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Bursac, Nenad

Overview:

Bursac's research interests include pluripotent stem cell therapies for heart and muscle disease. Cardiac and skeletal muscle tissue engineering. Cardiac electrophysiology and arrhythmias. Genetic modifications of stem and somatic cells. Micropatterning of proteins and hydrogels. Organ-on-chip technologies.


The focus of my research is application of stem cells and tissue engineering methodologies in experimental in vitro studies and cell and tissue replacement therapies. Micropatterning of extracellular matrix proteins or protein hydrogels and engineering of synthetic scaffolds are used to build stem cell-derived cardiac and skeletal muscle tissues that replicate the structure-function relationships present in healthy and diseased muscle. These systems are used to separate and systematically study the roles of structural and genetic factors that contribute cardiac and skeletal muscle function and disease at multiple organizational levels (from single cell to 3-dimensional tissue). Optical recordings with voltage and calcium sensitive dyes in synthetic tissues allow us to analyze and optimize normal electrical function as well as study complicated spatio-temporal changes in electrical activity encountered in cardiac arrhythmias and fibrillation. Contractile force measurements allow us to explore factors that would optimize mechanical function of engineered tissues. Examples of the current research projects include: 1) design of co-cultures made of cardiac and different types of stem cells to model and study cell and tissue therapies for cardiac infarction and arrhythmias, 2) local and global gene manipulation in cultures of cardiac and other cell types, 3) engineering of vascularized cardiac and skeletal muscle tissue constructs with controllable structure and function, 4) implantation of stem cell-derived cardiac tissue patches in animal models of cardiac infarction, and 5) design of synthetic excitable tissues for experimental studies and novel cell therapies.

Positions:

Professor of Biomedical Engineering

Biomedical Engineering
Pratt School of Engineering

Associate Professor in Medicine

Medicine, Cardiology
School of Medicine

Member of the Duke Cancer Institute

Duke Cancer Institute
School of Medicine

Co-Director of the Regeneration Next Initiative

Regeneration Next Initiative
School of Medicine

Education:

B.S.E. 1994

B.S.E. — University of Belgrade

Ph.D. 2000

Ph.D. — Boston University

News:

Grants:

Medical Scientist Training Program

Administered By
School of Medicine
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
July 01, 1997
End Date
June 30, 2022

Training Program in Developmental and Stem Cell Biology

Administered By
Basic Science Departments
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
May 01, 2001
End Date
April 30, 2022

Muscle-macrophage constructs for skeletal muscle repair

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
September 01, 2016
End Date
August 31, 2021

Multidisciplinary Heart and Vascular Diseases

Administered By
Medicine, Cardiology
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
July 01, 1975
End Date
March 31, 2021

Eliciting heart regeneration through cardiomyocyte division

Administered By
Cell Biology
AwardedBy
Fondation Leducq
Role
Co-Principal Investigator
Start Date
January 01, 2016
End Date
December 31, 2020

Engineering of Human Excitable Tissues from Unexcitable Cells

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
May 15, 2016
End Date
April 30, 2020

In Vitro and In Situ Engineering of Fibroblasts for Cardiac Repair

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
May 20, 2016
End Date
February 29, 2020

Systemic Inflammation in Microphysiological Models of Muscle and Vascular Disease

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Co Investigator
Start Date
August 01, 2017
End Date
June 30, 2019

Translational studies of GAA deficiency in bioengineered human muscle

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
September 18, 2013
End Date
August 31, 2018

Circulatory system and integrated muscle tissue for drug and tissue toxicity

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Co Investigator
Start Date
July 24, 2012
End Date
June 30, 2018

Integrated Cellular and Tissue Engineering for Ischemic Heart Disease

Administered By
Biomedical Engineering
AwardedBy
University of Alabama at Birmingham
Role
Principal Investigator
Start Date
September 15, 2016
End Date
May 31, 2018

Bioengineering a Living Tissue Conductor

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
June 01, 2015
End Date
May 31, 2018

Skeletal Muscle Bundle Technology to qualify Human Biomarkers for Muscle Degeneration / Necrosis

Administered By
Biomedical Engineering
AwardedBy
Pfizer, Inc.
Role
Principal Investigator
Start Date
July 27, 2017
End Date
April 26, 2018

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

Effects of Chondroitin Sulfate and Chrondroitin Sulfate/Glucosamine on Muscle Immune Signaling and Function in TNF-alpha Stimulated Three Dimensional Muscle Cultures

Administered By
Biomedical Engineering
AwardedBy
Bioiberica, S.A.
Role
Co Investigator
Start Date
February 15, 2016
End Date
February 14, 2017

Functional 3D Cardiac Patches Derived from Human Induced Pluripotent Stem Cells

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
September 01, 2014
End Date
August 31, 2016

Function and Integration of Stem Cell-derived Cardiac Tissue Patch

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
July 01, 2010
End Date
April 30, 2016

Modeling Cardiac Impulse Propagation at the Microscale

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Investigator
Start Date
April 01, 2009
End Date
March 31, 2015

Mechanisms for Stem Cell Differentiation into Cardiac Myocytes

Administered By
Pediatrics, Neonatology
AwardedBy
National Institutes of Health
Role
Co Investigator
Start Date
July 15, 2009
End Date
December 31, 2011
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Publications:

Tension Creates an Endoreplication Wavefront that Leads Regeneration of Epicardial Tissue.

Mechanisms that control cell-cycle dynamics during tissue regeneration require elucidation. Here we find in zebrafish that regeneration of the epicardium, the mesothelial covering of the heart, is mediated by two phenotypically distinct epicardial cell subpopulations. These include a front of large, multinucleate leader cells, trailed by follower cells that divide to produce small, mononucleate daughters. By using live imaging of cell-cycle dynamics, we show that leader cells form by spatiotemporally regulated endoreplication, caused primarily by cytokinesis failure. Leader cells display greater velocities and mechanical tension within the epicardial tissue sheet, and experimentally induced tension anisotropy stimulates ectopic endoreplication. Unbalancing epicardial cell-cycle dynamics with chemical modulators indicated autonomous regenerative capacity in both leader and follower cells, with leaders displaying an enhanced capacity for surface coverage. Our findings provide evidence that mechanical tension can regulate cell-cycle dynamics in regenerating tissue, stratifying the source cell features to improve repair.

Authors
Cao, J; Wang, J; Jackman, CP; Cox, AH; Trembley, MA; Balowski, JJ; Cox, BD; De Simone, A; Dickson, AL; Di Talia, S; Small, EM; Kiehart, DP; Bursac, N; Poss, KD
MLA Citation
Cao, J, Wang, J, Jackman, CP, Cox, AH, Trembley, MA, Balowski, JJ, Cox, BD, De Simone, A, Dickson, AL, Di Talia, S, Small, EM, Kiehart, DP, Bursac, N, and Poss, KD. "Tension Creates an Endoreplication Wavefront that Leads Regeneration of Epicardial Tissue." Developmental cell 42.6 (September 2017): 600-615.e4.
PMID
28950101
Source
epmc
Published In
Developmental Cell
Volume
42
Issue
6
Publish Date
2017
Start Page
600
End Page
615.e4
DOI
10.1016/j.devcel.2017.08.024

Overcoming the Roadblocks to Cardiac Cell Therapy Using Tissue Engineering.

Transplantations of various stem cells or their progeny have repeatedly improved cardiac performance in animal models of myocardial injury; however, the benefits observed in clinical trials have been generally less consistent. Some of the recognized challenges are poor engraftment of implanted cells and, in the case of human cardiomyocytes, functional immaturity and lack of electrical integration, leading to limited contribution to the heart's contractile activity and increased arrhythmogenic risks. Advances in tissue and genetic engineering techniques are expected to improve the survival and integration of transplanted cells, and to support structural, functional, and bioenergetic recovery of the recipient hearts. Specifically, application of a prefabricated cardiac tissue patch to prevent dilation and to improve pumping efficiency of the infarcted heart offers a promising strategy for making stem cell therapy a clinical reality.

Authors
Yanamandala, M; Zhu, W; Garry, DJ; Kamp, TJ; Hare, JM; Jun, H-W; Yoon, Y-S; Bursac, N; Prabhu, SD; Dorn, GW; Bolli, R; Kitsis, RN; Zhang, J
MLA Citation
Yanamandala, M, Zhu, W, Garry, DJ, Kamp, TJ, Hare, JM, Jun, H-W, Yoon, Y-S, Bursac, N, Prabhu, SD, Dorn, GW, Bolli, R, Kitsis, RN, and Zhang, J. "Overcoming the Roadblocks to Cardiac Cell Therapy Using Tissue Engineering." Journal of the American College of Cardiology 70.6 (August 2017): 766-775. (Review)
PMID
28774384
Source
epmc
Published In
JACC - Journal of the American College of Cardiology
Volume
70
Issue
6
Publish Date
2017
Start Page
766
End Page
775
DOI
10.1016/j.jacc.2017.06.012

The extracellular matrix protein agrin promotes heart regeneration in mice.

The adult mammalian heart is non-regenerative owing to the post-mitotic nature of cardiomyocytes. The neonatal mouse heart can regenerate, but only during the first week of life. Here we show that changes in the composition of the extracellular matrix during this week can affect cardiomyocyte growth and differentiation in mice. We identify agrin, a component of neonatal extracellular matrix, as required for the full regenerative capacity of neonatal mouse hearts. In vitro, recombinant agrin promotes the division of cardiomyocytes that are derived from mouse and human induced pluripotent stem cells through a mechanism that involves the disassembly of the dystrophin-glycoprotein complex, and Yap- and ERK-mediated signalling. In vivo, a single administration of agrin promotes cardiac regeneration in adult mice after myocardial infarction, although the degree of cardiomyocyte proliferation observed in this model suggests that there are additional therapeutic mechanisms. Together, our results uncover a new inducer of mammalian heart regeneration and highlight fundamental roles of the extracellular matrix in cardiac repair.

Authors
Bassat, E; Mutlak, YE; Genzelinakh, A; Shadrin, IY; Baruch Umansky, K; Yifa, O; Kain, D; Rajchman, D; Leach, J; Riabov Bassat, D; Udi, Y; Sarig, R; Sagi, I; Martin, JF; Bursac, N; Cohen, S; Tzahor, E
MLA Citation
Bassat, E, Mutlak, YE, Genzelinakh, A, Shadrin, IY, Baruch Umansky, K, Yifa, O, Kain, D, Rajchman, D, Leach, J, Riabov Bassat, D, Udi, Y, Sarig, R, Sagi, I, Martin, JF, Bursac, N, Cohen, S, and Tzahor, E. "The extracellular matrix protein agrin promotes heart regeneration in mice." Nature 547.7662 (July 2017): 179-184.
PMID
28581497
Source
epmc
Published In
Nature
Volume
547
Issue
7662
Publish Date
2017
Start Page
179
End Page
184
DOI
10.1038/nature22978

Age-dependent functional crosstalk between cardiac fibroblasts and cardiomyocytes in a 3D engineered cardiac tissue.

Complex heterocellular interactions between cardiomyocytes and fibroblasts in the heart involve their bidirectional signaling via cell-cell contacts, paracrine factors, and extracellular matrix (ECM). These interactions vary with heart development and pathology leading to changes in cardiac structure and function. Whether cardiac fibroblasts of different ages interact differentially with cardiomyocytes to distinctly impact their function remains unknown. Here, we explored the direct structural and functional effects of fetal and adult cardiac fibroblasts on cardiomyocytes using a tissue-engineered 3D co-culture system. We show that the age of cardiac fibroblasts is a strong determinant of the structure, function, and molecular properties of co-cultured tissues. In particular, in vitro expanded adult, but not fetal, cardiac fibroblasts significantly deteriorated electrical and mechanical function of the co-cultured cardiomyocytes, as evidenced by slower action potential conduction, prolonged action potential duration, weaker contractions, higher tissue stiffness, and reduced calcium transient amplitude. This functional deficit was associated with structural and molecular signatures of pathological remodeling including fibroblast proliferation, interstitial collagen deposition, and upregulation of pro-fibrotic markers. Our studies imply critical roles of the age of supporting cells in engineering functional cardiac tissues and provide a new physiologically relevant in vitro platform to investigate influence of heterocellular interactions on cardiomyocyte function, development, and disease.Previous studies have shown that cardiomyocytes and fibroblasts in the heart interact through direct contacts, paracrine factors, and matrix-mediated crosstalk. However, whether cardiac fibroblasts of different ages distinctly impact cardiomyocyte function remains elusive. We employed a tissue-engineered hydrogel-based co-culture system to study interactions of cardiomyocytes with fetal or adult cardiac fibroblasts. We show that the age of cardiac fibroblasts is a strong determinant of the structure, function, and molecular properties of engineered cardiac tissues and that key features of fibrotic myocardium are replicated by supplementing cardiomyocytes with expanded adult but not fetal fibroblasts. These findings relate to implantation of stem cell-derived cardiomyocytes in adult myocardium and warrant further studies of how age and source of non-myocytes impact cardiac function and maturation.

Authors
Li, Y; Asfour, H; Bursac, N
MLA Citation
Li, Y, Asfour, H, and Bursac, N. "Age-dependent functional crosstalk between cardiac fibroblasts and cardiomyocytes in a 3D engineered cardiac tissue." Acta biomaterialia 55 (June 2017): 120-130.
PMID
28455218
Source
epmc
Published In
Acta Biomaterialia
Volume
55
Publish Date
2017
Start Page
120
End Page
130
DOI
10.1016/j.actbio.2017.04.027

Developmental stage-dependent effects of cardiac fibroblasts on function of stem cell-derived engineered cardiac tissues.

We investigated whether the developmental stage of mouse cardiac fibroblasts (CFs) influences the formation and function of engineered cardiac tissues made of mouse embryonic stem cell-derived cardiomyocytes (mESC-CMs). Engineered cardiac tissue patches were fabricated by encapsulating pure mESC-CMs, mESC-CMs + adult CFs, or mESC-CMs + fetal CFs in fibrin-based hydrogel. Tissue patches containing fetal CFs exhibited higher velocity of action potential propagation and contractile force amplitude compared to patches containing adult CFs, while pure mESC-CM patches did not form functional syncytium. The functional improvements in mESC-CM + fetal CF patches were associated with differences in structural remodeling and increased expression of proteins involved in cardiac function. To determine role of paracrine signaling, we cultured pure mESC-CMs within miniature tissue "micro-patches" supplemented with media conditioned by adult or fetal CFs. Fetal CF-conditioned media distinctly enhanced CM spreading and contractile activity, which was shown by pathway inhibitor experiments and Western blot analysis to be mediated via MEK-ERK signaling. In mESC-CM monolayers, CF-conditioned media did not alter CM spreading or MEK-ERK activation. Collectively, our studies show that 3D co-culture of mESC-CMs with embryonic CFs is superior to co-culture with adult CFs for in vitro generation of functional myocardium. Ensuring consistent developmental stages of cardiomyocytes and supporting non-myocytes may be a critical factor for promoting functional maturation of engineered cardiac tissues.

Authors
Liau, B; Jackman, CP; Li, Y; Bursac, N
MLA Citation
Liau, B, Jackman, CP, Li, Y, and Bursac, N. "Developmental stage-dependent effects of cardiac fibroblasts on function of stem cell-derived engineered cardiac tissues." Scientific Reports 7 (February 9, 2017): 42290-.
PMID
28181589
Source
epmc
Published In
Scientific Reports
Volume
7
Publish Date
2017
Start Page
42290
DOI
10.1038/srep42290

Modeling an Excitable Biosynthetic Tissue with Inherent Variability for Paired Computational-Experimental Studies.

To understand how excitable tissues give rise to arrhythmias, it is crucially necessary to understand the electrical dynamics of cells in the context of their environment. Multicellular monolayer cultures have proven useful for investigating arrhythmias and other conduction anomalies, and because of their relatively simple structure, these constructs lend themselves to paired computational studies that often help elucidate mechanisms of the observed behavior. However, tissue cultures of cardiomyocyte monolayers currently require the use of neonatal cells with ionic properties that change rapidly during development and have thus been poorly characterized and modeled to date. Recently, Kirkton and Bursac demonstrated the ability to create biosynthetic excitable tissues from genetically engineered and immortalized HEK293 cells with well-characterized electrical properties and the ability to propagate action potentials. In this study, we developed and validated a computational model of these excitable HEK293 cells (called "Ex293" cells) using existing electrophysiological data and a genetic search algorithm. In order to reproduce not only the mean but also the variability of experimental observations, we examined what sources of variation were required in the computational model. Random cell-to-cell and inter-monolayer variation in both ionic conductances and tissue conductivity was necessary to explain the experimentally observed variability in action potential shape and macroscopic conduction, and the spatial organization of cell-to-cell conductance variation was found to not impact macroscopic behavior; the resulting model accurately reproduces both normal and drug-modified conduction behavior. The development of a computational Ex293 cell and tissue model provides a novel framework to perform paired computational-experimental studies to study normal and abnormal conduction in multidimensional excitable tissue, and the methodology of modeling variation can be applied to models of any excitable cell.

Authors
Gokhale, TA; Kim, JM; Kirkton, RD; Bursac, N; Henriquez, CS
MLA Citation
Gokhale, TA, Kim, JM, Kirkton, RD, Bursac, N, and Henriquez, CS. "Modeling an Excitable Biosynthetic Tissue with Inherent Variability for Paired Computational-Experimental Studies." PLoS computational biology 13.1 (January 20, 2017): e1005342-.
Website
http://hdl.handle.net/10161/14219
PMID
28107358
Source
epmc
Published In
PLoS computational biology
Volume
13
Issue
1
Publish Date
2017
Start Page
e1005342
DOI
10.1371/journal.pcbi.1005342

Modeling an Excitable Biosynthetic Tissue with Inherent Variability for Paired Computational-Experimental Studies.

To understand how excitable tissues give rise to arrhythmias, it is crucially necessary to understand the electrical dynamics of cells in the context of their environment. Multicellular monolayer cultures have proven useful for investigating arrhythmias and other conduction anomalies, and because of their relatively simple structure, these constructs lend themselves to paired computational studies that often help elucidate mechanisms of the observed behavior. However, tissue cultures of cardiomyocyte monolayers currently require the use of neonatal cells with ionic properties that change rapidly during development and have thus been poorly characterized and modeled to date. Recently, Kirkton and Bursac demonstrated the ability to create biosynthetic excitable tissues from genetically engineered and immortalized HEK293 cells with well-characterized electrical properties and the ability to propagate action potentials. In this study, we developed and validated a computational model of these excitable HEK293 cells (called "Ex293" cells) using existing electrophysiological data and a genetic search algorithm. In order to reproduce not only the mean but also the variability of experimental observations, we examined what sources of variation were required in the computational model. Random cell-to-cell and inter-monolayer variation in both ionic conductances and tissue conductivity was necessary to explain the experimentally observed variability in action potential shape and macroscopic conduction, and the spatial organization of cell-to-cell conductance variation was found to not impact macroscopic behavior; the resulting model accurately reproduces both normal and drug-modified conduction behavior. The development of a computational Ex293 cell and tissue model provides a novel framework to perform paired computational-experimental studies to study normal and abnormal conduction in multidimensional excitable tissue, and the methodology of modeling variation can be applied to models of any excitable cell.

Authors
Gokhale, TA; Kim, JM; Kirkton, RD; Bursac, N; Henriquez, CS
MLA Citation
Gokhale, TA, Kim, JM, Kirkton, RD, Bursac, N, and Henriquez, CS. "Modeling an Excitable Biosynthetic Tissue with Inherent Variability for Paired Computational-Experimental Studies." PLoS computational biology 13.1 (January 20, 2017): e1005342-.
Website
http://hdl.handle.net/10161/14219
PMID
28107358
Source
epmc
Published In
PLoS computational biology
Volume
13
Issue
1
Publish Date
2017
Start Page
e1005342
DOI
10.1371/journal.pcbi.1005342

Genetically Encoded Photoactuators and Photosensors for Characterization and Manipulation of Pluripotent Stem Cells.

Our knowledge of pluripotent stem cell biology has advanced considerably in the past four decades, but it has yet to deliver on the great promise of regenerative medicine. The slow progress can be mainly attributed to our incomplete understanding of the complex biologic processes regulating the dynamic developmental pathways from pluripotency to fully-differentiated states of functional somatic cells. Much of the difficulty arises from our lack of specific tools to query, or manipulate, the molecular scale circuitry on both single-cell and organismal levels. Fortunately, the last two decades of progress in the field of optogenetics have produced a variety of genetically encoded, light-mediated tools that enable visualization and control of the spatiotemporal regulation of cellular function. The merging of optogenetics and pluripotent stem cell biology could thus be an important step toward realization of the clinical potential of pluripotent stem cells. In this review, we have surveyed available genetically encoded photoactuators and photosensors, a rapidly expanding toolbox, with particular attention to those with utility for studying pluripotent stem cells.

Authors
Pomeroy, JE; Nguyen, HX; Hoffman, BD; Bursac, N
MLA Citation
Pomeroy, JE, Nguyen, HX, Hoffman, BD, and Bursac, N. "Genetically Encoded Photoactuators and Photosensors for Characterization and Manipulation of Pluripotent Stem Cells." Theranostics 7.14 (January 2017): 3539-3558. (Review)
Website
http://hdl.handle.net/10161/15568
PMID
28912894
Source
epmc
Published In
Theranostics
Volume
7
Issue
14
Publish Date
2017
Start Page
3539
End Page
3558
DOI
10.7150/thno.20593

Tissue-engineered 3-dimensional (3D) microenvironment enhances the direct reprogramming of fibroblasts into cardiomyocytes by microRNAs.

