The volume fraction of cells was altered by pretreatment with a hyperosmotic mannitol solution (1 M). It was observed that the pretreatment reduced the volumes of 4T1 and B16.F10 cells, suspended in an agarose gel, by 50 and 46%, respectively, over a 20-min period, but did not cause significant changes ex vivo in volumes of hind-leg tumor tissues grown from the same cells in mice. The mannitol pretreatment in vivo improved electric field-mediated gene delivery in the hind-leg tumor models, in terms of reporter gene expression, but resulted in minimal enhancement in pDNA electrophoresis over a few microns distance in the DSC tumor models. These data demonstrated that hyperosmotic mannitol solution could effectively improve electric field-mediated gene delivery around individual cells in vivo by increasing the extracellular space.

Authors
Henshaw, J; Mossop, B; Yuan, F
MLA Citation
Henshaw, J, Mossop, B, and Yuan, F. "Enhancement of electric field-mediated gene delivery through pretreatment of tumors with a hyperosmotic mannitol solution." Cancer Gene Ther 18.1 (January 2011): 26-33.
PMID
20847751
Source
pubmed
Published In
Cancer Gene Therapy
Volume
18
Issue
1
Publish Date
2011
Start Page
26
End Page
33
DOI
10.1038/cgt.2010.51

Cellular pharmacokinetic and pharmacodynamic analyses of ethacrynic acid: Implications in topical drug delivery in the eye.

PURPOSE: Ethacrynic acid (ECA) is a potential trabecular meshwork (TM) drug that has shown promising results in preclinical studies for treatment of primary open-angle glaucoma. However, topical application of ECA is currently limited by adverse effects in corneal tissues. To this end, we developed a new theoretical model to evaluate time-dependent toxicity induced by ECA in corneal epithelial cells. METHODS: The model consisted of a cellular pharmacokinetic (PK) module to determine intracellular concentration of ECA, and a pharmacodynamic (PD) module to determine the cytotoxicity of ECA. It was assumed that ECA-induced cytotoxicity depended on drug exposure time and peak concentration of bound ECA in cells. In addition to the model development, we experimentally determined the intracellular concentration of ECA as a function of drug dose and treatment time. RESULTS: The intracellular concentration increased linearly (i.e., no saturation) with increasing the dose of ECA. It also increased initially with time and then reached a steady-state at ~40 min. The percent of cells survived after treatment decreased with increasing the dose of drug or the time of treatment. The experimental data were fit by the new PK and PD models to obtain values of model constants. One of the unique applications of these models was to predict cell survival relative to control when extracellular concentration of ECA varied with time. The prediction showed that the toxicity of ECA might be significantly overestimated by using the traditional LC(50) determined in vitro. CONCLUSIONS: The new PK and PD models developed in this study were capable to fit experimental data and predict time-dependent toxicity of ECA in corneal epithelial cells. The models may be useful for optimizing the dose and schedule in topical application of ECA for glaucoma treatment.

Authors
Lin, C-W; Gonzalez, P; Yuan, F
MLA Citation
Lin, C-W, Gonzalez, P, and Yuan, F. "Cellular pharmacokinetic and pharmacodynamic analyses of ethacrynic acid: Implications in topical drug delivery in the eye." Mol Vis 17 (2011): 2507-2515.
PMID
21976961
Source
pubmed
Published In
Molecular vision
Volume
17
Publish Date
2011
Start Page
2507
End Page
2515

Special issue: Experiments and modeling in microand nano-biomechanics

Authors
Long, M; Yuan, F
MLA Citation
Long, M, and Yuan, F. "Special issue: Experiments and modeling in microand nano-biomechanics." Cellular and Molecular Bioengineering 4.3 (2011): 325-326.
Source
scival
Published In
Cellular and Molecular Bioengineering
Volume
4
Issue
3
Publish Date
2011
Start Page
325
End Page
326
DOI
10.1007/s12195-011-0192-9

Membrane binding of plasmid DNA and endocytic pathways are involved in electrotransfection of mammalian cells.

Electric field mediated gene delivery or electrotransfection is a widely used method in various studies ranging from basic cell biology research to clinical gene therapy. Yet, mechanisms of electrotransfection are still controversial. To this end, we investigated the dependence of electrotransfection efficiency (eTE) on binding of plasmid DNA (pDNA) to plasma membrane and how treatment of cells with three endocytic inhibitors (chlorpromazine, genistein, dynasore) or silencing of dynamin expression with specific, small interfering RNA (siRNA) would affect the eTE. Our data demonstrated that the presence of divalent cations (Ca(2+) and Mg(2+)) in electrotransfection buffer enhanced pDNA adsorption to cell membrane and consequently, this enhanced adsorption led to an increase in eTE, up to a certain threshold concentration for each cation. Trypsin treatment of cells at 10 min post electrotransfection stripped off membrane-bound pDNA and resulted in a significant reduction in eTE, indicating that the time period for complete cellular uptake of pDNA (between 10 and 40 min) far exceeded the lifetime of electric field-induced transient pores (∼10 msec) in the cell membrane. Furthermore, treatment of cells with the siRNA and all three pharmacological inhibitors yielded substantial and statistically significant reductions in the eTE. These findings suggest that electrotransfection depends on two mechanisms: (i) binding of pDNA to cell membrane and (ii) endocytosis of membrane-bound pDNA.

Authors
Wu, M; Yuan, F
MLA Citation
Wu, M, and Yuan, F. "Membrane binding of plasmid DNA and endocytic pathways are involved in electrotransfection of mammalian cells." PLoS One 6.6 (2011): e20923-.
Website
http://hdl.handle.net/10161/4640
PMID
21695134
Source
pubmed
Published In
PloS one
Volume
6
Issue
6
Publish Date
2011
Start Page
e20923
DOI
10.1371/journal.pone.0020923

Modeling the relative impact of capsular tissue effects on implanted glucose sensor time lag and signal attenuation.

Little is known mechanistically about why implanted glucose sensors lag behind blood glucose levels in both the time to peak sensor response and the magnitude of peak sensor response. A mathematical model of glucose transport from capillaries through surrounding tissue to the sensor surface was constructed to address how different aspects of the tissue affect glucose transport to an implanted sensor. Physiologically relevant values of capsule diffusion coefficient, capsule porosity, cellular glucose consumption, capsule thickness, and subcutaneous vessel density were used as inputs to create simulated sensor traces that mimic experimental instances of time lag and concentration attenuation relative to a given blood glucose profile. Using logarithmic sensitivity analysis, each parameter was analyzed to study the effect of these variables on both lag and attenuation. Results identify capsule thickness as the strongest determinant of sensor time lag, while subcutaneous vessel density and capsule porosity had the largest effects on attenuation of glucose that reaches the sensor surface. These findings provide mechanistic insight for the rational design of sensor modifications that may alleviate the deleterious consequences of tissue effects on implanted sensor performance.

Authors
Novak, MT; Yuan, F; Reichert, WM
MLA Citation
Novak, MT, Yuan, F, and Reichert, WM. "Modeling the relative impact of capsular tissue effects on implanted glucose sensor time lag and signal attenuation." Anal Bioanal Chem 398.4 (October 2010): 1695-1705.
PMID
20803006
Source
pubmed
Published In
Analytical and Bioanalytical Chemistry
Volume
398
Issue
4
Publish Date
2010
Start Page
1695
End Page
1705
DOI
10.1007/s00216-010-4097-6

Numerical simulations of ethacrynic acid transport from precorneal region to trabecular meshwork.

Topical application of drugs for treatment of intraocular diseases is often limited by inadequate transport and induced toxicity in corneal tissues. To improve the drug delivery, a mathematical model was developed to numerically simulate the transport process of ethacrynic acid (ECA), a potential drug for glaucoma treatment, in the anterior segment of a typical human eye. The model considered diffusion of ECA in all tissues and the aqueous humor (AH) as well as convection of ECA in the AH. The simulation results showed that ECA concentration in the eye depended on the rate of AH production, the half-life of ECA in the precorneal tear film, and the transport parameters in the model. In addition, the main pathway for ECA clearance from the eye was the trabecular meshwork (TM) and the rate of clearance was approximately proportional to the AH production rate. The model predicted that the most effective approach to improving topical drug delivery was to prolong its half-life in the precorneal tear film. These simulation results and model prediction, which could be verified experimentally, might be useful for improving delivery of ECA and other therapeutic agents to the TM as well as other tissues in the anterior segment of the eye.

Authors
Lin, C-W; Yuan, F
MLA Citation
Lin, C-W, and Yuan, F. "Numerical simulations of ethacrynic acid transport from precorneal region to trabecular meshwork." Ann Biomed Eng 38.3 (March 2010): 935-944.
PMID
20140518
Source
pubmed
Published In
Annals of Biomedical Engineering
Volume
38
Issue
3
Publish Date
2010
Start Page
935
End Page
944
DOI
10.1007/s10439-010-9947-z

Modeling the Relative Effects of Biofouling, Fibrous Encapsulation and Microvessel Density on Implanted Glucose Sensor Performance

Authors
Novak, MT; Yuan, F; Reichert, WM
MLA Citation
Novak, MT, Yuan, F, and Reichert, WM. "Modeling the Relative Effects of Biofouling, Fibrous Encapsulation and Microvessel Density on Implanted Glucose Sensor Performance." BIOPHYSICAL JOURNAL 98.3 (January 2010): 407A-407A.
Source
wos-lite
Published In
Biophysical Journal
Volume
98
Issue
3
Publish Date
2010
Start Page
407A
End Page
407A

Comparative effects of thermosensitive doxorubicin-containing liposomes and hyperthermia in human and murine tumours.

PURPOSE: In previous reports, laboratory-made lysolecithin-containing thermosensitive liposome encapsulating doxorubicin (LTSL-DOX) showed potent anticancer effects in FaDu human squamous cell carcinoma. To further study the spectrum of LTSL-DOX activity, the efficacy of its commercial formulation was re-examined in FaDu and compared in HCT116, PC3, SKOV-3 and 4T07 cancer cell lines. Factors that may influence differences in HT-LTSL-DOX efficacy were also examined. METHODS: Anticancer effect was measured using standard growth delay methods. We measured doubling time and clonogenic survival after doxorubicin exposure in vitro, and interstitial pH and drug concentrations in vivo. RESULTS: In all five tumour types, HT-LTSL-DOX increased median tumour growth time compared with untreated controls (p < 0.0006) and HT alone (p < 0.01), and compared with LTSL-DOX alone in FaDu, PC-3 and HCT-116 (p < 0.0006). HT-LTSL-DOX yielded significantly higher drug concentrations than LTSL-DOX (p < 0.0001). FaDu was most sensitive (p < 0.0014) to doxorubicin (IC(50) = 90 nM) in vitro, compared to the other cell lines (IC(50) = 129-168 nM). Of the parameters tested for correlation with efficacy, only the correlation of in vitro doubling time and in vivo median growth time was significant (Pearson r = 0.98, p = 0.0035). Slower-growing SKOV-3 and PC-3 had the greatest numbers of complete regressions and longest tumour growth delays, which are clinically important parameters. CONCLUSIONS: These results strongly suggest that variations in anti-tumour effect of HT-LTSL-DOX are primarily related to in vitro doubling time. In the clinic, the rate of tumour progression must be considered in design of treatment regimens involving HT-LTSL-DOX.

Authors
Yarmolenko, PS; Zhao, Y; Landon, C; Spasojevic, I; Yuan, F; Needham, D; Viglianti, BL; Dewhirst, MW
MLA Citation
Yarmolenko, PS, Zhao, Y, Landon, C, Spasojevic, I, Yuan, F, Needham, D, Viglianti, BL, and Dewhirst, MW. "Comparative effects of thermosensitive doxorubicin-containing liposomes and hyperthermia in human and murine tumours." Int J Hyperthermia 26.5 (2010): 485-498.
PMID
20597627
Source
pubmed
Published In
International Journal of Hyperthermia (Informa)
Volume
26
Issue
5
Publish Date
2010
Start Page
485
End Page
498
DOI
10.3109/02656731003789284

Tumor microvascular permeability is a key determinant for antivascular effects of doxorubicin encapsulated in a temperature sensitive liposome.

Previous data have demonstrated that doxorubicin (DOX) released from a lysolecithin-containing thermosensitive liposome (LTSL) can shut down blood flow in a human tumor xenograft (FaDu) in mice when the treatment is combined with hyperthermia (HT), suggesting that LTSL-DOX is a potential antivascular agent. To further understand mechanisms of the treatment, we investigated effects of LTSL-DOX (5 mg/kg body weight) plus HT (42 degrees C, 1 h) on microcirculation in another tumor (a murine mammary carcinoma, 4T07) implanted in mouse dorsal skin-fold chambers and dose responses of tumor (FaDu and 4T07) and endothelial cells to LTSL-DOX or free DOX with or without HT. We observed that LTSL-DOXHT could significantly reduce blood flow and microvascular density in 4T07 tumors. The antivascular efficacy of LTSLDOX- HT could be enhanced through increasing tumor microvascular permeability of liposomes by using platelet activating factor (PAF). We also observed that the dose responses of FaDu and 4T07 to DOX in vitro were similar to each other and could be enhanced by HT. Taken together, these data suggested that tumor microvascular permeability was more critical than the sensitivity of tumor cells to DOX in determining the antivascular efficacy of LTSL-DOX-HT treatment.

Authors
Chen, Q; Krol, A; Wright, A; Needham, D; Dewhirst, MW; Yuan, F
MLA Citation
Chen, Q, Krol, A, Wright, A, Needham, D, Dewhirst, MW, and Yuan, F. "Tumor microvascular permeability is a key determinant for antivascular effects of doxorubicin encapsulated in a temperature sensitive liposome." Int J Hyperthermia 24.6 (September 2008): 475-482.
PMID
18608573
Source
pubmed
Published In
International Journal of Hyperthermia (Informa)
Volume
24
Issue
6
Publish Date
2008
Start Page
475
End Page
482
DOI
10.1080/02656730701854767

Relaxin treatment of solid tumors: effects on electric field-mediated gene delivery.

Pulsed electric fields have been shown to enhance interstitial transport of plasmid DNA (pDNA) in solid tumors in vivo. However, the extent of enhancement is still limited partly due to the collagen component in extracellular matrix. To this end, effects of collagen remodeling on interstitial electrophoresis were investigated by pretreatment of tumor-bearing mice with a recombinant human relaxin (rh-Rlx). In the study, two tumor lines (4T1 and B16.F10) were examined and implanted s.c. to establish two murine models: dorsal skin-fold chamber (DSC) and hind leg. Effects of rh-Rlx on pDNA electrophoresis were measured either directly in the DSC model or indirectly in the hind leg model via reporter gene expression. It was observed that rh-Rlx treatment reduced collagen levels in the hind leg tumors but not in the DSC tumors. The observation correlated with the results from electromobility experiments, where rh-Rlx treatment enhanced transgene expression in 4T1 hind leg tumors but did not increase the electromobility of pDNA in the DSC tumors. In addition, it was observed that pDNA binding to collagen could block its diffusion in collagen gel in vitro. These observations showed that effects of rh-Rlx on the collagen content depended on microenvironment in solid tumors and that rh-Rlx treatment would enhance electric field-mediated gene delivery only if it could effectively reduce the collagen content in collagen-rich tumors.

Authors
Henshaw, J; Mossop, B; Yuan, F
MLA Citation
Henshaw, J, Mossop, B, and Yuan, F. "Relaxin treatment of solid tumors: effects on electric field-mediated gene delivery." Mol Cancer Ther 7.8 (August 2008): 2566-2573.
PMID
18723501
Source
pubmed
Published In
Molecular cancer therapeutics
Volume
7
Issue
8
Publish Date
2008
Start Page
2566
End Page
2573
DOI
10.1158/1535-7163.MCT-08-0435

Field distribution and DNA transport in solid tumors during electric field-mediated gene delivery.

Gene therapy has a great potential in cancer treatment. However, the efficacy of cancer gene therapy is currently limited by the lack of a safe and efficient means to deliver therapeutic genes into the nucleus of tumor cells. One method under investigation for improving local gene delivery is based on the use of pulsed electric field. Despite repeated demonstration of its effectiveness in vivo, the underlying mechanisms behind electric field-mediated gene delivery remain largely unknown. Without a thorough understanding of these mechanisms, it will be difficult to further advance the gene delivery. In this review, the electric field-mediated gene delivery in solid tumors will be examined by following individual transport processes that must occur in vivo for a successful gene transfer. The topics of examination include: (i) major barriers for gene delivery in the body, (ii) distribution of electric fields at both cell and tissue levels during the application of external fields, and (iii) electric field-induced transport of genes across each of the barriers. Through this approach, the review summarizes what is known about the mechanisms behind electric field-mediated gene delivery and what require further investigations in future studies.

Authors
Henshaw, JW; Yuan, F
MLA Citation
Henshaw, JW, and Yuan, F. "Field distribution and DNA transport in solid tumors during electric field-mediated gene delivery." J Pharm Sci 97.2 (February 2008): 691-711. (Review)
PMID
17624918
Source
pubmed
Published In
Journal of Pharmaceutical Sciences
Volume
97
Issue
2
Publish Date
2008
Start Page
691
End Page
711
DOI
10.1002/jps.21000

Dose response of angiogenesis to basic fibroblast growth factor in rat corneal pocket assay: II. Numerical simulations.

Angiogenesis involves interactions among various molecules and cells. To understand the complexity of interactions, we developed a mathematical model to numerically simulate angiogenesis induced by basic fibroblast growth factor (bFGF) in the corneal pocket assay. The model considered interstitial transport of bFGF, cellular uptake of bFGF, and dynamics of vessel growth. The model was validated by comparing simulated vascular networks, induced by bFGF at three different doses: 5 ng, 15 ng, and 50 ng, with experimental data obtained in the first part of the study, in terms of migration distance of vascular network, total vessel length, and number of vessels. The model was also used to simulate growth dynamics of vascular networks as well as spatial and temporal distribution of bFGF, which could not be measured experimentally. Taken together, results of the study suggested that the coupling between diffusion and cellular uptake of bFGF was critical for determining structures of vascular networks and that the mathematical model was appropriate for simulation of angiogenesis in the cornea.

Authors
Tong, S; Yuan, F
MLA Citation
Tong, S, and Yuan, F. "Dose response of angiogenesis to basic fibroblast growth factor in rat corneal pocket assay: II. Numerical simulations." Microvasc Res 75.1 (January 2008): 16-24.
PMID
18031768
Source
pubmed
Published In
Microvascular Research
Volume
75
Issue
1
Publish Date
2008
Start Page
16
End Page
24
DOI
10.1016/j.mvr.2007.09.005

Mechanistic analysis of electroporation-induced cellular uptake of macromolecules.

Pulsed electric field has been widely used as a nonviral gene delivery platform. The delivery efficiency can be improved through quantitative analysis of pore dynamics and intracellular transport of plasmid DNA. To this end, we investigated mechanisms of cellular uptake of macromolecules during electroporation. In the study, fluorescein isothiocyanate-labeled dextran (FD) with molecular weight of 4,000 (FD-4) or 2,000,000 (FD-2000) was added into suspensions of a murine mammary carcinoma cell (4T1) either before or at different time points (ie, 1, 2, or 10 sec) after the application of different pulsed electric fields (in high-voltage mode: 1.2-2.0 kV in amplitude, 99 microsec in duration, and 1-5 pulses; in low-voltage mode: 100-300 V in amplitude, 5-20 msec in duration, and 1-5 pulses). The intracellular concentrations of FD were quantified using a confocal microscopy technique. To understand transport mechanisms, a mathematical model was developed for numerical simulation of cellular uptake. We observed that the maximum intracellular concentration of FD-2000 was less than 3% of that in the pulsing medium. The intracellular concentrations increased linearly with pulse number and amplitude. In addition, the intracellular concentration of FD-2000 was approximately 40% lower than that of FD-4 under identical pulsing conditions. The numerical simulations predicted that the pores larger than FD-4 lasted <10 msec after the application of pulsed fields if the simulated concentrations were on the same order of magnitude as the experimental data. In addition, the simulation results indicated that diffusion was negligible for cellular uptake of FD molecules. Taken together, the data suggested that large pores induced in the membrane by pulsed electric fields disappeared rapidly after pulse application and convection was likely to be the dominant mode of transport for cellular uptake of uncharged macromolecules.

Authors
Zaharoff, DA; Henshaw, JW; Mossop, B; Yuan, F
MLA Citation
Zaharoff, DA, Henshaw, JW, Mossop, B, and Yuan, F. "Mechanistic analysis of electroporation-induced cellular uptake of macromolecules." Exp Biol Med (Maywood) 233.1 (January 2008): 94-105.
PMID
18156311
Source
pubmed
Published In
Experimental biology and medicine (Maywood, N.J.)
Volume
233
Issue
1
Publish Date
2008
Start Page
94
End Page
105
DOI
10.3181/0704-RM-113

Dose response of angiogenesis to basic fibroblast growth factor in rat corneal pocket assay: I. Experimental characterizations.

Understanding mechanisms of formation of vascular networks under different experimental conditions is essential for improving treatment of angiogenesis-dependent diseases. To this end, we investigated the dose response of angiogenesis to basic fibroblast growth factor (bFGF) using the rat corneal pocket assay. The response was quantified, in terms of (i) the migration distance of vascular networks, (ii) the total vessel length, (iii) the distribution of the projected width of vessels, (iv) the distribution of the number of vessels, and (v) the distribution of vessel diameters. The quantification was based on new image analysis methods developed in the study. It was observed that the migration distance and the total vessel length increased by 82% and 199%, respectively, when the dose of bFGF was increased from 5 ng to 50 ng. The number and the diameter of vessels increased with the dose of bFGF as well. However, the last two parameters at a given dose of bFGF were approximately independent of the location in the middle region between the pellet and the limbus. These results provided useful information for understanding mechanisms of angiogenesis induced by bFGF and important data for validating a mathematical model of angiogenesis described in the second part of the study.

Authors
Tong, S; Yuan, F
MLA Citation
Tong, S, and Yuan, F. "Dose response of angiogenesis to basic fibroblast growth factor in rat corneal pocket assay: I. Experimental characterizations." Microvasc Res 75.1 (January 2008): 10-15.
PMID
17706726
Source
pubmed
Published In
Microvascular Research
Volume
75
Issue
1
Publish Date
2008
Start Page
10
End Page
15
DOI
10.1016/j.mvr.2007.06.002

Effects of transmural fluid exchange on tumor blood flow

Authors
Yuan, F; Huang, A
MLA Citation
Yuan, F, and Huang, A. "Effects of transmural fluid exchange on tumor blood flow." BIORHEOLOGY 45.1-2 (2008): 39-39.
Source
wos-lite
Published In
Biorheology
Volume
45
Issue
1-2
Publish Date
2008
Start Page
39
End Page
39

Electric field-mediated transport of plasmid DNA in tumor interstitium in vivo.

Local pulsed electric field application is a method for improving non-viral gene delivery. Mechanisms of the improvement include electroporation and electrophoresis. To understand how electrophoresis affects pDNA delivery in vivo, we quantified the magnitude of electric field-induced interstitial transport of pDNA in 4T1 and B16.F10 tumors implanted in mouse dorsal skin-fold chambers. Four different electric pulse sequences were used in this study, each consisted of 10 identical pulses that were 100 or 400 V/cm in strength and 20 or 50 ms in duration. The interval between consecutive pulses was 1 s. The largest distance of transport was obtained with the 400 V/cm and 50 ms pulse, and was 0.23 and 0.22 microm/pulse in 4T1 and B16.F10 tumors, respectively. There were no significant differences in transport distances between 4T1 and B16.F10 tumors. Results from in vivo mapping and numerical simulations revealed an approximately uniform intratumoral electric field that was predominantly in the direction of the applied field. The data in the study suggested that interstitial transport of pDNA induced by a sequence of ten electric pulses was ineffective for macroscopic delivery of genes in tumors. However, the induced transport was more efficient than passive diffusion.

Authors
Henshaw, JW; Zaharoff, DA; Mossop, BJ; Yuan, F
MLA Citation
Henshaw, JW, Zaharoff, DA, Mossop, BJ, and Yuan, F. "Electric field-mediated transport of plasmid DNA in tumor interstitium in vivo." Bioelectrochemistry 71.2 (November 2007): 233-242.
PMID
17728192
Source
pubmed
Published In
Bioelectrochemistry
Volume
71
Issue
2
Publish Date
2007
Start Page
233
End Page
242
DOI
10.1016/j.bioelechem.2007.07.005

Electric fields around and within single cells during electroporation-a model study.

One of the key issues in electric field-mediated molecular delivery into cells is how the intracellular field is altered by electroporation. Therefore, we simulated the electric field in both the extracellular and intracellular domains of spherical cells during electroporation. The electroporated membrane was modeled macroscopically by assuming that its electric resistivity was smaller than that of the intact membrane. The size of the electroporated region on the membrane varied from zero to the entire surface of the cell. We observed that for a range of values of model constants, the intracellular current could vary several orders of magnitude whereas the maximum variations in the extracellular and total currents were less than 8% and 4%, respectively. A similar difference in the variations was observed when comparing the electric fields near the center of the cell and across the permeabilized membrane, respectively. Electroporation also caused redirection of the extracellular field that was significant only within a small volume in the vicinity of the permeabilized regions, suggesting that the electric field can only facilitate passive cellular uptake of charged molecules near the pores. Within the cell, the field was directed radially from the permeabilized regions, which may be important for improving intracellular distribution of charged molecules.

Authors
Mossop, BJ; Barr, RC; Henshaw, JW; Yuan, F
MLA Citation
Mossop, BJ, Barr, RC, Henshaw, JW, and Yuan, F. "Electric fields around and within single cells during electroporation-a model study." Ann Biomed Eng 35.7 (July 2007): 1264-1275.
PMID
17340194
Source
pubmed
Published In
Annals of Biomedical Engineering
Volume
35
Issue
7
Publish Date
2007
Start Page
1264
End Page
1275
DOI
10.1007/s10439-007-9282-1

Transscleral diffusion of ethacrynic acid and sodium fluorescein.

PURPOSE: One of the current limitations in developing novel glaucoma drugs that target the trabecular meshwork (TM) is the induced corneal toxicity from eyedrop formulations. To avoid the corneal toxicity, an alternative approach would be to deliver TM drugs through the sclera. To this end, we quantified ex vivo diffusion coefficient of a potential TM drug, ethacrynic acid (ECA), and investigated mechanisms of ECA transport in the sclera. METHODS: An Ussing-type diffusion apparatus was built to measure the apparent diffusion coefficient of ECA in fresh porcine sclera at 4 degrees C. To understand mechanisms of ECA transport, we quantified the transscleral transport of a fluorescent tracer, sodium fluorescein (NaF), that has a similar molecular weight but is more hydrophilic compared to ECA. Furthermore, we developed a mathematical model to simulate the transport processes and used it to analyze the experimental data. The model was also used to investigate the dependence of diffusion coefficients on volume fraction of viable cells and the binding of NaF and ECA to scleral tissues. RESULTS: The diffusion coefficients of ECA and NaF in the sclera were 48.5+/-15.1 x 10-7 cm(2)/s (n=9) and 5.23+/-1.93 x 10(-7) cm(2)/s (n=8), respectively. Both diffusion coefficients were insensitive to cell shrinkage caused by ECA during the diffusion experiments and cell damage caused by the storage of tissues ex vivo before the experiments. Binding of ECA to scleral tissues could not be detected. The apparent maximum binding capacity and the apparent equilibrium dissociation constant for NaF were 80+/-5 mM and 2.5+/-0.5 mM (n=3), respectively. CONCLUSIONS: These data demonstrated that ECA diffusion was minimally hindered by structures in the sclera, presumably due to the lack of cells and binding sites for ECA in the sclera.

Authors
Lin, C-W; Wang, Y; Challa, P; Epstein, DL; Yuan, F
MLA Citation
Lin, C-W, Wang, Y, Challa, P, Epstein, DL, and Yuan, F. "Transscleral diffusion of ethacrynic acid and sodium fluorescein. (Published online)" Mol Vis 13 (February 22, 2007): 243-251.
PMID
17356511
Source
pubmed
Published In
Molecular vision
Volume
13
Publish Date
2007
Start Page
243
End Page
251

Glucose recovery with bare and hydrogel-coated microdialysis probes: experiment and simulation of temporal effects.

In vitro microdialysis glucose sampling was used to test the transient and steady-state suitability of antifouling hydrogel coatings, composed of 2-hydroxyethyl methacrylate, vinylpyrrolidinone, and poly(ethylene glycol). The in vitro glucose diffusion coefficients of bare microdialysis membranes and hydrogel coatings were determined experimentally to be 1.1 x 10-6 and 3.2 x 10-6 cm2/s, respectively. These values were used to numerically simulate the effect of the hydrogel on glucose transport across the microdialysis membrane using a convection-diffusion transport model. The times for dialysate at the exit of the bare and hydrogel-coated microdialysis probes to reach 95% of steady state were calculated to be 20 and 66 s, respectively. However, the experimental data showed that 95% of steady-state glucose recoveries were reached after 4-5 min. Numerical simulations incorporating the Taylor dispersion in the outlet tubing showed the time difference was caused almost completely by convective transport in the outlet tubing with negligible contribution from analyte profile broadening. These data indicated that the hydrogel coatings imposed 44% reduction in glucose permeability and consequently 26% reduction in the percent recovery. The effect of hydrogel coatings on the time to reach the steady-state recovery was insignificant compared with the time required for convection of glucose in the outlet tubing.

Authors
Norton, LW; Yuan, F; Reichert, WM
MLA Citation
Norton, LW, Yuan, F, and Reichert, WM. "Glucose recovery with bare and hydrogel-coated microdialysis probes: experiment and simulation of temporal effects." Anal Chem 79.2 (January 15, 2007): 445-452.
PMID
17222006
Source
pubmed
Published In
Analytical Chemistry
Volume
79
Issue
2
Publish Date
2007
Start Page
445
End Page
452
DOI
10.1021/ac061234p

Engineering novel synthetic biological systems

Engineering principles and new applications for the nascent field of synthetic biology are just beginning to be explored. Here, we report the engineering of four novel synthetic biological systems: (1) a Bacterial Dynamo, for generating electricity using modified magnetotactic bacteria on a microfabricated device; (2) Cancer StickyBots, for targeting and destroying tumour cells using engineered Escherichia coli cells; (3) Human Encryption, an information encoding, storage, and retrieval scheme for potential security and medical diagnostic applications; and (4) X-Verter, new strategies and tools for biological circuit design and BioBrick management. While each of these systems had distinct aims, they shared a common philosophy of rationally building useful and beneficial synthetic biological systems using fundamental engineering principles. They also demonstrated the potential usefulness of BioBricks and contributed to the Registry of Standard Biological Parts and synthetic biology community-at-large. © 2007 The Institution of Engineering and Technology.

Authors
Reza, F; Chandran, K; Feltz, M; Heinz, A; Josephs, E; O'Brien, P; Dyke, BV; Chung, H; Indurkhya, S; Lakhani, N; Lee, J; Lin, S; Tang, N; Labean, T; You, L; Yuan, F; Tian, J
MLA Citation
Reza, F, Chandran, K, Feltz, M, Heinz, A, Josephs, E, O'Brien, P, Dyke, BV, Chung, H, Indurkhya, S, Lakhani, N, Lee, J, Lin, S, Tang, N, Labean, T, You, L, Yuan, F, and Tian, J. "Engineering novel synthetic biological systems." IET Synthetic Biology 1.1-2 (2007): 48-52.
Source
scival
Published In
IET Synthetic Biology
Volume
1
Issue
1-2
Publish Date
2007
Start Page
48
End Page
52
DOI
10.1049/iet-stb:20060004

Mapping engineering onto biology at the nanoscale: nature's encapsulation technologies as bioinspiration for nano-scale anti-tumor drug delivery

Authors
Needham, D; Wright, A; Tong, J; Dewhirst, MW; Ponce, A; Yuan, F
MLA Citation
Needham, D, Wright, A, Tong, J, Dewhirst, MW, Ponce, A, and Yuan, F. "Mapping engineering onto biology at the nanoscale: nature's encapsulation technologies as bioinspiration for nano-scale anti-tumor drug delivery." December 2006.
Source
crossref
Published In
Nanomedicine: Nanotechnology, Biology and Medicine
Volume
2
Issue
4
Publish Date
2006
Start Page
292
End Page
293
DOI
10.1016/j.nano.2006.10.077

A single molecule detection method for understanding mechanisms of electric field-mediated interstitial transport of genes.

The interstitial space is a rate limiting physiological barrier to non-viral gene delivery. External pulsed electric fields have been proposed to increase DNA transport in the interstitium, thereby improving non-viral gene delivery. In order to characterize and improve the interstitial transport, we developed a reproducible single molecule detection method to observe the electromobility of DNA in a range of pulsed, high field strength electric fields typically used during electric field-mediated gene delivery. Using agarose gel as an interstitium phantom, we investigated the dependence of DNA electromobility on field magnitude, pulse duration, pulse interval, and pore size in the interstitial space. We observed that the characteristic electromobility behavior, exhibited under most pulsing conditions, consisted of three distinct phases: stretching, reptation, and relaxation. Electromobility depended strongly on the field magnitude, pulse duration, and pulse interval of the applied pulse sequences, as well as the pore size of the fibrous matrix through which the DNA migrated. Our data also suggest the existence of a minimum pulse amplitude required to initiate electrophoretic transport. These results are useful for understanding the mechanisms of DNA electromobility and improving interstitial transport of genes during electric field-mediated gene delivery.

Authors
Henshaw, JW; Zaharoff, DA; Mossop, BJ; Yuan, F
MLA Citation
Henshaw, JW, Zaharoff, DA, Mossop, BJ, and Yuan, F. "A single molecule detection method for understanding mechanisms of electric field-mediated interstitial transport of genes." Bioelectrochemistry 69.2 (October 2006): 248-253.
PMID
16713747
Source
pubmed
Published In
Bioelectrochemistry
Volume
69
Issue
2
Publish Date
2006
Start Page
248
End Page
253
DOI
10.1016/j.bioelechem.2006.03.006

Electric fields in tumors exposed to external voltage sources: implication for electric field-mediated drug and gene delivery.

The intratumoral field, which determines the efficiency of electric field-mediated drug and gene delivery, can differ significantly from the applied field. Therefore, we investigated the distribution of the electric field in mouse tumors and tissue phantoms exposed to a large range of electric stimuli, and quantified the resistances of tumor, skin, and electrode-tissue interface. The samples used in the study included 4T1 and B16.F10 tumors, mouse skin, and tissue phantoms constructed with 1% agarose gel with or without 4T1 cells. When pulsed electric fields were applied to samples using a pair of parallel-plate electrodes, we determined the electric field and resistances in each sample as well as the resistance at the electrode-tissue interface. The electric fields in the center region of tissue phantoms and tumor slices ex vivo were macroscopically uniform and unidirectional between two parallel-plate electrodes. The field strengths in tumor tissues were significantly lower than the applied field under both ex vivo and in vivo conditions. During in vivo stimulation, the ratio of intratumoral versus applied fields was approximately either 20% or 55%, depending on the applied field. Meanwhile, the total resistance of skin and electrode-tissue interface was decreased by approximately 70% and the electric resistance at the center of both tumor models was minimally changed when the applied field was increased from 50 to 400 V/cm. These results may be useful for improving electric field-mediated drug and gene delivery in solid tumors.

Authors
Mossop, BJ; Barr, RC; Henshaw, JW; Zaharoff, DA; Yuan, F
MLA Citation
Mossop, BJ, Barr, RC, Henshaw, JW, Zaharoff, DA, and Yuan, F. "Electric fields in tumors exposed to external voltage sources: implication for electric field-mediated drug and gene delivery." Ann Biomed Eng 34.10 (October 2006): 1564-1572.
PMID
16917743
Source
pubmed
Published In
Annals of Biomedical Engineering
Volume
34
Issue
10
Publish Date
2006
Start Page
1564
End Page
1572
DOI
10.1007/s10439-006-9151-3

Preferential extravasation and accumulation of liposomal vincristine in tumor comparing to normal tissue enhances antitumor activity.

To quantitatively evaluate the extravasation, accumulation and selectivity to tumor tissues of liposomal vincristine (LV), dorsal skin-fold window chambers on athymic mice with or without LX-1, a human small cell lung cancer, xenograft implants and fluorescent intravital microscopy imaging were used. In vitro studies show that minimal loss of fluorescence marker DiI from liposomes occurs after 4 days of inoculation in murine plasma, and the release profiles of DiI-LV and LV were essentially the same with approximately 40% of the encapsulated vincristine sulfate (VCR) released after 26 h. Significantly faster extravasation of DiI-LV from tumor vessels was shown compared to non-tumor tissue after single dose i.v. administration. The relative interstitial amounts at 60 min (RIA(60)) for tumor and non-tumor tissues were 0.837+/-0.314 and 0.012+/-0.091, respectively (P=0.01). DiI-LV accumulation was significantly higher in tumor than in normal tissue, which continued beyond 48 h. Both DiI-LV and LV showed significant antitumor effects in window chambers and in flank tumors, compared with controls and VLS alone. The preferential extravasation of DiI-LV from tumor vasculature as well as its differential retention in tumor tissue provides the basis for the enhancement in antitumor activity of LV over VCR.

Authors
Shan, S; Flowers, C; Peltz, CD; Sweet, H; Maurer, N; Kwon, E-JG; Krol, A; Yuan, F; Dewhirst, MW
MLA Citation
Shan, S, Flowers, C, Peltz, CD, Sweet, H, Maurer, N, Kwon, E-JG, Krol, A, Yuan, F, and Dewhirst, MW. "Preferential extravasation and accumulation of liposomal vincristine in tumor comparing to normal tissue enhances antitumor activity." Cancer Chemother Pharmacol 58.2 (August 2006): 245-255.
PMID
16341532
Source
pubmed
Published In
Cancer Chemotherapy and Pharmacology
Volume
58
Issue
2
Publish Date
2006
Start Page
245
End Page
255
DOI
10.1007/s00280-005-0145-x

Nonlinear dependence of hydraulic conductivity on tissue deformation during intratumoral infusion.

Efficiency of intratumoral infusion for drug and gene delivery depends on intrinsic tissue structures as well as infusion-induced changes in these structures. To this end, we investigated effects of infusion pressure (P(inf)) and infusion-induced tissue deformation on infusion rate (Q) in three mouse tumor models (B16.F10, 4T1, and U87) and developed a poroelastic model for interpreting data and understanding mechanisms of fluid transport in tumors. The collagen concentrations in these tumors were 2.9+/-1.2, 12.2+/-0.9, and 18.1+/-3.5 microg/mg wet wt. of tissues, respectively. During the infusion, there existed a threshold infusion pressure (P(t)), below which fluid flow could not be initiated. The values of P(t) for these tumors were 7.36, 36.8, and 29.4 mmHg, respectively. Q was a bell-shaped function of P(inf) in 4T1 tumors but increased monotonically with increasing P(inf) in other tumors. These observations were consistent with results from numerical simulations based on the poroelastic model, suggesting that both the existence of P(t) and the nonlinear relationships between Q and P(inf) could be explained by infusion-induced tissue deformation that anisotropically affected the hydraulic conductivity of tissues. These results may be useful for further investigations of intratumoral infusion of drugs and genes.

Authors
McGuire, S; Zaharoff, D; Yuan, F
MLA Citation
McGuire, S, Zaharoff, D, and Yuan, F. "Nonlinear dependence of hydraulic conductivity on tissue deformation during intratumoral infusion." Ann Biomed Eng 34.7 (July 2006): 1173-1181.
PMID
16791492
Source
pubmed
Published In
Annals of Biomedical Engineering
Volume
34
Issue
7
Publish Date
2006
Start Page
1173
End Page
1181
DOI
10.1007/s10439-006-9136-2

Hyperthermia mediated liposomal drug delivery.

Drug delivery systems have been developed for cancer therapy in an attempt to increase the tumour drug concentration while limiting systemic exposure. Liposomes have achieved passive targeting of solid tumours through enhanced vascular permeability, which is greatly augmented by hyperthermia. However, anti-tumour efficacy has often been limited by slow release of bioavailable drug within the tumour. Local hyperthermia has become the most widely used stimulus for triggered release of liposomal drugs, through the use of specific lipids, polymers or other modifiers. A temperature-sensitive liposome containing doxorubicin has been shown to release 100% of contents through stabilized membrane pores within 10-20 s at 41 degrees C. This formulation has exhibited dramatic improvements in pre-clinical drug delivery and tumour regression and is now in clinical trials. Significantly, recent studies show that this liposome, in combination with local hyperthermia, exhibits vascular shutdown as a mechanism of anti-tumour effect that is not observed with free doxorubicin.

Authors
Ponce, AM; Vujaskovic, Z; Yuan, F; Needham, D; Dewhirst, MW
MLA Citation
Ponce, AM, Vujaskovic, Z, Yuan, F, Needham, D, and Dewhirst, MW. "Hyperthermia mediated liposomal drug delivery." Int J Hyperthermia 22.3 (May 2006): 205-213.
PMID
16754340
Source
pubmed
Published In
International Journal of Hyperthermia (Informa)
Volume
22
Issue
3
Publish Date
2006
Start Page
205
End Page
213
DOI
10.1080/02656730600582956

Tumor vascular permeability, accumulation, and penetration of macromolecular drug carriers.

BACKGROUND: Delivery of anticancer therapeutic agents to solid tumors is problematic. Macromolecular drug carriers are an attractive alternative drug delivery method because they appear to target tumors and have limited toxicity in normal tissues. We investigated how molecular weight influences the accumulation of a model macromolecular drug carrier, dextran covalently linked to a fluorophore, in tumors. METHODS: We used dextrans with molecular weights from 3.3 kDa to 2 MDa. Vascular permeability, accumulation, and three-dimensional penetration of these dextrans were simultaneously measured in solid tumors via a dorsal skin fold window chamber, intravital laser-scanning confocal microscopy, and custom image analysis. RESULTS: Increasing the molecular weight of dextran statistically significantly reduced its vascular permeability by approximately two orders of magnitude (i.e., from 154 x 10(-7) cm/s, 95% confidence interval [CI] = 134 to 174 x 10(-7) cm/s, for 3.3-kDa dextran to 1.7 x 10(-7) cm/s, 95% CI = 0.7 to 2.6 x 10(-7) cm/s for 2-MDa dextran; P < .001, two-sided Kruskal-Wallis test) but increased its plasma half-life, which provided ample time for extravasation (i.e., to enter tumor tissue from the vasculature). Tumor accumulation was maximal for dextrans with molecular weights between 40 and 70 kDa. Dextrans of 3.3 and 10 kDa penetrated deeply (greater than 35 microm) and homogeneously into tumor tissue from the vessel wall. After a 30-minute period, a high concentration was observed only approximately 15 microm from the vessel wall for 40- to 70-kDa dextrans and only 5 microm for 2-MDa dextrans. CONCLUSIONS: Increasing the molecular weight of dextran statistically significantly reduced its tumor vascular permeability. Dextrans of 40 and 70 kDa had the highest accumulation in solid tumors but were largely concentrated near the vascular surface.