We have recently shown that a combination of microRNAs, miR combo, can directly reprogram cardiac fibroblasts into functional cardiomyocytes in vitro and in vivo. Reprogramming of cardiac fibroblasts by miR combo in vivo is associated with improved cardiac function following myocardial infarction. However, the efficiency of direct reprogramming in vitro is relatively modest and new strategies beyond the traditional two-dimensional (2D) culture should be identified to improve reprogramming process. Here, we report that a tissue-engineered three-dimensional (3D) hydrogel environment enhanced miR combo reprogramming of neonatal cardiac and tail-tip fibroblasts. This was associated with significantly increased MMPs expression in 3D vs. 2D cultured cells, while pharmacological inhibition of MMPs blocked the effect of the 3D culture on enhanced miR combo mediated reprogramming. We conclude that 3D tissue-engineered environment can enhance the direct reprogramming of fibroblasts to cardiomyocytes via a MMP-dependent mechanism.

Authors
Li, Y; Dal-Pra, S; Mirotsou, M; Jayawardena, TM; Hodgkinson, CP; Bursac, N; Dzau, VJ
MLA Citation
Li, Y, Dal-Pra, S, Mirotsou, M, Jayawardena, TM, Hodgkinson, CP, Bursac, N, and Dzau, VJ. "Tissue-engineered 3-dimensional (3D) microenvironment enhances the direct reprogramming of fibroblasts into cardiomyocytes by microRNAs." Scientific reports 6 (December 12, 2016): 38815-.
PMID
27941896
Source
epmc
Published In
Scientific Reports
Volume
6
Publish Date
2016
Start Page
38815
DOI
10.1038/srep38815

Dynamic culture yields engineered myocardium with near-adult functional output.

Engineered cardiac tissues hold promise for cell therapy and drug development, but exhibit inadequate function and maturity. In this study, we sought to significantly improve the function and maturation of rat and human engineered cardiac tissues. We developed dynamic, free-floating culture conditions for engineering "cardiobundles", 3-dimensional cylindrical tissues made from neonatal rat cardiomyocytes or human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) embedded in fibrin-based hydrogel. Compared to static culture, 2-week dynamic culture of neonatal rat cardiobundles significantly increased expression of sarcomeric proteins, cardiomyocyte size (∼2.1-fold), contractile force (∼3.5-fold), and conduction velocity of action potentials (∼1.4-fold). The average contractile force per cross-sectional area (59.7 mN/mm(2)) and conduction velocity (52.5 cm/s) matched or approached those of adult rat myocardium, respectively. The inferior function of statically cultured cardiobundles was rescued by transfer to dynamic conditions, which was accompanied by an increase in mTORC1 activity and decline in AMPK phosphorylation and was blocked by rapamycin. Furthermore, dynamic culture effects did not stimulate ERK1/2 pathway and were insensitive to blockers of mechanosensitive channels, suggesting increased nutrient availability rather than mechanical stimulation as the upstream activator of mTORC1. Direct comparison with phenylephrine treatment confirmed that dynamic culture promoted physiological cardiomyocyte growth rather than pathological hypertrophy. Optimized dynamic culture conditions also augmented function of human cardiobundles made reproducibly from cardiomyocytes derived from multiple hPSC lines, resulting in significantly increased contraction force (∼2.5-fold) and conduction velocity (∼1.4-fold). The average specific force of 23.2 mN/mm(2) and conduction velocity of 25.8 cm/s approached the functional metrics of adult human myocardium. In conclusion, we have developed a versatile methodology for engineering cardiac tissues with a near-adult functional output without the need for exogenous electrical or mechanical stimulation, and have identified mTOR signaling as an important mechanism for advancing tissue maturation and function in vitro.

Authors
Jackman, CP; Carlson, AL; Bursac, N
MLA Citation
Jackman, CP, Carlson, AL, and Bursac, N. "Dynamic culture yields engineered myocardium with near-adult functional output." Biomaterials 111 (December 2016): 66-79.
PMID
27723557
Source
epmc
Published In
Biomaterials
Volume
111
Publish Date
2016
Start Page
66
End Page
79
DOI
10.1016/j.biomaterials.2016.09.024

Striated muscle function, regeneration, and repair.

As the only striated muscle tissues in the body, skeletal and cardiac muscle share numerous structural and functional characteristics, while exhibiting vastly different size and regenerative potential. Healthy skeletal muscle harbors a robust regenerative response that becomes inadequate after large muscle loss or in degenerative pathologies and aging. In contrast, the mammalian heart loses its regenerative capacity shortly after birth, leaving it susceptible to permanent damage by acute injury or chronic disease. In this review, we compare and contrast the physiology and regenerative potential of native skeletal and cardiac muscles, mechanisms underlying striated muscle dysfunction, and bioengineering strategies to treat muscle disorders. We focus on different sources for cellular therapy, biomaterials to augment the endogenous regenerative response, and progress in engineering and application of mature striated muscle tissues in vitro and in vivo. Finally, we discuss the challenges and perspectives in translating muscle bioengineering strategies to clinical practice.

Authors
Shadrin, IY; Khodabukus, A; Bursac, N
MLA Citation
Shadrin, IY, Khodabukus, A, and Bursac, N. "Striated muscle function, regeneration, and repair." Cellular and molecular life sciences : CMLS 73.22 (November 2016): 4175-4202. (Review)
PMID
27271751
Source
epmc
Published In
Cellular and Molecular Life Sciences
Volume
73
Issue
22
Publish Date
2016
Start Page
4175
End Page
4202
DOI
10.1007/s00018-016-2285-z

Engineering prokaryotic channels for control of mammalian tissue excitability.

The ability to directly enhance electrical excitability of human cells is hampered by the lack of methods to efficiently overexpress large mammalian voltage-gated sodium channels (VGSC). Here we describe the use of small prokaryotic sodium channels (BacNav) to create de novo excitable human tissues and augment impaired action potential conduction in vitro. Lentiviral co-expression of specific BacNav orthologues, an inward-rectifying potassium channel, and connexin-43 in primary human fibroblasts from the heart, skin or brain yields actively conducting cells with customizable electrophysiological phenotypes. Engineered fibroblasts ('E-Fibs') retain stable functional properties following extensive subculture or differentiation into myofibroblasts and rescue conduction slowing in an in vitro model of cardiac interstitial fibrosis. Co-expression of engineered BacNav with endogenous mammalian VGSCs enhances action potential conduction and prevents conduction failure during depolarization by elevated extracellular K(+), decoupling or ischaemia. These studies establish the utility of engineered BacNav channels for induction, control and recovery of mammalian tissue excitability.

Authors
Nguyen, HX; Kirkton, RD; Bursac, N
MLA Citation
Nguyen, HX, Kirkton, RD, and Bursac, N. "Engineering prokaryotic channels for control of mammalian tissue excitability." Nature communications 7 (October 18, 2016): 13132-.
PMID
27752065
Source
epmc
Published In
Nature Communications
Volume
7
Publish Date
2016
Start Page
13132
DOI
10.1038/ncomms13132

Distilling complexity to advance cardiac tissue engineering.

The promise of cardiac tissue engineering is in the ability to recapitulate in vitro the functional aspects of a healthy heart and disease pathology as well as to design replacement muscle for clinical therapy. Parts of this promise have been realized; others have not. In a meeting of scientists in this field, five central challenges or "big questions" were articulated that, if addressed, could substantially advance the current state of the art in modeling heart disease and realizing heart repair.

Authors
Ogle, BM; Bursac, N; Domian, I; Huang, NF; Menasché, P; Murry, CE; Pruitt, B; Radisic, M; Wu, JC; Wu, SM; Zhang, J; Zimmermann, W-H; Vunjak-Novakovic, G
MLA Citation
Ogle, BM, Bursac, N, Domian, I, Huang, NF, Menasché, P, Murry, CE, Pruitt, B, Radisic, M, Wu, JC, Wu, SM, Zhang, J, Zimmermann, W-H, and Vunjak-Novakovic, G. "Distilling complexity to advance cardiac tissue engineering." Science translational medicine 8.342 (June 2016): 342ps13-. (Review)
PMID
27280684
Source
epmc
Published In
Science Translational Medicine
Volume
8
Issue
342
Publish Date
2016
Start Page
342ps13
DOI
10.1126/scitranslmed.aad2304

Design, evaluation, and application of engineered skeletal muscle.

For over two decades, research groups have been developing methods to engineer three-dimensional skeletal muscle tissues. These tissues hold great promise for use in disease modeling and pre-clinical drug development, and have potential to serve as therapeutic grafts for functional muscle repair. Recent advances in the field have resulted in the engineering of regenerative muscle constructs capable of survival, vascularization, and functional maturation in vivo as well as the first-time creation of functional human engineered muscles for screening of therapeutics in vitro. In this review, we will discuss the methodologies that have progressed work in the muscle tissue engineering field to its current state. The emphasis will be placed on the existing procedures to generate myogenic cell sources and form highly functional muscle tissues in vitro, techniques to monitor and evaluate muscle maturation and performance in vitro and in vivo, and surgical strategies to both create diseased environments and ensure implant survival and rapid integration into the host. Finally, we will suggest the most promising methodologies that will enable continued progress in the field.

Authors
Juhas, M; Ye, J; Bursac, N
MLA Citation
Juhas, M, Ye, J, and Bursac, N. "Design, evaluation, and application of engineered skeletal muscle." Methods (San Diego, Calif.) 99 (April 2016): 81-90. (Review)
PMID
26455485
Source
epmc
Published In
Methods
Volume
99
Publish Date
2016
Start Page
81
End Page
90
DOI
10.1016/j.ymeth.2015.10.002

Cell Density and Joint microRNA-133a and microRNA-696 Inhibition Enhance Differentiation and Contractile Function of Engineered Human Skeletal Muscle Tissues.

To utilize three-dimensional (3D) engineered human skeletal muscle tissue for translational studies and in vitro studies of drug toxicity, there is a need to promote differentiation and functional behavior. In this study, we identified conditions to promote contraction of engineered human skeletal muscle bundles and examined the effects of transient inhibition of microRNAs (miRs) on myogenic differentiation and function of two-dimensional (2D) and 3D cultures of human myotubes. In 2D cultures, simultaneously inhibiting both miR-133a, which promotes myoblast proliferation, and miR-696, which represses oxidative metabolism, resulted in an increase in sarcomeric α-actinin protein and the metabolic coactivator PGC-1α protein compared to transfection with a scrambled miR sequence (negative control). Although PGC-1α was elevated following joint inhibition of miRs 133a and 696, there was no difference in myosin heavy chain (MHC) protein isoforms. 3D engineered human skeletal muscle myobundles seeded with 5 × 10(6) human skeletal myoblasts (HSkM)/mL and cultured for 2 weeks after onset of differentiation consistently did not contract when stimulated electrically, whereas those seeded with myoblasts at 10 × 10(6) HSkM/mL or higher did contract. When HSkM were transfected with both anti-miRs and seeded into fibrin hydrogels and cultured for 2 weeks under static conditions, twitch and tetanic specific forces after electrical stimulation were greater than for myobundles prepared with HSkM transfected with scrambled sequences. Immunofluorescence and Western blots of 3D myobundles indicate that anti-miR-133a or anti-miR-696 treatment led to modest increases in slow MHC, but no consistent increase in fast MHC. Similar to results in 2D, only myobundles prepared with myoblasts treated with anti-miR-133a and anti-miR-696 produced an increase in PGC-1α mRNA. PGC-1α targets were differentially affected by the treatment. HIF-2α mRNA showed an expression pattern similar to that of PGC-1α mRNA, but COXII mRNA levels were not affected by the anti-miRs. Overall, joint inhibition of miR-133a and miR-696 accelerated differentiation, elevated the metabolic coactivator PGC-1α, and increased the contractile force in 3D engineered human skeletal muscle bundles.

Authors
Cheng, CS; Ran, L; Bursac, N; Kraus, WE; Truskey, GA
MLA Citation
Cheng, CS, Ran, L, Bursac, N, Kraus, WE, and Truskey, GA. "Cell Density and Joint microRNA-133a and microRNA-696 Inhibition Enhance Differentiation and Contractile Function of Engineered Human Skeletal Muscle Tissues." Tissue engineering. Part A 22.7-8 (April 2016): 573-583.
PMID
26891613
Source
epmc
Published In
Tissue Engineering, Part A
Volume
22
Issue
7-8
Publish Date
2016
Start Page
573
End Page
583
DOI
10.1089/ten.tea.2015.0359

PGE - Product generation engineering - Case study of the dual mass flywheel

Authors
Albers, A; Bursac, N; Rapp, S
MLA Citation
Albers, A, Bursac, N, and Rapp, S. "PGE - Product generation engineering - Case study of the dual mass flywheel." January 1, 2016.
Source
scopus
Published In
Proceedings of International Design Conference, DESIGN
Volume
DS 84
Publish Date
2016
Start Page
791
End Page
800

STIM1-Ca2+ signaling modulates automaticity of the mouse sinoatrial node.

Cardiac pacemaking is governed by specialized cardiomyocytes located in the sinoatrial node (SAN). SAN cells (SANCs) integrate voltage-gated currents from channels on the membrane surface (membrane clock) with rhythmic Ca(2+) release from internal Ca(2+) stores (Ca(2+) clock) to adjust heart rate to meet hemodynamic demand. Here, we report that stromal interaction molecule 1 (STIM1) and Orai1 channels, key components of store-operated Ca(2+) entry, are selectively expressed in SANCs. Cardiac-specific deletion of STIM1 in mice resulted in depletion of sarcoplasmic reticulum (SR) Ca(2+) stores of SANCs and led to SAN dysfunction, as was evident by a reduction in heart rate, sinus arrest, and an exaggerated autonomic response to cholinergic signaling. Moreover, STIM1 influenced SAN function by regulating ionic fluxes in SANCs, including activation of a store-operated Ca(2+) current, a reduction in L-type Ca(2+) current, and enhancing the activities of Na(+)/Ca(2+) exchanger. In conclusion, these studies reveal that STIM1 is a multifunctional regulator of Ca(2+) dynamics in SANCs that links SR Ca(2+) store content with electrical events occurring in the plasma membrane, thereby contributing to automaticity of the SAN.

Authors
Zhang, H; Sun, AY; Kim, JJ; Graham, V; Finch, EA; Nepliouev, I; Zhao, G; Li, T; Lederer, WJ; Stiber, JA; Pitt, GS; Bursac, N; Rosenberg, PB
MLA Citation
Zhang, H, Sun, AY, Kim, JJ, Graham, V, Finch, EA, Nepliouev, I, Zhao, G, Li, T, Lederer, WJ, Stiber, JA, Pitt, GS, Bursac, N, and Rosenberg, PB. "STIM1-Ca2+ signaling modulates automaticity of the mouse sinoatrial node." October 2015.
PMID
26424448
Source
epmc
Published In
Proceedings of the National Academy of Sciences of USA
Volume
112
Issue
41
Publish Date
2015
Start Page
E5618
End Page
E5627
DOI
10.1073/pnas.1503847112

Engineering Regenerative Skeletal Muscle Tissues

Authors
Juhas, M; Wang, J; Ye, J; Shadrin, I; Bursac, N
MLA Citation
Juhas, M, Wang, J, Ye, J, Shadrin, I, and Bursac, N. "Engineering Regenerative Skeletal Muscle Tissues." September 1, 2015.
Source
wos-lite
Published In
Tissue Engineering, Part A
Volume
21
Publish Date
2015
Start Page
S310
End Page
S310

Novel In Vitro Exercise Model of Engineered Human Skeletal Muscle

Authors
Madden, L; Jackman, C; Wang, J; Kraus, W; Truskey, G; Bursac, N
MLA Citation
Madden, L, Jackman, C, Wang, J, Kraus, W, Truskey, G, and Bursac, N. "Novel In Vitro Exercise Model of Engineered Human Skeletal Muscle." September 1, 2015.
Source
wos-lite
Published In
Tissue Engineering, Part A
Volume
21
Publish Date
2015
Start Page
S46
End Page
S46

Rapid fusion between mesenchymal stem cells and cardiomyocytes yields electrically active, non-contractile hybrid cells.

Cardiac cell therapies involving bone marrow-derived human mesenchymal stem cells (hMSCs) have shown promising results, although their mechanisms of action are still poorly understood. Here, we investigated direct interactions between hMSCs and cardiomyocytes in vitro. Using a genetic Ca(2+) indicator gCaMP3 to efficiently label hMSCs in co-cultures with neonatal rat ventricular myocytes (NRVMs), we determined that 25-40% of hMSCs (from 4 independent donors) acquired periodic Ca(2+) transients and cardiac markers through spontaneous fusion with NRVMs. Sharp electrode and voltage-clamp recordings in fused cells showed action potential properties and Ca(2+) current amplitudes in between those of non-fused hMSCs and NRVMs. Time-lapse video-microscopy revealed the first direct evidence of active fusion between hMSCs and NRVMs within several hours of co-culture. Application of blebbistatin, nifedipine or verapamil caused complete and reversible inhibition of fusion, suggesting potential roles for actomyosin bridging and Ca(2+) channels in the fusion process. Immunostaining for Cx43, Ki67, and sarcomeric α-actinin showed that fused cells remain strongly coupled to surrounding NRVMs, but downregulate sarcomeric structures over time, acquiring a non-proliferative and non-contractile phenotype. Overall, these results describe the phenotype and mechanisms of hybrid cell formation via fusion of hMSCs and cardiomyocytes with potential implications for cardiac cell therapy.

Authors
Shadrin, IY; Yoon, W; Li, L; Shepherd, N; Bursac, N
MLA Citation
Shadrin, IY, Yoon, W, Li, L, Shepherd, N, and Bursac, N. "Rapid fusion between mesenchymal stem cells and cardiomyocytes yields electrically active, non-contractile hybrid cells." Scientific Reports 5 (July 10, 2015): 12043-.
PMID
26159124
Source
epmc
Published In
Scientific Reports
Volume
5
Publish Date
2015
Start Page
12043
DOI
10.1038/srep12043

BIOENGINEERED HUMAN MUSCLE FOR PHYSIOLOGICAL STUDIES AND DISEASE MODELING

Authors
Madden, L; Koeberl, D; Bursac, N
MLA Citation
Madden, L, Koeberl, D, and Bursac, N. "BIOENGINEERED HUMAN MUSCLE FOR PHYSIOLOGICAL STUDIES AND DISEASE MODELING." March 2015.
Source
wos-lite
Published In
Molecular Genetics and Metabolism
Volume
114
Issue
3
Publish Date
2015
Start Page
304
End Page
305

Human Cardiac Tissue Engineering: From Pluripotent Stem Cells to Heart Repair.

Engineered cardiac tissues hold great promise for use in drug and toxicology screening, in vitro studies of human physiology and disease, and as transplantable tissue grafts for myocardial repair. In this review, we discuss recent progress in cell-based therapy and functional tissue engineering using pluripotent stem cell-derived cardiomyocytes and we describe methods for delivery of cells into the injured heart. While significant hurdles remain, notable advances have been made in the methods to derive large numbers of pure human cardiomyocytes, mature their phenotype, and produce and implant functional cardiac tissues, bringing the field a step closer to widespread in vitro and in vivo applications.

Authors
Jackman, CP; Shadrin, IY; Carlson, AL; Bursac, N
MLA Citation
Jackman, CP, Shadrin, IY, Carlson, AL, and Bursac, N. "Human Cardiac Tissue Engineering: From Pluripotent Stem Cells to Heart Repair." Current opinion in chemical engineering 7 (February 2015): 57-64.
PMID
25599018
Source
epmc
Published In
Current Opinion in Chemical Engineering
Volume
7
Publish Date
2015
Start Page
57
End Page
64
DOI
10.1016/j.coche.2014.11.004

Stoichiometry of Gata4, Mef2c, and Tbx5 influences the efficiency and quality of induced cardiac myocyte reprogramming

RATIONALE:: Generation of induced cardiac myocytes (iCMs) directly from fibroblasts offers great opportunities for cardiac disease modeling and cardiac regeneration. A major challenge of iCM generation is the low conversion rate of fibroblasts to fully reprogrammed iCMs, which could in part be attributed to unbalanced expression of reprogramming factors Gata4 (G), Mef2c (M), and Tbx5 (T) using the current gene delivery approach. OBJECTIVE:: We aimed to establish a system to express distinct ratios of G, M, T proteins in fibroblasts and determine the effect of G, M, T stoichiometry on iCM reprogramming. METHODS AND RESULTS:: We took advantage of the inherent feature of the polycistronic system and generated all possible combinations of G, M, T with identical 2A sequences in a single transgene. We demonstrated that each splicing order of G, M, T gave rise to distinct G, M, T protein expression levels. Combinations that resulted in higher protein level of Mef2c with lower levels of Gata4 and Tbx5 significantly enhanced reprogramming efficiency compared with separate G, M, T transduction. Importantly, after further optimization, the MGT vector resulted in more than 10-fold increase in the number of mature beating iCM loci. Molecular characterization revealed that more optimal G, M, T stoichiometry correlated with higher expression of mature cardiac myocyte markers. CONCLUSIONS:: Our results demonstrate that stoichiometry of G, M, T protein expression influences the efficiency and quality of iCM reprogramming. The established optimal G, M, T expression condition will provide a valuable platform for future iCM studies.

Authors
Wang, L; Liu, Z; Yin, C; Asfour, H; Chen, O; Li, Y; Bursac, N; Liu, J; Qian, L
MLA Citation
Wang, L, Liu, Z, Yin, C, Asfour, H, Chen, O, Li, Y, Bursac, N, Liu, J, and Qian, L. "Stoichiometry of Gata4, Mef2c, and Tbx5 influences the efficiency and quality of induced cardiac myocyte reprogramming." Circulation Research 116.2 (January 16, 2015): 237-244.
Source
scopus
Published In
Circulation Research
Volume
116
Issue
2
Publish Date
2015
Start Page
237
End Page
244
DOI
10.1161/CIRCRESAHA.116.305547

Bioengineered human myobundles mimic clinical responses of skeletal muscle to drugs.