Authors
Dreher, MR; Liu, W; Michelich, CR; Dewhirst, MW; Yuan, F; Chilkoti, A
MLA Citation
Dreher, MR, Liu, W, Michelich, CR, Dewhirst, MW, Yuan, F, and Chilkoti, A. "Tumor vascular permeability, accumulation, and penetration of macromolecular drug carriers." J Natl Cancer Inst 98.5 (March 1, 2006): 335-344.
PMID
16507830
Source
pubmed
Published In
Journal of the National Cancer Institute
Volume
98
Issue
5
Publish Date
2006
Start Page
335
End Page
344
DOI
10.1093/jnci/djj070

Effects of rate, volume, and dose of intratumoral infusion on virus dissemination in local gene delivery.

Recent studies have shown that up to 90% of viral vectors could disseminate to normal organs following intratumoral infusion. The amount of dissemination might be dependent on the infusion conditions. Therefore, we investigated the effects of infusion rate, volume, and dose on transgene expression in liver and tumor tissues after intratumoral infusion of an adenoviral vector encoding luciferase. Luciferase expression was determined through bioluminescence intensity measurement. We observed that the luciferase expression in the liver was independent of the infusion rate but increased with the infusion dose, whereas the luciferase expression in the tumor was a bell-shaped function of the infusion rate. The latter observation was consistent with the distribution pattern of Evans blue-labeled albumin after its solution was infused into tumors at the same infusion rates. We also observed that the infusion volume could affect luciferase expression in the tumor but not in the liver. These observations implied that virus dissemination was determined mainly by the infusion dose, whereas the amount of transgene expression in the tumor depended on the distribution volume of viral vectors in the tumor as well as the infusion dose.

Authors
Wang, Y; Wang, H; Li, C-Y; Yuan, F
MLA Citation
Wang, Y, Wang, H, Li, C-Y, and Yuan, F. "Effects of rate, volume, and dose of intratumoral infusion on virus dissemination in local gene delivery." Mol Cancer Ther 5.2 (February 2006): 362-366.
PMID
16505110
Source
pubmed
Published In
Molecular cancer therapeutics
Volume
5
Issue
2
Publish Date
2006
Start Page
362
End Page
366
DOI
10.1158/1535-7163.MCT-05-0266

Delivery of viral vectors to tumor cells: extracellular transport, systemic distribution, and strategies for improvement.

It is a challenge to deliver therapeutic genes to tumor cells using viral vectors because (i) the size of these vectors are close to or larger than the space between fibers in extracellular matrix and (ii) viral proteins are potentially toxic in normal tissues. In general, gene delivery is hindered by various physiological barriers to virus transport from the site of injection to the nucleus of tumor cells and is limited by normal tissue tolerance of toxicity determined by local concentrations of transgene products and viral proteins. To illustrate the obstacles encountered in the delivery and yet limit the scope of discussion, this review focuses only on extracellular transport in solid tumors and distribution of viral vectors in normal organs after they are injected intravenously or intratumorally. This review also discusses current strategies for improving intratumoral transport and specificity of viral vectors.

Authors
Wang, Y; Yuan, F
MLA Citation
Wang, Y, and Yuan, F. "Delivery of viral vectors to tumor cells: extracellular transport, systemic distribution, and strategies for improvement." Ann Biomed Eng 34.1 (January 2006): 114-127. (Review)
PMID
16520902
Source
pubmed
Published In
Annals of Biomedical Engineering
Volume
34
Issue
1
Publish Date
2006
Start Page
114
End Page
127
DOI
10.1007/s10439-005-9007-2

Quantitative comparison of the inhibitory effects of GW5638 and tamoxifen on angiogenesis in the cornea pocket assay.

GW5638 is a novel tissue-selective estrogen receptor (ER) modulator. Structurally, it is a derivative of tamoxifen that is known for its inhibitory effects on angiogenesis in an ER-independent manner. Therefore, it is possible that GW5638 has the same effects as tamoxifen on angiogenesis. To test this hypothesis, we used the rat cornea pocket assay and developed a new method that could precisely determine the total projected area of microvessels induced by basic fibroblast growth factor (bFGF) in the cornea. Animals in the study were treated with corn oil (control group), tamoxifen, or GW5638. After treatment, we observed that both GW5638 and tamoxifen could inhibit angiogenesis in the cornea (P<0.05) and that the inhibitory effects were not mediated by blocking functions of estrogen. Meanwhile, GW5638 had minimal effects on the body weight of animals whereas tamoxifen significantly reduced the body weight. Based on these observations, we concluded that GW5638 was as effective as tamoxifen in antiangiogenic treatment but less toxic than tamoxifen.

Authors
Tong, S; Chen, Q; Shan, S-Q; Dewhirst, MW; Yuan, F
MLA Citation
Tong, S, Chen, Q, Shan, S-Q, Dewhirst, MW, and Yuan, F. "Quantitative comparison of the inhibitory effects of GW5638 and tamoxifen on angiogenesis in the cornea pocket assay." Angiogenesis 9.2 (2006): 53-58.
PMID
16622786
Source
pubmed
Published In
Angiogenesis
Volume
9
Issue
2
Publish Date
2006
Start Page
53
End Page
58
DOI
10.1007/s10456-006-9029-x

Alginate encapsulation is a highly reproducible method for tumor cell implantation in dorsal skinfold chambers.

Authors
Wang, Y; Chen, Q; Yuan, F
MLA Citation
Wang, Y, Chen, Q, and Yuan, F. "Alginate encapsulation is a highly reproducible method for tumor cell implantation in dorsal skinfold chambers." Biotechniques 39.6 (December 2005): 834-839.
PMID
16382900
Source
pubmed
Published In
BioTechniques
Volume
39
Issue
6
Publish Date
2005
Start Page
834
End Page
839

A novel method for viral gene delivery in solid tumors.

Intratumoral infusion is the most commonly used method for viral gene delivery in clinical trials for cancer treatment. However, a potential problem in this approach is that viral vectors may disseminate from tumor to normal tissues during and after the infusion. To reduce the dissemination, we developed a novel method based on a biocompatible polymer, poloxamer 407, which could significantly increase the viscosity of virus suspension when the temperature was changed from 4 degrees C to 37 degrees C. With this method, we could significantly increase transgene expression in solid tumors and reduce virus dissemination by 2 orders of magnitude after intratumoral infusion of adenoviral vectors. The mechanism of reduction was likely to be that the viscous poloxamer solution blocked convection of viral vectors in the interstitial space and the lumen of microvessels in the vicinity of the infusion site. This method has a potential to be used in the clinic for enhancing efficacy and reducing toxicity in viral gene therapy.

Authors
Wang, Y; Liu, S; Li, C-Y; Yuan, F
MLA Citation
Wang, Y, Liu, S, Li, C-Y, and Yuan, F. "A novel method for viral gene delivery in solid tumors." Cancer Res 65.17 (September 1, 2005): 7541-7545.
PMID
16140915
Source
pubmed
Published In
Cancer Research
Volume
65
Issue
17
Publish Date
2005
Start Page
7541
End Page
7545
DOI
10.1158/0008-5472.CAN-05-1112

Characterisation of systemic dissemination of nonreplicating adenoviral vectors from tumours in local gene delivery.

Systemic virus dissemination is a potential problem during local gene delivery in solid tumours. However, the kinetics and pathways of the dissemination have not been well characterised during the first 24 h after the infusion is started. To this end, we infused adenoviral vectors for luciferase or enhanced green fluorescence protein into three different tumour models in mice. During and/or after the infusion, we determined the amount of adenoviruses in the tumour, blood, and liver, and examined the transgene expression in the liver, lung, blood, and tumour. In addition, we intravenously injected tumour cells expressing luciferase and examined the biodistribution of these cells in the body. We observed transgene expression in the liver and tumour at 24 h after the infusion, but could not detect transgene expression in the blood and lung. The peak concentration of viral vectors in the plasma occurred during the intratumoral infusion. At 10 min after the infusion, few viral vectors remained in the blood and the ratio of copy numbers of adenoviruses between liver and tumour was > 2 in 80% and > or = 10 in 40% of the mice. Most tumour cells injected intravenously accumulated in the lung within the first 24 h. Taken together, these data indicated that systemic virus dissemination occurred mainly during the first 10 min after the intratumoral infusion was started, and that the dissemination was due to infusion-induced convective transport of viral vectors into leaky tumour microvessels.

Authors
Wang, Y; Yang, Z; Liu, S; Kon, T; Krol, A; Li, C-Y; Yuan, F
MLA Citation
Wang, Y, Yang, Z, Liu, S, Kon, T, Krol, A, Li, C-Y, and Yuan, F. "Characterisation of systemic dissemination of nonreplicating adenoviral vectors from tumours in local gene delivery." Br J Cancer 92.8 (April 25, 2005): 1414-1420.
PMID
15812558
Source
pubmed
Published In
British Journal of Cancer
Volume
92
Issue
8
Publish Date
2005
Start Page
1414
End Page
1420
DOI
10.1038/sj.bjc.6602494

Ex vivo and in vivo mapping of electric fields in tumor tissues

Electric field-mediated gene delivery is a promising therapeutic modality that uses an externally applied voltage source to introduce exogenous genetic materials to target cells by field-dependent phenomena, such as electrophoresis and electroporation. In previous studies, the genes and cells inside a tumor are assumed to encounter the applied field. However, several factors, such as ionic polarization at the electrode interface, the skin barrier (for in vivo transfection), and the presence of cells, may affect both the magnitude and direction of the intra-tumoral field. Herein, we described a novel method for measuring the electric field in tumors in response to an applied voltage stimulus in both ex vivo and in vivo mouse models. For comparison, we also measured the electric field in tissue phantoms, which consisted of 1% agarose gels, with or without cells. Our results showed that the electric field in tumor tissues could be as low as 69% and 24% of the applied field magnitude in ex vivo and in vivo situations, respectively.

Authors
Mossop, BJ; Henshaw, JW; Zaharoff, DA; Yuan, F
MLA Citation
Mossop, BJ, Henshaw, JW, Zaharoff, DA, and Yuan, F. "Ex vivo and in vivo mapping of electric fields in tumor tissues." Proceedings of the 2005 Summer Bioengineering Conference 2005 (2005): 197-198.
Source
scival
Published In
Proceedings of the 2005 Summer Bioengineering Conference
Volume
2005
Publish Date
2005
Start Page
197
End Page
198

In vivo electric field-mediated transport of plasmid DNA in tumor interstitium

Authors
Henshaw, JW; Zaharoff, DA; Mossop, BJ; Yuan, F
MLA Citation
Henshaw, JW, Zaharoff, DA, Mossop, BJ, and Yuan, F. "In vivo electric field-mediated transport of plasmid DNA in tumor interstitium." Proceedings of the 2005 Summer Bioengineering Conference 2005 (2005): 149-150.
Source
scival
Published In
Proceedings of the 2005 Summer Bioengineering Conference
Volume
2005
Publish Date
2005
Start Page
149
End Page
150

Numerical simulations of transcorneal tranport of ethacrynic acid

Potential trabecular meshwork (TM) drugs can be delivered with a lower concentration on the cornea surface over a long period of time for reducing the induced corneal toxicity. To determine the concentration of drugs that can be achieved in the TM, we developed a mathematical model to simulate axisymmetric transport of ethacrynic acid (ECA) from the cornea surface to the TM in a human eye. The results showed that the concentration of ECA could reach the therapeutic level at the TM site while the concentration of ECA on the cornea surface was maintained at an optimal level (75 μM) below the toxicity threshold. These results can be used to guide the design of controlled drug release devices.

Authors
Lin, C-W; Yuan, F
MLA Citation
Lin, C-W, and Yuan, F. "Numerical simulations of transcorneal tranport of ethacrynic acid." Proceedings of the 2005 Summer Bioengineering Conference 2005 (2005): 289-290.
Source
scival
Published In
Proceedings of the 2005 Summer Bioengineering Conference
Volume
2005
Publish Date
2005
Start Page
289
End Page
290

Targeting tumor microvessels using doxorubicin encapsulated in a novel thermosensitive liposome.

Liposomal drugs accumulate only in perivascular regions in tumors after i.v. injection. Thus, they cannot kill tumor cells in deeper tissue layers. To circumvent this problem, we investigated effects of doxorubicin (DOX) encapsulated in a lysolecithin-containing thermosensitive liposome (LTSL) on tumor microcirculation because damaging microvessels would stop nutrient supply to deeper tumor cells. We used LTSL-DOX in combination with hyperthermia to treat a human squamous carcinoma xenograft (FaDu) implanted in dorsal skinfold chambers in nude mice. Before the treatment, the RBC velocity in tumors was 0.428 +/- 0.037 mm/s and the microvascular density was 3.93 +/- 0.44 mm/mm(2). At 24 hours after the treatment, they were reduced to 0.003 +/- 0.003 mm/s and 0.86 +/- 0.27 mm/mm(2), respectively. The same treatment, however, caused only 32% decrease in the RBC velocity and no apparent change in microvascular networks in normal s.c. tissues over the same period. LTSL and LTSL-DOX alone had no effect on tumor microcirculation, and LTSL plus hyperthermia caused only a transient decrease in the RBC velocity in tumors. At 24 hours after treatments, tumor microcirculation in all these control experiments was insignificantly different from that before the treatments. We also examined apoptosis of cells in tumors at different time points after LTSL-DOX plus hyperthermia treatment and observed few apoptotic cells in tumor microvessels. In conclusion, the rapid release of DOX during hyperthermia could make the drug to shutdown tumor blood flow while have only minor effects on normal microcirculation in s.c. tissues.

Authors
Chen, Q; Tong, S; Dewhirst, MW; Yuan, F
MLA Citation
Chen, Q, Tong, S, Dewhirst, MW, and Yuan, F. "Targeting tumor microvessels using doxorubicin encapsulated in a novel thermosensitive liposome." Mol Cancer Ther 3.10 (October 2004): 1311-1317.
PMID
15486198
Source
pubmed
Published In
Molecular cancer therapeutics
Volume
3
Issue
10
Publish Date
2004
Start Page
1311
End Page
1317

Electric fields within cells as a function of membrane resistivity--a model study.

Externally applied electric fields play an important role in many therapeutic modalities, but the fields they produce inside cells remain largely unknown. This study makes use of a three-dimensional model to determine the electric field that exists in the intracellular domain of a 10-microm spherical cell exposed to an applied field of 100 V/cm. The transmembrane potential resulting from the applied field was also determined and its change was compared to those of the intracellular field. The intracellular field increased as the membrane resistance decreased over a wide range of values. The results showed that the intracellular electric field was about 1.1 mV/cm for Rm of 10,000 omega x cm2, increasing to about 111 mV/cm as Rm decreased to 100 omega x cm2. Over this range of Rm the transmembrane potential was nearly constant. The transmembrane potential declined only as Rm decreased below 1 omega x cm2. The simulation results suggest that intracellular electric field depends on Rm in its physiologic range, and may not be negligible in understanding some mechanisms of electric field-mediated therapies.

Authors
Mossop, BJ; Barr, RC; Zaharoff, DA; Yuan, F
MLA Citation
Mossop, BJ, Barr, RC, Zaharoff, DA, and Yuan, F. "Electric fields within cells as a function of membrane resistivity--a model study." IEEE Trans Nanobioscience 3.3 (September 2004): 225-231.
PMID
15473075
Source
pubmed
Published In
IEEE Transactions on Nanobioscience
Volume
3
Issue
3
Publish Date
2004
Start Page
225
End Page
231

Controlled release of ethacrynic acid from poly(lactide-co-glycolide) films for glaucoma treatment.

Ethacrynic acid (ECA) is a potential glaucoma drug that can reduce intraocular pressure. However, conventional methods of ECA administration may cause toxicity to normal eye tissues and are inconvenient to patients. Therefore, we developed and characterized an ECA loaded poly(lactide-co-glycolide) (PLGA) copolymer film, and quantified the therapeutic efficacy of the film implanted in the rabbit eye. In the aqueous medium, the release of ECA from the PLGA50:50 film was time dependent and more than 90% of ECA was released within a week. This release profile was consistent with the kinetics of water uptake and microstructural changes of PLGA50:50 films as revealed by an electron microscopy examination. ECA release and PLGA degradation caused a gradual pH decrease in the release medium. The total pH decrease was 0.4 unit in 3 days. We also observed that the initial rate of ECA release was positively correlated with the weight ratio of ECA versus PLGA and inversely correlated with the molar ratio of lactide versus glycolide in PLGA films. At the end of a 3-day incubation, the cumulative release of ECA from PLGA50:50, PLGA85:15 and PLGA100:00 films were 78.8%, 9.35% and 3.60%, respectively. When the PLGA50:50 film loaded with ECA was implanted into the sclera of rabbit eyes, the intraocular pressure was significantly reduced and the reduction was maintained for at least 10 days. These data indicate that PLGA films have a potential to be used as a controlled ECA release device for glaucoma treatment.

Authors
Wang, Y; Challa, P; Epstein, DL; Yuan, F
MLA Citation
Wang, Y, Challa, P, Epstein, DL, and Yuan, F. "Controlled release of ethacrynic acid from poly(lactide-co-glycolide) films for glaucoma treatment." Biomaterials 25.18 (August 2004): 4279-4285.
PMID
15046918
Source
pubmed
Published In
Biomaterials
Volume
25
Issue
18
Publish Date
2004
Start Page
4279
End Page
4285
DOI
10.1016/j.biomaterials.2003.10.075

Effects of pulse strength and pulse duration on in vitro DNA electromobility.

Interstitial transport of DNA is a rate-limiting step in electric field-mediated gene delivery in vivo. Interstitial transport of macromolecules, such as plasmid DNA, over a distance of several cell layers, is inefficient due to small diffusion coefficient and inadequate convection. Therefore, we explored electric field as a novel driving force for interstitial transport of plasmid DNA. In this study, agarose gels were used to mimic the interstitium in tissues as they had been well characterized and could be prepared reproducibly. We measured the electrophoretic movements of fluorescently labeled plasmid DNA in agarose gels with three different concentrations (1.0%, 2.0% and 3.0%) subjected to electric pulses at three different field strengths (100, 200 and 400 V/cm) and four different pulse durations (10, 50, 75, 99 ms). We observed that: (1) shorter pulses (10 ms) were not as efficient as longer pulses in facilitating plasmid transport through agarose gels; (2) plasmid electromobility reached a plateau at longer pulse durations; and (3) plasmid electromobility increased with applied electric energy, up to a threshold, in all three gels. These data suggested that both pulse strength and duration needed to be adequately high for efficient plasmid transport through extracellular matrix. We also found that electric field was better than concentration gradient of DNA as a driving force for interstitial transport of plasmid DNA.

Authors
Zaharoff, DA; Yuan, F
MLA Citation
Zaharoff, DA, and Yuan, F. "Effects of pulse strength and pulse duration on in vitro DNA electromobility." Bioelectrochemistry 62.1 (April 2004): 37-45.
PMID
14990324
Source
pubmed
Published In
Bioelectrochemistry
Volume
62
Issue
1
Publish Date
2004
Start Page
37
End Page
45
DOI
10.1016/j.bioelechem.2003.10.011

Simulation of angiogenesis in engineered tissues: Effects of VEGF binding to matrix components

Authors
Olbrich, KC; Yuan, F
MLA Citation
Olbrich, KC, and Yuan, F. "Simulation of angiogenesis in engineered tissues: Effects of VEGF binding to matrix components." March 23, 2004.
Source
wos-lite
Published In
The FASEB journal : official publication of the Federation of American Societies for Experimental Biology
Volume
18
Issue
4
Publish Date
2004
Start Page
A372
End Page
A372

Systemic virus dissemination during local gene delivery in solid tumors and its control with an alginate solution.

Intratumoral infusion, a routine method for local gene delivery in solid tumors, may cause a systemic dissemination of gene vectors. This is because tumor vessels are intrinsically leaky and intratumoral injection can also result in damage of tumor vessels. To this end, we investigated the extent of virus dissemination during and after local infusion of adenoviral vectors into a murine adenocarcinoma (4T1) transplanted in mice. Three different vectors were used in this study, they contained genes encoding either mouse interleukin-12 (IL-12), luciferase, or enhanced green fluorescence protein (EGFP). The virus distribution in the body was determined as the transgene expression in normal and tumor tissues. Our data demonstrated that a large fraction of injected viral vectors disseminated into liver tissues. To reduce the dissemination problem, we developed a novel method for viral vector delivery based on an alginate solution. We observed that this vehicle could significantly reduce virus dissemination without compromising the therapeutic efficacy of adenoviral vectors. Taken together, the data suggests that systemic virus dissemination is a serious problem in local gene therapy in tumors and that the dissemination can be significantly reduced by an alginate-based polymeric vehicle.

Authors
Wang, Y; Li, C-Y; Yuan, F
MLA Citation
Wang, Y, Li, C-Y, and Yuan, F. "Systemic virus dissemination during local gene delivery in solid tumors and its control with an alginate solution." Conf Proc IEEE Eng Med Biol Soc 5 (2004): 3524-3526.
PMID
17271050
Source
pubmed
Published In
Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings
Volume
5
Publish Date
2004
Start Page
3524
End Page
3526
DOI
10.1109/IEMBS.2004.1403991

Systemic dissemination of viral vectors during intratumoral injection.

Intratumoral injection is a routine method for local viral gene delivery that may improve interstitial transport of viral vectors in tumor tissues and reduce systemic toxicity. However, the concentration of transgene products in normal organs, such as in the liver, may still exceed normal tissue tolerance if the products are highly toxic. The elevated concentration in normal tissues is likely to be caused by the dissemination of viral vectors from the tumor. Therefore, we investigated transgene expression in the liver, the serum, and a mouse mammary carcinoma (4T1) in mice after intratumoral injection of adenoviral vectors for mouse interleukin-12, luciferase, enhanced green fluorescence protein, or beta-galactosidase. We also performed numerical simulations of virus transport in tumors after intratumoral injection, based on the Krogh cylinder model. Our experimental data and numerical simulations demonstrated that virus dissemination was significant in mice and it occurred mainly during the intratumoral injection. To reduce virus dissemination, we mixed these vectors with a viscous alginate solution and injected the mixture into the tumors. Our data showed that the alginate solution could significantly reduce virus dissemination while having minimal effects on transgene expression in tumors and on interleukin-12-induced tumor growth delay. These data suggest that virus dissemination is a potential problem in local viral gene therapy of cancer and that the dissemination could be significantly reduced by the alginate solution without compromising the efficacy of gene therapy.

Authors
Wang, Y; Hu, JK; Krol, A; Li, Y-P; Li, C-Y; Yuan, F
MLA Citation
Wang, Y, Hu, JK, Krol, A, Li, Y-P, Li, C-Y, and Yuan, F. "Systemic dissemination of viral vectors during intratumoral injection." Mol Cancer Ther 2.11 (November 2003): 1233-1242.
PMID
14617797
Source
pubmed
Published In
Molecular cancer therapeutics
Volume
2
Issue
11
Publish Date
2003
Start Page
1233
End Page
1242

Progress report of a Phase I study of the intracerebral microinfusion of a recombinant chimeric protein composed of transforming growth factor (TGF)-alpha and a mutated form of the Pseudomonas exotoxin termed PE-38 (TP-38) for the treatment of malignant brain tumors.

TP-38 is a recombinant chimeric targeted toxin composed of the EGFR binding ligand TGF-alpha and a genetically engineered form of the Pseudomonas exotoxin, PE-38. After in vitro and in vivo animal studies that showed specific activity and defined the maximum tolerated dose (MTD), we investigated this agent in a Phase I trial. The primary objective of this study was to define the MTD and dose limiting toxicity of TP-38 delivered by convection-enhanced delivery in patients with recurrent malignant brain tumors. Twenty patients were enrolled in the study and doses were escalated from 25 ng/mL to 100 with a 40 mL infusion volume delivered by two catheters. One patient developed Grade IV fatigue at the 100 ng/mL dose, but the MTD has not been established. The overall median survival after TP-38 for all patients was 23 weeks whereas for those without radiographic evidence of residual disease at the time of therapy, the median survival was 31.9 weeks. Overall, 3 of 15 patients, with residual disease at the time of therapy, have demonstrated radiographic responses and one patient with a complete response and has survived greater than 83 weeks.

Authors
Sampson, JH; Akabani, G; Archer, GE; Bigner, DD; Berger, MS; Friedman, AH; Friedman, HS; Herndon, JE; Kunwar, S; Marcus, S; McLendon, RE; Paolino, A; Penne, K; Provenzale, J; Quinn, J; Reardon, DA; Rich, J; Stenzel, T; Tourt-Uhlig, S; Wikstrand, C; Wong, T; Williams, R; Yuan, F; Zalutsky, MR; Pastan, I
MLA Citation
Sampson, JH, Akabani, G, Archer, GE, Bigner, DD, Berger, MS, Friedman, AH, Friedman, HS, Herndon, JE, Kunwar, S, Marcus, S, McLendon, RE, Paolino, A, Penne, K, Provenzale, J, Quinn, J, Reardon, DA, Rich, J, Stenzel, T, Tourt-Uhlig, S, Wikstrand, C, Wong, T, Williams, R, Yuan, F, Zalutsky, MR, and Pastan, I. "Progress report of a Phase I study of the intracerebral microinfusion of a recombinant chimeric protein composed of transforming growth factor (TGF)-alpha and a mutated form of the Pseudomonas exotoxin termed PE-38 (TP-38) for the treatment of malignant brain tumors." J Neurooncol 65.1 (October 2003): 27-35.
PMID
14649883
Source
pubmed
Published In
Journal of Neuro-Oncology
Volume
65
Issue
1
Publish Date
2003
Start Page
27
End Page
35

A clinical model of dermal wound angiogenesis.

Full-thickness dermal biopsies were performed in healthy volunteers to establish the range of angiogenic responses in wound healing in a normal population. Four-millimeter punch biopsies were made in the forearms of 15 healthy volunteers. Each wound was evaluated microscopically 4-5 times per week for 2 weeks. A semiquantitative wound scoring system to evaluate the neovasculature at the wound periphery was investigated. A vascular score was calculated for each wound at each observation. Two independent observers analyzed the microscopic wound images using the scoring system. At the end of the 14-day period, repeat biopsies were performed on some of the volunteers, and the granulation tissue was stained with anti-CD31. The Kaplan-Meier method was used to estimate the distribution of the time to reach predetermined target average vascular scores. A mixed-effects regression model indicated that time, age, and observer were predictors for the average vascular score outcome. The pattern and time course for wound neovascularization was highly reproducible in this group of healthy volunteers, and the assay was feasible and well tolerated. This wound angiogenesis model may be useful for monitoring the effects of antiangiogenic agents on normal wound neovascularization.

Authors
Lockhart, AC; Braun, RD; Yu, D; Ross, JR; Dewhirst, MW; Klitzman, B; Yuan, F; Grichnik, JM; Proia, AD; Conway, DA; Mann, G; Hurwitz, HI
MLA Citation
Lockhart, AC, Braun, RD, Yu, D, Ross, JR, Dewhirst, MW, Klitzman, B, Yuan, F, Grichnik, JM, Proia, AD, Conway, DA, Mann, G, and Hurwitz, HI. "A clinical model of dermal wound angiogenesis." Wound Repair Regen 11.4 (July 2003): 306-313.
PMID
12846919
Source
pubmed
Published In
Wound Repair and Regeneration
Volume
11
Issue
4
Publish Date
2003
Start Page
306
End Page
313

Transmembrane transport of marker molecules and cell membrane kinetics during electropermeabilization

Authors
Zaharoff, DA; Yuan, F
MLA Citation
Zaharoff, DA, and Yuan, F. "Transmembrane transport of marker molecules and cell membrane kinetics during electropermeabilization." May 2003.
Source
wos-lite
Published In
Molecular Therapy
Volume
7
Issue
5
Publish Date
2003
Start Page
S64
End Page
S64

Simulation modeling of angiogenesis in engineered tissues: effects of growth factor supplementation

Authors
Olbrich, KC; Tong, S; Yuan, F
MLA Citation
Olbrich, KC, Tong, S, and Yuan, F. "Simulation modeling of angiogenesis in engineered tissues: effects of growth factor supplementation." March 14, 2003.
Source
wos-lite
Published In
The FASEB journal : official publication of the Federation of American Societies for Experimental Biology
Volume
17
Issue
4
Publish Date
2003
Start Page
A147
End Page
A147

Effects of cell damage and glycosaminoglycan degradation on available extravascular space of different dextrans in a rat fibrosarcoma.

Drug delivery to solid tumors may be enhanced through increasing the available volume fraction (K(AV)) of drugs. Therefore, two approaches were investigated that may increase K(AV) of dextrans in a rat fibrosarcoma: (a) damaging cells in tumours via ex vivo incubation of tumour tissues, and (b) degrading tumour glycosaminoglycans (GAGs) with exogenous hyaluronidase. The molecular weights of dextrans used in this study were approximately 10,000 (D10), 70,000 (D70) and 2,000,000 (D2000), respectively. It was found that GAG degradation had minimal effects on K(AV) of dextrans. Ex vivo incubation at 37 degrees C for up to 3 h caused only minor cell damage and had minimal effects on K(AV) of D10 and D70. However, the ex vivo incubation reduced K(AV) of D2000 (p < 0.05). When the incubation at 37 degrees C was maintained for 20 h, the amount of viable cells in tumours was reduced by 56% and K(AV) of all dextrans were significantly increased (p < 0.05). Ex vivo incubation at 41 degrees C for 3 h caused similar cell damage to that at 37 degrees C for 20 h, but only K(AV) of D10 and D70 were increased significantly (p < 0.05). There was no significant change in K(AV) of D2000, although it was higher than that in tumours incubated at 37 degrees C for 3 h (p < 0.05). These data suggest that cell damage is a more effective approach than GAG degradation for increasing K(AV) of macromolecules and that the amount of increase depends on the degree of cell damage and the size of molecules.

Authors
Krol, A; Dewhirst, MW; Yuan, F
MLA Citation
Krol, A, Dewhirst, MW, and Yuan, F. "Effects of cell damage and glycosaminoglycan degradation on available extravascular space of different dextrans in a rat fibrosarcoma." Int J Hyperthermia 19.2 (March 2003): 154-164.
PMID
12623638
Source
pubmed
Published In
International Journal of Hyperthermia (Informa)
Volume
19
Issue
2
Publish Date
2003
Start Page
154
End Page
164

Reduction of wound angiogenesis in patients treated with BMS-275291, a broad spectrum matrix metalloproteinase inhibitor.

PURPOSE: The purpose of this study was to evaluate the feasibility of incorporating a novel wound angiogenesis assay into a Phase I study of BMS-275291, a broad-spectrum matrix metalloproteinase inhibitor, and to determine whether the wound angiogenesis assay was able to detect the inhibition of angiogenesis in patients treated with BMS-275291. EXPERIMENTAL DESIGN: Before treatment began, a 4-mm skin biopsy was performed. The wound was imaged for 14 days. Treatment was started on day 0, and a separate 4-mm biopsy was performed 14 days later. The second wound was also imaged for 14 days. Wound angiogenesis was scored by two independent observers who were blinded to treatment status. RESULTS: The median times in days (95% confidence interval) to reach the target average vascular score (AVS) of 1.5 and 2.0 based on the data of Observer 1 were 3.7 (2.2-6.9) and 8.0 (5.0-10.0) pretreatment whereas on-treatment the values were 4.9 (3.7-8.0) and 9.3 (7.0-11.5), respectively. The delay in the median time to reach an AVS of 1.5 was 1.2 days or a 32% reduction when comparing pretreatment with on-treatment (P = 0.06). For the target AVS of 2.0 the delay in the median time pretreatment versus on-treatment was 1.3 days or a 16% reduction (P = 0.04). CONCLUSIONS: The wound angiogenesis assay used in this study was practical, well tolerated, and reproducible. Delays in wound angiogenesis because of BMS-275291 were detectable with this assay. This technique warrants additional investigation in clinical trials of other antiangiogenic agents.

Authors
Lockhart, AC; Braun, RD; Yu, D; Ross, JR; Dewhirst, MW; Humphrey, JS; Thompson, S; Williams, KM; Klitzman, B; Yuan, F; Grichnik, JM; Proia, AD; Conway, DA; Hurwitz, HI
MLA Citation
Lockhart, AC, Braun, RD, Yu, D, Ross, JR, Dewhirst, MW, Humphrey, JS, Thompson, S, Williams, KM, Klitzman, B, Yuan, F, Grichnik, JM, Proia, AD, Conway, DA, and Hurwitz, HI. "Reduction of wound angiogenesis in patients treated with BMS-275291, a broad spectrum matrix metalloproteinase inhibitor." Clin Cancer Res 9.2 (February 2003): 586-593.
PMID
12576422
Source
pubmed
Published In
Clinical cancer research : an official journal of the American Association for Cancer Research
Volume
9
Issue
2
Publish Date
2003
Start Page
586
End Page
593

Electromobility of plasmid DNA in tumor tissues during electric field-mediated gene delivery.

Interstitial transport is a crucial step in plasmid DNA-based gene therapy. However, interstitial diffusion of large nucleic acids is prohibitively slow. Therefore, we proposed to facilitate interstitial transport of DNA via pulsed electric fields. To test the feasibility of this approach to gene delivery, we developed an ex vivo technique to quantify the magnitude of DNA movement due to pulsed electric fields in two tumor tissues: B16.F10 (a mouse melanoma) and 4T1 (a mouse mammary carcinoma). When the pulse duration and strength were 50 ms and 233 V/cm, respectively, we found that the average plasmid DNA movements per 10 pulses were 1.47 microm and 0.35 microm in B16.F10 and 4T1 tumors, respectively. The average plasmid DNA movements could be approximately tripled, ie to reach 3.69 microm and 1.01 microm, respectively, when the pulse strength was increased to 465 V/cm. The plasmid DNA mobility was correlated with the tumor collagen content, which was approximately eight times greater in 4T1 than in B16.F10 tumors. These data suggest that electric field can be a powerful driving force for improving interstitial transport of DNA during gene delivery.

Authors
Zaharoff, DA; Barr, RC; Li, C-Y; Yuan, F
MLA Citation
Zaharoff, DA, Barr, RC, Li, C-Y, and Yuan, F. "Electromobility of plasmid DNA in tumor tissues during electric field-mediated gene delivery." Gene Ther 9.19 (October 2002): 1286-1290.
PMID
12224011
Source
pubmed
Published In
Gene Therapy
Volume
9
Issue
19
Publish Date
2002
Start Page
1286
End Page
1290
DOI
10.1038/sj.gt.3301799

An equivalent length model of microdialysis sampling.

One of the critical issues in microdialysis sampling is how to predict the extraction fraction (E(d)), based on transport properties of analytes in both tissues and probes. A one-dimensional (1-D) model has been used widely in previous studies to predict E(d) at the steady state. However, this model is valid only for long probes. To this end, an equivalent length (EL) model was developed for probes with any length used in experiments. The key idea in the model was to replace the probe length (L) in the 1-D model with an equivalent length (L(E)) when calculating transport resistance in surrounding tissues. The length difference, (L(E)-L), was assumed to be proportional to the penetration depth of analytes (Gamma). The proportionality constant (lambda) was determined through minimizing the errors in predicted E(d). We found that, the EL model could accurately predict E(d) when lambda=0.369. The maximum error in EL model predictions was <6%, for model constants varying in the same ranges as those in microdialysis experiments. This error was one order of magnitude smaller than that in 1-D model predictions.

Authors
Tong, S; Yuan, F
MLA Citation
Tong, S, and Yuan, F. "An equivalent length model of microdialysis sampling." J Pharm Biomed Anal 28.2 (April 15, 2002): 269-278.
PMID
11929669
Source
pubmed
Published In
Journal of Pharmaceutical and Biomedical Analysis
Volume
28
Issue
2
Publish Date
2002
Start Page
269
End Page
278

Intravital fluorescence facilitates measurement of multiple physiologic functions and gene expression in tumors of live animals.

The purpose of this report is to present an overview of the use of fluorescence imaging in vivo, with particular emphasis on oncology. It is important to note, however, that many of the methods described herein have been applied to the study of non-malignant tissues as well. Modern medicine and biology research has benefited greatly from an ever-expanding assortment of fluorescent markers and labels. These markers and labels have allowed investigators to observe the behavior and properties of cell and molecular entities of interest in the context of complicated biological systems such as a mammalian cell or a whole mouse. Methods developed to image fluorescence in whole mice have been valuable in studying patterns of tumor growth and metastases. Alternatively, more detailed information and a wide variety of endpoints can be obtained using "intravital" preparations. This review focuses on use of fluorescence imaging for intravital preparations. For detail on fluorescence imaging of whole animals, refer to reviews on this subject [1,2]. For oncologic applications, studies have focused primarily on window chamber preparations that allow for real-time visualization of tumor growth, vascularity, vascular responses to stimulation, vascular permeability, vascular orientation, flow instability, and the like. These endpoints have been used to show that there are functional differences between tumor and normal tissues with respect to these functions under baseline conditions and after therapeutic manipulation. Examples of some of these differences are provided in this review as a means to illustrate how they can be used.

Authors
Dewhirst, MW; Shan, S; Cao, Y; Moeller, B; Yuan, F; Li, C-Y
MLA Citation
Dewhirst, MW, Shan, S, Cao, Y, Moeller, B, Yuan, F, and Li, C-Y. "Intravital fluorescence facilitates measurement of multiple physiologic functions and gene expression in tumors of live animals." Dis Markers 18.5-6 (2002): 293-311. (Review)
PMID
14646042
Source
pubmed
Published In
Disease markers
Volume
18
Issue
5-6
Publish Date
2002
Start Page
293
End Page
311

Reducing systemic toxicity in local tumor gene therapy using an alginate solution

To reduce dissemination of viral vectors and their gene products during and after local gene therapy, we mixed adenoviral vectors with an alginate solution and subsequently injected the mixture into mouse tumors. We found that the alginate solution significantly reduced the dissemination of adenoviral vectors for EGFP and IL-12 into the liver and the IL-12 concentration in the serum. On the other hand, the alginate solution had no effects on EGFP and IL-12 expressions in tumors as well as the growth of IL-12 vector treated tumors.

Authors
Wang, Y; Hu, JK; Krol, A; Li, Y-P; Li, C-Y; Yuan, F
MLA Citation
Wang, Y, Hu, JK, Krol, A, Li, Y-P, Li, C-Y, and Yuan, F. "Reducing systemic toxicity in local tumor gene therapy using an alginate solution." Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings 1 (2002): 565--.
Source
scival
Published In
Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings
Volume
1
Publish Date
2002
Start Page
565-

Effects of tissue stretching or cell shrinkage on penetration depth of macromolecules in a rat fibrosarcoma

Interstitial penetration is critical for drug delivery in tumor tissues. To experimentally determine the penetration depth of macromolecules at the steady state, rat fibrosarcoma tissues were sectioned into 600μm slices and incubated in solutions of dextrans with molecular weights of 10 kDa, 70 kDa, and 2000 kDa, respectively. After incubation, 10 μm cross-sections were taken and imaged to determine normalized steady-state concentration profiles as a function of molecular size. 10 kDa dextran had a relatively uniform concentration distribution. However, the concentration profile was nonuniform for 70 kDa dextran and the least uniform for 2000 kDa dextran. Stretching or incubation of tissues in 1 M mannitol solution improved the penetration of macromolecules in tissues. These results indicate that creating more interstitial space by either stretching or reducing cell size improves macromolecule distribution in tissues.

Authors
McGuire, SM; Yuan, F
MLA Citation
McGuire, SM, and Yuan, F. "Effects of tissue stretching or cell shrinkage on penetration depth of macromolecules in a rat fibrosarcoma." Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings 1 (2002): 516-517.
Source
scival
Published In
Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings
Volume
1
Publish Date
2002
Start Page
516
End Page
517

Transscleral diffusion of ethacrynic acid and sodium fluorescein

Transscleral drug delivery is an effective method for treatment of eye diseases in posterior segment. Therefore, we investigated transscleral permeability of ethacrynic acid (ECA), a potential drug for treating glaucoma. To determine the ex vivo permeability of ECA across the sclera, we quantified the diffusion coefficients of two molecules, ECA and sodium fluorescein, in fresh porcine sclera mounted in a two-chamber diffusion apparatus. All experiments were conducted with phosphate-buffered solution (PBS) at 4°C for a period ranging from 2 to 14 hours. The concentrations of ECA and sodium fluorescein were measured at room temperature (25°C) with UV and fluorescence spectrophotometers, respectively. The results showed that the permeability of ECA (303 Da) was 4.21±0.82×10-5 cm/sec (n=9), whereas the permeability of sodium fluorescein (376 Da) was 1.06±0.88×10-6 cm/sec (n=12). These results suggest that the sclera tissue is more permeable to ECA than sodium fluorescein.

Authors
Lin, C-W; Wang, Y; Yuan, F
MLA Citation
Lin, C-W, Wang, Y, and Yuan, F. "Transscleral diffusion of ethacrynic acid and sodium fluorescein." Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings 1 (2002): 515--.
Source
scival
Published In
Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings
Volume
1
Publish Date
2002
Start Page
515-

Effects of electric pulse strength and pulse duration on plasmid DNA electromobility

Interstitial transport of DNA is a rate-limiting step in electric field-mediated gene delivery. Interstitial transport of macromolecules such as plasmid DNA is limited by small diffusion coefficient, large diffusion distance and inadequate convection. Here, we explore electric field as a novel interstitial driving force for plasmid DNA transport. We measured the electrophoretic movement, and hence, electromobility of fluorescently-labeled plasmid DNA in agarose gels of three concentrations (1, 2, and 3%), subjected to electric pulses at three levels of field strength (100, 200 and 400V/cm) and four levels of pulse duration (10, 50, 75, 99ms). In our experiments, electrophoresis is up to four orders of magnitude greater than diffusion for plasmid transport in agarose gel. In all gels, we found that shorter duration pulses (<10ms) are not as efficient as longer duration pulses for pushing DNA. We also found that electromobility increases monotonically with applied voltage resulting in a maximum value at the highest applied voltage (400V/cm) in all three gels. The rate of electromobility increase with applied voltage was amplified at higher gel concentration. These results indicate that plasmid DNA electromobility in porous media can be optimized through pulse duration and pulse strength.

Authors
Zaharoff, DA; Yuan, F
MLA Citation
Zaharoff, DA, and Yuan, F. "Effects of electric pulse strength and pulse duration on plasmid DNA electromobility." Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings 1 (2002): 546-547.
Source
scival
Published In
Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings
Volume
1
Publish Date
2002
Start Page
546
End Page
547

Available space and extracellular transport of macromolecules: effects of pore size and connectedness.

Molecular exclusion in tumor tissues is one of the limiting factors for drug delivery to tumor cells. It can be quantified by the available volume fraction of solutes (K(AV)). We found in a previous study that K(AV) of dextran in tumor tissues decreased sharply when the molecular weight (MW) of dextran was increased from 40,000 to 70,000. Outside this range, K(AV) was less sensitive to the MW of dextran. To understand the mechanisms of the MW dependence of K(AV), we investigated K(AV) in tissue phantoms composed of tumor cells in 1% agarose gels, and performed numerical simulations of the available volume fraction in pore networks. We found that the MW dependence of K(AV) in tissue phantoms was similar to that in tumor tissues when the volume fraction of cells in the former was approximately 30%. Our numerical simulations revealed that the sharp decrease in K(AV) required two necessary conditions: (i) the existence of at least two populations of pores and (ii) the lack of connectedness of available pores in the interstitial space. Furthermore, results in this study suggest that it is important to consider not only the local structures of pores but also their connectedness in analyses of molecular transport in tissues.