Existing in vitro models of human skeletal muscle cannot recapitulate the organization and function of native muscle, limiting their use in physiological and pharmacological studies. Here, we demonstrate engineering of electrically and chemically responsive, contractile human muscle tissues ('myobundles') using primary myogenic cells. These biomimetic constructs exhibit aligned architecture, multinucleated and striated myofibers, and a Pax7(+) cell pool. They contract spontaneously and respond to electrical stimuli with twitch and tetanic contractions. Positive correlation between contractile force and GCaMP6-reported calcium responses enables non-invasive tracking of myobundle function and drug response. During culture, myobundles maintain functional acetylcholine receptors and structurally and functionally mature, evidenced by increased myofiber diameter and improved calcium handling and contractile strength. In response to diversely acting drugs, myobundles undergo dose-dependent hypertrophy or toxic myopathy similar to clinical outcomes. Human myobundles provide an enabling platform for predictive drug and toxicology screening and development of novel therapeutics for muscle-related disorders.

Authors
Madden, L; Juhas, M; Kraus, WE; Truskey, GA; Bursac, N
MLA Citation
Madden, L, Juhas, M, Kraus, WE, Truskey, GA, and Bursac, N. "Bioengineered human myobundles mimic clinical responses of skeletal muscle to drugs." eLife 4 (January 9, 2015): e04885-.
Website
http://hdl.handle.net/10161/9364
PMID
25575180
Source
epmc
Published In
eLife
Volume
4
Publish Date
2015
Start Page
e04885
DOI
10.7554/elife.04885

Stoichiometry of Gata4, Mef2c, and Tbx5 influences the efficiency and quality of induced cardiac myocyte reprogramming

© 2014 American Heart Association, Inc. RATIONALE:: Generation of induced cardiac myocytes (iCMs) directly from fibroblasts offers great opportunities for cardiac disease modeling and cardiac regeneration. A major challenge of iCM generation is the low conversion rate of fibroblasts to fully reprogrammed iCMs, which could in part be attributed to unbalanced expression of reprogramming factors Gata4 (G), Mef2c (M), and Tbx5 (T) using the current gene delivery approach. OBJECTIVE:: We aimed to establish a system to express distinct ratios of G, M, T proteins in fibroblasts and determine the effect of G, M, T stoichiometry on iCM reprogramming. METHODS AND RESULTS:: We took advantage of the inherent feature of the polycistronic system and generated all possible combinations of G, M, T with identical 2A sequences in a single transgene. We demonstrated that each splicing order of G, M, T gave rise to distinct G, M, T protein expression levels. Combinations that resulted in higher protein level of Mef2c with lower levels of Gata4 and Tbx5 significantly enhanced reprogramming efficiency compared with separate G, M, T transduction. Importantly, after further optimization, the MGT vector resulted in more than 10-fold increase in the number of mature beating iCM loci. Molecular characterization revealed that more optimal G, M, T stoichiometry correlated with higher expression of mature cardiac myocyte mar kers. CONCLUSIONS:: Our results demonstrate that stoichiometry of G, M, T protein expression influences the efficiency and quality of iCM reprogramming. The established optimal G, M, T expression condition will provide a valuable platform for future iCM studies.

Authors
Wang, L; Liu, Z; Yin, C; Asfour, H; Chen, O; Li, Y; Bursac, N; Liu, J; Qian, L
MLA Citation
Wang, L, Liu, Z, Yin, C, Asfour, H, Chen, O, Li, Y, Bursac, N, Liu, J, and Qian, L. "Stoichiometry of Gata4, Mef2c, and Tbx5 influences the efficiency and quality of induced cardiac myocyte reprogramming." Circulation Research 116.2 (January 1, 2015): 237-244.
Source
scopus
Published In
Circulation Research
Volume
116
Issue
2
Publish Date
2015
Start Page
237
End Page
244
DOI
10.1161/CIRCRESAHA.116.305547

Stoichiometry of Gata4, Mef2c, and Tbx5 influences the efficiency and quality of induced cardiac myocyte reprogramming.

Generation of induced cardiac myocytes (iCMs) directly from fibroblasts offers great opportunities for cardiac disease modeling and cardiac regeneration. A major challenge of iCM generation is the low conversion rate of fibroblasts to fully reprogrammed iCMs, which could in part be attributed to unbalanced expression of reprogramming factors Gata4 (G), Mef2c (M), and Tbx5 (T) using the current gene delivery approach.We aimed to establish a system to express distinct ratios of G, M, T proteins in fibroblasts and determine the effect of G, M, T stoichiometry on iCM reprogramming.We took advantage of the inherent feature of the polycistronic system and generated all possible combinations of G, M, T with identical 2A sequences in a single transgene. We demonstrated that each splicing order of G, M, T gave rise to distinct G, M, T protein expression levels. Combinations that resulted in higher protein level of Mef2c with lower levels of Gata4 and Tbx5 significantly enhanced reprogramming efficiency compared with separate G, M, T transduction. Importantly, after further optimization, the MGT vector resulted in more than 10-fold increase in the number of mature beating iCM loci. Molecular characterization revealed that more optimal G, M, T stoichiometry correlated with higher expression of mature cardiac myocyte markers.Our results demonstrate that stoichiometry of G, M, T protein expression influences the efficiency and quality of iCM reprogramming. The established optimal G, M, T expression condition will provide a valuable platform for future iCM studies.

Authors
Wang, L; Liu, Z; Yin, C; Asfour, H; Chen, O; Li, Y; Bursac, N; Liu, J; Qian, L
MLA Citation
Wang, L, Liu, Z, Yin, C, Asfour, H, Chen, O, Li, Y, Bursac, N, Liu, J, and Qian, L. "Stoichiometry of Gata4, Mef2c, and Tbx5 influences the efficiency and quality of induced cardiac myocyte reprogramming." Circulation research 116.2 (January 2015): 237-244.
PMID
25416133
Source
epmc
Published In
Circulation Research
Volume
116
Issue
2
Publish Date
2015
Start Page
237
End Page
244
DOI
10.1161/circresaha.116.305547

Synergizing Engineering and Biology to Treat and Model Skeletal Muscle Injury and Disease.

Although skeletal muscle is one of the most regenerative organs in our body, various genetic defects, alterations in extrinsic signaling, or substantial tissue damage can impair muscle function and the capacity for self-repair. The diversity and complexity of muscle disorders have attracted much interest from both cell biologists and, more recently, bioengineers, leading to concentrated efforts to better understand muscle pathology and develop more efficient therapies. This review describes the biological underpinnings of muscle development, repair, and disease, and discusses recent bioengineering efforts to design and control myomimetic environments, both to study muscle biology and function and to aid in the development of new drug, cell, and gene therapies for muscle disorders. The synergy between engineering-aided biological discovery and biology-inspired engineering solutions will be the path forward for translating laboratory results into clinical practice.

Authors
Bursac, N; Juhas, M; Rando, TA
MLA Citation
Bursac, N, Juhas, M, and Rando, TA. "Synergizing Engineering and Biology to Treat and Model Skeletal Muscle Injury and Disease." Annual review of biomedical engineering 17 (January 2015): 217-242. (Review)
PMID
26643021
Source
epmc
Published In
Annual Review of Biomedical Engineering
Volume
17
Publish Date
2015
Start Page
217
End Page
242
DOI
10.1146/annurev-bioeng-071114-040640

Roles of adherent myogenic cells and dynamic culture in engineered muscle function and maintenance of satellite cells.

Highly functional engineered skeletal muscle constructs could serve as physiological models of muscle function and regeneration and have utility in therapeutic replacement of damaged or diseased muscle tissue. In this study, we examined the roles of different myogenic cell fractions and culturing conditions in the generation of highly functional engineered muscle. Fibrin-based muscle bundles were fabricated using either freshly-isolated myogenic cells or their adherent fraction pre-cultured for 36 h. Muscle bundles made of these cells were cultured in both static and dynamic conditions and systematically characterized with respect to early myogenic events and contractile function. Following 2 weeks of culture, we observed both individual and synergistic benefits of using the adherent cell fraction and dynamic culture on muscle formation and function. In particular, optimal culture conditions resulted in significant increase in the total cross-sectional muscle area (- 3-fold), myofiber size (- 1.6-fold), myonuclei density (- 1.2-fold), and force generation (- 9-fold) compared to traditional use of freshly-isolated cells and static culture. Curiously, we observed that only a simultaneous use of the adherent cell fraction and dynamic culture resulted in accelerated formation of differentiated myofibers which were critical for providing a niche-like environment for maintenance of a satellite cell pool early during culture. Our study identifies key parameters for engineering large-size, highly functional skeletal muscle tissues with improved ability for retention of functional satellite cells.

Authors
Juhas, M; Bursac, N
MLA Citation
Juhas, M, and Bursac, N. "Roles of adherent myogenic cells and dynamic culture in engineered muscle function and maintenance of satellite cells." Biomaterials 35.35 (November 2014): 9438-9446.
PMID
25154662
Source
epmc
Published In
Biomaterials
Volume
35
Issue
35
Publish Date
2014
Start Page
9438
End Page
9446
DOI
10.1016/j.biomaterials.2014.07.035

Physiology and metabolism of tissue-engineered skeletal muscle.

Skeletal muscle is a major target for tissue engineering, given its relative size in the body, fraction of cardiac output that passes through muscle beds, as well as its key role in energy metabolism and diabetes, and the need for therapies for muscle diseases such as muscular dystrophy and sarcopenia. To date, most studies with tissue-engineered skeletal muscle have utilized murine and rat cell sources. On the other hand, successful engineering of functional human muscle would enable different applications including improved methods for preclinical testing of drugs and therapies. Some of the requirements for engineering functional skeletal muscle include expression of adult forms of muscle proteins, comparable contractile forces to those produced by native muscle, and physiological force-length and force-frequency relations. This review discusses the various strategies and challenges associated with these requirements, specific applications with cultured human myoblasts, and future directions.

Authors
Cheng, CS; Davis, BNJ; Madden, L; Bursac, N; Truskey, GA
MLA Citation
Cheng, CS, Davis, BNJ, Madden, L, Bursac, N, and Truskey, GA. "Physiology and metabolism of tissue-engineered skeletal muscle." Experimental biology and medicine (Maywood, N.J.) 239.9 (September 2014): 1203-1214. (Review)
PMID
24912506
Source
epmc
Published In
Experimental biology and medicine (Maywood, N.J.)
Volume
239
Issue
9
Publish Date
2014
Start Page
1203
End Page
1214
DOI
10.1177/1535370214538589

Use of flow, electrical, and mechanical stimulation to promote engineering of striated muscles.

The field of tissue engineering involves design of high-fidelity tissue substitutes for predictive experimental assays in vitro and cell-based regenerative therapies in vivo. Design of striated muscle tissues, such as cardiac and skeletal muscle, has been particularly challenging due to a high metabolic demand and complex cellular organization and electromechanical function of the native tissues. Successful engineering of highly functional striated muscles may thus require creation of biomimetic culture conditions involving medium perfusion, electrical and mechanical stimulation. When optimized, these external cues are expected to synergistically and dynamically activate important intracellular signaling pathways leading to accelerated muscle growth and development. This review will discuss the use of different types of tissue culture bioreactors aimed at providing conditions for enhanced structural and functional maturation of engineered striated muscles.

Authors
Rangarajan, S; Madden, L; Bursac, N
MLA Citation
Rangarajan, S, Madden, L, and Bursac, N. "Use of flow, electrical, and mechanical stimulation to promote engineering of striated muscles." Ann Biomed Eng 42.7 (July 2014): 1391-1405. (Review)
PMID
24366526
Source
pubmed
Published In
Annals of Biomedical Engineering
Volume
42
Issue
7
Publish Date
2014
Start Page
1391
End Page
1405
DOI
10.1007/s10439-013-0966-4

Introduction to the special issue on tissue engineering and regenerative medicine.

Authors
Hsiai, T; Li, S; Bursac, N
MLA Citation
Hsiai, T, Li, S, and Bursac, N. "Introduction to the special issue on tissue engineering and regenerative medicine." Annals of biomedical engineering 42.7 (July 2014): 1355-1356.
PMID
24923380
Source
epmc
Published In
Annals of Biomedical Engineering
Volume
42
Issue
7
Publish Date
2014
Start Page
1355
End Page
1356
DOI
10.1007/s10439-014-1053-1

Cardiac fibroblasts in pressure overload hypertrophy: the enemy within?

Cardiac fibroblasts have been long recognized as active participants in heart disease; however, their exact physiological and pathological roles remain elusive, mainly due to the lack of specific markers. In this issue of the JCI, Moore-Morris and colleagues used a fibroblast-specific collagen1a1-GFP reporter to demonstrate that fibroblast accumulation after aortic banding in murine hearts arises almost exclusively from proliferation of resident fibroblasts originating from both the epicardium and a previously unrecognized source, the endocardium. Further characterization of fibroblast origin and function in different types and stages of heart disease could lead to development of improved fibroblast-targeted cardiac therapies.

Authors
Bursac, N
MLA Citation
Bursac, N. "Cardiac fibroblasts in pressure overload hypertrophy: the enemy within?." The Journal of clinical investigation 124.7 (July 2014): 2850-2853.
PMID
24937423
Source
epmc
Published In
Journal of Clinical Investigation
Volume
124
Issue
7
Publish Date
2014
Start Page
2850
End Page
2853
DOI
10.1172/jci76628

Introduction to the Special Issue on Tissue Engineering and Regenerative Medicine

Authors
Hsiai, T; Li, S; Bursac, N
MLA Citation
Hsiai, T, Li, S, and Bursac, N. "Introduction to the Special Issue on Tissue Engineering and Regenerative Medicine." Annals of Biomedical Engineering 42.7 (July 2014): 1355-1356.
Source
crossref
Published In
Annals of Biomedical Engineering
Volume
42
Issue
7
Publish Date
2014
Start Page
1355
End Page
1356
DOI
10.1007/s10439-014-1053-1

Controlling the structural and functional anisotropy of engineered cardiac tissues.

The ability to control the degree of structural and functional anisotropy in 3D engineered cardiac tissues would have high utility for both in vitro studies of cardiac muscle physiology and pathology as well as potential tissue engineering therapies for myocardial infarction. Here, we applied a high aspect ratio soft lithography technique to generate network-like tissue patches seeded with neonatal rat cardiomyocytes. Fabricating longer elliptical pores within the patch networks increased the overall cardiomyocyte and extracellular matrix alignment within the patch. Improved uniformity of cell and matrix alignment yielded an increase in anisotropy of action potential propagation and faster longitudinal conduction velocity (LCV). Cardiac tissue patches with a higher degree of cardiomyocyte alignment and electrical anisotropy also demonstrated greater isometric twitch forces. After two weeks of culture, specific measures of electrical and contractile function (LCV = 26.8 ± 0.8 cm s(-1), specific twitch force = 8.9 ± 1.1 mN mm(-2) for the longest pores studied) were comparable to those of neonatal rat myocardium. We have thus described methodology for engineering of highly functional 3D engineered cardiac tissues with controllable degree of anisotropy.

Authors
Bian, W; Jackman, CP; Bursac, N
MLA Citation
Bian, W, Jackman, CP, and Bursac, N. "Controlling the structural and functional anisotropy of engineered cardiac tissues." Biofabrication 6.2 (June 2014): 24109-24109.
PMID
24717534
Source
epmc
Published In
Biofabrication
Volume
6
Issue
2
Publish Date
2014
Start Page
24109
End Page
24109
DOI
10.1088/1758-5082/6/2/024109

Adjunctive β2-agonist treatment reduces glycogen independently of receptor-mediated acid α-glucosidase uptake in the limb muscles of mice with Pompe disease.

Enzyme or gene replacement therapy with acid α-glucosidase (GAA) has achieved only partial efficacy in Pompe disease. We evaluated the effect of adjunctive clenbuterol treatment on cation-independent mannose-6-phosphate receptor (CI-MPR)-mediated uptake and intracellular trafficking of GAA during muscle-specific GAA expression with an adeno-associated virus (AAV) vector in GAA-knockout (KO) mice. Clenbuterol, which increases expression of CI-MPR in muscle, was administered with the AAV vector. This combination therapy increased latency during rotarod and wirehang testing at 12 wk, in comparison with vector alone. The mean urinary glucose tetrasaccharide (Glc4), a urinary biomarker, was lower in GAA-KO mice following combination therapy, compared with vector alone. Similarly, glycogen content was lower in cardiac and skeletal muscle following 12 wk of combination therapy in heart, quadriceps, diaphragm, and soleus, compared with vector alone. These data suggested that clenbuterol treatment enhanced trafficking of GAA to lysosomes, given that GAA was expressed within myofibers. The integral role of CI-MPR was demonstrated by the lack of effectiveness from clenbuterol in GAA-KO mice that lacked CI-MPR in muscle, where it failed to reverse the high glycogen content of the heart and diaphragm or impaired wirehang performance. However, the glycogen content of skeletal muscle was reduced by the addition of clenbuterol in the absence of CI-MPR, as was lysosomal vacuolation, which correlated with increased AKT signaling. In summary, β2-agonist treatment enhanced CI-MPR-mediated uptake and trafficking of GAA in mice with Pompe disease, and a similarly enhanced benefit might be expected in other lysosomal storage disorders.

Authors
Farah, BL; Madden, L; Li, S; Nance, S; Bird, A; Bursac, N; Yen, PM; Young, SP; Koeberl, DD
MLA Citation
Farah, BL, Madden, L, Li, S, Nance, S, Bird, A, Bursac, N, Yen, PM, Young, SP, and Koeberl, DD. "Adjunctive β2-agonist treatment reduces glycogen independently of receptor-mediated acid α-glucosidase uptake in the limb muscles of mice with Pompe disease." FASEB journal : official publication of the Federation of American Societies for Experimental Biology 28.5 (May 2014): 2272-2280.
Website
http://hdl.handle.net/10161/10802
PMID
24448824
Source
epmc
Published In
The FASEB journal : official publication of the Federation of American Societies for Experimental Biology
Volume
28
Issue
5
Publish Date
2014
Start Page
2272
End Page
2280
DOI
10.1096/fj.13-244202

Tissue Engineered Human Skeletal Muscle as a Pre-Clinical Model for AAV Treatment of Pompe Disease

Authors
Madden, LR; Koeberl, DD; Bursac, N
MLA Citation
Madden, LR, Koeberl, DD, and Bursac, N. "Tissue Engineered Human Skeletal Muscle as a Pre-Clinical Model for AAV Treatment of Pompe Disease." May 2014.
Source
wos-lite
Published In
Molecular Therapy
Volume
22
Publish Date
2014
Start Page
S157
End Page
S157

Human Pluripotent Stem Cell-Derived Cardiac Tissue Patch for Use in Cell-Based Cardiac Therapy

Authors
Shadrin, IY; Carlson, AL; Bursac, N
MLA Citation
Shadrin, IY, Carlson, AL, and Bursac, N. "Human Pluripotent Stem Cell-Derived Cardiac Tissue Patch for Use in Cell-Based Cardiac Therapy." May 2014.
Source
wos-lite
Published In
Molecular Therapy
Volume
22
Publish Date
2014
Start Page
S206
End Page
S206

Gene Therapy for Heart Disease Using Electrically Active Fibroblasts

Authors
Nguyen, H; Bursac, N
MLA Citation
Nguyen, H, and Bursac, N. "Gene Therapy for Heart Disease Using Electrically Active Fibroblasts." May 2014.
Source
wos-lite
Published In
Molecular Therapy
Volume
22
Publish Date
2014
Start Page
S144
End Page
S145

Bioengineered Skeletal Muscle With Functional Stem Cell Pool and Capacity for Vascular Integration and Maturation In Vivo

Authors
Juhas, M; Engelmayr, G; Bursac, N
MLA Citation
Juhas, M, Engelmayr, G, and Bursac, N. "Bioengineered Skeletal Muscle With Functional Stem Cell Pool and Capacity for Vascular Integration and Maturation In Vivo." May 2014.
Source
wos-lite
Published In
Molecular Therapy
Volume
22
Publish Date
2014
Start Page
S53
End Page
S54

Spatiotemporal genetic control of cellular systemsEngineering of skeletal muscle regeneration: Principles, current state, and challengesThree-dimensional micropatterning of biomaterial scaffolds for tissue engineering

Authors
Polstein, LR; Gersbach, CA; Bian, W; Juhas, M; Bursac, N; Hoffmann, JC; West, JL
MLA Citation
Polstein, LR, Gersbach, CA, Bian, W, Juhas, M, Bursac, N, Hoffmann, JC, and West, JL. "Spatiotemporal genetic control of cellular systemsEngineering of skeletal muscle regeneration: Principles, current state, and challengesThree-dimensional micropatterning of biomaterial scaffolds for tissue engineering (PublishedPublishedPublished)." Tissue and Organ Regeneration: Advances in Micro- and Nanotechnology. April 30, 2014. 156-197.
Source
scopus
Publish Date
2014
Start Page
156
End Page
197
DOI
10.4032/9789814411684

Robust T-tubulation and maturation of cardiomyocytes using tissue-engineered epicardial mimetics.

Complex three-dimensional (3-D) heart structure is an important determinant of cardiac electrical and mechanical function. In this study, we set to develop a versatile tissue-engineered system that can promote important aspects of cardiac functional maturation and reproduce variations in myofiber directions present in native ventricular epicardium. We cultured neonatal rat cardiomyocytes within a 3-D hydrogel environment using microfabricated elastomeric molds with hexagonal posts. By varying individual post orientations along the directions derived from diffusion tensor magnetic resonance imaging (DTMRI) maps of human ventricle, we created large (2.5 × 2.5 cm(2)) 3-D cardiac tissue patches with cardiomyocyte alignment that replicated human epicardial fiber orientations. After 3 weeks of culture, the advanced structural and functional maturation of the engineered 3-D cardiac tissues compared to age-matched 2-D monolayers was evident from: 1) the presence of dense, aligned and electromechanically-coupled cardiomyocytes, quiescent fibroblasts, and interspersed capillary-like structures, 2) action potential propagation with near-adult conduction velocity and directional dependence on local cardiomyocyte orientation, and 3) robust formation of T-tubules aligned with Z-disks, co-localization of L-type Ca(2+) channels and ryanodine receptors, and accelerated Ca(2+) transient kinetics. This biomimetic tissue-engineered platform can enable systematic in vitro studies of cardiac structure-function relationships and promote the development of advanced tissue engineering strategies for cardiac repair and regeneration.

Authors
Bian, W; Badie, N; Himel, HD; Bursac, N
MLA Citation
Bian, W, Badie, N, Himel, HD, and Bursac, N. "Robust T-tubulation and maturation of cardiomyocytes using tissue-engineered epicardial mimetics." Biomaterials 35.12 (April 2014): 3819-3828.
PMID
24508078
Source
epmc
Published In
Biomaterials
Volume
35
Issue
12
Publish Date
2014
Start Page
3819
End Page
3828
DOI
10.1016/j.biomaterials.2014.01.045

Biomimetic engineered muscle with capacity for vascular integration and functional maturation in vivo.

Tissue-engineered skeletal muscle can serve as a physiological model of natural muscle and a potential therapeutic vehicle for rapid repair of severe muscle loss and injury. Here, we describe a platform for engineering and testing highly functional biomimetic muscle tissues with a resident satellite cell niche and capacity for robust myogenesis and self-regeneration in vitro. Using a mouse dorsal window implantation model and transduction with fluorescent intracellular calcium indicator, GCaMP3, we nondestructively monitored, in real time, vascular integration and the functional state of engineered muscle in vivo. During a 2-wk period, implanted engineered muscle exhibited a steady ingrowth of blood-perfused microvasculature along with an increase in amplitude of calcium transients and force of contraction. We also demonstrated superior structural organization, vascularization, and contractile function of fully differentiated vs. undifferentiated engineered muscle implants. The described in vitro and in vivo models of biomimetic engineered muscle represent enabling technology for novel studies of skeletal muscle function and regeneration.

Authors
Juhas, M; Engelmayr, GC; Fontanella, AN; Palmer, GM; Bursac, N
MLA Citation
Juhas, M, Engelmayr, GC, Fontanella, AN, Palmer, GM, and Bursac, N. "Biomimetic engineered muscle with capacity for vascular integration and functional maturation in vivo." Proceedings of the National Academy of Sciences of the United States of America 111.15 (April 2014): 5508-5513.
Website
http://hdl.handle.net/10161/8413
PMID
24706792
Source
epmc
Published In
Proceedings of the National Academy of Sciences of USA
Volume
111
Issue
15
Publish Date
2014
Start Page
5508
End Page
5513
DOI
10.1073/pnas.1402723111

Maturation of functional cardiac tissue patches

Our knowledge regarding native heart development is relatively comprehensive; however, we remain largely dependent on empiricism in our approaches to recapitulate cardiomyogenesis in vitro. Toward clinical translation, it is critical that we understand how different biochemical, biophysical and biomaterial parameters of tissue culture govern the maturation and functional output of engineered myocardium, particularly when using pluripotent stem cell-based approaches. Here we review the processes of native myocardial maturation, compare them with those observed during the culture of engineered cardiac tissues, and discuss potential approaches toward promoting functional cardiomyogenesis in vitro. We conclude by offering our impressions on the important next steps. © 2014 Woodhead Publishing Limited All rights reserved.

Authors
Engelmayr, GC; Zhang, D; Bursac, N
MLA Citation
Engelmayr, GC, Zhang, D, and Bursac, N. "Maturation of functional cardiac tissue patches." (February 1, 2014): 248-282. (Chapter)
Source
scopus
Publish Date
2014
Start Page
248
End Page
282
DOI
10.1533/9780857096715.2.248

Use of flow, electrical, and mechanical stimulation to promote engineering of striated muscles

The field of tissue engineering involves design of high-fidelity tissue substitutes for predictive experimental assays in vitro and cell-based regenerative therapies in vivo. Design of striated muscle tissues, such as cardiac and skeletal muscle, has been particularly challenging due to a high metabolic demand and complex cellular organization and electromechanical function of the native tissues. Successful engineering of highly functional striated muscles may thus require creation of biomimetic culture conditions involving medium perfusion, electrical and mechanical stimulation. When optimized, these external cues are expected to synergistically and dynamically activate important intracellular signaling pathways leading to accelerated muscle growth and development. This review will discuss the use of different types of tissue culture bioreactors aimed at providing conditions for enhanced structural and functional maturation of engineered striated muscles. © 2013 Biomedical Engineering Society.

Authors
Rangarajan, S; Madden, L; Bursac, N
MLA Citation
Rangarajan, S, Madden, L, and Bursac, N. "Use of flow, electrical, and mechanical stimulation to promote engineering of striated muscles." Annals of Biomedical Engineering 42.7 (January 1, 2014): 1391-1405.
Source
scopus
Published In
Annals of Biomedical Engineering
Volume
42
Issue
7
Publish Date
2014
Start Page
1391
End Page
1405
DOI
10.1007/s10439-013-0966-4

Quantifying electrical interactions between cardiomyocytes and other cells in micropatterned cell pairs.

Micropatterning is a powerful technique to control cell shape and position on a culture substrate. In this chapter, we describe the method to reproducibly create large numbers of micropatterned heterotypic cell pairs with defined size, shape, and length of cell-cell contact. These cell pairs can be utilized in patch clamp recordings to quantify electrical interactions between cardiomyocytes and non-cardiomyocytes.

Authors
Nguyen, H; Badie, N; McSpadden, L; Pedrotty, D; Bursac, N
MLA Citation
Nguyen, H, Badie, N, McSpadden, L, Pedrotty, D, and Bursac, N. "Quantifying electrical interactions between cardiomyocytes and other cells in micropatterned cell pairs." Methods in molecular biology (Clifton, N.J.) 1181 (January 2014): 249-262.
PMID
25070342
Source
epmc
Published In
Methods in molecular biology (Clifton, N.J.)
Volume
1181
Publish Date
2014
Start Page
249
End Page
262
DOI
10.1007/978-1-4939-1047-2_21

Quantifying electrical interactions between cardiomyocytes and other cells in micropatterned cell pairs

Micropatterning is a powerful technique to control cell shape and position on a culture substrate. In this chapter, we describe the method to reproducibly create large numbers of micropatterned heterotypic cell pairs with defined size, shape, and length of cell-cell contact. These cell pairs can be utilized in patch clamp recordings to quantify electrical interactions between cardiomyocytes and non-cardiomyocytes. © 2014 Springer Science+Business Media New York.

Authors
Nguyen, H; Badie, N; McSpadden, L; Pedrotty, D; Bursac, N
MLA Citation
Nguyen, H, Badie, N, McSpadden, L, Pedrotty, D, and Bursac, N. "Quantifying electrical interactions between cardiomyocytes and other cells in micropatterned cell pairs." Methods in Molecular Biology 1181 (2014): 249-262.
Source
scopus
Published In
Methods in molecular biology (Clifton, N.J.)
Volume
1181
Publish Date
2014
Start Page
249
End Page
262
DOI
10.1007/978-1-4939-1047-2-21

Design considerations for an integrated microphysiological muscle tissue for drug and tissue toxicity testing

Microphysiological systems provide a tool to simulate normal and pathological function of organs for prolonged periods. These systems must incorporate the key functions of the individual organs and enable interactions among the corresponding microphysiological units. The relative size of different microphysiological organs and their flow rates are scaled in proportion to in vivo values. We have developed a microphysiological three-dimensional engineered human skeletal muscle system connected to a circulatory system that consists of a tissue-engineered blood vessel as part of a high-pressure arterial system. The engineered human skeletal muscle tissue reproduces key mechanical behaviors of skeletal muscle in vivo. Pulsatile flow is produced using a novel computer-controlled magnetically activated ferrogel. The system is versatile and the muscle unit can be integrated with other organ systems. Periodic monitoring of biomechanical function provides a non-invasive assessment of the health of the tissue and a way to measure the response to drugs and toxins. © 2013 BioMed Central Ltd.

Authors
Truskey, GA; Achneck, HE; Bursac, N; Chan, HF; Cheng, CS; Fernandez, C; Hong, S; Jung, Y; Koves, T; Kraus, WE; Leong, K; Madden, L; Reichert, WM; Zhao, X
MLA Citation
Truskey, GA, Achneck, HE, Bursac, N, Chan, HF, Cheng, CS, Fernandez, C, Hong, S, Jung, Y, Koves, T, Kraus, WE, Leong, K, Madden, L, Reichert, WM, and Zhao, X. "Design considerations for an integrated microphysiological muscle tissue for drug and tissue toxicity testing." Stem Cell Research and Therapy 4.SUPPL.1 (December 20, 2013). (Review)
PMID
24565225
Source
scopus
Published In
Stem Cell Research and Therapy
Volume
4
Issue
SUPPL.1
Publish Date
2013
DOI
10.1186/scrt371

Spatial profiles of electrical mismatch determine vulnerability to conduction failure across a host-donor cell interface.

BACKGROUND: Electrophysiological mismatch between host cardiomyocytes and donor cells can directly affect the electrical safety of cardiac cell therapies; however, the ability to study host-donor interactions at the microscopic scale in situ is severely limited. We systematically explored how action potential (AP) differences between cardiomyocytes and other excitable cells modulate vulnerability to conduction failure in vitro. METHODS AND RESULTS: AP propagation was optically mapped at 75 μm resolution in micropatterned strands (n=152) in which host neonatal rat ventricular myocytes (AP duration=153.2±2.3 ms, conduction velocity=22.3±0.3 cm/s) seamlessly interfaced with genetically engineered excitable donor cells expressing inward rectifier potassium (Kir2.1) and cardiac sodium (Na(v)1.5) channels with either weak (conduction velocity=3.1±0.1 cm/s) or strong (conduction velocity=22.1±0.4 cm/s) electrical coupling. Selective prolongation of engineered donor cell AP duration (31.9-139.1 ms) by low-dose BaCl2 generated a wide range of host-donor repolarization time (RT) profiles with maximum gradients (∇RT(max)) of 5.5 to 257 ms/mm. During programmed stimulation of donor cells, the vulnerable time window for conduction block across the host-donor interface most strongly correlated with ∇RT(max). Compared with well-coupled donor cells, the interface composed of poorly coupled cells significantly shortened the RT profile width by 19.7% and increased ∇RT(max) and vulnerable time window by 22.2% and 19%, respectively. Flattening the RT profile by perfusion of 50 μmol/L BaCl2 eliminated coupling-induced differences in vulnerability to block. CONCLUSIONS: Our results quantify how the degree of electrical mismatch across a cardiomyocyte-donor cell interface affects vulnerability to conduction block, with important implications for the design of safe cardiac cell and gene therapies.

Authors
Kirkton, RD; Badie, N; Bursac, N
MLA Citation
Kirkton, RD, Badie, N, and Bursac, N. "Spatial profiles of electrical mismatch determine vulnerability to conduction failure across a host-donor cell interface." Circ Arrhythm Electrophysiol 6.6 (December 2013): 1200-1207.
PMID
24235268
Source
pubmed
Published In
Circulation: Arrhythmia and Electrophysiology
Volume
6
Issue
6
Publish Date
2013
Start Page
1200
End Page
1207
DOI
10.1161/CIRCEP.113.001050

Engineering skeletal muscle repair.

Healthy skeletal muscle has a remarkable capacity for regeneration. Even at a mature age, muscle tissue can undergo a robust rebuilding process that involves the formation of new muscle cells and extracellular matrix and the re-establishment of vascular and neural networks. Understanding and reverse-engineering components of this process is essential for our ability to restore loss of muscle mass and function in cases where the natural ability of muscle for self-repair is exhausted or impaired. In this article, we will describe current approaches to restore the function of diseased or injured muscle through combined use of myogenic stem cells, biomaterials, and functional tissue-engineered muscle. Furthermore, we will discuss possibilities for expanding the future use of human cell sources toward the development of cell-based clinical therapies and in vitro models of human muscle disease.

Authors
Juhas, M; Bursac, N
MLA Citation
Juhas, M, and Bursac, N. "Engineering skeletal muscle repair." Curr Opin Biotechnol 24.5 (October 2013): 880-886. (Review)
PMID
23711735
Source
pubmed
Published In
Current Opinion in Biotechnology
Volume
24
Issue
5
Publish Date
2013
Start Page
880
End Page
886
DOI
10.1016/j.copbio.2013.04.013

Tissue-engineered cardiac patch for advanced functional maturation of human ESC-derived cardiomyocytes.

Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) provide a promising source for cell therapy and drug screening. Several high-yield protocols exist for hESC-CM production; however, methods to significantly advance hESC-CM maturation are still lacking. Building on our previous experience with mouse ESC-CMs, we investigated the effects of 3-dimensional (3D) tissue-engineered culture environment and cardiomyocyte purity on structural and functional maturation of hESC-CMs. 2D monolayer and 3D fibrin-based cardiac patch cultures were generated using dissociated cells from differentiated Hes2 embryoid bodies containing varying percentage (48-90%) of CD172a (SIRPA)-positive cardiomyocytes. hESC-CMs within the patch were aligned uniformly by locally controlling the direction of passive tension. Compared to hESC-CMs in age (2 weeks) and purity (48-65%) matched 2D monolayers, hESC-CMs in 3D patches exhibited significantly higher conduction velocities (CVs), longer sarcomeres (2.09 ± 0.02 vs. 1.77 ± 0.01 μm), and enhanced expression of genes involved in cardiac contractile function, including cTnT, αMHC, CASQ2 and SERCA2. The CVs in cardiac patches increased with cardiomyocyte purity, reaching 25.1 cm/s in patches constructed with 90% hESC-CMs. Maximum contractile force amplitudes and active stresses of cardiac patches averaged to 3.0 ± 1.1 mN and 11.8 ± 4.5 mN/mm(2), respectively. Moreover, contractile force per input cardiomyocyte averaged to 5.7 ± 1.1 nN/cell and showed a negative correlation with hESC-CM purity. Finally, patches exhibited significant positive inotropy with isoproterenol administration (1.7 ± 0.3-fold force increase, EC50 = 95.1 nm). These results demonstrate highly advanced levels of hESC-CM maturation after 2 weeks of 3D cardiac patch culture and carry important implications for future drug development and cell therapy studies.

Authors
Zhang, D; Shadrin, IY; Lam, J; Xian, H-Q; Snodgrass, HR; Bursac, N
MLA Citation
Zhang, D, Shadrin, IY, Lam, J, Xian, H-Q, Snodgrass, HR, and Bursac, N. "Tissue-engineered cardiac patch for advanced functional maturation of human ESC-derived cardiomyocytes." Biomaterials 34.23 (July 2013): 5813-5820.
Website
http://hdl.handle.net/10161/8422
PMID
23642535
Source
pubmed
Published In
Biomaterials
Volume
34
Issue
23
Publish Date
2013
Start Page
5813
End Page
5820
DOI
10.1016/j.biomaterials.2013.04.026

Cardiac Fibroblasts and Arrhythmogenesis

Authors
Bursac, N; Kim, JJ
MLA Citation
Bursac, N, and Kim, JJ. "Cardiac Fibroblasts and Arrhythmogenesis." Cardiac Electrophysiology: From Cell to Bedside: Sixth Edition. January 1, 2013. 297-308.
Source
scopus
Publish Date
2013
Start Page
297
End Page
308
DOI
10.1016/B978-1-4557-2856-5.00030-3

Transcription factors MYOCD, SRF, Mesp1 and SMARCD3 enhance the cardio-inducing effect of GATA4, TBX5, and MEF2C during direct cellular reprogramming.

Transient overexpression of defined combinations of master regulator genes can effectively induce cellular reprogramming: the acquisition of an alternative predicted phenotype from a differentiated cell lineage. This can be of particular importance in cardiac regenerative medicine wherein the heart lacks the capacity to heal itself, but simultaneously contains a large pool of fibroblasts. In this study we determined the cardio-inducing capacity of ten transcription factors to actuate cellular reprogramming of mouse embryonic fibroblasts into cardiomyocyte-like cells. Overexpression of transcription factors MYOCD and SRF alone or in conjunction with Mesp1 and SMARCD3 enhanced the basal but necessary cardio-inducing effect of the previously reported GATA4, TBX5, and MEF2C. In particular, combinations of five or seven transcription factors enhanced the activation of cardiac reporter vectors, and induced an upregulation of cardiac-specific genes. Global gene expression analysis also demonstrated a significantly greater cardio-inducing effect when the transcription factors MYOCD and SRF were used. Detection of cross-striated cells was highly dependent on the cell culture conditions and was enhanced by the addition of valproic acid and JAK inhibitor. Although we detected Ca(2+) transient oscillations in the reprogrammed cells, we did not detect significant changes in resting membrane potential or spontaneously contracting cells. This study further elucidates the cardio-inducing effect of the transcriptional networks involved in cardiac cellular reprogramming, contributing to the ongoing rational design of a robust protocol required for cardiac regenerative therapies.

Authors
Christoforou, N; Chellappan, M; Adler, AF; Kirkton, RD; Wu, T; Addis, RC; Bursac, N; Leong, KW
MLA Citation
Christoforou, N, Chellappan, M, Adler, AF, Kirkton, RD, Wu, T, Addis, RC, Bursac, N, and Leong, KW. "Transcription factors MYOCD, SRF, Mesp1 and SMARCD3 enhance the cardio-inducing effect of GATA4, TBX5, and MEF2C during direct cellular reprogramming. (Published online)" PLoS One 8.5 (2013): e63577-.
Website
http://hdl.handle.net/10161/8424
PMID
23704920
Source
pubmed
Published In
PloS one
Volume
8
Issue
5
Publish Date
2013
Start Page
e63577
DOI
10.1371/journal.pone.0063577

Induced pluripotent stem cell-derived cardiac progenitors differentiate to cardiomyocytes and form biosynthetic tissues.

The mammalian heart has little capacity to regenerate, and following injury the myocardium is replaced by non-contractile scar tissue. Consequently, increased wall stress and workload on the remaining myocardium leads to chamber dilation, dysfunction, and heart failure. Cell-based therapy with an autologous, epigenetically reprogrammed, and cardiac-committed progenitor cell source could potentially reverse this process by replacing the damaged myocardium with functional tissue. However, it is unclear whether cardiac progenitor cell-derived cardiomyocytes are capable of attaining levels of structural and functional maturity comparable to that of terminally-fated cardiomyocytes. Here, we first describe the derivation of mouse induced pluripotent stem (iPS) cells, which once differentiated allow for the enrichment of Nkx2-5(+) cardiac progenitors, and the cardiomyocyte-specific expression of the red fluorescent protein. We show that the cardiac progenitors are multipotent and capable of differentiating into endothelial cells, smooth muscle cells and cardiomyocytes. Moreover, cardiac progenitor selection corresponds to cKit(+) cell enrichment, while cardiomyocyte cell-lineage commitment is concomitant with dual expression of either cKit/Flk1 or cKit/Sca-1. We proceed to show that the cardiac progenitor-derived cardiomyocytes are capable of forming electrically and mechanically coupled large-scale 2D cell cultures with mature electrophysiological properties. Finally, we examine the cell progenitors' ability to form electromechanically coherent macroscopic tissues, using a physiologically relevant 3D culture model and demonstrate that following long-term culture the cardiomyocytes align, and form robust electromechanical connections throughout the volume of the biosynthetic tissue construct. We conclude that the iPS cell-derived cardiac progenitors are a robust cell source for tissue engineering applications and a 3D culture platform for pharmacological screening and drug development studies.

Authors
Christoforou, N; Liau, B; Chakraborty, S; Chellapan, M; Bursac, N; Leong, KW
MLA Citation
Christoforou, N, Liau, B, Chakraborty, S, Chellapan, M, Bursac, N, and Leong, KW. "Induced pluripotent stem cell-derived cardiac progenitors differentiate to cardiomyocytes and form biosynthetic tissues. (Published online)" PLoS One 8.6 (2013): e65963-.
Website
http://hdl.handle.net/10161/8423
PMID
23785459
Source
pubmed
Published In
PloS one
Volume
8
Issue
6
Publish Date
2013
Start Page
e65963
DOI
10.1371/journal.pone.0065963

WNT3 is a biomarker capable of predicting the definitive endoderm differentiation potential of hESCs

Generation of functional cells from human pluripotent stem cells (PSCs) through in vitro differentiation is a promising approach for drug screening and cell therapy. However, the observed large and unavoidable variation in the differentiation potential of different human embryonic stem cell (hESC)/induced PSC (iPSC) lines makes the selection of an appropriate cell line for the differentiation of a particular cell lineage difficult. Here, we report identification of WNT3 as a biomarker capable of predicting definitive endoderm (DE) differentiation potential of hESCs. We show that the mRNA level of WNT3 in hESCs correlates with their DE differentiation efficiency. In addition, manipulations of hESCs through WNT3 knockdown or overexpression can respectively inhibit or promote DE differentiation in a WNT3 level-dependent manner. Finally, analysis of several hESC lines based on their WNT3 expression levels allowed accurate prediction of their DE differentiation potential. Collectively, our study supports the notion that WNT3 can serve as a biomarker for predicting DE differentiation potential of hESCs. © 2013 The Authors.