Authors
Yuan, F; Krol, A; Tong, S
MLA Citation
Yuan, F, Krol, A, and Tong, S. "Available space and extracellular transport of macromolecules: effects of pore size and connectedness." Ann Biomed Eng 29.12 (December 2001): 1150-1158.
PMID
11853267
Source
pubmed
Published In
Annals of Biomedical Engineering
Volume
29
Issue
12
Publish Date
2001
Start Page
1150
End Page
1158

Quantitative analysis of intratumoral infusion of color molecules.

Intratumoral infusion has a potential for improving distribution of drugs. To optimize the infusion, we developed a novel technique to quantify the distribution volume of color molecules (Vd) in solid tumors. Evans blue-labeled albumin was infused locally with the use of a needle into a rat fibrosarcoma ex vivo under different pressures. After the infusion, tumor tissues were sectioned serially into thin slices. The blue area in each slice was quantified with the use of the newly developed technique. The Vd was calculated based on the blue area and the slice thickness. Our data showed that infusion pressure and volume (V(i)) had significant effects on Vd. The median of Vd/V(i) decreased from 2.99 to 1.79 when infusion pressure was increased from 50 to 163 cmH2O, presumably due to retardation of convective transport. In addition, the coefficient of variation in Vd/V(i) was increased from 0.13 at 50 cmH2O to 0.64 at 163 cmH2O. The dependence of Vd/V(i) and its variation on infusion pressure suggests that 1) infusion-induced tissue deformation is unpredictable and 2) both the unpredictability and the interstitial retardation of convective transport increase with infusion pressure.

Authors
McGuire, S; Yuan, F
MLA Citation
McGuire, S, and Yuan, F. "Quantitative analysis of intratumoral infusion of color molecules." Am J Physiol Heart Circ Physiol 281.2 (August 2001): H715-H721.
PMID
11454575
Source
pubmed
Published In
American journal of physiology. Heart and circulatory physiology
Volume
281
Issue
2
Publish Date
2001
Start Page
H715
End Page
H721

Effective tumor therapy with plasmid-encoded cytokines combined with in vivo electroporation.

Plasmids may have unique advantages as a gene delivery system. However, a major obstacle is the low in vivo transduction efficiency. In this study, an electroporation-based gene transduction approach was taken to study the effect of interleukin (IL)-2 or IL-12 gene transduction on the growth of experimental murine tumors. Significant intratumoral gene transduction was achieved by electroporation of tumors that had been injected with naked plasmids encoding reporter genes and cytokine genes (IL-2 and IL-12) under the control of a constitutive cytomegalovirus promoter. In addition, significant tumor growth delay could be achieved in a murine melanoma line B16.F10 with the cytokine genes. Most importantly, systemic transgene levels were negligible when compared with intratumoral adenovirus-mediated IL-12 gene delivery, which leads to significantly higher systemic cytokine levels. Therefore, naked plasmid- and in vivo electroporation-mediated cancer gene therapy may be therapeutically efficacious while maintaining low systemic toxicity.

Authors
Lohr, F; Lo, DY; Zaharoff, DA; Hu, K; Zhang, X; Li, Y; Zhao, Y; Dewhirst, MW; Yuan, F; Li, CY
MLA Citation
Lohr, F, Lo, DY, Zaharoff, DA, Hu, K, Zhang, X, Li, Y, Zhao, Y, Dewhirst, MW, Yuan, F, and Li, CY. "Effective tumor therapy with plasmid-encoded cytokines combined with in vivo electroporation." Cancer Res 61.8 (April 15, 2001): 3281-3284.
PMID
11309280
Source
pubmed
Published In
Cancer Research
Volume
61
Issue
8
Publish Date
2001
Start Page
3281
End Page
3284

Numerical simulations of angiogenesis in the cornea.

Angiogenesis plays important roles in many physiologic and pathologic processes in the body. To understand mechanisms of angiogenesis, we developed a mathematical model for quantitative analysis of various biological events involved in angiogenesis. Our model was focused on two-dimensional angiogenesis in the cornea. The model considered diffusion of angiogenic factors, uptake of these factors by endothelial cells, and randomness in the rate of sprout formation and the direction of sprout growth. Our simulation results indicated that redistribution and uptake of angiogenic factors during angiogenesis had significant effects on the structure of vascular networks. A decrease in the uptake rate resulted in increases in vessel density, self-loop formation, and front migration speed of vascular networks. The randomness in the direction of sprout formation determined the curvature of vessels, whereas the probability of sprout formation from a vessel segment had a significant effect on the total number of vessels in vascular networks. The vascular networks generated in numerical simulations were similar to those observed experimentally. The mathematical model developed in this study can be used to evaluate effects of individual factors on angiogenesis, understand mechanisms of interactions among different factors during angiogenesis, and generate experimentally testable hypotheses.

Authors
Tong, S; Yuan, F
MLA Citation
Tong, S, and Yuan, F. "Numerical simulations of angiogenesis in the cornea." Microvasc Res 61.1 (January 2001): 14-27.
PMID
11162192
Source
pubmed
Published In
Microvascular Research
Volume
61
Issue
1
Publish Date
2001
Start Page
14
End Page
27
DOI
10.1006/mvre.2000.2282

Quantitative analysis of intratumoral infusion of color molecules

Intratumoral infusion has a potential for improving distribution of drugs. To optimize the infusion, we developed a novel technique to quantify the distribution volume of color molecules (Vd) in solid tumors. Evans blue-labeled albumin was infused locally with the use of a needle into a rat fibrosarcoma ex vivo under different pressures. After the infusion, tumor tissues were sectioned serially into thin slices. The blue area in each slice was quantified with the use of the newly developed technique. The Vd was calculated based on the blue area and the slice thickness. Our data showed that infusion pressure and volume (Vi) had significant effects on Vd. The median of Vd/Vi decreased from 2.99 to 1.79 when infusion pressure was increased from 50 to 163 cmH2O, presumably due to retardation of convective transport. In addition, the coefficient of variation in Vd/Vi was increased from 0.13 at 50 cmH2O to 0.64 at 163 cmH2O. The dependence of Vd/Vi and its variation on infusion pressure suggests that 1) infusion-induced tissue deformation is unpredictable and 2) both the unpredictability and the interstitial retardation of convective transport increase with infusion pressure.

Authors
McGuire, S; Yuan, F
MLA Citation
McGuire, S, and Yuan, F. "Quantitative analysis of intratumoral infusion of color molecules." American Journal of Physiology - Heart and Circulatory Physiology 281.2 50-2 (2001): H715-H721.
Source
scival
Published In
American journal of physiology. Heart and circulatory physiology
Volume
281
Issue
2 50-2
Publish Date
2001
Start Page
H715
End Page
H721

Interstitial hydraulic conductivity in a fibrosarcoma.

Convective transport of therapeutic agents in solid tumors can be improved through intratumoral infusion. To optimize the convection, we investigated the dependence of the hydraulic conductivity on tissue deformation induced by interstitial fluid pressure gradient during the infusion. Two experimental systems were used in the investigation: 1) one-dimensional perfusion through tumor slices and 2) intratumoral infusion using a needle. With these systems, we found that the apparent hydraulic conductivity (K(app)) could be altered by several orders of magnitude in fibrosarcomas through changes in perfusion conditions. When the perfusion pressure was less than a threshold level, fluid flow in tissues could not be detected. When the perfusion pressure was increased above the threshold level, K(app) depended on perfusion system and pressure. The maximum variation in K(app) in fibrosarcomas reached 80,260-fold in our experiments. The large variation in K(app) could be explained by perfusion pressure-induced tissue deformation. These experimental data suggest that the hydraulic conductivity is very sensitive to tissue deformation and imply that it is possible to improve intratumoral infusion of therapeutic agents through optimization of infusion conditions.

Authors
Zhang, XY; Luck, J; Dewhirst, MW; Yuan, F
MLA Citation
Zhang, XY, Luck, J, Dewhirst, MW, and Yuan, F. "Interstitial hydraulic conductivity in a fibrosarcoma." Am J Physiol Heart Circ Physiol 279.6 (December 2000): H2726-H2734.
PMID
11087227
Source
pubmed
Published In
American journal of physiology. Heart and circulatory physiology
Volume
279
Issue
6
Publish Date
2000
Start Page
H2726
End Page
H2734

Wound angiogenesis inhibition as a marker for anti-angiogenic efficacy.

Authors
Lockhart, AC; Braun, RD; Dewhirst, MW; Humphrey, JS; Yuan, F; Grichnick, J; Proia, A; Conway, D; Klitzman, B; Hurwitz, HI
MLA Citation
Lockhart, AC, Braun, RD, Dewhirst, MW, Humphrey, JS, Yuan, F, Grichnick, J, Proia, A, Conway, D, Klitzman, B, and Hurwitz, HI. "Wound angiogenesis inhibition as a marker for anti-angiogenic efficacy." March 15, 2000.
Source
wos-lite
Published In
The FASEB journal : official publication of the Federation of American Societies for Experimental Biology
Volume
14
Issue
4
Publish Date
2000
Start Page
A35
End Page
A35

Numerical simulation of angiogenesis in the cornea

Authors
Tong, S; Yuan, F
MLA Citation
Tong, S, and Yuan, F. "Numerical simulation of angiogenesis in the cornea." FASEB JOURNAL 14.4 (March 15, 2000): A35-A35.
Source
wos-lite
Published In
The FASEB journal : official publication of the Federation of American Societies for Experimental Biology
Volume
14
Issue
4
Publish Date
2000
Start Page
A35
End Page
A35

Available volume fraction of macromolecules in tumor tissues.

Authors
Krol, A; Nagaraj, S; Dewhirst, M; Yuan, F
MLA Citation
Krol, A, Nagaraj, S, Dewhirst, M, and Yuan, F. "Available volume fraction of macromolecules in tumor tissues." FASEB JOURNAL 14.4 (March 15, 2000): A167-A167.
Source
wos-lite
Published In
The FASEB journal : official publication of the Federation of American Societies for Experimental Biology
Volume
14
Issue
4
Publish Date
2000
Start Page
A167
End Page
A167

Numerical simulations of angiogenesis in the cornea

To understand the mechanisms of angiogenesis, a mathematical model was developed for quantitative analysis of various biological events involved in angiogenesis. The model was focused on twodimensional angiogenesis in the cornea. The model considered diffusion of angiogenic factors, uptake of these factors by endothelial cells, and randomness in the direction and the probability of sprout formation. The mathematical model can be used to evaluate effects of individual factors on angiogenesis, understand mechanisms of interactions among different factors during angiogenesis, and generate experimentally testable hypotheses.

Authors
Tong, S; Yuan, F
MLA Citation
Tong, S, and Yuan, F. "Numerical simulations of angiogenesis in the cornea." Annals of Biomedical Engineering 28.SUPPL 1 (2000): 77-. (Academic Article)
Source
manual
Published In
Annals of Biomedical Engineering
Volume
28
Issue
SUPPL 1
Publish Date
2000
Start Page
77

Mobility of plasmid DNA subject to pulsed electric fields

The mobility of plasmid DNA in high amplitude/low duration electric fields was assessed. The influences of pulse amplitude, pulse duration and agarose gel concentration on mobility were compared. Movement of plasmid DNA in an electroporation setting was increased over diffusion one to two orders of magnitude, depending on pulse duration and frequency.

Authors
Zaharoff, D; Barr, R; Li, C-Y; Yuan, F
MLA Citation
Zaharoff, D, Barr, R, Li, C-Y, and Yuan, F. "Mobility of plasmid DNA subject to pulsed electric fields." Annals of Biomedical Engineering 28.SUPPL 1 (2000): 25-. (Academic Article)
Source
manual
Published In
Annals of Biomedical Engineering
Volume
28
Issue
SUPPL 1
Publish Date
2000
Start Page
25

New technique for measurement of distribution volume of color molecules in solid tumors

To optimize intramural infusion of macromolecules, a novel technique was developed to quantify the distribution volume of color molecules in solid tumors. It was shown that infusion pressure and volume significantly affects the distribution volume of drugs.

Authors
McGuire, S; Zhang, X-Y; Dewhirst, M; Yuan, F
MLA Citation
McGuire, S, Zhang, X-Y, Dewhirst, M, and Yuan, F. "New technique for measurement of distribution volume of color molecules in solid tumors." Annals of Biomedical Engineering 28.SUPPL 1 (2000): 25-. (Academic Article)
Source
manual
Published In
Annals of Biomedical Engineering
Volume
28
Issue
SUPPL 1
Publish Date
2000
Start Page
25

Mobility of plasmid DNA subject to pulsed electric fields

The mobility of plasmid DNA in high amplitude/low duration electric fields was assessed. The influences of pulse amplitude, pulse duration and agarose gel concentration on mobility were compared. Movement of plasmid DNA in an electroporation setting was increased over diffusion one to two orders of magnitude, depending on pulse duration and frequency.

Authors
Zaharoff, D; Barr, R; Li, C-Y; Yuan, F
MLA Citation
Zaharoff, D, Barr, R, Li, C-Y, and Yuan, F. "Mobility of plasmid DNA subject to pulsed electric fields." Annals of Biomedical Engineering 28.SUPPL. 1 (2000): S-25.
Source
scival
Published In
Annals of Biomedical Engineering
Volume
28
Issue
SUPPL. 1
Publish Date
2000
Start Page
S
End Page
25

Interstitial hydraulic conductivity in a fibrosarcoma

Convective transport of therapeutic agents in solid tumors can be improved through intratumoral infusion. To optimize the convection, we investigated the dependence of the hydraulic conductivity on tissue deformation induced by interstitial fluid pressure gradient during the infusion. Two experimental systems were used in the investigation: 1) one-dimensional perfusion through tumor slices and 2) intratumoral infusion using a needle. With these systems, we found that the apparent hydraulic conductivity (K(app)) could be altered by several orders of magnitude in fibrosarcomas through changes in perfusion conditions. When the perfusion pressure was less than a threshold level, fluid flow in tissues could not be detected. When the perfusion pressure was increased above the threshold level, K(app) depended on perfusion system and pressure. The maximum variation in K(app) in fibrosarcomas reached 80,260-fold in our experiments. The large variation in K(app) could be explained by perfusion pressure-induced tissue deformation. These experimental data suggest that the hydraulic conductivity is very sensitive to tissue deformation and imply that it is possible to improve intratumoral infusion of therapeutic agents through optimization of infusion conditions.

Authors
Zhang, X-Y; Luck, J; Dewhirst, MW; Yuan, F
MLA Citation
Zhang, X-Y, Luck, J, Dewhirst, MW, and Yuan, F. "Interstitial hydraulic conductivity in a fibrosarcoma." American Journal of Physiology - Heart and Circulatory Physiology 279.6 48-6 (2000): H2726-H2734.
Source
scival
Published In
American journal of physiology. Heart and circulatory physiology
Volume
279
Issue
6 48-6
Publish Date
2000
Start Page
H2726
End Page
H2734

Delivery of plasmid DNA through intratumoral infusion and electroporation

We investigated DNA transport in the interstitial space and across cell membrane facilitated by intratumoral infusion and in vivo electroporation, respectively. In the study, a rat fibrosarcoma was perfused ex vivo, and apparent hydraulic conductivity (Kapp) was quantified under different perfusion conditions. In addition, three plasmid DNA vectors were infused into solid tumors. Immediately after infusion, tumors were treated with or without electric pulses. Gene expression and tumor growth delay were determined at different time points after electroporation. We found that Kapp was very sensitive to the perfusion pressure, presumably due to perfusion-induced tissue deformation. Treatment of tumors with electric pulse facilitated gene expression in vivo. The growth of tumors treated with plasmid DNA encoding interleukin 12 (IL-12) and electric pulses was slower than those treated with IL-12 or electric pulses alone. These data suggest that gene delivery in solid tumors could be improved significantly through combination of intratumoral infusion and in vivo electroporation.

Authors
Yuan, F; Zaharoff, D; Zhang, X-Y; Lohr, F; Dewhirst, MW; Li, C-Y
MLA Citation
Yuan, F, Zaharoff, D, Zhang, X-Y, Lohr, F, Dewhirst, MW, and Li, C-Y. "Delivery of plasmid DNA through intratumoral infusion and electroporation." American Society of Mechanical Engineers, Bioengineering Division (Publication) BED 48 (2000): 173-176.
Source
scival
Published In
American Society of Mechanical Engineers, Bioengineering Division (Publication) BED
Volume
48
Publish Date
2000
Start Page
173
End Page
176

New technique for measurement of distribution volume of color molecules in solid tumors

To optimize intramural infusion of macromolecules, a novel technique was developed to quantify the distribution volume of color molecules in solid tumors. It was shown that infusion pressure and volume significantly affects the distribution volume of drugs.

Authors
McGuire, S; Zhang, X-Y; Dewhirst, M; Yuan, F
MLA Citation
McGuire, S, Zhang, X-Y, Dewhirst, M, and Yuan, F. "New technique for measurement of distribution volume of color molecules in solid tumors." Annals of Biomedical Engineering 28.SUPPL. 1 (2000): S-25.
Source
scival
Published In
Annals of Biomedical Engineering
Volume
28
Issue
SUPPL. 1
Publish Date
2000
Start Page
S
End Page
25

Available volume fraction of macromolecules in solid tumors

An ex vivo method was developed to quantify available volume fraction (Kav) in tumor tissues and polymer gels. It was shown that Kav is an important transport parameter that depends on physichochemical properties of drugs and tissue structures.

Authors
Krol, A; Yuan, F; Dewhirst, M
MLA Citation
Krol, A, Yuan, F, and Dewhirst, M. "Available volume fraction of macromolecules in solid tumors." Annals of Biomedical Engineering 28.SUPPL. 1 (2000): S-25.
Source
scival
Published In
Annals of Biomedical Engineering
Volume
28
Issue
SUPPL. 1
Publish Date
2000
Start Page
S
End Page
25

Numerical simulations of angiogenesis in the cornea

To understand the mechanisms of angiogenesis, a mathematical model was developed for quantitative analysis of various biological events involved in angiogenesis. The model was focused on twodimensional angiogenesis in the cornea. The model considered diffusion of angiogenic factors, uptake of these factors by endothelial cells, and randomness in the direction and the probability of sprout formation. The mathematical model can be used to evaluate effects of individual factors on angiogenesis, understand mechanisms of interactions among different factors during angiogenesis, and generate experimentally testable hypotheses.

Authors
Tong, S; Yuan, F
MLA Citation
Tong, S, and Yuan, F. "Numerical simulations of angiogenesis in the cornea." Annals of Biomedical Engineering 28.SUPPL. 1 (2000): S-77.
Source
scival
Published In
Annals of Biomedical Engineering
Volume
28
Issue
SUPPL. 1
Publish Date
2000
Start Page
S
End Page
77

Vascular permeability in a human tumour xenograft: Molecular charge dependence

Molecular charge is one of the main determinants of transvascular transport. There are, however, no data available on the effect of molecular charge on microvascular permeability of macromolecules in solid tumours. To this end, we measured tumour microvascular permeability to different proteins having similar size but different charge. Measurements were performed in the human colon adenocarcinoma LS174T transplanted in transparent dorsal skinfold chambers in severe combined immunodeficient (SCID) mice. Bovine serum albumin (BSA) and IgG were fluorescently labelled and were either cationized by conjugation with hexamethylenediamine or anionized by succinylation. The molecules were injected i.v. and the fluorescence in tumour tissue was quantified by intravital fluorescence microscopy. The fluorescence intensity and pharmacokinetic data were used to calculate the microvascular permeability. We found that tumour vascular permeability of cationized BSA (pI-range: 8.6-9.1) and IgG (pI: 8.6-9.3) was more than two-fold higher (4.25 and 4.65 x 10-7 cm s-1) than that of the anionized BSA (pI approximate 2.0) and IgG (pI: 3.0-3.9; 1.11 and 1.93 x 10-7 cm s-1, respectively). Our results indicate that positively charged molecules extravasate faster in solid tumours compared to the similar-sized compounds with neutral or negative charges. However, the plasma clearance of cationic molecules was ~2 x faster than that of anionic ones, indicating that the modification of proteins enhances drug delivery to normal organs as well. Therefore, caution should be exercised when such a strategy is used to improve drug and gene delivery to solid tumours. (C) 2000 Cancer Research Campaign.

Authors
Dellian, M; Yuan, F; Trubetskoy, VS; Torchilin, VP; Jain, RK
MLA Citation
Dellian, M, Yuan, F, Trubetskoy, VS, Torchilin, VP, and Jain, RK. "Vascular permeability in a human tumour xenograft: Molecular charge dependence." British Journal of Cancer 82.9 (2000): 1513-1518.
PMID
10789717
Source
scival
Published In
British Journal of Cancer
Volume
82
Issue
9
Publish Date
2000
Start Page
1513
End Page
1518
DOI
10.1054/bjoc.1999.1171

Available volume fraction of macromolecules in the extravascular space of a fibrosarcoma: implications for drug delivery.

Steric exclusion of molecules in the extravascular space of tissues can be quantified by the available volume fraction (K(AV)). Despite its clinical importance, however, there is a paucity of data in the literature regarding the available volume fraction of macromolecules in the extravascular space of tumor tissues. In this study, we quantified K(AV) of inulin, BSA, and dextran molecules of Mr 10,000-2,000,000 in polymer gels and fibrosarcoma tissues. The measurement involved: (a) sectioning of gels or tumor tissues into thin slices (approximately 600 microm) using a Vibratome, (b) ex vivo incubation of the slices in solutions containing fluorescently labeled tracers, and (c) quantification of the equilibrium tracer concentrations in both slices and solutions. We found that K(AV) in gels decreased monotonically when the Mr of dextran was increased from Mr 10,000 to 2,000,000. However, K(AV) in tumor tissues was insensitive to the molecular weight of dextran in the range between Mr 10,000 and 40,000. There was a sharp decrease in K(AV) from 0.28 +/- 0.14 to 0.10 +/- 0.06 when the molecular weight was increased from Mr 40,000 to 70,000. In addition to the molecular weight dependence, K(AV) was heterogeneous in tumors, with intertumoral difference being greater than intratumoral variation. The interstitial fluid space, which was quantified by K(AV) of inulin, was 50% of the total tissue volume. These data indicate that the fraction of the extravascular volume in tumors that is accessible to large therapeutic agents is heterogeneous and depends on the size of agents.