Authors
Jiang, W; Zhang, D; Bursac, N; Zhang, Y
MLA Citation
Jiang, W, Zhang, D, Bursac, N, and Zhang, Y. "WNT3 is a biomarker capable of predicting the definitive endoderm differentiation potential of hESCs." Stem Cell Reports 1.1 (2013): 46-52.
Website
http://hdl.handle.net/10161/8425
PMID
24052941
Source
scival
Published In
Stem Cell Reports
Volume
1
Issue
1
Publish Date
2013
Start Page
46
End Page
52
DOI
10.1016/j.stemcr.2013.03.003

Engineering skeletal muscle repair

Healthy skeletal muscle has a remarkable capacity for regeneration. Even at a mature age, muscle tissue can undergo a robust rebuilding process that involves the formation of new muscle cells and extracellular matrix and the re-establishment of vascular and neural networks. Understanding and reverse-engineering components of this process is essential for our ability to restore loss of muscle mass and function in cases where the natural ability of muscle for self-repair is exhausted or impaired. In this article, we will describe current approaches to restore the function of diseased or injured muscle through combined use of myogenic stem cells, biomaterials, and functional tissue-engineered muscle. Furthermore, we will discuss possibilities for expanding the future use of human cell sources toward the development of cell-based clinical therapies and in vitro models of human muscle disease. © 2013 Elsevier Ltd.

Authors
Juhas, M; Bursac, N
MLA Citation
Juhas, M, and Bursac, N. "Engineering skeletal muscle repair." Current Opinion in Biotechnology 24.5 (2013): 880-886.
Source
scival
Published In
Current Opinion in Biotechnology
Volume
24
Issue
5
Publish Date
2013
Start Page
880
End Page
886
DOI
10.1016/j.copbio.2013.04.013

Human Embryonic Stem Cell-Derived Cardiac Tissue Patch with Advanced Structure and Function

Authors
Zhang, D; Lam, J; Liau, B; Snodgrass, R; Bursac, N
MLA Citation
Zhang, D, Lam, J, Liau, B, Snodgrass, R, and Bursac, N. "Human Embryonic Stem Cell-Derived Cardiac Tissue Patch with Advanced Structure and Function." CIRCULATION 126.21 (November 20, 2012).
Source
wos-lite
Published In
Circulation
Volume
126
Issue
21
Publish Date
2012

Genetic engineering of somatic cells to study and improve cardiac function.

AIMS: To demonstrate the utility of genetically engineered excitable cells for studies of basic electrophysiology and cardiac cell therapy. METHODS AND RESULTS: 'Zig-zag' networks of neonatal rat ventricular myocytes (NRVMs) were micropatterned onto thin elastomeric films to mimic the slow action potential (AP) conduction found in fibrotic myocardium. Addition of genetically engineered excitable human embryonic kidney cells (HEK-293 cells) ('Ex-293' cells stably expressing Kir2.1, Na(v)1.5, and Cx43 channels) increased both cardiac conduction velocity by 370% and twitch force amplitude by 64%. Furthermore, we stably expressed mutant Na(v)1.5 [A1924T (fast sodium channel mutant (substitution of alanine by threonine at amino acid 1924)] channels with hyperpolarized steady-state activation and showed that, despite a 71.6% reduction in peak I(Na), these cells propagated APs at the same velocity as the wild-type Na(v)1.5-expressing Ex-293 cells. Stable expression of Ca(v)3.3 (T-type voltage-gated calcium) channels in Ex-293 cells (to generate an 'ExCa-293' line) significantly increased their AP duration and reduced repolarization gradients in cocultures of these cells and NRVMs. Additional expression of an optogenetic construct [ChIEF (light-gated Channelrhodopsin mutant)]enabled light-based control of AP firing in ExCa-293 cells. CONCLUSION: We show that, despite being non-contractile, genetically engineered excitable cells can significantly improve both electrical and mechanical function of engineered cardiac tissues in vitro. We further demonstrate the utility of engineered cells for tissue-level studies of basic electrophysiology and cardiac channelopathies. In the future, this novel platform could be utilized in the high-throughput design of new genetically encoded indicators of cell electrical function, validation, and improvement of computer models of AP conduction, and development of novel engineered somatic cell therapies for the treatment of cardiac infarction and arrhythmias.

Authors
Kirkton, RD; Bursac, N
MLA Citation
Kirkton, RD, and Bursac, N. "Genetic engineering of somatic cells to study and improve cardiac function." Europace 14 Suppl 5 (November 2012): v40-v49.
PMID
23104914
Source
pubmed
Published In
Europace (Elsevier)
Volume
14 Suppl 5
Publish Date
2012
Start Page
v40
End Page
v49
DOI
10.1093/europace/eus269

Size and ionic currents of unexcitable cells coupled to cardiomyocytes distinctly modulate cardiac action potential shape and pacemaking activity in micropatterned cell pairs.

BACKGROUND: Cardiac cell therapies can yield electric coupling of unexcitable donor cells to host cardiomyocytes with functional consequences that remain unexplored. METHODS AND RESULTS: We micropatterned cell pairs consisting of a neonatal rat ventricular myocyte (NRVM) coupled to an engineered human embryonic kidney 293 (HEK293) cell expressing either connexin-43 (Cx43 HEK) or inward rectifier potassium channel 2.1 (Kir2.1) and Cx43 (Kir2.1+Cx43 HEK). The NRVM-HEK contact length was fixed yielding a coupling strength of 68.9±9.7 nS, whereas HEK size was systematically varied. With increase in Cx43 HEK size, NRVM maximal diastolic potential was reduced from -71.7±0.6 mV in single NRVMs to -35.1±1.3 mV in pairs with an HEK:NRVM cell surface area ratio of 1.7±0.1, whereas the action potential upstroke ([dV(m)/dt](max)) and duration decreased to 1.6±0.7% and increased to 177±32% in single NRVM values, respectively (n=21 cell pairs). Pacemaking occurred in all NRVM-Cx43 HEK pairs with cell surface area ratios of 1.1 to 1.9. In contrast, NRVMs, coupled with Kir2.1+Cx43 HEKs of increasing size, had similar maximal diastolic potentials, exhibited no spontaneous activity, and showed a gradual decrease in action potential duration (n=23). Furthermore, coupling single NRVMs to a dynamic clamp model of HEK cell ionic current reproduced the cardiac maximal diastolic potentials and pacemaking rates recorded in cell pairs, whereas reproducing changes in (dV(m)/dt)(max) and action potential duration required coupling to an HEK model that also included cell membrane capacitance. CONCLUSIONS: Size and ionic currents of unexcitable cells electrically coupled to cardiomyocytes distinctly affect cardiac action potential shape and initiation with important implications for the safety of cardiac cell and gene therapies.

Authors
McSpadden, LC; Nguyen, H; Bursac, N
MLA Citation
McSpadden, LC, Nguyen, H, and Bursac, N. "Size and ionic currents of unexcitable cells coupled to cardiomyocytes distinctly modulate cardiac action potential shape and pacemaking activity in micropatterned cell pairs." Circ Arrhythm Electrophysiol 5.4 (August 1, 2012): 821-830.
PMID
22679057
Source
pubmed
Published In
Circulation: Arrhythmia and Electrophysiology
Volume
5
Issue
4
Publish Date
2012
Start Page
821
End Page
830
DOI
10.1161/CIRCEP.111.969329

X-linked inhibitor of apoptosis protein-mediated attenuation of apoptosis, using a novel cardiac-enhanced adeno-associated viral vector.

Successful amelioration of cardiac dysfunction and heart failure through gene therapy approaches will require a transgene effective at attenuating myocardial injury, and subsequent remodeling, using an efficient and safe delivery vehicle. Our laboratory has established a well-curated, high-quality repository of human myocardial tissues that we use as a discovery engine to identify putative therapeutic transgene targets, as well as to better understand the molecular basis of human heart failure. By using this rare resource we were able to examine age- and sex-matched left ventricular samples from (1) end-stage failing human hearts and (2) nonfailing human hearts and were able to identify the X-linked inhibitor of apoptosis protein (XIAP) as a novel target for treating cardiac dysfunction. We demonstrate that XIAP is diminished in failing human hearts, indicating that this potent inhibitor of apoptosis may be central in protecting the human heart from cellular injury culminating in heart failure. Efforts to ameliorate heart failure through delivery of XIAP compelled the design of a novel adeno-associated viral (AAV) vector, termed SASTG, that achieves highly efficient transduction in mouse heart and in cultured neonatal rat cardiomyocytes. Increased XIAP expression achieved with the SASTG vector inhibits caspase-3/7 activity in neonatal cardiomyocytes after induction of apoptosis through three common cardiac stresses: protein kinase C-γ inhibition, hypoxia, or β-adrenergic receptor agonist. These studies demonstrate the potential benefit of XIAP to correct heart failure after highly efficient delivery to the heart with the rationally designed SASTG AAV vector.

Authors
Piacentino, V; Milano, CA; Bolanos, M; Schroder, J; Messina, E; Cockrell, AS; Jones, E; Krol, A; Bursac, N; Mao, L; Devi, GR; Samulski, RJ; Bowles, DE
MLA Citation
Piacentino, V, Milano, CA, Bolanos, M, Schroder, J, Messina, E, Cockrell, AS, Jones, E, Krol, A, Bursac, N, Mao, L, Devi, GR, Samulski, RJ, and Bowles, DE. "X-linked inhibitor of apoptosis protein-mediated attenuation of apoptosis, using a novel cardiac-enhanced adeno-associated viral vector." Hum Gene Ther 23.6 (June 2012): 635-646.
PMID
22339372
Source
pubmed
Published In
Human Gene Therapy
Volume
23
Issue
6
Publish Date
2012
Start Page
635
End Page
646
DOI
10.1089/hum.2011.186

Engineering an electromechanically functional 3d biosynthetic tissue using embryonic or induced pluripotent stem cells

Authors
Christoforou, N; Liau, B; Bursac, N; Leong, KW
MLA Citation
Christoforou, N, Liau, B, Bursac, N, and Leong, KW. "Engineering an electromechanically functional 3d biosynthetic tissue using embryonic or induced pluripotent stem cells." May 15, 2012.
Source
wos-lite
Published In
Circulation
Volume
125
Issue
19
Publish Date
2012
Start Page
E735
End Page
E735

Single-detector simultaneous optical mapping of V(m) and [Ca(2+)](i) in cardiac monolayers.

Simultaneous mapping of transmembrane voltage (V(m)) and intracellular Ca(2+) concentration (Ca(i)) has been used for studies of normal and abnormal impulse propagation in cardiac tissues. Existing dual mapping systems typically utilize one excitation and two emission bandwidths, requiring two photodetectors with precise pixel registration. In this study we describe a novel, single-detector mapping system that utilizes two excitation and one emission band for the simultaneous recording of action potentials and calcium transients in monolayers of neonatal rat cardiomyocytes. Cells stained with the Ca(2+)-sensitive dye X-Rhod-1 and the voltage-sensitive dye Di-4-ANEPPS were illuminated by a programmable, multicolor LED matrix. Blue and green LED pulses were flashed 180° out of phase at a rate of 488.3 Hz using a custom-built dual bandpass excitation filter that transmitted blue (482 ± 6 nm) and green (577 ± 31 nm) light. A long-pass emission filter (>605 nm) and a 504-channel photodiode array were used to record combined signals from cardiomyocytes. Green excitation yielded Ca(i) transients without significant crosstalk from V(m). Crosstalk present in V(m) signals obtained with blue excitation was removed by subtracting an appropriately scaled version of the Ca(i) transient. This method was applied to study delay between onsets of action potentials and Ca(i) transients in anisotropic cardiac monolayers.

Authors
Scull, JA; McSpadden, LC; Himel, HD; Badie, N; Bursac, N
MLA Citation
Scull, JA, McSpadden, LC, Himel, HD, Badie, N, and Bursac, N. "Single-detector simultaneous optical mapping of V(m) and [Ca(2+)](i) in cardiac monolayers." Ann Biomed Eng 40.5 (May 2012): 1006-1017.
PMID
22124794
Source
pubmed
Published In
Annals of Biomedical Engineering
Volume
40
Issue
5
Publish Date
2012
Start Page
1006
End Page
1017
DOI
10.1007/s10439-011-0478-z

Local tissue geometry determines contractile force generation of engineered muscle networks.

The field of skeletal muscle tissue engineering is currently hampered by the lack of methods to form large muscle constructs composed of dense, aligned, and mature myofibers and limited understanding of structure-function relationships in developing muscle tissues. In our previous studies, engineered muscle sheets with elliptical pores ("muscle networks") were fabricated by casting cells and fibrin gel inside elastomeric tissue molds with staggered hexagonal posts. In these networks, alignment of cells around the elliptical pores followed the local distribution of tissue strains that were generated by cell-mediated compaction of fibrin gel against the hexagonal posts. The goal of this study was to assess how systematic variations in pore elongation affect the morphology and contractile function of muscle networks. We found that in muscle networks with more elongated pores the force production of individual myofibers was not altered, but the myofiber alignment and efficiency of myofiber formation were significantly increased yielding an increase in the total contractile force despite a decrease in the total tissue volume. Beyond a certain pore length, increase in generated contractile force was mainly contributed by more efficient myofiber formation rather than enhanced myofiber alignment. Collectively, these studies show that changes in local tissue geometry can exert both direct structural and indirect myogenic effects on the functional output of engineered muscle. Different hydrogel formulations and pore geometries will be explored in the future to further augment contractile function of engineered muscle networks and promote their use for basic structure-function studies in vitro and, eventually, for efficient muscle repair in vivo.

Authors
Bian, W; Juhas, M; Pfeiler, TW; Bursac, N
MLA Citation
Bian, W, Juhas, M, Pfeiler, TW, and Bursac, N. "Local tissue geometry determines contractile force generation of engineered muscle networks." Tissue Eng Part A 18.9-10 (May 2012): 957-967.
PMID
22115339
Source
pubmed
Published In
Tissue Engineering, Part A
Volume
18
Issue
9-10
Publish Date
2012
Start Page
957
End Page
967
DOI
10.1089/ten.TEA.2011.0313

Colonizing the heart from the epicardial side.

The clinical use of stem cells, such as bone marrow-derived and, more recently, resident cardiac stem cells, offers great promise for treatment of myocardial infarction and heart failure. The epicardium-derived cells have also attracted attention for their angiogenic paracrine actions and ability to differentiate into cardiomyocytes and vascular cells when activated during cardiac injury. In a recent study, Chong and colleagues have described a distinct population of epicardium-derived mesenchymal stem cells that reside in a perivascular niche of the heart and have a broad multilineage potential. Exploring the therapeutic capacity of these cells will be an exciting future endeavor.

Authors
Bursac, N
MLA Citation
Bursac, N. "Colonizing the heart from the epicardial side. (Published online)" Stem Cell Res Ther 3.2 (April 30, 2012): 15-.
Website
http://hdl.handle.net/10161/8428
PMID
22546531
Source
pubmed
Published In
Stem Cell Research and Therapy
Volume
3
Issue
2
Publish Date
2012
Start Page
15
DOI
10.1186/scrt106

Functional cardiac tissue engineering.

Heart attack remains the leading cause of death in both men and women worldwide. Stem cell-based therapies, including the use of engineered cardiac tissues, have the potential to treat the massive cell loss and pathological remodeling resulting from heart attack. Specifically, embryonic and induced pluripotent stem cells are a promising source for generation of therapeutically relevant numbers of functional cardiomyocytes and engineering of cardiac tissues in vitro. This review will describe methodologies for successful differentiation of pluripotent stem cells towards the cardiovascular cell lineages as they pertain to the field of cardiac tissue engineering. The emphasis will be placed on comparing the functional maturation in engineered cardiac tissues and developing heart and on methods to quantify cardiac electrical and mechanical function at different spatial scales.

Authors
Liau, B; Zhang, D; Bursac, N
MLA Citation
Liau, B, Zhang, D, and Bursac, N. "Functional cardiac tissue engineering." Regen Med 7.2 (March 2012): 187-206. (Review)
PMID
22397609
Source
pubmed
Published In
Regenerative medicine
Volume
7
Issue
2
Publish Date
2012
Start Page
187
End Page
206
DOI
10.2217/rme.11.122

Conduction block in micropatterned cardiomyocyte cultures replicating the structure of ventricular cross-sections.

AIMS: Structural and functional heterogeneities in cardiac tissue have been implicated in conduction block and arrhythmogenesis. However, the propensity of specific sites within the heart to initiate conduction block has not been systematically explored. We utilized cardiomyocyte cultures replicating the realistic, magnetic resonance imaging-measured tissue boundaries and fibre directions of ventricular cross-sections to investigate their roles in the development of conduction block. METHODS AND RESULTS: The Sprague-Dawley neonatal rat cardiomyocytes were micropatterned to obtain cultures with realistic ventricular tissue boundaries and either random or realistic fibre directions. Rapid pacing was applied at multiple sites, with action potential propagation optically mapped. Excitation either failed at the stimulus site or conduction block developed remotely, often initiating reentry. The incidence of conduction block in isotropic monolayers (0% of cultures) increased with the inclusion of realistic tissue boundaries (17%) and further with realistic fibre directions (34%). Conduction block incidence was stimulus site-dependent and highest (77%) with rapid pacing from the right ventricular (RV) free wall. Furthermore, conduction block occurred exclusively at the insertion of the RV free wall into the septum, where structure-mediated current source-load mismatches acutely reduced wavefront and waveback velocity. Tissue boundaries and sharp gradients in fibre direction uniquely determined the evolution, shape, and position of conduction block lines. CONCLUSION: Our study suggests that specific micro- and macrostructural features of the ventricle determine the incidence and spatiotemporal characteristics of conduction block, independent of spatial heterogeneities in ion channel expression.

Authors
Badie, N; Scull, JA; Klinger, RY; Krol, A; Bursac, N
MLA Citation
Badie, N, Scull, JA, Klinger, RY, Krol, A, and Bursac, N. "Conduction block in micropatterned cardiomyocyte cultures replicating the structure of ventricular cross-sections." Cardiovasc Res 93.2 (February 1, 2012): 263-271.
PMID
22072633
Source
pubmed
Published In
Cardiovascular Research
Volume
93
Issue
2
Publish Date
2012
Start Page
263
End Page
271
DOI
10.1093/cvr/cvr304

Soluble miniagrin enhances contractile function of engineered skeletal muscle.

Neural agrin plays a pleiotropic role in skeletal muscle innervation and maturation, but its specific effects on the contractile function of aneural engineered muscle remain unknown. In this study, neonatal rat skeletal myoblasts cultured within 3-dimensional engineered muscle tissue constructs were treated with 10 nM soluble recombinant miniagrin and assessed using histological, biochemical, and functional assays. Depending on the treatment duration and onset time relative to the stage of myogenic differentiation, miniagrin was found to induce up to 1.7-fold increase in twitch and tetanus force amplitude. This effect was associated with the 2.3-fold up-regulation of dystrophin gene expression at 6 d after agrin removal and enhanced ACh receptor (AChR) cluster formation, but no change in cell number, expression of muscle myosin, or important aspects of intracellular Ca(2+) handling. In muscle constructs with endogenous ACh levels suppressed by the application of α-NETA, miniagrin increased AChR clustering and twitch force amplitude but failed to improve intracellular Ca(2+) handling and increase tetanus-to-twitch ratio. Overall, our studies suggest that besides its synaptogenic function that could promote integration of engineered muscle constructs in vivo, neural agrin can directly promote the contractile function of aneural engineered muscle via mechanisms distinct from those involving endogenous ACh.

Authors
Bian, W; Bursac, N
MLA Citation
Bian, W, and Bursac, N. "Soluble miniagrin enhances contractile function of engineered skeletal muscle." FASEB J 26.2 (February 2012): 955-965.
PMID
22075647
Source
pubmed
Published In
The FASEB journal : official publication of the Federation of American Societies for Experimental Biology
Volume
26
Issue
2
Publish Date
2012
Start Page
955
End Page
965
DOI
10.1096/fj.11-187575

Calcium dependent CAMTA1 in adult stem cell commitment to a myocardial lineage.

The phenotype of somatic cells has recently been found to be reversible. Direct reprogramming of one cell type into another has been achieved with transduction and over expression of exogenous defined transcription factors emphasizing their role in specifying cell fate. To discover early and novel endogenous transcription factors that may have a role in adult-derived stem cell acquisition of a cardiomyocyte phenotype, mesenchymal stem cells from human and mouse bone marrow and rat liver were co-cultured with neonatal cardiomyocytes as an in vitro cardiogenic microenvironment. Cell-cell communications develop between the two cell types as early as 24 hrs in co-culture and are required for elaboration of a myocardial phenotype in the stem cells 8-16 days later. These intercellular communications are associated with novel Ca(2+) oscillations in the stem cells that are synchronous with the Ca(2+) transients in adjacent cardiomyocytes and are detected in the stem cells as early as 24-48 hrs in co-culture. Early and significant up-regulation of Ca(2+)-dependent effectors, CAMTA1 and RCAN1 ensues before a myocardial program is activated. CAMTA1 loss-of-function minimizes the activation of the cardiac gene program in the stem cells. While the expression of RCAN1 suggests involvement of the well-characterized calcineurin-NFAT pathway as a response to a Ca(2+) signal, the CAMTA1 up-regulated expression as a response to such a signal in the stem cells was unknown. Cell-cell communications between the stem cells and adjacent cardiomyocytes induce Ca(2+) signals that activate a myocardial gene program in the stem cells via a novel and early Ca(2+)-dependent intermediate, up-regulation of CAMTA1.