Authors
Krol, A; Maresca, J; Dewhirst, MW; Yuan, F
MLA Citation
Krol, A, Maresca, J, Dewhirst, MW, and Yuan, F. "Available volume fraction of macromolecules in the extravascular space of a fibrosarcoma: implications for drug delivery." Cancer Res 59.16 (August 15, 1999): 4136-4141.
PMID
10463619
Source
pubmed
Published In
Cancer Research
Volume
59
Issue
16
Publish Date
1999
Start Page
4136
End Page
4141

Pressure and temperature-dependence of the hydraulic conductivity in a fibrosarcoma

Intratumor infusion has been used to deliver therapeutic agents to tumor cells. The distribution volume of infused agents depends on the hydraulic conductivity (K) in tumors, which may vary with the infusion pressure. Therefore, we quantified K in a rat fibrosarcoma at different pressures, using an ex vivo perfusion technique. We found that both perfusion rate and K depended significantly on the perfusion pressure, and the pressure-induced changes in K could not be recovered completely within 12 hrs after perfusion. The change in K was presumably due to tissue compression. In addition, the perfusion rate and K depended on tissue temperature. The temperature dependence was mainly caused by the viscosity change in the perfusate. These data suggest that effects of perfusion pressure on K can not be neglected in optimization of intratumor infusion of therapeutic agents.

Authors
Yuan, F; Zhang, X; Dewhirst, MW; Luck, JA
MLA Citation
Yuan, F, Zhang, X, Dewhirst, MW, and Luck, JA. "Pressure and temperature-dependence of the hydraulic conductivity in a fibrosarcoma." Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings 1 (1999): 91--.
Source
scival
Published In
Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings
Volume
1
Publish Date
1999
Start Page
91-

Augmentation of transvascular transport of macromolecules and nanoparticles in tumors using vascular endothelial growth factor

The goal of this investigation was to measure changes in vascular permeability, pore cutoff size, and number of transvascular transport pathways as a function of time and in response to vascular endothelial growth factor (VEGF), placenta growth factor (P1GF-1 and P1GF-2), or basic fibroblast growth factor (bFGF). Two human and two murine tumors were implanted in the dorsal skin chamber or cranial window. Vascular permeability to BSA (≃7 nm in diameter) and extravasation of polyethylene glycol- stabilized long-circulating liposomes (100-400 nm) and latex microspheres (≃800 nm) were determined by intravital microscopy. Vascular permeability was found to be temporally heterogeneous. VEGF superfusion (100 ng/ml) significantly increased vascular permeability to albumin in normal s.c. vessels, whereas a 30-fold higher dose of VEGF (3000 ng/ml) was required to increase permeability in pial vessels, suggesting that different tissues exhibit different dose thresholds for VEGF activity. Furthermore, VEGF superfusion (1000 ng/ml) increased vascular permeability to albumin in a hypopermeable human glioma xenograft in cranial window, whereas VEGF superfusion (10-1000 ng/ml) failed to increase permeability in a variety of hyperpermeable tumors grown in dorsal skin chamber. Interestingly, low-dose VEGF treatment (10 ng/ml) doubled the maximum pore size (from 400 to 800 nm) and significantly increased the frequency of large (400 nm) pores in human colon carcinoma xenografts. P1GF-1, P1GF-2, or bFGF did not show any significant effect on permeability or pore size in tumors. These findings suggest that exogenous VEGF may be useful for augmenting the transvascular delivery of larger antineoplastic agents such as gene targeting vectors and encapsulated drug carriers (typical range, 100-300 nm) into tumors.

Authors
Monsky, WL; Fukumura, D; Gohongi, T; Ancukiewcz, M; Weich, HA; Torchilin, VP; Yuan, F; Jain, RK
MLA Citation
Monsky, WL, Fukumura, D, Gohongi, T, Ancukiewcz, M, Weich, HA, Torchilin, VP, Yuan, F, and Jain, RK. "Augmentation of transvascular transport of macromolecules and nanoparticles in tumors using vascular endothelial growth factor." Cancer Research 59.16 (1999): 4129-4135.
PMID
10463618
Source
scival
Published In
Cancer Research
Volume
59
Issue
16
Publish Date
1999
Start Page
4129
End Page
4135

Transvascular drug delivery in solid tumors.

The microvessel wall is a barrier for the delivery of various therapeutic agents to tumor cells. Tumor microvessels are, in general, more permeable to macromolecules than normal vessels. The hyperpermeability is presumably due to the existence of large pore structures in the vessel wall, induced by various cytokines. The cutoff pore size is tumor dependent, as determined by transport studies of nanoparticles. The vascular permeability is heterogeneous in tumors and dependent on physicochemical properties of molecules as well as the ultrastructure of the vessel wall. The ultrastructure is dynamic and can be modulated by the tumor microenvironment. The microenvironment itself can be altered by the transvascular transport because the transport may facilitate angiogenesis, reduce blood flow, and induce interstitial hypertension in tumors. Future studies of transport need to address mechanisms of the barrier formation and emphasize development of novel strategies for circumventing or exploiting the vascular barrier.

Authors
Yuan, F
MLA Citation
Yuan, F. "Transvascular drug delivery in solid tumors." Semin Radiat Oncol 8.3 (July 1998): 164-175. (Review)
PMID
9634493
Source
pubmed
Published In
Seminars in Radiation Oncology
Volume
8
Issue
3
Publish Date
1998
Start Page
164
End Page
175

Endothelial cell death, angiogenesis, and microvascular function after castration in an androgen-dependent tumor: Role of vascular endothelial growth factor

The sequence of events that leads to tumor vessel regression and the functional characteristics of these vessels during hormone-ablation therapy are not known. This is because of the lack of an appropriate animal model and monitoring technology. By using in vivo microscopy and in situ molecular analysis of the androgen-dependent Shionogi carcinoma grown in severe combined immunodeficient mice, we show that castration of these mice leads to tumor regression and a concomitant decrease in vascular endothelial growth factor (VEGF) expression. Androgen withdrawal is known to induce apoptosis in Shionogi tumor cells. Surprisingly, tumor endothelial cells begin to undergo apoptosis before neoplastic cells, and rarefaction of tumor vessels precedes the decrease in tumor size. The regressing vessels begin to exhibit normal phenotype, i.e., lower diameter, tortuosity, vascular permeability, and leukocyte adhesion. Two weeks after castration, a second wave of angiogenesis and tumor growth begins with a concomitant increase in VEGF expression. Because human tumors often relapse following hormone-ablation therapy, our data suggest that these patients may benefit from combined anti-VEGF therapy.

Authors
Jain, RK; Safabakhsh, N; Sckell, A; Chen, Y; Jiang, P; Benjamin, L; Yuan, F; Keshet, E
MLA Citation
Jain, RK, Safabakhsh, N, Sckell, A, Chen, Y, Jiang, P, Benjamin, L, Yuan, F, and Keshet, E. "Endothelial cell death, angiogenesis, and microvascular function after castration in an androgen-dependent tumor: Role of vascular endothelial growth factor." Proceedings of the National Academy of Sciences of the United States of America 95.18 (1998): 10820-10825.
PMID
9724788
Source
scival
Published In
Proceedings of the National Academy of Sciences of USA
Volume
95
Issue
18
Publish Date
1998
Start Page
10820
End Page
10825
DOI
10.1073/pnas.95.18.10820

Regulation of transport pathways in tumor vessels: Role of tumor type and microenvironment

Novel anti-neoplastic agents such as gene targeting vectors and encapsulated carriers are quite large (approximately 100-300 nm in diameter). An understanding of the functional size and physiological regulation of transvascular pathways is necessary to optimize delivery of these agents. Here we analyze the functional limits of transvascular transport and its modulation by the microenvironment. One human and five murine tumors including mammary and colorectal carcinomas hepatoma, glioma, and sarcoma were implanted in the dorsal skin-fold chamber or cranial window, and the pore cutoff size, a functional measure of transvascular gap size, was determined. The microenvironment was modulated: (i) spatially, by growing tumors in subcutaneous or cranial locations and (ii) temporally, by inducing vascular regression in hormone-dependent tumors. Tumors grown subcutaneously exhibited a characteristic pore cutoff size ranging from 200 nm to 1.2 μm. This pore cutoff size was reduced in tumors grown in the cranium or in regressing tumors after hormone withdrawal vessels induced in basic fibroblast growth factor-containing gels had a pore cutoff size of 200 nm. Albumin permeability was independent of pore cutoff size. These results have three major implications for the delivery of therapeutic agents: (i) delivery may be less efficient in cranial tumors than in subcutaneous tumors, (ii) delivery may be reduced during tumor regression induced by hormonal ablation, and (iii) permeability to a molecule is independent of pore cutoff size as long as the diameter of the molecule is much less than the pore diameter.

Authors
Hobbs, SK; Monsky, WL; Yuan, F; Roberts, WG; Griffith, L; Torchilin, VP; Jain, RK
MLA Citation
Hobbs, SK, Monsky, WL, Yuan, F, Roberts, WG, Griffith, L, Torchilin, VP, and Jain, RK. "Regulation of transport pathways in tumor vessels: Role of tumor type and microenvironment." Proceedings of the National Academy of Sciences of the United States of America 95.8 (1998): 4607-4612.
PMID
9539785
Source
scival
Published In
Proceedings of the National Academy of Sciences of USA
Volume
95
Issue
8
Publish Date
1998
Start Page
4607
End Page
4612
DOI
10.1073/pnas.95.8.4607

Modulation of intratumoral drug delivery by the tumor microenvironment and vascular endothelial growth factor

Authors
Monsky, WL; Hobbs, SK; Yuan, F; Torchilin, VP; Jain, RK
MLA Citation
Monsky, WL, Hobbs, SK, Yuan, F, Torchilin, VP, and Jain, RK. "Modulation of intratumoral drug delivery by the tumor microenvironment and vascular endothelial growth factor." Proceedings of the Controlled Release Society 25 (1998): 207-208.
Source
scival
Published In
Proceedings of the Controlled Release Society
Issue
25
Publish Date
1998
Start Page
207
End Page
208

Interlaboratory variation in oxygen tension measurement by Eppendorf "Histograph" and comparison with hypoxic marker.

BACKGROUND AND OBJECTIVES: The median of pO2 values in tumor measured by Eppendorf "Histograph" with a needle-type electrode has been used as a prognostic indicator in cancer patients. However, it is not established that a pretreatment measured pO2 value can be used as a universal predictor of local control probability, because the variation in pO2 values, especially in hypoxic tissue, among institutes may not allow comparison of measured "absolute pO2 values." The purpose of this study was to examine the variation in oxygen tension measurement by Eppendorf "Histograph" among six laboratories using a single batch of mice and tumors and the same detailed protocol. These results were also compared to the immunohistochemical staining of 2-nitromidazole adducts. METHODS: C3H mice bearing FSaII murine fibrosarcoma subcutaneously were shipped to all laboratories, and the oxygen status in tumors and in normal subcutis was examined using Eppendorf "Histograph" and immunohistochemical hypoxic marker. RESULTS: All laboratories showed that the FSaII tumor was hypoxic with at least 77% of measured points under 10 mmHg in pO2 and with a median pO2 value less than that of normal subcutis. These results were further confirmed immunohistochemically. These findings are interpreted as evidence that the pO2 values measured by Eppendorf "Histograph" can be useful. However, the median values of tumor pO2 varied from 1.5 mmHg to 5.6 mmHg among the laboratories, and pO2 of normal subcutis also varied from 28 mmHg to 38 mmHg. There were also significant differences in hypoxic fraction, defined as the fraction under a given oxygen partial pressure (i.e., under 2.5, 5, or 10 mmHg), among institutes. CONCLUSIONS: Caution needs to be exercised in using the absolute, median, or distribution of pO2 values measured by the Eppendorf "Histograph" to compare the data between laboratories or to predict the radiation response in an individual subject.

Authors
Nozue, M; Lee, I; Yuan, F; Teicher, BA; Brizel, DM; Dewhirst, MW; Milross, CG; Milas, L; Song, CW; Thomas, CD; Guichard, M; Evans, SM; Koch, CJ; Lord, EM; Jain, RK; Suit, HD
MLA Citation
Nozue, M, Lee, I, Yuan, F, Teicher, BA, Brizel, DM, Dewhirst, MW, Milross, CG, Milas, L, Song, CW, Thomas, CD, Guichard, M, Evans, SM, Koch, CJ, Lord, EM, Jain, RK, and Suit, HD. "Interlaboratory variation in oxygen tension measurement by Eppendorf "Histograph" and comparison with hypoxic marker." J Surg Oncol 66.1 (September 1997): 30-38.
PMID
9290690
Source
pubmed
Published In
Journal of Surgical Oncology
Volume
66
Issue
1
Publish Date
1997
Start Page
30
End Page
38

Quantitative angiogenesis assays: Progress and problems

Authors
Jain, RK; Schlenger, K; Höckel, M; Yuan, F
MLA Citation
Jain, RK, Schlenger, K, Höckel, M, and Yuan, F. "Quantitative angiogenesis assays: Progress and problems." Nature Medicine 3.11 (1997): 1203-1208.
PMID
9359693
Source
scival
Published In
Nature Medicine
Volume
3
Issue
11
Publish Date
1997
Start Page
1203
End Page
1208

Effect of host microenvironment on the microcirculation of human colon adenocarcinoma

It is generally accepted that the host microenvironment influences tumor biology. There are discrepancies in growth rate, metastatic potential, and efficacy of systemic treatment between ectopic and orthotopic tumors. Liver is the most common and critical site of distant metastasis of colorectal carcinoma. Tumorigenicity and efficacy of chemotherapeutic agents in colorectal tumors are different in liver and subcutaneous sites. Thus, we hypothesize that the liver (orthotopic) versus subcutaneous (ectopic) microenvironment would have different effects on the angiogenesis and maintenance of the microcirculation of colorectal tumor. To this end, we developed a new method to monitor and to quantify microcirculatory parameters in the tumor grown in the liver. Using this approach, we compared the microcirculation of LS174T, a human colon adenocarcinoma, metastasized to the liver with that of the host liver vessels and that of the same tumor grown in the subcutaneous space. In the liver metastasis model, 5 x 106 LS174T cells were injected into the spleen of nude mice. Four to eight weeks later, the liver with metastatic tumors was exteriorized and placed on a special stage and observed under an intravital fluorescence microscope. The dorsal skinfold chamber model was used to study the subcutaneous tumors. Red blood cell velocity, vessel diameter, density, permeability, and leukocyte-endothelial interactions were measured using fluorescence microscopy and image analysis. Vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) mRNA expression was determined by the Northern blot analysis. LS174T tumor foci in the liver had tortuous vascular architecture, heterogeneous blood flow, significantly lower vascular density, and significantly higher vascular permeability than normal liver tissue. Tumors grown in the liver had significantly lower vessel density, especially in the center coincident with central necrosis, than the subcutaneous tumors. The frequency distribution of vessel diameters of liver tumor was slightly shifted to smaller size compared with that of subcutaneous tumor. Leukocyte rolling in liver tumor was twofold lower than that in subcutaneous tumor. These physiological findings were consistent with the measurement of VEGF/VPF in that the VEGF/VPF mRNA level was lower in the liver tumor than that in the subcutaneous tumor. However, macromolecular vascular permeability in the liver tumor was significantly higher than in the subcutaneous tumor. Liver sinusoidal endothelial cells, the origin of liver tumor vessel endothelium, are known to be fenestrated and not to have a basement membrane, suggesting that the difference in endothelial cell origin may explain the difference in tumor vascular permeability in two sites. These findings demonstrate that liver microenvironment has different effects on some aspects of the tumor angiogenesis and microcirculation compared with the subcutaneous tissues. The new model/method described in this paper has significant implications in two research areas: 1) the liver microenvironment and its effect on tumor pathophysiology in conjunction with cytokine/growth factor regulation and 2) the delivery of drags, cells, and genes to liver tumors.

Authors
Fukumura, D; Yuan, F; Monsky, WL; Chen, Y; Jain, RK
MLA Citation
Fukumura, D, Yuan, F, Monsky, WL, Chen, Y, and Jain, RK. "Effect of host microenvironment on the microcirculation of human colon adenocarcinoma." American Journal of Pathology 151.3 (1997): 679-688.
PMID
9284816
Source
scival
Published In
The American journal of pathology
Volume
151
Issue
3
Publish Date
1997
Start Page
679
End Page
688

Direct in vivo measurement of targeted binding in a human tumor xenograft

Binding is crucial to the function of most biologically active molecules, but difficult to quantify directly in living tissue. To this end, fluorescence recovery after photobleaching was used to detect the immobilization of fluorescently labeled ligand caused by binding to receptors in vivo. Measurements of mAb affinity to target antigen within human tumor xenografts revealed a saturable binding isotherm, from which an in vivo carcinoembryonic antigen density of 0.56 nmol/g (5.0 x 105/cell) and an association constant of K(a) ≤ 4 x 107 M-1 were estimated. The present method can be adapted for in vivo studies of cell signaling, targeted drugs, gene therapy, and other processes involving receptor-ligand binding.

Authors
Berk, DA; Yuan, F; Leunig, M; Jain, RK
MLA Citation
Berk, DA, Yuan, F, Leunig, M, and Jain, RK. "Direct in vivo measurement of targeted binding in a human tumor xenograft." Proceedings of the National Academy of Sciences of the United States of America 94.5 (1997): 1785-1790.
PMID
9050856
Source
scival
Published In
Proceedings of the National Academy of Sciences of USA
Volume
94
Issue
5
Publish Date
1997
Start Page
1785
End Page
1790
DOI
10.1073/pnas.94.5.1785

Role of nitric oxide in tumor microcirculation: Blood flow, vascular permeability, and leukocyte-endothelial interactions

The present study was designed to define the role of nitric oxide (NO) in tumor microcirculation, through the direct intravital microcirculatory observations after administration of NO synthase (NOS) inhibitor and NO donor both regionally and systemically. More specifically, we tested the following hypotheses: 1) endogenous NO derived from tumor vascular endothelium and/or tumor cells increases and/or maintains tumor blood flow, decreases leukocyte- endothelial interactions, and increases vascular permeability, 2) exogenous NO can increase tumor blood flow via vessel dilatation and decrease leukocyte-endothelial interactions, and 3) NO production and tissue responses to NO are tumor dependent. To this end, a murine mammary adenocarcinoma (MCaIV) and a human colon adenocarcinoma (LS174T) were implanted in the dorsal skin fold chamber in C3H and severe combined immunodeficient mice, respectively and observed by means of intravital fluorescence microscopy. Both regional and systemic inhibition of endogenous NO by Nω-nitro-L- arginine methyl ester (L-NAME; 100 μmol/L superfusion or 10 mg/kg intravenously) significantly decreased vessel diameter and local blood flow rate. The diameter change was dominant on the arteriolar side. Superfusion of NO donor (spermine NO, 100 μmol/L) increased tumor vessel diameter and flow rate, whereas systemic injection of spermine NO (2.62 mg/kg) had no significant effect on these parameters. Rolling and stable adhesion of leukocytes were significantly increased by intravenous injection of L-NAME. In untreated animals, both MCaIV and LS174T tumor vessels were leaky to albumin. Systemic NO inhibition significantly attenuated tumor vascular permeability of MCaIV but not of LS174T tumor. Immunohistochemical studies, using polyclonal antibodies to endothelial NOS and inducible NOS, revealed a diffuse pattern of positive labeling in both MCaIV and LS174T tumors. Nitrite and nitrate levels in tumor interstitial fluid of MCaIV but not of LS174T were significantly higher than that in normal subcutaneous interstitial fluid. These results support our hypotheses regarding the microcirculatory response to NO in tumors. Modulation of NO level in tumors is a potential strategy for altering tumor hemodynamics and thus improving oxygen, drug, gene vector, and effector cell delivery to solid tumors.

Authors
Fukumura, D; Yuan, F; Endo, M; Jain, RK
MLA Citation
Fukumura, D, Yuan, F, Endo, M, and Jain, RK. "Role of nitric oxide in tumor microcirculation: Blood flow, vascular permeability, and leukocyte-endothelial interactions." American Journal of Pathology 150.2 (1997): 713-725.
PMID
9033284
Source
scival
Published In
The American journal of pathology
Volume
150
Issue
2
Publish Date
1997
Start Page
713
End Page
725

Stress is good and bad for tumors

Authors
Yuan, F
MLA Citation
Yuan, F. "Stress is good and bad for tumors." Nature Biotechnology 15.8 (1997): 722-723.
PMID
9255781
Source
scival
Published In
Nature Biotechnology
Volume
15
Issue
8
Publish Date
1997
Start Page
722
End Page
723

Effect of basic fibroblast growth factor on angiogenesis and growth of isografted bone: Quantitative in vitro-in vivo analysis in mice

Basic fibroblast growth factor (bFGF), a constituent of bone and cartilage matrix, has been shown to be a potent mitogen for osteoblasts and chondrocytes and yet an inhibitor of chondrocyte terminal differentiation in cell culture. To characterize the effect of bFGF on bone formation, whole neonatal murine femora were cultured in the presence or absence of bFGF and a neutralizing antibody against bFGF. In vitro, femoral elongation was provided by cartilage growth only; the calcified diaphyseal zone stained by oxytetracycline did not increase. When bFGF was added to the culture medium, longitudinal growth of the proximal and distal cartilage was inhibited in a dose-dependent manner (p < 0.05), and the number of hypertrophic chondrocytes in the growth plate was reduced. This phenomenon was absent in the presence of a neutralizing antibody, which when given alone significantly promoted femoral elongation. In contrast, in vivo after transplantation into adult mice bearing dorsal skin fold chambers, femora rapidly calcified after revascularization. This observation supports the notion that bone formation largely depends on angiogenesis-mediated events. To verify this hypothesis, angiogenesis and bone formation were quantified using bFGF known to be a stimulator of angiogenesis. Calcification of grafted femora was accelerated by bFGF given intraperitoneally. The neutralizing antibody slightly suppressed angiogenesis and femoral elongation (not statistically significant), whereas intravenous injections of both substances did not reveal a significant modulatory effect. In vivo the effect of systemically administered bFGF was inhomogeneous, but there was a strong correlation between angiogenesis and endochondral calcification (p < 0.001). These results suggest that exogenous bFGF modulates bone formation in vitro by inhibition of terminal differentiation of chondrocytes in the growth plate, and angiogenesis and concomitant in vivo events are pivotal in the promotion of rapid bone formation. © 1997 S. Karger AG.