Authors
Muller-Borer, B; Esch, G; Aldina, R; Woon, W; Fox, R; Bursac, N; Hiller, S; Maeda, N; Shepherd, N; Jin, JP; Hutson, M; Anderson, P; Kirby, ML; Malouf, NN
MLA Citation
Muller-Borer, B, Esch, G, Aldina, R, Woon, W, Fox, R, Bursac, N, Hiller, S, Maeda, N, Shepherd, N, Jin, JP, Hutson, M, Anderson, P, Kirby, ML, and Malouf, NN. "Calcium dependent CAMTA1 in adult stem cell commitment to a myocardial lineage." PLoS One 7.6 (2012): e38454-.
Website
http://hdl.handle.net/10161/8429
PMID
22715383
Source
pubmed
Published In
PloS one
Volume
7
Issue
6
Publish Date
2012
Start Page
e38454
DOI
10.1371/journal.pone.0038454

Pluripotent stem cell-derived cardiac tissue patch with advanced structure and function.

Recent advances in pluripotent stem cell research have provided investigators with potent sources of cardiogenic cells. However, tissue engineering methodologies to assemble cardiac progenitors into aligned, 3-dimensional (3D) myocardial tissues capable of physiologically relevant electrical conduction and force generation are lacking. In this study, we introduced 3D cell alignment cues in a fibrin-based hydrogel matrix to engineer highly functional cardiac tissues from genetically purified mouse embryonic stem cell-derived cardiomyocytes (CMs) and cardiovascular progenitors (CVPs). Procedures for CM and CVP derivation, purification, and functional differentiation in monolayer cultures were first optimized to yield robust intercellular coupling and maximize velocity of action potential propagation. A versatile soft-lithography technique was then applied to reproducibly fabricate engineered cardiac tissues with controllable size and 3D architecture. While purified CMs assembled into a functional 3D syncytium only when supplemented with supporting non-myocytes, purified CVPs differentiated into cardiomyocytes, smooth muscle, and endothelial cells, and autonomously supported the formation of functional cardiac tissues. After a total culture time similar to period of mouse embryonic development (21 days), the engineered cardiac tissues exhibited unprecedented levels of 3D organization and functional differentiation characteristic of native neonatal myocardium, including: 1) dense, uniformly aligned, highly differentiated and electromechanically coupled cardiomyocytes, 2) rapid action potential conduction with velocities between 22 and 25 cm/s, and 3) significant contractile forces of up to 2 mN. These results represent an important advancement in stem cell-based cardiac tissue engineering and provide the foundation for exploiting the exciting progress in pluripotent stem cell research in the future tissue engineering therapies for heart disease.

Authors
Liau, B; Christoforou, N; Leong, KW; Bursac, N
MLA Citation
Liau, B, Christoforou, N, Leong, KW, and Bursac, N. "Pluripotent stem cell-derived cardiac tissue patch with advanced structure and function." Biomaterials 32.35 (December 2011): 9180-9187.
PMID
21906802
Source
pubmed
Published In
Biomaterials
Volume
32
Issue
35
Publish Date
2011
Start Page
9180
End Page
9187
DOI
10.1016/j.biomaterials.2011.08.050

Size and Ionic Currents of Unexcitable Cells Coupled to Cardiomyocytes Distinctly Modulate Cardiac Action Potential Shape and Pacemaking Activity

Authors
McSpadden, LC; Bursac, N
MLA Citation
McSpadden, LC, and Bursac, N. "Size and Ionic Currents of Unexcitable Cells Coupled to Cardiomyocytes Distinctly Modulate Cardiac Action Potential Shape and Pacemaking Activity." CIRCULATION 124.21 (November 22, 2011).
Source
wos-lite
Published In
Circulation
Volume
124
Issue
21
Publish Date
2011

Fibroblast growth factor homologous factor 13 regulates Na+ channels and conduction velocity in murine hearts.

RATIONALE: Fibroblast growth factor homologous factors (FHFs), a subfamily of fibroblast growth factors (FGFs) that are incapable of functioning as growth factors, are intracellular modulators of Na(+) channels and have been linked to neurodegenerative diseases. Although certain FHFs have been found in embryonic heart, they have not been reported in adult heart, and they have not been shown to regulate endogenous cardiac Na(+) channels or to participate in cardiac pathophysiology. OBJECTIVE: We tested whether FHFs regulate Na(+) channels in murine heart. METHODS AND RESULTS: We demonstrated that isoforms of FGF13 are the predominant FHFs in adult mouse ventricular myocytes. FGF13 binds directly to, and colocalizes with, the Na(V)1.5 Na(+) channel in the sarcolemma of adult mouse ventricular myocytes. Knockdown of FGF13 in adult mouse ventricular myocytes revealed a loss of function of Na(V)1.5-reduced Na(+) current density, decreased Na(+) channel availability, and slowed Na(V)1.5-reduced Na(+) current recovery from inactivation. Cell surface biotinylation experiments showed ≈45% reduction in Na(V)1.5 protein at the sarcolemma after FGF13 knockdown, whereas no changes in whole-cell Na(V)1.5 protein or in mRNA level were observed. Optical imaging in neonatal rat ventricular myocyte monolayers demonstrated slowed conduction velocity and a reduced maximum capture rate after FGF13 knockdown. CONCLUSION: These findings show that FHFs are potent regulators of Na(+) channels in adult ventricular myocytes and suggest that loss-of-function mutations in FHFs may underlie a similar set of cardiac arrhythmias and cardiomyopathies that result from Na(V)1.5 loss-of-function mutations.

Authors
Wang, C; Hennessey, JA; Kirkton, RD; Wang, C; Graham, V; Puranam, RS; Rosenberg, PB; Bursac, N; Pitt, GS
MLA Citation
Wang, C, Hennessey, JA, Kirkton, RD, Wang, C, Graham, V, Puranam, RS, Rosenberg, PB, Bursac, N, and Pitt, GS. "Fibroblast growth factor homologous factor 13 regulates Na+ channels and conduction velocity in murine hearts." Circ Res 109.7 (September 16, 2011): 775-782.
PMID
21817159
Source
pubmed
Published In
Circulation Research
Volume
109
Issue
7
Publish Date
2011
Start Page
775
End Page
782
DOI
10.1161/CIRCRESAHA.111.247957

A method to measure myocardial calcium handling in adult Drosophila.

RATIONALE: Normal cardiac physiology requires highly regulated cytosolic Ca(2+) concentrations and abnormalities in Ca(2+) handling are associated with heart failure. The majority of approaches to identifying the components that regulate intracellular Ca(2+) dynamics rely on cells in culture, mouse models, and human samples. However, a genetically robust system for unbiased screens of mutations that affect Ca(2+) handling remains a challenge. OBJECTIVE: We sought to develop a new method to measure myocardial Ca(2+) cycling in adult Drosophila and determine whether cardiomyopathic fly hearts recapitulate aspects of diseased mammalian myocardium. METHODS AND RESULTS: Using engineered transgenic Drosophila that have cardiac-specific expression of Ca(2+)-sensing fluorescent protein, GCaMP2, we developed methods to measure parameters associated with myocardial Ca(2+) handling. The following key observations were identified: (1) Control w(1118) Drosophila hearts have readily measureable Ca(2+)-dependent fluorescent signals that are dependent on L-type Ca(2+) channels and SR Ca(2+) stores and originate from rostral and caudal pacemakers. (2) A fly mutant, held-up(2) (hdp(2)), that has a point mutation in troponin I and has a dilated cardiomyopathic phenotype demonstrates abnormalities in myocardial Ca(2+) handling that include increases in the duration of the 50% rise in intensity to peak intensity, the half-time of fluorescence decline from peak, the full duration at half-maximal intensity, and decreases in the linear slope of decay from 80% to 20% intensity decay. (3) Hearts from hdp(2) mutants had reductions in caffeine-induced Ca(2+) increases and reductions in ryanodine receptor (RyR) without changes in L-type Ca(2+) channel transcripts in comparison with w(1118). CONCLUSIONS: Our results show that the cardiac-specific expression of GCaMP2 provides a means of characterizing propagating Ca(2+) transients in adult fly hearts. Moreover, the adult fruit fly heart recapitulates several aspects of Ca(2+) regulation observed in mammalian myocardium. A mutation in Drosophila that causes an enlarged cardiac chamber and impaired contractile function is associated with abnormalities in the cytosolic Ca(2+) transient as well as changes in transcript levels of proteins associated with Ca(2+) handling. This new methodology has the potential to permit an examination of evolutionarily conserved myocardial Ca(2+)-handing mechanisms by applying the vast resources available in the fly genomics community to conduct genetic screens to identify new genes involved in generated Ca(2+) transients and arrhythmias.

Authors
Lin, N; Badie, N; Yu, L; Abraham, D; Cheng, H; Bursac, N; Rockman, HA; Wolf, MJ
MLA Citation
Lin, N, Badie, N, Yu, L, Abraham, D, Cheng, H, Bursac, N, Rockman, HA, and Wolf, MJ. "A method to measure myocardial calcium handling in adult Drosophila." Circ Res 108.11 (May 27, 2011): 1306-1315.
PMID
21493892
Source
pubmed
Published In
Circulation Research
Volume
108
Issue
11
Publish Date
2011
Start Page
1306
End Page
1315
DOI
10.1161/CIRCRESAHA.110.238105

The role of extracellular matrix composition in structure and function of bioengineered skeletal muscle.

One of the obstacles to the potential clinical utility of bioengineered skeletal muscle is its limited force generation capacity. Since engineered muscle, unlike most native muscle tissue, is composed of relatively short myofibers, we hypothesized that, its force production and transmission would be profoundly influenced by cell-matrix interactions. To test this hypothesis, we systematically varied the matrix protein type (collagen I/fibrin/Matrigel) and concentration in engineered, hydrogel-based neonatal rat skeletal muscle bundles and assessed the resulting tissue structure, generation of contractile force, and intracellular Ca(2+) handling. After two weeks of culture, the muscle bundles consisted of highly aligned and cross-striated myofibers and exhibited standard force-length and force-frequency relationships achieving tetanus at 40 Hz. The use of 2 mg/ml fibrin (control) yielded isometric tetanus amplitude of 1.4 ± 0.3 mN as compared to 0.9 ± 0.4 mN measured in collagen I-based bundles. Higher fibrin and Matrigel concentrations synergistically yielded further increase in active force generation to 2.8 ± 0.5 mN without significantly affecting passive mechanical properties, tetanus-to-twitch ratio, and twitch kinetics. Optimized matrix composition yielded significant cellular hypertrophy (protein/DNA ratio = 11.4 ± 4.1 vs. 6.5 ± 1.9 μg/μg in control) and a prolonged Ca(2+) transient half-width (Ca(50) = 232.8 ± 33.3 vs. 101.7 ± 19.8 ms). The use of growth-factor-reduced Matrigel, instead of standard Matrigel did not alter the obtained results suggesting enhanced cell-matrix interactions rather than growth factor supplementation as an underlying cause for the measured increase in contractile force. In summary, biomaterial-based manipulation of cell-matrix interactions represents an important target for improving contractile force generation in engineered skeletal muscle.

Authors
Hinds, S; Bian, W; Dennis, RG; Bursac, N
MLA Citation
Hinds, S, Bian, W, Dennis, RG, and Bursac, N. "The role of extracellular matrix composition in structure and function of bioengineered skeletal muscle." Biomaterials 32.14 (May 2011): 3575-3583.
PMID
21324402
Source
pubmed
Published In
Biomaterials
Volume
32
Issue
14
Publish Date
2011
Start Page
3575
End Page
3583
DOI
10.1016/j.biomaterials.2011.01.062

FGF13 is a Regulator of the Cardiac Voltage-Gated Sodium Channel Nav1.5

Authors
Wang, C; Hennessey, JA; Kirkton, RD; Wang, C; Bryson, V; Rosenberg, PB; Bursac, N; Pitt, GS
MLA Citation
Wang, C, Hennessey, JA, Kirkton, RD, Wang, C, Bryson, V, Rosenberg, PB, Bursac, N, and Pitt, GS. "FGF13 is a Regulator of the Cardiac Voltage-Gated Sodium Channel Nav1.5." February 2, 2011.
Source
wos-lite
Published In
Biophysical Journal
Volume
100
Issue
3
Publish Date
2011
Start Page
420
End Page
421

Engineering biosynthetic excitable tissues from unexcitable cells for electrophysiological and cell therapy studies.

Patch-clamp recordings in single-cell expression systems have been traditionally used to study the function of ion channels. However, this experimental setting does not enable assessment of tissue-level function such as action potential (AP) conduction. Here we introduce a biosynthetic system that permits studies of both channel activity in single cells and electrical conduction in multicellular networks. We convert unexcitable somatic cells into an autonomous source of electrically excitable and conducting cells by stably expressing only three membrane channels. The specific roles that these expressed channels have on AP shape and conduction are revealed by different pharmacological and pacing protocols. Furthermore, we demonstrate that biosynthetic excitable cells and tissues can repair large conduction defects within primary 2- and 3-dimensional cardiac cell cultures. This approach enables novel studies of ion channel function in a reproducible tissue-level setting and may stimulate the development of new cell-based therapies for excitable tissue repair.

Authors
Kirkton, RD; Bursac, N
MLA Citation
Kirkton, RD, and Bursac, N. "Engineering biosynthetic excitable tissues from unexcitable cells for electrophysiological and cell therapy studies." Nat Commun 2 (2011): 300-.
PMID
21556054
Source
pubmed
Published In
Nature Communications
Volume
2
Publish Date
2011
Start Page
300
DOI
10.1038/ncomms1302

Whole cell imaging based on wide-field interferometric phase microscopy and its application to cardiomyocytes

Whole cell imaging is a novel technique using which the time-dependent quantitative phase profiles of live unstained biological cells are analyzed numerically to learn on the cell functionally. Dynamic phase profiles of the sample are first acquired by wide-field digital interferometry (WFDI), a quantitative holographic approach, without the need for scanning or using exogenous contrast agents. The resulting phase profiles are proportional to the multiplication between the cell thickness profile and its integral refractive index profile. However, many morphological parameters, including cell volume and cell force distribution, are based on the cell thickness profile, rather than on its WFDI phase profile. For cells with heterogeneous refractive index structure, more than a single exposure is typically needed to decouple thickness from integral refractive index using the phase profile, with the risk of losing transient acquisition. The presented whole-cell-imaging approach show that the WFDI phase profiles are useful for numerically analyzing cells even in cases where decoupling of thickness and integral refractive index is not possible or desired. We thus define new numerical parameters that directly utilize the WFDI phase profile and demonstrate their usefulness for characterizing contracting cardiomyocytes, cells with complex and highly-dynamic refractive-index structure. © 2011 SPIE.

Authors
Shaked, NT; Satterwhite, LL; Bursac, N; Wax, A
MLA Citation
Shaked, NT, Satterwhite, LL, Bursac, N, and Wax, A. "Whole cell imaging based on wide-field interferometric phase microscopy and its application to cardiomyocytes." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 7904 (2011).
Source
scival
Published In
Proceedings of SPIE
Volume
7904
Publish Date
2011
DOI
10.1117/12.874224

Engineering of Functional Cardiac Tissue Patch with Realistic Myofiber Orientations

Authors
Bian, W; Liau, B; Badie, N; Bursac, N
MLA Citation
Bian, W, Liau, B, Badie, N, and Bursac, N. "Engineering of Functional Cardiac Tissue Patch with Realistic Myofiber Orientations." CIRCULATION 122.21 (November 23, 2010).
Source
wos-lite
Published In
Circulation
Volume
122
Issue
21
Publish Date
2010

Engineered Somatic Cells for Cardiac Repair

Authors
Kirkton, RD; Bursac, N
MLA Citation
Kirkton, RD, and Bursac, N. "Engineered Somatic Cells for Cardiac Repair." CIRCULATION 122.21 (November 23, 2010).
Source
wos-lite
Published In
Circulation
Volume
122
Issue
21
Publish Date
2010

X-Linked Inhibitor of Apoptosis Protein (XIAP)-Mediated Attenuation of Apoptosis Using a Novel Cardiac Enhanced Adeno-Associated Viral Vector

Authors
Piacentino, V; Bolanos, M; Schroder, J; Messina, E; Jones, E; Krol, A; Bursac, N; Devi, G; Mao, L; Samulski, RJ; Milano, C; Bowles, D
MLA Citation
Piacentino, V, Bolanos, M, Schroder, J, Messina, E, Jones, E, Krol, A, Bursac, N, Devi, G, Mao, L, Samulski, RJ, Milano, C, and Bowles, D. "X-Linked Inhibitor of Apoptosis Protein (XIAP)-Mediated Attenuation of Apoptosis Using a Novel Cardiac Enhanced Adeno-Associated Viral Vector." CIRCULATION 122.21 (November 23, 2010).
Source
wos-lite
Published In
Circulation
Volume
122
Issue
21
Publish Date
2010

Whole-cell-analysis of live cardiomyocytes using wide-field interferometric phase microscopy.

We apply wide-field interferometric microscopy techniques to acquire quantitative phase profiles of ventricular cardiomyocytes in vitro during their rapid contraction with high temporal and spatial resolution. The whole-cell phase profiles are analyzed to yield valuable quantitative parameters characterizing the cell dynamics, without the need to decouple thickness from refractive index differences. Our experimental results verify that these new parameters can be used with wide field interferometric microscopy to discriminate the modulation of cardiomyocyte contraction dynamics due to temperature variation. To demonstrate the necessity of the proposed numerical analysis for cardiomyocytes, we present confocal dual-fluorescence-channel microscopy results which show that the rapid motion of the cell organelles during contraction preclude assuming a homogenous refractive index over the entire cell contents, or using multiple-exposure or scanning microscopy.

Authors
Shaked, NT; Satterwhite, LL; Bursac, N; Wax, A
MLA Citation
Shaked, NT, Satterwhite, LL, Bursac, N, and Wax, A. "Whole-cell-analysis of live cardiomyocytes using wide-field interferometric phase microscopy. (Published online)" Biomed Opt Express 1.2 (August 23, 2010): 706-719.
Website
http://hdl.handle.net/10161/8427
PMID
21258502
Source
pubmed
Published In
Biomedical Optics Express
Volume
1
Issue
2
Publish Date
2010
Start Page
706
End Page
719
DOI
10.1364/BOE.1.000706

Implantation of mouse embryonic stem cell-derived cardiac progenitor cells preserves function of infarcted murine hearts.

Stem cell transplantation holds great promise for the treatment of myocardial infarction injury. We recently described the embryonic stem cell-derived cardiac progenitor cells (CPCs) capable of differentiating into cardiomyocytes, vascular endothelium, and smooth muscle. In this study, we hypothesized that transplanted CPCs will preserve function of the infarcted heart by participating in both muscle replacement and neovascularization. Differentiated CPCs formed functional electromechanical junctions with cardiomyocytes in vitro and conducted action potentials over cm-scale distances. When transplanted into infarcted mouse hearts, CPCs engrafted long-term in the infarct zone and surrounding myocardium without causing teratomas or arrhythmias. The grafted cells differentiated into cross-striated cardiomyocytes forming gap junctions with the host cells, while also contributing to neovascularization. Serial echocardiography and pressure-volume catheterization demonstrated attenuated ventricular dilatation and preserved left ventricular fractional shortening, systolic and diastolic function. Our results demonstrate that CPCs can engraft, differentiate, and preserve the functional output of the infarcted heart.

Authors
Christoforou, N; Oskouei, BN; Esteso, P; Hill, CM; Zimmet, JM; Bian, W; Bursac, N; Leong, KW; Hare, JM; Gearhart, JD
MLA Citation
Christoforou, N, Oskouei, BN, Esteso, P, Hill, CM, Zimmet, JM, Bian, W, Bursac, N, Leong, KW, Hare, JM, and Gearhart, JD. "Implantation of mouse embryonic stem cell-derived cardiac progenitor cells preserves function of infarcted murine hearts. (Published online)" PLoS One 5.7 (July 12, 2010): e11536-.
Website
http://hdl.handle.net/10161/8426
PMID
20634944
Source
pubmed
Published In
PloS one
Volume
5
Issue
7
Publish Date
2010
Start Page
e11536
DOI
10.1371/journal.pone.0011536

A computer model of engineered cardiac monolayers.

Engineered monolayers created using microabrasion and micropatterning methods have provided a simplified in vitro system to study the effects of anisotropy and fiber direction on electrical propagation. Interpreting the behavior in these culture systems has often been performed using classical computer models with continuous properties. However, such models do not account for the effects of random cell shapes, cell orientations, and cleft spaces inherent in these monolayers on the resulting wavefront conduction. This work presents a novel methodology for modeling a monolayer of cardiac tissue in which the factors governing cell shape, cell-to-cell coupling, and degree of cleft space are not constant but rather are treated as spatially random with assigned distributions. This modeling approach makes it possible to simulate wavefront propagation in a manner analogous to performing experiments on engineered monolayer tissues. Simulated results are compared to previously published measured data from monolayers used to investigate the role of cellular architecture on conduction velocities and anisotropy ratios. We also present an estimate for obtaining the electrical properties from these networks and demonstrate how variations in the discrete cellular architecture affect the macroscopic conductivities. The simulations support the common assumption that under normal ranges of coupling strength, tissues with relatively uniform distributions of cell shapes and connectivity can be represented using continuous models with conductivities derived from random discrete cellular architecture using either global or local estimates. The results also reveal that in the presence of abrupt changes in cell orientation, local estimates of tissue properties predict smoother changes in conductivity that may not adequately predict the discrete nature of propagation at the transition sites.

Authors
Kim, JM; Bursac, N; Henriquez, CS
MLA Citation
Kim, JM, Bursac, N, and Henriquez, CS. "A computer model of engineered cardiac monolayers." Biophys J 98.9 (May 19, 2010): 1762-1771.
PMID
20441739
Source
pubmed
Published In
Biophysical Journal
Volume
98
Issue
9
Publish Date
2010
Start Page
1762
End Page
1771
DOI
10.1016/j.bpj.2010.01.008

Reflective interferometric chamber for quantitative phase imaging of biological sample dynamics.