Authors
Leunig, M; Yuan, F; Gerweck, LE; Jain, RK
MLA Citation
Leunig, M, Yuan, F, Gerweck, LE, and Jain, RK. "Effect of basic fibroblast growth factor on angiogenesis and growth of isografted bone: Quantitative in vitro-in vivo analysis in mice." International Journal of Microcirculation-Clinical and Experimental 17.1 (1997): 1-9.
PMID
9176719
Source
scival
Published In
International journal of microcirculation, clinical and experimental / sponsored by the European Society for Microcirculation
Volume
17
Issue
1
Publish Date
1997
Start Page
1
End Page
9

Interstitial pH and pO2 gradients in solid tumors in vivo: High-resolution measurements reveal a lack of correlation

The partial pressure of oxygen (pO2) and pH play critical roles in tumor biology and therapy. We report here the first combined, high-resolution (≤ 10 μm) measurements of interstitial pH and pO2 profiles between adjacent vessels in a human tumor xenograft, using fluorescence ratio imaging and phosphorescence quenching microscopy. We found (1) heterogeneity in shapes of pH and pO2 profiles; (2) a discordant relation between local pH profiles and corresponding pO2 profiles, yet a strong correlation between mean pH and pO2 profiles; (3) no correlation between perivascular pH/pO2 and nearest vessel blood flow; and (4) well-perfused tumor vessels that were hypoxic and, consequently, large hypoxic areas in the surrounding interstitium. Such multiparameter measurements of the in vivo microenvironment provide unique insights into biological processes in tumors and their response to treatment.

Authors
Helmlinger, G; Yuan, F; Dellian, M; Jain, RK
MLA Citation
Helmlinger, G, Yuan, F, Dellian, M, and Jain, RK. "Interstitial pH and pO2 gradients in solid tumors in vivo: High-resolution measurements reveal a lack of correlation." Nature Medicine 3.2 (1997): 177-182.
PMID
9018236
Source
scival
Published In
Nature Medicine
Volume
3
Issue
2
Publish Date
1997
Start Page
177
End Page
182
DOI
10.1038/nm0297-177

Time-dependent vascular regression and permeability changes in established human tumor xenografts induced by an anti-vascular endothelial growth factor/vascular permeability factor antibody

The hyperpermeability of tumor vessels to macromolecules, compared with normal vessels, is presumably due to vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) released by neoplastic and/or host cells. In addition, VEGF/VPF is a potent angiogenic factor. Removal of this growth factor may reduce the permeability and inhibit tumor angiogenesis. To test these hypotheses, we transplanted a human glioblastoma (U87), a human colon adenocarcinoma (LS174T), and a human melanoma (P-MEL) into two locations in immunodeficient mice: the cranial window and the dorsal skinfold chamber. The mice bearing vascularized tumors were treated with a bolus (0.2 ml) of either a neutralizing antibody (A4.6.1) (492 μg/ml) against VEGF/VPF or PBS (control). We found that tumor vascular permeability to albumin in antibody-treated groups was lower than in the matched controls and that the effect of the antibody was time-dependent and influenced by the mode of injection. Tumor vascular permeability did not respond to i.p. injection of the antibody until 4 days posttreatment. However, the permeability was reduced within 6 h after i.v. injection of the same amount of antibody. In addition to the reduction in vascular permeability, the tumor vessels became smaller in diameter and less tortuous after antibody injections and eventually disappeared from the surface after four consecutive treatments in U87 tumors. These results demonstrate that tumor vascular permeability can be reduced by neutralization of endogenous VEGF/VPF and suggest that angiogenesis and the maintenance of integrity of tumor vessels require the presence of VEGF/VPF in the tissue microenvironment. The latter finding reveals a new mechanism of tumor vessel regression-i.e., blocking the interactions between VEGF/VPF and endothelial cells or inhibiting VEGF/VPF synthesis in solid tumors causes dramatic reduction in vessel diameter, which may block the passage of blood elements and thus lead to vascular regression.

Authors
Yuan, F; Chen, Y; Dellian, M; Safabakhsh, N; Ferrara, N; Jain, RK
MLA Citation
Yuan, F, Chen, Y, Dellian, M, Safabakhsh, N, Ferrara, N, and Jain, RK. "Time-dependent vascular regression and permeability changes in established human tumor xenografts induced by an anti-vascular endothelial growth factor/vascular permeability factor antibody." Proceedings of the National Academy of Sciences of the United States of America 93.25 (1996): 14765-14770.
PMID
8962129
Source
scival
Published In
Proceedings of the National Academy of Sciences of USA
Volume
93
Issue
25
Publish Date
1996
Start Page
14765
End Page
14770
DOI
10.1073/pnas.93.25.14765

Quantitation and physiological characterization of angiogenic vessels in mice: Effect of basic fibroblast growth factor, vascular endothelial growth factor/vascular permeability factor, and host microenvironment

A prerequisite for the development of novel angiogenic and anti- angiogenic agents is the availability of routine in vive assays that permit 1) repeated, long-term quantitation of angiogenesis and 2) physiological characterization of angiogenic vessels. We report here the development of such an assay in mice. Using this assay, we tested the hypothesis that the physiological properties of angiogenic vessels are governed by the microenvironment and vessel origin rather than the initial angiogenic stimulus. Gels containing basic fibroblast growth factor (bFGF) or vascular endothelial growth factor (VEGF) were implanted in transparent windows in the dorsal skin or cranium of mice. Vessels could be continuously and non- invasively monitored and easily quantified for more than 5 weeks after gel implantation. Newly formed vessels were first visible on day 4 in the cranial window and day 10 in the dorsal skinfold chamber, respectively. The number of vessels was dependent on the dose of hFGF and VEGF. At 3000 ng/mL bFGF- and VEGF-induced blood vessels had similar diameters, red blood cell velocities, and microvascular permeability to albumin. However, red blood cell velocities and microvascular permeability to albumin were higher in the cranial window than in the dorsal skinfold chamber. Leukocyte-endothelial interaction was nearly zero in both sites. Thus, newly grown microvessels resembled vessels of granulation and neoplastic tissue in many aspects. Their physiological properties were mainly determined by the microenvironment, whereas the initial angiogenic response was stimulated by growth factors.

Authors
Dellian, M; Witwer, BP; Salehi, HA; Yuan, F; Jain, RK
MLA Citation
Dellian, M, Witwer, BP, Salehi, HA, Yuan, F, and Jain, RK. "Quantitation and physiological characterization of angiogenic vessels in mice: Effect of basic fibroblast growth factor, vascular endothelial growth factor/vascular permeability factor, and host microenvironment." American Journal of Pathology 149.1 (1996): 59-71.
PMID
8686763
Source
scival
Published In
The American journal of pathology
Volume
149
Issue
1
Publish Date
1996
Start Page
59
End Page
71

Perfusion of Single Tumor Microvessels: Application to Vascular Permeability Measurement

Objective: To develop a new method for determining the relative importance of convection versus diffusion in macromolecular transport across tumor microvessel walls. Methods: The human colon adenocarcinoma LS174T was transplanted in the dorsal skinfold chamber in a severe combined immunodeficient (SCID) mouse. The vasculature at the tumor surface was exposed by carefully removing the glass window of the chamber. A tumor microvessel was randomly selected, which was ∼20-40 μm in diameter, embedded in the connective tissue 10-12 μm below the surface of the tumor. The vessel was cannulated with a micropipette and perfused with fluorescein isothiocyanate (FITC)-labeled bovine serurn albumin (BSA) at different perfusion pressures. The fluorescence intensity was recorded on videotapes via a video system attached to the fluorescence microscope for offline analysis. The apparent vascular permeability was determined based on the time-dependence of fluorescence intensity and the vessel diameter. Results: The apparent vascular permeability of single vessels to FITC-labeled BSA was quantified at perfusion pressures of 20-45 cmH2O. The pressure dependence of vascular permeability in LS174T tumors was heterogeneous. On average, there was no correlation between the apparent vascular permeability and the perfusion pressure in the range of 20-35 cmH2O (p = 0.73), even though the apparent permeability increased significantly when the pressure was increased from 20 to 45 cmH2O (p = 0.008). Conclusions: These results indicate that convection in the transvascular transport of albumin is not significant in non-peripheral regions of solid tumors in which the pressure difference across the vessel wall is small or even negligible. In addition to the permeability studies, this preparation can be used to study cell-cell interactions in single tumor vessels under defined flow conditions.

Authors
Lichtenbeld, HC; Yuan, F; Michel, CC; Jain, RK
MLA Citation
Lichtenbeld, HC, Yuan, F, Michel, CC, and Jain, RK. "Perfusion of Single Tumor Microvessels: Application to Vascular Permeability Measurement." Microcirculation 3.4 (1996): 349-357.
PMID
9086446
Source
scival
Published In
Microcirculation
Volume
3
Issue
4
Publish Date
1996
Start Page
349
End Page
357

Fluorescence ratio imaging of interstitial pH in solid tumours: Effect of glucose on spatial and temporal gradients

Tumour pH plays a significant role in cancer treatment. However, because of the limitations of the current measurement techniques, spatially and temporally resolved pH data, obtained non-invasively in solid tumours, are not available. Fluorescence ratio imaging microscopy (FRIM) has been used previously for noninvasive, dynamic evaluation of pH in neoplastic tissue in vivo However, owing to problems associated with quantitative fluorescence in thick biological tissues, these studies were limited to thin (50 μm) rumours. We, therefore, adapted the FRIM technique for pH determination in thick(≃2 mm) solid tumours in vivo using a pinhole illumination-optical sectioning (PIOS) method. Results show that (1) steep interstitial pH gradients (5 μm resolution), with different spatial patterns, exist between tumour blood vessels; (2) pH decreased by an average of 0.10 pH units over a distance of 40 pm away from the blood vessel wall, and by 0.33 pH units over a 70 μm distance; (3) the maximum pH drop, defined as the pH difference between the intervessel midpoint and the vessel wall, was positively correlated with the intervessel distance; (4) 45 min following a systemic glucose injection (6 g kg-1 i.v.), interstitial pH gradients were shifted to lower pH values by an average of 0.15 pH units, while the spatial gradient (slope) was maintained, when compared with preglucose values. This pH decrease was not accompanied by significant changes in local blood flow. pH gradients returned to near-baseline values 90 min after glucose injection; (5) interstitial tumour pH before hyperglycaemia and the glucose-induced pH drop strongly depended on the local vessel density; and (6) sodium bicarbonate treatment, either acute (1 M, 0.119 ml h-1 for 3 h i.v.) or chronic (1% in drinking water for 8 days), did not significantly change interstitial tumour pH. Modified FRIM may be combined with other optical methods (e.g. phosphorescence quenching) to evaluate non-invasively the spatial and temporal characteristics of extracellular pH, intracellular pH and pO2 in solid rumours. This will offer unique information about tumour metabolism and its modification by treatment modalities used in different cancer therapies.

Authors
Dellian, M; Helmlinger, G; Yuan, F; Jain, RK
MLA Citation
Dellian, M, Helmlinger, G, Yuan, F, and Jain, RK. "Fluorescence ratio imaging of interstitial pH in solid tumours: Effect of glucose on spatial and temporal gradients." British Journal of Cancer 74.8 (1996): 1206-1215.
PMID
8883406
Source
scival
Published In
British Journal of Cancer
Volume
74
Issue
8
Publish Date
1996
Start Page
1206
End Page
1215

Heating or freezing bone. Effects on angiogenesis induction and growth potential in mice

We have characterized the effect of bone graft treatment by heating or freezing (with or without dimethyl sulfoxide (DMSO). Tissue culture and dorsal skinfold chambers in mice were used as sites to quantify the effect on angiogenesis, growth and calcification of neonatal femora. Fresh femora increased in both length and cartilage diameter (calcification in vivo only), but cryopreservation or heating abolished the increase in femoral dimensions. In vivo, femora of all experimental groups elicited an angiogenic response from the host tissue, which was most pronounced for fresh femora, weaker for DMSO-preserved frozen bone and poor for unprotected frozen bone and boiled femora. Freezing in the presence of a cryopreservative (DMSO) was found to preserve the angiogenic potential of frozen bone, whereas unprotected heating or freezing significantly impaired angiogenesis induction and growth potential.

Authors
Leunig, M; Yuan, F; Berk, DA; Gerweck, LE; Jain, RK
MLA Citation
Leunig, M, Yuan, F, Berk, DA, Gerweck, LE, and Jain, RK. "Heating or freezing bone. Effects on angiogenesis induction and growth potential in mice." Acta Orthopaedica Scandinavica 67.4 (1996): 383-388.
PMID
8792744
Source
scival
Published In
Acta orthopaedica Scandinavica
Volume
67
Issue
4
Publish Date
1996
Start Page
383
End Page
388

Vascular permeability in a human tumor xenograft: Molecular size dependence and cutoff size

Molecular size is one of the key determinants of transvascular transport of therapeutic agents in tumors. However, there are no data in the literature on the molecular size dependence of microvascular permeability in tumors. Therefore, we measured microvascular permeability to various macromolecules in the human colon adenocarcinoma LS174T transplanted in dorsal skin chambers in severe combined immunodeficient mice. These molecules were fluorescently labeled and injected i.v. into mice. The microvascular permeability was calculated from the fluorescence intensity measured by the intravital fluorescence microscopy technique. The value of permeability varied approximately 2-fold in the range of molecular weight from 25,000 to 160,000. These data indicate that tumor vessels are less permselective than normal vessels, presumably due to large pores in the vessel wall. The transport of macromolecules appears to be limited by diffusion through these pores. The cutoff size of the pores was estimated by observations of transvascular transport of sterically stabilized liposomes of 100-600 nm in diameter. We found that tumor vessels in our model were permeable to liposomes of up to 400 nm in diameter, suggesting that the cutoff size of the pores is between 400 and 600 nm in diameter.

Authors
Yuan, F; Dellian, M; Fukumura, D; Leunig, M; Berk, DA; Torchilin, VP; Jain, RK
MLA Citation
Yuan, F, Dellian, M, Fukumura, D, Leunig, M, Berk, DA, Torchilin, VP, and Jain, RK. "Vascular permeability in a human tumor xenograft: Molecular size dependence and cutoff size." Cancer Research 55.17 (1995): 3752-3756.
PMID
7641188
Source
scival
Published In
Cancer Research
Volume
55
Issue
17
Publish Date
1995
Start Page
3752
End Page
3756

Rolling in P-Selectin - Deficient Mice Is Reduced but Not Eliminated in the Dorsal Skin

P-selectin-mediated rolling is believed to be important in the recruitment of leukocytes to tissue after ischemia-reperfusion injury. The dorsal skin chamber was used to examine differences in the rolling and stable adhesion of circulating leukocytes in subcutaneous (SC) vessels of P-selectin-deficient and age-matched wild-type mice, both under basal conditions and after ischemia-reperfusion. Rolling in the postcapillary venules in SC tissue of P-selectin-deficient mice was significantly lower than that in wild-type mice under the basal conditions and post-ischemia-reperfusion (P < .05), but was not eliminated by the deletion of the P-selectin gene. No significant difference between P-selectin-deficient and wild-type mice in shear rate or leukocyte-endothelial adhesion was observed up to 24 hours after ischemia-reperfusion. These results show that P-selectin-mediated rolling is not a prerequisite for ischemia-reperfusion-induced leukocyte-endothelial adhesion in the skin. © 1995 by The American Society of Hematology.

Authors
Yamada, S; Mayadas, TN; Yuan, F; Wagner, DD; Hynes, RO; Melder, RJ; Jain, RK
MLA Citation
Yamada, S, Mayadas, TN, Yuan, F, Wagner, DD, Hynes, RO, Melder, RJ, and Jain, RK. "Rolling in P-Selectin - Deficient Mice Is Reduced but Not Eliminated in the Dorsal Skin." Blood 86.9 (1995): 3487-3492.
PMID
7579454
Source
scival
Published In
Blood
Volume
86
Issue
9
Publish Date
1995
Start Page
3487
End Page
3492

Quantitative analysis of angiogenesis and growth of bone: effect of indomethacin exposure in a combined in vitro-in vivo approach

Nonsteroidal anti-inflammatory agents have been used experimentally and clinically to suppress a variety of physiological events, including angiogenesis and formation of bone. The exact mechanisms by which indomethacin alters skeletal tissue generation are unknown, due in part to methodological limitations. By the use of an organ culture assay and an animal model using intravital microscopy in mice bearing dorsal skinfold chambers, the effect of indomethacin on growth and angiogenesis of neonatal femora was characterized over 16 days. In both assays, femora significantly elongated with time (P<0.05). The in vitro growth rate was more rapid than in vivo and dependent on the serum concentration, culture medium and age of mice. Although enthancing the serum content promoted cellular proliferation in organ culture, it dose-dependently suppressed femoral elongation, leading at 20% fetal calf serum to growth rates identical to those observed in vivo. Indomethacin supplementation (2 and 10 mg l-1) significantly accelerated longitudinal femoral growth in organ culture (P<0.05), whereas in vivo indomethacin (2 mg kg-1) did not modulate either angiogenesis or elongation of bone. Our in vitro data propose a central role of serum in the regulation of bone formation. Although indomethacin altered femoral gowth in vitro, our findings do not suggest that indomethacin suppresses angiogenesis or growth of bone in vivo. The complexity of physiological events in vivo may be obscuring a detectable effect. © 1995 Springer-Verlag.

Authors
Leunig, M; Yuan, F; Gerweck, LE; Berk, DA; Jain, RK
MLA Citation
Leunig, M, Yuan, F, Gerweck, LE, Berk, DA, and Jain, RK. "Quantitative analysis of angiogenesis and growth of bone: effect of indomethacin exposure in a combined in vitro-in vivo approach." Research in Experimental Medicine 195.1 (1995): 275-288.
PMID
8578003
Source
scival
Published In
Research in Experimental Medicine
Volume
195
Issue
1
Publish Date
1995
Start Page
275
End Page
288
DOI
10.1007/BF02576798

Microvascular permeability and interstitial penetration of sterically stabilized (stealth) liposomes in a human tumor xenograft

Microvascular permeability and interstitial penetration of sterically stabilized liposomes in both normal s.c. tissue and human colon adenocarcinoma LS174T xenograft were quantified by using the dorsal skin- fold chamber implanted in severe combined immunodeficient mice and intravital fluorescence microscopy. Significant extravascular accumulation was the dominant feature of liposome distribution in tumors, whereas only minimal intramural accumulation in postcapillary and collecting venules was observed in normal s.c. tissue. The extravasated liposomes in tumors distributed heterogeneously and formed perivascular clusters that did not move significantly and could be observed for up to 1 week. The effective permeability of tumor vessels to liposomes (2.0 ± 1.6 x 10-8 cm/s; n = 23) was six times smaller than that to bovine serum albumin (1.2 ± 0.5 x 10-7 cm/s; n = 6). These results provide new insights into the mechanisms of transendothelial pathways of liposomes and improvements in liposome-mediated drug delivery.

Authors
Yuan, F; Leunig, M; Huang, SK; Berk, DA; Papahadjopoulos, D; Jain, RK
MLA Citation
Yuan, F, Leunig, M, Huang, SK, Berk, DA, Papahadjopoulos, D, and Jain, RK. "Microvascular permeability and interstitial penetration of sterically stabilized (stealth) liposomes in a human tumor xenograft." Cancer Research 54.13 (1994): 3352-3356.
PMID
8012948
Source
scival
Published In
Cancer Research
Volume
54
Issue
13
Publish Date
1994
Start Page
3352
End Page
3356

Vascular permeability and microcirculation of gliomas and mammary carcinomas transplanted in rat and mouse cranial windows

Many brain tumors are highly resistant to chemotherapy, presumably due to the presence of a tight blood-tumor barrier. For a better understanding of the regulation of this barrier by the brain environment, a new intravital microscopy model was established by transplanting tumor tissue into cranial windows in both rats and mice. The model was characterized by RBC velocities, vessel diameters, and vascular permeabilities of various tumors: R3230AC (a rat mammary adenocarcinoma), MCaIV (a mouse mammary adenocarcinoma), and U87 and HGL21 (human malignant astrocytomas). Our results showed that tumor blood flow in cranial windows was one to three orders of magnitude lower than the blood flow in pial vessels and similar to that in dorsal skin-fold chambers observed in previous studies. The mean vessel diameter ranged from 6.8 ± 1.3 μm for HGL21 to 30.4 ± 8.5 μm for MCaIV. At least one order of magnitude difference in vascular permeability to albumin was observed between tumor lines: 0.11 ± 0.05 x 10-7 cm/s for HGL21 versus 3.8 ± 1.2 x 10-7 cm/s for U87. The low vascular permeability of HGL21, which was also confirmed by both sodium fluorescein and Lissamine green injections, suggests that not all tumors are leaky to tracer molecules and that the blood-tumor barrier of this tumor still possesses some characteristics of blood-brain barrier as observed in other intracranial tumors. The model presented here will allow us to manipulate the vascular permeability in brain tumors and thus may provide new information on the regulation of the blood-tumor barrier and new strategies for improving drug delivery in brain tumors.

Authors
Yuan, F; Salehi, HA; Boucher, Y; Vasthare, US; Tuma, RF; Jain, RK
MLA Citation
Yuan, F, Salehi, HA, Boucher, Y, Vasthare, US, Tuma, RF, and Jain, RK. "Vascular permeability and microcirculation of gliomas and mammary carcinomas transplanted in rat and mouse cranial windows." Cancer Research 54.17 (1994): 4564-4568.
PMID
8062241
Source
scival
Published In
Cancer Research
Volume
54
Issue
17
Publish Date
1994
Start Page
4564
End Page
4568

Noninvasive measurement of microvascular and interstitial oxygen profiles in a human tumor in SCID mice

Simultaneous measurements of intravascular and interstitial oxygen partial pressure (PO2) in any tissue have not previously been reported, despite the importance of oxygen in health and in disease. This is due to the limitations of current techniques, both invasive and noninvasive. We have optically measured microscopic profiles of PO2 with high spatial resolution in subcutaneous tissue and transplanted tumors in mice by combining an oxygen- dependent phosphorescence quenching method and a transparent tissue preparation. The strengths of our approach include the ability to follow PO2 in the same location for several weeks and to relate these measurements to local blood flow and vascular architecture. Our results show that (i) PO2 values in blood vessels in well-vascularized regions of a human colon adenocarcinoma xenograft are comparable to those in surrounding arterioles and venules, (ii) carbogen (95% O2/5% CO2) breathing increases microvascular PO2 in tumors, and (iii) in unanesthetized and anesthetized mice PO2 drops to hypoxic values at <200 μm from isolated vessels but drops by <5 mmHg (1 mmHg = 133 Pa) in highly vascularized tumor regions. Our method should permit noninvasive evaluations of oxygen-modifying agents and offer further mechanistic information about tumor pathophysiology in tissue preparations where the surface of the tissue can be observed.

Authors
Filho, IPT; Leunig, M; Yuan, F; Intaglietta, M; Jain, RK
MLA Citation
Filho, IPT, Leunig, M, Yuan, F, Intaglietta, M, and Jain, RK. "Noninvasive measurement of microvascular and interstitial oxygen profiles in a human tumor in SCID mice." Proceedings of the National Academy of Sciences of the United States of America 91.6 (1994): 2081-2085.
PMID
8134352
Source
scival
Published In
Proceedings of the National Academy of Sciences of the United States of America
Volume
91
Issue
6
Publish Date
1994
Start Page
2081
End Page
2085

Methods in laboratory investigation. Angiogenesis and growth of isografted bone: Quantitative in vivo assay in nude mice

BACKGROUND: Understanding the regulation of vascularization and formation of bone after skeletal trauma is essential for the development of methods to promote healing. The lack of information on the biology of bone healing led us to establish an experimental model that facilitates the in vivo assessment of angiogenesis and growth of bone. EXPERIMENTAL DESIGN: Fresh, cryopreserved (frozen in the presence or absence of 10% dimethyl sulfoxide (DMSO)) or boiled neonatal femora were transplanted into dorsal skin fold chambers in adult mice of the identical strain, and angiogenesis and growth were monitored over 16 days. Computerized analysis of brightfield and epifluorescence images was employed to characterize the process of angiogenesis. Bone formation was quantified in vivo by the use of oxytetracycline. RESULTS: Reperfusion of pre-existing blood vessels of the graft was observed only in fresh transplanted femora, whereas femora of all experimental groups elicited angiogenic response from the host tissue. The rank order of the angiogenic response was: fresh > cryopreservation with DMSO > cryopreservation without DMSO > boiled. Growth of femora was completely abolished after cryopreservation or boiling. Only fresh transplanted femora increased in length (95 μm/day) and in cartilage diameter (41 μm/day). CONCLUSIONS: Our study demonstrates that (a) angiogenesis and growth of transplanted femora can be chronically assessed using in vivo microscopy; (b) the introduction of oxytetracycline for in vivo fluorescence microscopy allows the differential quantification of bone and cartilage growth; and (c) cryoprotection using DMSO enhances restoration of angiogenic potency after freezing. We consider this assay an excellent experimental model to study in vivo effects of agents or procedures that potentially modulate angiogenesis and growth of bone.

Authors
Leunig, M; Yuan, F; Berk, DA; Gerweck, LE; Jain, RK
MLA Citation
Leunig, M, Yuan, F, Berk, DA, Gerweck, LE, and Jain, RK. "Methods in laboratory investigation. Angiogenesis and growth of isografted bone: Quantitative in vivo assay in nude mice." Laboratory Investigation 71.2 (1994): 300-307.
PMID
7521447
Source
scival
Published In
Laboratory Investigation
Volume
71
Issue
2
Publish Date
1994
Start Page
300
End Page
307

Flow velocity in the superficial lymphatic network of the mouse tail

The present study had two goals: 1) to establish an animal model in which a large network of the initial lymphatics of the skin can be investigated in vivo and 2) to measure effective flow velocity (defined as axial component of the flow velocity in the lymph capillary network of the skin for the first time. A fluorescence microlymphography technique was used to stain the lymph capillaries in the superficial layer of the skin of the nude mouse tail in 10 female animals (mean age 45.8 ± 2.4 days; mean wt 21.2 ± 0.8 g). With the use of densitometric image analysis, effective flow velocity along the tail was measured. The network consisted of a honeycomb-like layer of hexagonally shaped meshes that could be stained in all animals. Effective lymph flow velocities were in the range of 1.4-20.4 μm/s with a mean value of 7.7 ± 5.9 μm/s; median value was 6.2 μm/s (4.5-10.5; 25 and 75% percentiles). This new animal model allows studies of a large network of lymph capillaries in the skin and should provide new insight into the physiology and pathophysiology of the initial lymphatics.

Authors
Leu, AJ; Berk, DA; Yuan, F; Jain, RK
MLA Citation
Leu, AJ, Berk, DA, Yuan, F, and Jain, RK. "Flow velocity in the superficial lymphatic network of the mouse tail." American Journal of Physiology - Heart and Circulatory Physiology 267.4 36-4 (1994): H1507-H1513.
PMID
7943396
Source
scival
Published In
American Journal of Physiology - Heart and Circulatory Physiology
Volume
267
Issue
4 36-4
Publish Date
1994
Start Page
H1507
End Page
H1513

Microvascular permeability of albumin, vascular surface area, and vascular volume measured in human adenocarcinoma LS174T using dorsal chamber in SCID mice

A novel method was developed to measure the effective permeability of microvessels in three-dimensional tumors. Two unique features characterized our approach: (i) Texas Red (with peak excitation and peak emission wavelengths of 596 and 615 nm, respectively) was used for macromolecular labeling, to minimize the absorption of fluorescence light by hemoglobin in blood. Thus the tumor tissue could be treated approximately as a uniform medium with respect to light absorption. (ii) The light absorption and scattering in tumor tissues were accounted for in relating the fluorescence intensity to the amount of Texas Red-labeled macromolecules extravasated. The vascular permeability of Texas Red-labeled bovine serum albumin in human tumor xenograft LS174T implanted in dorsal skin-fold chamber in severe combined immunodeficient mice was measured using this method. The average permeability-surface area product per unit volume (PS/V, x 10-4 sec-1) and the average effective permeability (P, x 10-7 cm/sec) were found to be 1.26 ± 0.72 and 6.06 ± 4.30, respectively; the fractional volume of tumor vessels (V(ves)/V, %) was found to be 9.2 ± 2.9, and the total surface area of vessels per unit volume (S/V, cm2/cm3) was found to be 239 ± 82. The errors in the estimation of these parameters are discussed. The method described here is general and can be adapted to study the microvascular permeability of superficial tumors in various organs in patients or animals.

Authors
Yuan, F; Leunig, M; Berk, DA; Jain, RK
MLA Citation
Yuan, F, Leunig, M, Berk, DA, and Jain, RK. "Microvascular permeability of albumin, vascular surface area, and vascular volume measured in human adenocarcinoma LS174T using dorsal chamber in SCID mice." Microvascular Research 45.3 (1993): 269-289.
PMID
8321142
Source
scival
Published In
Microvascular Research
Volume
45
Issue
3
Publish Date
1993
Start Page
269
End Page
289
DOI
10.1006/mvre.1993.1024

Fluorescence photobleaching with spatial Fourier analysis: Measurement of diffusion in light-scattering media

A new method for the measurement of diffusion in thick samples is introduced, based upon the spatial Fourier analysis of Tsay and Jacobson (Biophys. J. 60:360-368, 1991) for the video image analysis of fluorescence recovery after photobleaching (FRAP). In this approach, the diffusion coefficient is calculated from the decay of Fourier transform coefficients in successive fluorescence images. Previously, the application of FRAP in thick samples has been confounded by the optical effects of out-of-focus light and scattering and absorption by the sample. The theory of image formation is invoked to show that the decay rate is the same for both the observed fluorescence intensity and the true concentration distribution in the tissue. The method was tested in a series of macromolecular diffusion measurements in aqueous solution, in agarose gel, and in simulated tissue consisting of tumor cells (45% v/v) and blood cells (5% v/v) in an agarose gel. For a range of fluorescently labeled proteins (MW = 14 to 600 kD) and dextrans (MW = 4.4 to 147.8 kD), the diffusion coefficients in aqueous solution were comparable to previously published values. A comparison of the spatial Fourier analysis with a conventional direct photometric method revealed that even for the weakly scattering agarose sample, the conventional method gives a result that is inaccurate and dependent on sample thickness whereas the diffusion coefficient calculated by the spatial Fourier method agreed with published values and was independent of sample thickness. The diffusion coefficient of albumin in the simulated tissue samples, as determined by the spatial Fourier analysis, varied slightly with sample thickness. In contrast, when the same video images were analyzed by direct photometric analysis, the calculated diffusion coefficients were grossly inaccurate and highly dependent on sample thickness. No simple correction could be devised to ensure the accuracy of the direct photometric method of analysis. These in vitro experiments demonstrate the advantage of our new analysis for obtaining an accurate measure of the local diffusion coefficient in microscopic samples that are thick (thickness greater than the microscope depth of focus) and scatter light.

Authors
Berk, DA; Yuan, F; Leunig, M; Jain, RK
MLA Citation
Berk, DA, Yuan, F, Leunig, M, and Jain, RK. "Fluorescence photobleaching with spatial Fourier analysis: Measurement of diffusion in light-scattering media." Biophysical Journal 65.6 (1993): 2428-2436.
PMID
8312481
Source
scival
Published In
Biophysical Journal
Volume
65
Issue
6
Publish Date
1993
Start Page
2428
End Page
2436
DOI
10.1016/S0006-3495(93)81326-2

Pharmacokinetic analysis of the perivascular distribution of bifunctional antibodies and haptens: Comparison with experimental data

A mathematical model is developed to describe the concentration profiles around individual tumor blood vessels for two-step approaches to cancer treatment. The model incorporates plasma pharmacokinetics, interstitial diffusion, reversible binding between antibody and hapten and between antibody and tumor-associated antigens, and physiological parameters to evaluate present experimental approaches and to suggest new guidelines for the effective use of two-step approaches. Results show considerable interaction between the binding kinetics, initial drug doses, and antigen density, with optimal parameter ranges depending on the desired goal: treatment or detection. The hapten concentration in tumors was found to be nonuniform because of specific binding to antibodies. While binding of the hapten to the bifunctional antibody is necessary for improved retention, too large a binding affinity may lead to very poor penetration of the hapten into regions far away from blood vessels. The time delay between antibody and hapten injection was found to be an important parameter. Longer time delays were found to be advantageous, subject to constraints such as internalization of the antibody and tumor growth during treatment. A proper combination of initial doses for the two species was also seen to be crucial for maximum effectiveness. Comparison of the model with the experimental data of Le Doussal et al. (Cancer Res., 51: 6650-6655, 1991) and Stickney et al. (Cancer Res., 50: 3445-3452, 1990) suggests two novel, yet testable, hypotheses: (a) the early pharmacokinetics of low molecular weight agents can have an important effect on later concentrations using two-step approaches; and (b) metabolism may play an important role in reducing concentrations in the tumor and tumor:plasma concentration ratios. These results should help in the effective design of two-step strategies.

Authors
Baxter, LT; Yuan, F; Jain, RK
MLA Citation
Baxter, LT, Yuan, F, and Jain, RK. "Pharmacokinetic analysis of the perivascular distribution of bifunctional antibodies and haptens: Comparison with experimental data." Cancer Research 52.20 (1992): 5838-5844.
PMID
1394212
Source
scival
Published In
Cancer Research
Volume
52
Issue
20
Publish Date
1992
Start Page
5838
End Page
5844

Angiogenesis, microvascular architecture, microhemodynamics, and interstitial fluid pressure during early growth of human adenocarcinoma LS174T in SCID mice

To date, most quantitative information on tumor angiogenesis, microcirculation, and transport has been derived from rodent tumors grown in transparent chamber preparations. In this paper we present a chamber technique adapted to immunodeficient mice for the study of human tumor xenografts. Microcirculatory parameters in severe combined immunodeficient mice bearing a dorsal skin fold chamber preparation were quantified using intravital microscopy and image analysis. The take rate of the human colon adenocarcinoma LS174T in the chamber preparation was 100%, and the tumor area doubling time was 6.5 days. Three days following implantation of 2 × 105 tumor cells onto the striated skin muscle, capillary sprouts were noted in the tumor cell mass. Microvasculature in the tumors was established after 10 days. Capillary density, vessel diameter, red blood cell velocity, and blood flow rates in individual microvessels measured on days 10, 14, 18, and 22 showed no statistical difference in the striated muscle (capillaries) and subcutaneous tissue (arterioles and venules) of the skin of tumor-free animals (N = 6), whereas these parameters increased slightly, but not significantly, in the LS174T tumors (N = 7). Mean interstitial fluid pressure (±SD) in these small tumors was 4.6 ± 1.7 mmHg (N = 4) on day 10 and 5.1 ± 0.9 mmHg (N = 4) on day 22 and significantly elevated compared to that in the subcutaneous and skin tissue (-0.9 ± 0.8 mmHg) (N = 4) (P < 0.001). To our knowledge, this is the first model enabling intravital microscopic studies of human tumor xenografts in a transparent chamber preparation in severe combined immunodeficient mice. Studies on angiogenesis, microcirculation, and transport using such a preparation should provide new insights into microcirculation-mediated mechanisms for cancer treatment.

Authors
Leunig, M; Yuan, F; Menger, MD; Boucher, Y; Goetz, AE; Messmer, K; Jain, RK
MLA Citation
Leunig, M, Yuan, F, Menger, MD, Boucher, Y, Goetz, AE, Messmer, K, and Jain, RK. "Angiogenesis, microvascular architecture, microhemodynamics, and interstitial fluid pressure during early growth of human adenocarcinoma LS174T in SCID mice." Cancer Research 52.23 (1992): 6553-6560.
PMID
1384965
Source
scival
Published In
Cancer Research
Volume
52
Issue
23
Publish Date
1992
Start Page
6553
End Page
6560

Pharmacokinetic analysis of two-step approaches using bifunctional and enzyme-conjugated antibodies

Bifunctional antibodies (BFA) and enzyme-conjugated antibodies (ECA) can be used to preferentially deliver a hapten or drug to tumor sites for diagnosis and therapy. We present here a simple pharmacokinetic model for the above two systems by considering only two compartments, the plasma and tumor. The models predict that the longer the time delay between the BFA and hapten or between the ECA and prodrug injections, the higher the tumor-plasma concentration ratio of the hapten or drug. In addition, multiple injections of the hapten or prodrug is predicted to give a more uniform concentration of the hapten or drug in both the tumor and plasma than bolus injection. We suggest that, initially, the most effective dose of BFA should be selected and then the hapten concentration chosen accordingly. The decrease of the ECA injection dose would increase the tumor:plasma concentration ratio of the drug and yet decrease the tumor concentration of the drug. In clinical application of the ECA system, consideration of ECA dose should be balanced between the tumor concentration and the tumorplasma concentration ratio of the drug. The dose of the prodrug injection is suggested to be equal to the required toxic concentration of the drug in the tumor. There are several ways to improve the tumonplasma concentration ratio of the hapten or drug, such as changing the binding kinetics of the antibody to tumor or the hapten to BFA and removing the antibody from the plasma before the injection of the hapten or prodrug. One notable difference between the BFA and ECA approaches is that there is an upper limit for maximum hapten concentration in the former, and hence, from the point of drug delivery alone the latter approach is presumably superior. The limitations of the models and therapeutic implications are also discussed.

Authors
Yuan, F; Baxter, LT; Jain, RK
MLA Citation
Yuan, F, Baxter, LT, and Jain, RK. "Pharmacokinetic analysis of two-step approaches using bifunctional and enzyme-conjugated antibodies." Cancer Research 51.12 (1991): 3119-3130.
PMID
2039991
Source
scival
Published In
Cancer Research
Volume
51
Issue
12
Publish Date
1991
Start Page
3119
End Page
3130

A new view of convective-diffusive transport processes in the arterial intima

In this paper a new theoretical framework is presented for analyzing the filtration and macromolecular convective-diffusive transport processes in the intimal region of an artery wall with widely dispersed macromolecular cellular leakage sites, as proposed in the leaky junction-cell turnover hypothesis of Weinbaum et al. [11]. In contrast to existing convection-diffusive models, which assume that the transport is either 1-D, or convection is primarily in a direction normal to the endothelial surface, the present model considers for the first time the nonuniform subendothelial pressure field that arises from the different hydraulic resistances of normal and leaky endothelial clefts and the special role of the internal elastic lamina (IEL) in modulating the horizontal transport of macromolecules after they have passed through the leaky clefts of cells that are either in mitosis or demonstrate IgG labeling. The new theory is able to quantitatively explain the growing body of recent experiments in which an unexpectedly rapid early-time growth of the leakage spot has been observed and the longer time asymptotic behavior in which the leakage spot appears to approach an equilibrium diameter. The new theory also predicts the observed doubling in macromolecular permeability between EBA labeled blue and white areas when the frequency of leakage sites is doubled. This frequency for doubling of permeability, however, is an order of magnitude smaller than predicted by the author's previous model, Tzeghai et al. [10], in which only convection normal to the endothelial surface was considered and the pressure was uniform in the intima. The longer time model predictions are used to explain the time scale for the formation of liposomes [4] in subendothelial tissue matrix in animal feeding experiments where it has been observed that the extracellular lipid concentration rises sharply prior to the entry of monocytes into the intima.

Authors
Yuan, F; Chien, S; Weinbaum, S
MLA Citation
Yuan, F, Chien, S, and Weinbaum, S. "A new view of convective-diffusive transport processes in the arterial intima." Journal of Biomechanical Engineering 113.3 (1991): 314-329.
PMID
1921359
Source
scival
Published In
Journal of Biomechanical Engineering
Volume
113
Issue
3
Publish Date
1991
Start Page
314
End Page
329

A mathematical model for the receptor mediated cellular regulation of the low density lipoprotein metabolism

A prototype mathematical model for Brown and Goldstein's pioneering studies on the LDL receptor mediated pathway for the regulation of the cellular content of cholesterol has been developed in this paper. In order to analyze the essential features of this complex system quantitatively and still reflect the framework of the total system, six important processes are considered in the model. They are: (1A, B) the hydrolysis and synthesis of the LDL receptor; (2) the binding of LDL to its receptors; (3) the hydrolysis of LDL; (4) the storage of cholesteryl esters; (5) the regulation of de novo synthesis of cholesterol; and (6) the efflux of free cholesterol to the external medium. All these processes form a system to let the cells take up enough cholesterol from the external medium for their utilization and yet avoid the excessive accumulation of the lipid within the cells.

Authors
Yuan, F; Weinbaum, S; Pfeffer, R; Chien, S
MLA Citation
Yuan, F, Weinbaum, S, Pfeffer, R, and Chien, S. "A mathematical model for the receptor mediated cellular regulation of the low density lipoprotein metabolism." Journal of Biomechanical Engineering 113.1 (1991): 1-10.
PMID
2020167
Source
scival
Published In
Journal of Biomechanical Engineering
Volume
113
Issue
1
Publish Date
1991
Start Page
1
End Page
10

New view of convective-diffusive processes in the arterial intima

Macromolecular transport across the arterial wall is closely linked to a variety of processes in the intima that are believed to play an important role in the subendothelial accumulation of lipid and the formation of the early foam cell lesion. In this paper the authors present a new conceptual two-dimensional, time-dependent model for macromolecular transport across the arterial wall in which special emphasis is placed on the modeling of the convective-diffusive transport processes in the subendothelial intima and across the internal elastic lamina. This model is an important extension of the leaky junction-cell turnover theory proposed by Weinbaum et al., and, they believe, sheds a new light on the role that the internal elastic lamina plays in modulating both the subendothelial water and macromolecular fluxes in the artery wall and the structure of normal arterial interendothelial clefts.

Authors
Yuan, F; Chien, S; Weinbaum, S
MLA Citation
Yuan, F, Chien, S, and Weinbaum, S. "New view of convective-diffusive processes in the arterial intima." American Society of Mechanical Engineers, Bioengineering Division (Publication) BED 17 (1990): 33-35.
Source
scival
Published In
American Society of Mechanical Engineers, Bioengineering Division (Publication) BED
Volume
17
Publish Date
1990
Start Page
33
End Page
35

The displacement wave theory of blood vessel

Authors
Fan, Y; Wang-yi, W
MLA Citation
Fan, Y, and Wang-yi, W. "The displacement wave theory of blood vessel." Applied Mathematics and Mechanics 10.6 (June 1989): 487-493.
Source
crossref
Published In
Applied Mathematics and Mechanics
Volume
10
Issue
6
Publish Date
1989
Start Page
487
End Page
493
DOI
10.1007/BF02017892
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