We introduce a new interferometric setup for single-exposure wide-field holographic phase imaging of highly dynamic biological samples. In this setup, the interferometric signal originates from a specially designed reflective interferometric chamber (InCh), creating an off-axis interferogram on the output plane of the system. The setup only requires the InCh and a simple reflection-mode two lens imaging system, without the need for additional optical elements such as gratings in the beam path. In addition, due to the close-to-common-path geometry of the setup, phase noise is greatly reduced. We experimentally compare the inherent phase stability of the system in ambient conditions to that of a conventional interferometer. We also demonstrate use of this system for wide-field quantitative phase imaging of two different highly dynamic, optically transparent biological samples: beating myocardial cells and moving unicellular microorganisms.

Authors
Shaked, NT; Zhu, Y; Badie, N; Bursac, N; Wax, A
MLA Citation
Shaked, NT, Zhu, Y, Badie, N, Bursac, N, and Wax, A. "Reflective interferometric chamber for quantitative phase imaging of biological sample dynamics." J Biomed Opt 15.3 (May 2010): 030503-. (Letter)
PMID
20614989
Source
pubmed
Published In
Journal of Biomedical Optics
Volume
15
Issue
3
Publish Date
2010
Start Page
030503
DOI
10.1117/1.3420179

Collision-based spiral acceleration in cardiac media: roles of wavefront curvature and excitable gap.

We have previously shown in experimental cardiac cell monolayers that rapid point pacing can convert basic functional reentry (single spiral) into a stable multiwave spiral that activates the tissue at an accelerated rate. Here, our goal is to further elucidate the biophysical mechanisms of this rate acceleration without the potential confounding effects of microscopic tissue heterogeneities inherent to experimental preparations. We use computer simulations to show that, similar to experimental observations, single spirals can be converted by point stimuli into stable multiwave spirals. In multiwave spirals, individual waves collide, yielding regions with negative wavefront curvature. When a sufficient excitable gap is present and the negative-curvature regions are close to spiral tips, an electrotonic spread of excitatory currents from these regions propels each colliding spiral to rotate faster than the single spiral, causing an overall rate acceleration. As observed experimentally, the degree of rate acceleration increases with the number of colliding spiral waves. Conversely, if collision sites are far from spiral tips, excitatory currents have no effect on spiral rotation and multiple spirals rotate independently, without rate acceleration. Understanding the mechanisms of spiral rate acceleration may yield new strategies for preventing the transition from monomorphic tachycardia to polymorphic tachycardia and fibrillation.

Authors
Tranquillo, JV; Badie, N; Henriquez, CS; Bursac, N
MLA Citation
Tranquillo, JV, Badie, N, Henriquez, CS, and Bursac, N. "Collision-based spiral acceleration in cardiac media: roles of wavefront curvature and excitable gap." Biophys J 98.7 (April 7, 2010): 1119-1128.
PMID
20371311
Source
pubmed
Published In
Biophysical Journal
Volume
98
Issue
7
Publish Date
2010
Start Page
1119
End Page
1128
DOI
10.1016/j.bpj.2009.12.4281

Characterizing functional stem cell-cardiomyocyte interactions.

Despite the progress in traditional pharmacological and organ transplantation therapies, heart failure still afflicts 5.3 million Americans. Since June 2000, stem cell-based approaches for the prevention and treatment of heart failure have been pursued in clinics with great excitement; however, the exact mechanisms of how transplanted cells improve heart function remain elusive. One of the main difficulties in answering these questions is the limited ability to directly access and study interactions between implanted cells and host cardiomyocytes in situ. With the growing number of candidate cell types for potential clinical use, it is becoming increasingly more important to establish standardized, well-controlled in vitro and in situ assays to compare the efficacy and safety of different stem cells in cardiac repair. This article describes recent innovative methodologies to characterize direct functional interactions between stem cells and cardiomyocytes, aimed to facilitate the rational design of future cell-based therapies for heart disease.

Authors
Bursac, N; Kirkton, RD; McSpadden, LC; Liau, B
MLA Citation
Bursac, N, Kirkton, RD, McSpadden, LC, and Liau, B. "Characterizing functional stem cell-cardiomyocyte interactions." Regen Med 5.1 (January 2010): 87-105. (Review)
PMID
20017697
Source
pubmed
Published In
Regenerative medicine
Volume
5
Issue
1
Publish Date
2010
Start Page
87
End Page
105
DOI
10.2217/rme.09.69

A method to replicate the microstructure of heart tissue in vitro using DTMRI-based cell micropatterning.

A novel cell culture methodology is described in which diffusion tensor magnetic resonance imaging (DTMRI) and cell micropatterning are combined to fabricate cell monolayers that replicate realistic cross-sectional tissue structure. As a proof-of-principle, neonatal rat ventricular myocyte (NRVM) monolayers were cultured to replicate the tissue microstructure of murine ventricular cross-sections. Specifically, DTMRI-measured in-plane cardiac fiber directions were converted into soft-lithography photomasks. Silicone stamps fabricated from the photomasks deposit fibronectin patterns to guide local cellular alignment. Fibronectin patterns consisted of a matrix of 190 microm(2) subregions, each comprised of parallel lines 11-20 microm-wide, spaced 2-8.5 microm apart, and angled to match local DTMRI-measured fiber directions. Within 6 days of culture, NRVMs established confluent, electrically coupled monolayers, and for 18 microm-wide, 5 microm-spaced lines, directions of cell alignment in subregions microscopically replicated DTMRI-measurements with a local error of 7.2 +/- 4.1 degrees . By adjusting fibronectin line widths and spacings, cell elongation, gap junctional membrane distribution, and local cellular disarray were altered without changing the dominant directions of cell alignment in individual subregions. Changes in the anisotropy of electrical propagation were assessed by optically mapping membrane potentials. This novel methodology is expected to enable systematic studies of intramural structure-function relationships in both healthy and structurally remodeled hearts.

Authors
Badie, N; Satterwhite, L; Bursac, N
MLA Citation
Badie, N, Satterwhite, L, and Bursac, N. "A method to replicate the microstructure of heart tissue in vitro using DTMRI-based cell micropatterning." Ann Biomed Eng 37.12 (December 2009): 2510-2521.
PMID
19806455
Source
pubmed
Published In
Annals of Biomedical Engineering
Volume
37
Issue
12
Publish Date
2009
Start Page
2510
End Page
2521
DOI
10.1007/s10439-009-9815-x

Electromechanically Functional Cardiac Tissue Constructs Engineered From Embryonic Stem Cells

Authors
Liau, B; Christoforou, N; Bursac, N
MLA Citation
Liau, B, Christoforou, N, and Bursac, N. "Electromechanically Functional Cardiac Tissue Constructs Engineered From Embryonic Stem Cells." November 3, 2009.
Source
wos-lite
Published In
Circulation
Volume
120
Issue
18
Publish Date
2009
Start Page
S810
End Page
S811

Cardiac Fibroblasts Strongly Affect Cardiac Action Potential Propagation by Paracrine Rather Than Coupling Mechanisms

Authors
Bursac, N
MLA Citation
Bursac, N. "Cardiac Fibroblasts Strongly Affect Cardiac Action Potential Propagation by Paracrine Rather Than Coupling Mechanisms." November 3, 2009.
Source
wos-lite
Published In
Circulation
Volume
120
Issue
18
Publish Date
2009
Start Page
S635
End Page
S635

Cell Therapies for Arrhythmias: Genetically Engineered Coupling Determines the Effect on Anisotropic Cardiac Conduction

Authors
McSpadden, LC; Kirkton, RD; Bursac, N
MLA Citation
McSpadden, LC, Kirkton, RD, and Bursac, N. "Cell Therapies for Arrhythmias: Genetically Engineered Coupling Determines the Effect on Anisotropic Cardiac Conduction." November 3, 2009.
Source
wos-lite
Published In
Circulation
Volume
120
Issue
18
Publish Date
2009
Start Page
S765
End Page
S766

Large 3-Dimensional Tissue Engineered Cardiac Patch With Controlled Electrical Anisotropy

Authors
Bian, W; Bursac, N
MLA Citation
Bian, W, and Bursac, N. "Large 3-Dimensional Tissue Engineered Cardiac Patch With Controlled Electrical Anisotropy." November 3, 2009.
Source
wos-lite
Published In
Circulation
Volume
120
Issue
18
Publish Date
2009
Start Page
S821
End Page
S821

Cardiac fibroblast paracrine factors alter impulse conduction and ion channel expression of neonatal rat cardiomyocytes.

AIMS: The pathological proliferation of cardiac fibroblasts (CFs) in response to heart injury results in fibrosis, which correlates with arrhythmia generation and heart failure. Here we systematically examined the effect of fibroblast-derived paracrine factors on electrical propagation in cardiomyocytes. METHODS AND RESULTS: Neonatal rat cardiac monolayers were exposed for 24 h to media conditioned by CFs. Optical mapping, sharp microelectrode recordings, quantitative RT-PCR, and immunostaining were used to assess the changes in the propagation and shape of the action potential and underlying changes in gene and protein expression. The fibroblast paracrine factors produced a 52% reduction in cardiac conduction velocity, a 217% prolongation of action potential duration, a 64% decrease of maximum capture rate, a 21% increase in membrane resting potential, and an 80% decrease of action potential upstroke velocity. These effects were dose dependent and partially reversible with removal of the conditioned media. No fibroblast proliferation, cardiomyocyte apoptosis, or decreased connexin-43 expression, phosphorylation, and function were found in conditioned cardiac cultures. In contrast, the expression of the fast sodium, inward rectifying potassium, and transient outward potassium channels were, respectively, reduced 3.8-, 6.6-fold, and to undetectable levels. The expression of beta-myosin heavy chain increased 17.4-fold. No electrophysiological changes were observed from media conditioned by CFs in the presence of cardiomyocytes. CONCLUSION: Paracrine factors from neonatal CFs alone produced significant electrophysiological changes in neonatal rat cardiomyocytes resembling those found in several cardiac pathologies.

Authors
Pedrotty, DM; Klinger, RY; Kirkton, RD; Bursac, N
MLA Citation
Pedrotty, DM, Klinger, RY, Kirkton, RD, and Bursac, N. "Cardiac fibroblast paracrine factors alter impulse conduction and ion channel expression of neonatal rat cardiomyocytes." Cardiovasc Res 83.4 (September 1, 2009): 688-697.
PMID
19477968
Source
pubmed
Published In
Cardiovascular Research
Volume
83
Issue
4
Publish Date
2009
Start Page
688
End Page
697
DOI
10.1093/cvr/cvp164

Electrotonic loading of anisotropic cardiac monolayers by unexcitable cells depends on connexin type and expression level.

Understanding how electrotonic loading of cardiomyocytes by unexcitable cells alters cardiac impulse conduction may be highly relevant to fibrotic heart disease. In this study, we optically mapped electrical propagation in confluent, aligned neonatal rat cardiac monolayers electrotonically loaded with cardiac fibroblasts, control human embryonic kidney (HEK-293) cells, or HEK-293 cells genetically engineered to overexpress the gap junction proteins connexin-43 or connexin-45. Gap junction expression and function were assessed by immunostaining, immunoblotting, and fluorescence recovery after photobleaching and were correlated with the optically mapped propagation of action potentials. We found that neonatal rat ventricular fibroblasts negative for the myofibroblast marker smooth muscle alpha-actin expressed connexin-45 rather than connexin-43 or connexin-40, weakly coupled to cardiomyocytes, and, without significant depolarization of cardiac resting potential, slowed cardiac conduction to 75% of control only at high (>60%) coverage densities, similar to loading effects found from HEK-293 cells expressing similar levels of connexin-45. In contrast, HEK-293 cells with connexin-43 expression similar to that of cardiomyocytes significantly decreased cardiac conduction velocity and maximum capture rate to as low as 22% and 25% of control values, respectively, while increasing cardiac action potential duration to 212% of control and cardiac resting potential from -71.6 +/- 4.9 mV in controls to -65.0 +/- 3.8 mV. For all unexcitable cell types and coverage densities, velocity anisotropy ratio remained unchanged. Despite the induced conduction slowing, none of the loading cell types increased the proportion of spontaneously active monolayers. These results signify connexin isoform and expression level as important contributors to potential electrical interactions between unexcitable cells and myocytes in cardiac tissue.

Authors
McSpadden, LC; Kirkton, RD; Bursac, N
MLA Citation
McSpadden, LC, Kirkton, RD, and Bursac, N. "Electrotonic loading of anisotropic cardiac monolayers by unexcitable cells depends on connexin type and expression level." Am J Physiol Cell Physiol 297.2 (August 2009): C339-C351.
PMID
19494239
Source
pubmed
Published In
American journal of physiology. Cell physiology
Volume
297
Issue
2
Publish Date
2009
Start Page
C339
End Page
C351
DOI
10.1152/ajpcell.00024.2009

Novel micropatterned cardiac cell cultures with realistic ventricular microstructure.

Systematic studies of cardiac structure-function relationships to date have been hindered by the intrinsic complexity and variability of in vivo and ex vivo model systems. Thus, we set out to develop a reproducible cell culture system that can accurately replicate the realistic microstructure of native cardiac tissues. Using cell micropatterning techniques, we aligned cultured cardiomyocytes at micro- and macroscopic spatial scales to follow local directions of cardiac fibers in murine ventricular cross sections, as measured by high-resolution diffusion tensor magnetic resonance imaging. To elucidate the roles of ventricular tissue microstructure in macroscopic impulse conduction, we optically mapped membrane potentials in micropatterned cardiac cultures with realistic tissue boundaries and natural cell orientation, cardiac cultures with realistic tissue boundaries but random cell orientation, and standard isotropic monolayers. At 2 Hz pacing, both microscopic changes in cell orientation and ventricular tissue boundaries independently and synergistically increased the spatial dispersion of conduction velocity, but not the action potential duration. The realistic variations in intramural microstructure created unique spatial signatures in micro- and macroscopic impulse propagation within ventricular cross-section cultures. This novel in vitro model system is expected to help bridge the existing gap between experimental structure-function studies in standard cardiac monolayers and intact heart tissues.

Authors
Badie, N; Bursac, N
MLA Citation
Badie, N, and Bursac, N. "Novel micropatterned cardiac cell cultures with realistic ventricular microstructure." Biophys J 96.9 (May 6, 2009): 3873-3885.
PMID
19413993
Source
pubmed
Published In
Biophysical Journal
Volume
96
Issue
9
Publish Date
2009
Start Page
3873
End Page
3885
DOI
10.1016/j.bpj.2009.02.019

Engineered skeletal muscle tissue networks with controllable architecture.

The engineering of functional skeletal muscle tissue substitutes holds promise for the treatment of various muscular diseases and injuries. However, no tissue fabrication technology currently exists for the generation of a relatively large and thick bioartificial muscle made of densely packed, uniformly aligned, and differentiated myofibers. In this study, we describe a versatile cell/hydrogel micromolding approach where polydimethylsiloxane (PDMS) molds containing an array of elongated posts were used to fabricate relatively large neonatal rat skeletal muscle tissue networks with reproducible and controllable architecture. By combining cell-mediated fibrin gel compaction and precise microfabrication of mold dimensions including the length and height of the PDMS posts, we were able to simultaneously support high cell viability, guide cell alignment along the microfabricated tissue pores, and reproducibly control the overall tissue porosity, size, and thickness. The interconnected muscle bundles within the porous tissue networks were composed of densely packed, aligned, and highly differentiated myofibers. The formed myofibers expressed myogenin, developed abundant cross-striations, and generated spontaneous tissue contractions at the macroscopic spatial scale. The proliferation of non-muscle cells was significantly reduced compared to monolayer cultures. The more complex muscle tissue architectures were fabricated by controlling the spatial distribution and direction of the PDMS posts.

Authors
Bian, W; Bursac, N
MLA Citation
Bian, W, and Bursac, N. "Engineered skeletal muscle tissue networks with controllable architecture." Biomaterials 30.7 (March 2009): 1401-1412.
PMID
19070360
Source
pubmed
Published In
Biomaterials
Volume
30
Issue
7
Publish Date
2009
Start Page
1401
End Page
1412
DOI
10.1016/j.biomaterials.2008.11.015

Cardiac tissue engineering using stem cells.

Authors
Bursac, N
MLA Citation
Bursac, N. "Cardiac tissue engineering using stem cells." IEEE Eng Med Biol Mag 28.2 (March 2009): 80-89. (Review)
PMID
19353830
Source
pubmed
Published In
IEEE Engineering in Medicine and Biology Magazine
Volume
28
Issue
2
Publish Date
2009
Start Page
80
End Page
89

Mesoscopic hydrogel molding to control the 3D geometry of bioartificial muscle tissues.

This protocol describes a cell/hydrogel molding method for precise and reproducible biomimetic fabrication of three-dimensional (3D) muscle tissue architectures in vitro. Using a high aspect ratio soft lithography technique, we fabricate polydimethylsiloxane (PDMS) molds containing arrays of mesoscopic posts with defined size, elongation and spacing. On cell/hydrogel molding, these posts serve to enhance the diffusion of nutrients to cells by introducing elliptical pores in the cell-laden hydrogels and to guide local 3D cell alignment by governing the spatial pattern of mechanical tension. Instead of ultraviolet or chemical cross-linking, this method utilizes natural hydrogel polymerization and topographically constrained cell-mediated gel compaction to create the desired 3D tissue structures. We apply this method to fabricate several square centimeter large, few hundred micron-thick bioartificial muscle tissues composed of viable, dense, uniformly aligned and highly differentiated cardiac or skeletal muscle fibers. The protocol takes 4-5 d to fabricate PDMS molds followed by 2 weeks of cell culture.

Authors
Bian, W; Liau, B; Badie, N; Bursac, N
MLA Citation
Bian, W, Liau, B, Badie, N, and Bursac, N. "Mesoscopic hydrogel molding to control the 3D geometry of bioartificial muscle tissues." Nat Protoc 4.10 (2009): 1522-1534.
PMID
19798085
Source
pubmed
Published In
Nature Protocols
Volume
4
Issue
10
Publish Date
2009
Start Page
1522
End Page
1534
DOI
10.1038/nprot.2009.155

Micropatterned Ventricular Slice: Role of Realistic Tissue Microstructure In Impulse Conduction

Authors
Badle, N; Bursac, N
MLA Citation
Badle, N, and Bursac, N. "Micropatterned Ventricular Slice: Role of Realistic Tissue Microstructure In Impulse Conduction." CIRCULATION 118.18 (October 28, 2008): S493-S493.
Source
wos-lite
Published In
Circulation
Volume
118
Issue
18
Publish Date
2008
Start Page
S493
End Page
S493

In Vitro Cellular Implantation Assay To Quantitatively Compare The Ability Of Different Donor Cells To Electrically Conduct Within Cardiac Tissue

Authors
Klinger, R; Bursac, N
MLA Citation
Klinger, R, and Bursac, N. "In Vitro Cellular Implantation Assay To Quantitatively Compare The Ability Of Different Donor Cells To Electrically Conduct Within Cardiac Tissue." CIRCULATION 118.18 (October 28, 2008): S395-S395.
Source
wos-lite
Published In
Circulation
Volume
118
Issue
18
Publish Date
2008
Start Page
S395
End Page
S395

Effect of Electromechanical Stimulation on the Maturation of Myotubes on Aligned Electrospun Fibers.

Tissue engineering may provide an alternative to cell injection as a therapeutic solution for myocardial infarction. A tissue-engineered muscle patch may offer better host integration and higher functional performance. This study examined the differentiation of skeletal myoblasts on aligned electrospun polyurethane (PU) fibers and in the presence of electromechanical stimulation. Skeletal myoblasts cultured on aligned PU fibers showed more pronounced elongation, better alignment, higher level of transient receptor potential cation channel-1 (TRPC-1) expression, upregulation of contractile proteins and higher percentage of striated myotubes compared to those cultured on random PU fibers and film. The resulting tissue constructs generated tetanus forces of 1.1 mN with a 10-ms time to tetanus. Additional mechanical, electrical, or synchronized electromechanical stimuli applied to myoblasts cultured on PU fibers increased the percentage of striated myotubes from 70 to 85% under optimal stimulation conditions, which was accompanied by an upregulation of contractile proteins such as α-actinin and myosin heavy chain. In describing how electromechanical cues can be combined with topographical cue, this study helped move towards the goal of generating a biomimetic microenvironment for engineering of functional skeletal muscle.

Authors
Liao, I-C; Liu, JB; Bursac, N; Leong, KW
MLA Citation
Liao, I-C, Liu, JB, Bursac, N, and Leong, KW. "Effect of Electromechanical Stimulation on the Maturation of Myotubes on Aligned Electrospun Fibers." Cell Mol Bioeng 1.2-3 (September 1, 2008): 133-145.
PMID
19774099
Source
pubmed
Published In
Cellular and Molecular Bioengineering
Volume
1
Issue
2-3
Publish Date
2008
Start Page
133
End Page
145
DOI
10.1007/s12195-008-0021-y

Tissue engineering of functional skeletal muscle: challenges and recent advances.

Authors
Bian, W; Bursac, N
MLA Citation
Bian, W, and Bursac, N. "Tissue engineering of functional skeletal muscle: challenges and recent advances." IEEE Eng Med Biol Mag 27.5 (September 2008): 109-113. (Review)
PMID
18799400
Source
pubmed
Published In
IEEE Engineering in Medicine and Biology Magazine
Volume
27
Issue
5
Publish Date
2008
Start Page
109
End Page
113
DOI
10.1109/MEMB.2008.928460

Structural coupling of cardiomyocytes and noncardiomyocytes: quantitative comparisons using a novel micropatterned cell pair assay.

Well-controlled studies of the structural and functional interactions between cardiomyocytes and other cells are essential for understanding heart pathophysiology and for the further development of safe and efficient cell therapies. We established a novel in vitro assay composed of a large number of individual micropatterned cell pairs with reproducible shape, size, and region of cell-cell contact. This assay was applied to quantify and compare the frequency of expression and distribution of electrical (connexin43) and mechanical (N-cadherin) coupling proteins in 5,000 cell pairs made of cardiomyocytes (CMs), cardiac fibroblasts (CFs), skeletal myoblasts (SKMs), and mesenchymal stem cells (MSCs). We found that for all cell pair types, side-side contacts between two cells formed 4.5-14.3 times more often than end-end contacts. Both connexin43 and N-cadherin were expressed in all homotypic CM pairs but in only 13.4-91.6% of pairs containing noncardiomyocytes, where expression was either junctional (at the site of cell-cell contact) or diffuse (inside the cytoplasm). CM expression was exclusively junctional in homotypic pairs but predominantly diffuse in heterotypic pairs. Noncardiomyocyte homotypic pairs exhibited diffuse expression 1.7-8.7 times more often than junctional expression, which was increased 2.6-4.4 times in heterotypic pairs. Junctional connexin43 and N-cadherin expression, respectively, were found in 38.6 +/- 7.3 and 39.6 +/- 6.2% of CM-MSC pairs, 21.9 +/- 5.0 and 13.6 +/- 1.9% of CM-SKM pairs, and in only 3.8-9.6% of CM-CF pairs. Measured frequencies of protein expression and distribution were stable for at least 4 days. Described studies in micropatterned cell pairs shed new light on cellular interactions relevant for cardiac function and cell therapies.

Authors
Pedrotty, DM; Klinger, RY; Badie, N; Hinds, S; Kardashian, A; Bursac, N
MLA Citation
Pedrotty, DM, Klinger, RY, Badie, N, Hinds, S, Kardashian, A, and Bursac, N. "Structural coupling of cardiomyocytes and noncardiomyocytes: quantitative comparisons using a novel micropatterned cell pair assay." Am J Physiol Heart Circ Physiol 295.1 (July 2008): H390-H400.
PMID
18502901
Source
pubmed
Published In
American journal of physiology. Heart and circulatory physiology
Volume
295
Issue
1
Publish Date
2008
Start Page
H390
End Page
H400
DOI
10.1152/ajpheart.91531.2007

Genetic engineering and stem cells: combinatorial approaches for cardiac cell therapy.

Authors
Kirkton, RD; Bursac, N
MLA Citation
Kirkton, RD, and Bursac, N. "Genetic engineering and stem cells: combinatorial approaches for cardiac cell therapy." IEEE Eng Med Biol Mag 27.3 (May 2008): 85-88.
PMID
18519188
Source
pubmed
Published In
IEEE Engineering in Medicine and Biology Magazine
Volume
27
Issue
3
Publish Date
2008
Start Page
85
End Page
88
DOI
10.1109/MEMB.2008.922356

Cardiac cell therapy in vitro: reproducible assays for comparing the efficacy of different donor cells.

Authors
Klinger, R; Bursac, N
MLA Citation
Klinger, R, and Bursac, N. "Cardiac cell therapy in vitro: reproducible assays for comparing the efficacy of different donor cells." IEEE Eng Med Biol Mag 27.1 (January 2008): 72-80.
PMID
18270054
Source
pubmed
Published In
IEEE Engineering in Medicine and Biology Magazine
Volume
27
Issue
1
Publish Date
2008
Start Page
72
End Page
80
DOI
10.1109/MEMB.2007.913849

Micromolded cardiac network patches for treatment of infarcted heart

Authors
Bian, W; Bursac, N
MLA Citation
Bian, W, and Bursac, N. "Micromolded cardiac network patches for treatment of infarcted heart." CIRCULATION 116.16 (October 16, 2007): 68-69.
Source
wos-lite
Published In
Circulation
Volume
116
Issue
16
Publish Date
2007
Start Page
68
End Page
69

Paracrine factors from cardiac fibroblasts slow conduction velocity and prolong the action potential duration of cardiomyocytes

Authors
Pedrotty, D; Klinger, R; Bursac, N
MLA Citation
Pedrotty, D, Klinger, R, and Bursac, N. "Paracrine factors from cardiac fibroblasts slow conduction velocity and prolong the action potential duration of cardiomyocytes." CIRCULATION 116.16 (October 16, 2007): 87-87.
Source
wos-lite
Published In
Circulation
Volume
116
Issue
16
Publish Date
2007
Start Page
87
End Page
87

Novel anisotropic engineered cardiac tissues: studies of electrical propagation.

The goal of this study was to engineer cardiac tissue constructs with uniformly anisotropic architecture, and to evaluate their electrical function using multi-site optical mapping of cell membrane potentials. Anisotropic polymer scaffolds made by leaching of aligned sucrose templates were seeded with neonatal rat cardiac cells and cultured in rotating bioreactors for 6-14 days. Cells aligned and interconnected inside the scaffolds and when stimulated by a point electrode, supported macroscopically continuous, anisotropic impulse propagation. By culture day 14, the ratio of conduction velocities along vs. across cardiac fibers reached a value of 2, similar to that in native neonatal ventricles, while action potential duration and maximum capture rate, respectively, decreased to 120ms and increased to approximately 5Hz. The shorter culture time and larger scaffold thickness were associated with increased incidence of sustained reentrant arrhythmias. In summary, this study is the first successful attempt to engineer a cm(2)-size, functional anisotropic cardiac tissue patch.

Authors
Bursac, N; Loo, Y; Leong, K; Tung, L
MLA Citation
Bursac, N, Loo, Y, Leong, K, and Tung, L. "Novel anisotropic engineered cardiac tissues: studies of electrical propagation." Biochem Biophys Res Commun 361.4 (October 5, 2007): 847-853.
PMID
17689494
Source
pubmed
Published In
Biochemical and Biophysical Research Communications
Volume
361
Issue
4
Publish Date
2007
Start Page
847
End Page
853
DOI
10.1016/j.bbrc.2007.07.138

Stem cell therapies for heart disease: why do we need bioengineers?

Authors
Bursac, N
MLA Citation
Bursac, N. "Stem cell therapies for heart disease: why do we need bioengineers?." IEEE Eng Med Biol Mag 26.4 (July 2007): 76-79. (Review)
PMID
17672236
Source
pubmed
Published In
IEEE Engineering in Medicine and Biology Magazine
Volume
26
Issue
4
Publish Date
2007
Start Page
76
End Page
79

Sodium channel kinetic changes that produce Brugada syndrome or progressive cardiac conduction system disease.

Some mutations of the sodium channel gene Na(V1.5) are multifunctional, causing combinations of LQTS, Brugada syndrome and progressive cardiac conduction system disease (PCCD). The combination of Brugada syndrome and PCCD is uncommon, although they both result from a reduction in the sodium current. We hypothesize that slow conduction is sufficient to cause S-T segment elevation and undertook a combined experimental and theoretical study to determine whether conduction slowing alone can produce the Brugada phenotype. Deletion of lysine 1479 in one of two positively charged clusters in the III/IV inter-domain linker causes both syndromes. We have examined the functional effects of this mutation using heterologous expression of the wild-type and mutant sodium channel in HEK-293-EBNA cells. We show that DeltaK1479 shifts the potential of half-activation, V(1/2m), to more positive potentials (V(1/2m) = -36.8 +/- 0.8 and -24.5 +/- 1.3 mV for the wild-type and DeltaK1479 mutant respectively, n = 11, 10). The depolarizing shift increases the extent of depolarization required for activation. The potential of half-inactivation, V(1/2h), is also shifted to more positive potentials (V(1/2h) = -85 +/- 1.1 and -79.4 +/- 1.2 mV for wild-type and DeltaK1479 mutant respectively), increasing the fraction of channels available for activation. These shifts are quantitatively the same as a mutation that produces PCCD only, G514C. We incorporated experimentally derived parameters into a model of the cardiac action potential and its propagation in a one dimensional cable (simulating endo-, mid-myocardial and epicardial regions). The simulations show that action potential and ECG changes consistent with Brugada syndrome may result from conduction slowing alone; marked repolarization heterogeneity is not required. The findings also suggest how Brugada syndrome and PCCD which both result from loss of sodium channel function are sometimes present alone and at other times in combination.

Authors
Zhang, Z-S; Tranquillo, J; Neplioueva, V; Bursac, N; Grant, AO
MLA Citation
Zhang, Z-S, Tranquillo, J, Neplioueva, V, Bursac, N, and Grant, AO. "Sodium channel kinetic changes that produce Brugada syndrome or progressive cardiac conduction system disease." Am J Physiol Heart Circ Physiol 292.1 (January 2007): H399-H407.
PMID
16877553
Source
pubmed
Published In
American journal of physiology. Heart and circulatory physiology
Volume
292
Issue
1
Publish Date
2007
Start Page
H399
End Page
H407
DOI
10.1152/ajpheart.01025.2005

Micropatterned heart slice cultures for studies of intramural cardiac electrophysiology

Authors
Badie, N; Bursac, N
MLA Citation
Badie, N, and Bursac, N. "Micropatterned heart slice cultures for studies of intramural cardiac electrophysiology." CIRCULATION 114.18 (October 31, 2006): 331-331.
Source
wos-lite
Published In
Circulation
Volume
114
Issue
18
Publish Date
2006
Start Page
331
End Page
331

Electrical pacing counteracts intrinsic shortening of action potential duration of neonatal rat ventricular cells in culture.

Previous studies have demonstrated the relationship between the functional electrophysiological properties of cultured neonatal rat ventricular myocytes (NRVMs) and the ability of the substrate to induce and sustain arrhythmia. The goal of this study was to examine the effects of chronic pacing at a constant rate akin to that in vivo, on the functional electrophysiological properties of NRVM monolayers. Confluent NRVM monolayers grown on 20 mm diameter cover slips were left either unpaced or were stimulated at 3 Hz for the duration of the culture, and were optically mapped on days 4, 6, or 8. Action potential duration at 80% repolarization (APD80), conduction velocity (CV), and Kv4.3 (Ito) and NCX protein expression were measured. The effects of the excitation-contraction uncoupler 2,3-butadione monoxime (BDM) were also investigated. The 2 Hz APD80 of non-paced monolayers decreased significantly on days 6 (137.1+/-13.9 ms) and 8 (109.8+/-9.0 ms) compared with day 4 (197.0+/-11.8 ms), while that of paced monolayers did not (206.8+/-9.7, 209.1+/-9.2, and 210.6+/-9.9 ms, respectively). The 2 Hz CV of non-paced monolayers increased significantly on days 6 (26.0+/-1.6 cm/s) and 8 (26.5+/-1.0 cm/s) compared with day 4 (20.0+/-1.0 cm/s), while that of paced monolayers did not change significantly (26.0+/-2.0, 26.0+/-1.0, and 23.8+/-1.2 cm/s, respectively). The restitution curves of APD80 and CV of paced monolayers were also unchanging from days 4 through 8. Despite the unchanging APD80 and CV, a decrease in Kv4.3 expression and an increase in NCX expression were observed in paced compared with non-paced monolayers. Cessation of pacing or administration of BDM caused a reversal of phenotype back to that of non-paced monolayers. In summary, chronic electrical stimulation of confluent NRVM monolayers results in stabilization of APD80 and an advancement of the developmental rise of CV that is mediated by electromechanical coupling. These effects produce a steadier functional phenotype that may be beneficial for electrophysiological studies.

Authors
Sathaye, A; Bursac, N; Sheehy, S; Tung, L
MLA Citation
Sathaye, A, Bursac, N, Sheehy, S, and Tung, L. "Electrical pacing counteracts intrinsic shortening of action potential duration of neonatal rat ventricular cells in culture." J Mol Cell Cardiol 41.4 (October 2006): 633-641.
PMID
16950369
Source
pubmed
Published In
Journal of Molecular and Cellular Cardiology
Volume
41
Issue
4
Publish Date
2006
Start Page
633
End Page
641
DOI
10.1016/j.yjmcc.2006.06.076

Acceleration of functional reentry by rapid pacing in anisotropic cardiac monolayers: formation of multi-wave functional reentries.

OBJECTIVE: Attempts to cardiovert tachycardia by rapid point pacing can sometimes result in transient or stable increase of the heart rate (acceleration), changed ECG morphology, and/or fibrillation. The goal of this study was to investigate the effect of rapid pacing on the dynamics of functional reentry in monolayer cultures of cardiac cells. METHODS: Fully confluent, uniformly anisotropic monolayers of neonatal rat ventricular myocytes were prepared using methods of microabrasion. Cells were paced by a point electrode at rest and during functional reentry, and membrane voltages were optically mapped. RESULTS: Point pacing readily induced single loop anisotropic functional reentry with monomorphic optical pseudo-ECG (pECG) and average rotation period of 193+/-52 ms (n=71 monolayers). Attempts to cardiovert reentry by rapid pacing at rates 10-50% faster than the reentry rate were successful in 57/71 monolayers. In 14/71 monolayers, the number of rotating waves was stably increased by 1 to 4, yielding a 10-70% acceleration of pECG rate and change to a different monomorphic or polymorphic pECG. The resulting multi-wave functional reentries were classified based on the number and direction of their rotating waves. The higher the number of waves in the multi-wave reentry, the more accelerated was the rate of cell firing in the monolayer. Importantly, stable acceleration was only inducible in monolayers with relatively deep and broad conduction velocity restitution relationships. Reapplication of point pacing further accelerated, decelerated, or eventually terminated the reentrant activity. CONCLUSIONS: These results suggest that stable multiplication of rotating waves in conjunction with a deep and broad conduction velocity restitution relationship is a possible mechanism for stable acceleration of functional reentry by rapid pacing.

Authors
Bursac, N; Tung, L
MLA Citation
Bursac, N, and Tung, L. "Acceleration of functional reentry by rapid pacing in anisotropic cardiac monolayers: formation of multi-wave functional reentries." Cardiovasc Res 69.2 (February 1, 2006): 381-390.
PMID
16274682
Source
pubmed
Published In
Cardiovascular Research
Volume
69
Issue
2
Publish Date
2006
Start Page
381
End Page
390
DOI
10.1016/j.cardiores.2005.09.014

The role restitution in pacing induced spiral wave acceleration.

Attempts to terminate monomorphic tachycardia by rapid pacing occasionally lead to acceleration of the tachycardia rate followed by fibrillation. Previous experimental studies have shown that rapid pacing can convert a single-wave functional reentry into a stable multi-wave reentry with accelerated rate, but only when the single spiral rate is significantly lower than the rate the tissue can sustain. In addition the acceleration was facilitated by broad and deep conduction velocity restitution. This study explores the mechanisms that modulate the potential for and degree of acceleration. Results demonstrate that ionic changes that affect CV restitution and increase core size of the functional reentry facilitate acceleration by wave multiplication. Understanding the mechanisms for reentry acceleration may yield new strategies that prevent the degeneration of tachycardia to fibrillation.

Authors
Tranquillo, JV; Bursac, N
MLA Citation
Tranquillo, JV, and Bursac, N. "The role restitution in pacing induced spiral wave acceleration." Conference proceedings : .. Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference (2006): 3919-3922.
Source
scival
Published In
Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings
Publish Date
2006
Start Page
3919
End Page
3922

The role restitution in pacing induced spiral wave acceleration.

Attempts to terminate monomorphic tachycardia by rapid pacing occasionally lead to acceleration of the tachycardia rate followed by fibrillation. Previous experimental studies have shown that rapid pacing can convert a single-wave functional reentry into a stable multi-wave reentry with accelerated rate, but only when the single spiral rate is significantly lower than the rate the tissue can sustain. In addition the acceleration was facilitated by broad and deep conduction velocity restitution. This study explores the mechanisms that modulate the potential for and degree of acceleration. Results demonstrate that ionic changes that affect CV restitution and increase core size of the functional reentry facilitate acceleration by wave multiplication. Understanding the mechanisms for reentry acceleration may yield new strategies that prevent the degeneration of tachycardia to fibrillation.

Authors
Tranquillo, JV; Bursac, N
MLA Citation
Tranquillo, JV, and Bursac, N. "The role restitution in pacing induced spiral wave acceleration." Conf Proc IEEE Eng Med Biol Soc 1 (2006): 3919-3922.
PMID
17946208
Source
pubmed
Published In
Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings
Volume
1
Publish Date
2006
Start Page
3919
End Page
3922
DOI
10.1109/IEMBS.2006.260035

The role restitution in pacing induced spiral wave acceleration

Attempts to terminate monomorphic tachycardia by rapid pacing occasionally lead to acceleration of the tachycardia rate followed by fibrillation. Previous experimental studies have shown that rapid pacing can convert a single-wave functional reentry into a stable multi-wave reentry with accelerated rate, but only when the single spiral rate is significantly lower than the rate the tissue can sustain. In addition the acceleration was facilitated by broad and deep conduction velocity restitution. This study explores the mechanisms that modulate the potential for and degree of acceleration. Results demonstrate that ionic changes that affect CV restitution and increase core size of the functional reentry facilitate acceleration by wave multiplication. Understanding the mechanisms for reentry acceleration may yield new strategies that prevent the degeneration of tachycardia to fibrillation. © 2006 IEEE.

Authors
Tranquillo, JV; Bursac, N
MLA Citation
Tranquillo, JV, and Bursac, N. "The role restitution in pacing induced spiral wave acceleration." Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings (2006): 3919-3922.
Source
scival
Published In
Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings
Publish Date
2006
Start Page
3919
End Page
3922
DOI
10.1109/IEMBS.2006.260035

The role restitution in pacing induced spiral wave acceleration

Authors
Tranquillo, JV; Bursac, N; IEEE,
MLA Citation
Tranquillo, JV, Bursac, N, and IEEE, . "The role restitution in pacing induced spiral wave acceleration." 2006.
Source
wos-lite
Published In
2006 28TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-15
Publish Date
2006
Start Page
2420
End Page
+

Paracrine factors from stem cells improve electrical conduction in cardiac tissue

Authors
Pedrotty, D; McSpadden, L; Bursac, N
MLA Citation
Pedrotty, D, McSpadden, L, and Bursac, N. "Paracrine factors from stem cells improve electrical conduction in cardiac tissue." October 25, 2005.
Source
wos-lite
Published In
Circulation
Volume
112
Issue
17
Publish Date
2005
Start Page
U145
End Page
U146

Mechanoelectrical excitation by fluid jets in monolayers of cultured cardiac myocytes.

Although the prevailing view of mechanoelectric feedback (MEF) in the heart is in terms of longitudinal cell stretch, other mechanical forces are considerable during the cardiac cycle, including intramyocardial pressure and shear stress. Their contribution to MEF is largely unknown. In this study, mechanical stimuli in the form of localized fluid jet pulses were applied to neonatal rat ventricular cells cultured as confluent monolayers. Such pulses result in pressure and shear stresses (but not longitudinal stretch) in the monolayer at the point of impingement. The goal was to determine whether these mechanical stimuli can trigger excitation, initiate a propagated wave, and induce reentry. Cells were stained with the voltage-sensitive dye RH237, and multi-site optical mapping was used to record the spread of electrical activity in isotropic and anisotropic monolayers. Pulses (10 ms) with velocities ranging from 0.3 to 1.8 m/s were applied from a 0.4-mm diameter nozzle located 1 mm above the cell monolayer. Fluid jet pulses resulted in circular wavefronts that propagated radially from the stimulus site. The likelihood for mechanical stimulation was quantified as an average stimulus success rate (ASSR). ASSR increased with jet amplitude and time waited between stimuli and decreased with the application of gadolinium and streptomycin, blockers of stretch-activated channels, but not with nifedipine, a blocker of the L-type Ca channel. Absence of cellular injury was confirmed by smooth propagation maps and propidium iodide stains. In rare instances, the mechanical pulse resulted in the induction of reentrant activity. We conclude that mechanical stimuli other than stretch can evoke action potentials, propagated activity, and reentrant arrhythmia in two-dimensional sheets of cardiac cells.

Authors
Kong, C-R; Bursac, N; Tung, L
MLA Citation
Kong, C-R, Bursac, N, and Tung, L. "Mechanoelectrical excitation by fluid jets in monolayers of cultured cardiac myocytes." J Appl Physiol (1985) 98.6 (June 2005): 2328-2336.
PMID
15731396
Source
pubmed
Published In
Journal of applied physiology (Bethesda, Md. : 1985)
Volume
98
Issue
6
Publish Date
2005
Start Page
2328
End Page
2336
DOI
10.1152/japplphysiol.01084.2004

Cardiomyoplasty: the prospect of human stem cells.

Authors
Pedrotty, DM; Bursac, N
MLA Citation
Pedrotty, DM, and Bursac, N. "Cardiomyoplasty: the prospect of human stem cells." IEEE Eng Med Biol Mag 24.3 (May 2005): 125-127.
PMID
15971852
Source
pubmed
Published In
IEEE Engineering in Medicine and Biology Magazine
Volume
24
Issue
3
Publish Date
2005
Start Page
125
End Page
127

Multiarm spirals in a two-dimensional cardiac substrate.

A variety of chemical and biological nonlinear excitable media, including heart tissue, can support stable, self-organized waves of activity in a form of rotating single-arm spirals. In particular, heart tissue can support stationary and meandering spirals of electrical excitation, which have been shown to underlie different forms of cardiac arrhythmias. In contrast to single-arm spirals, stable multiarm spirals (multiple spiral waves that rotate in the same direction around a common organizing center) have not been demonstrated and studied yet in living excitable tissues. Here, we show that persistent multiarm spirals of electrical activity can be induced in monolayer cultures of neonatal rat heart cells by a short, rapid train of electrical point stimuli applied during single-arm-spiral activity. Stable formation is accomplished only in monolayers that show a relatively broad and steep dependence of impulse wavelength and propagation velocity on rate of excitation. The resulting multiarm spirals emit waves of electrical activity at rates faster than for single-arm spirals and exhibit two distinct behaviors, namely "arm-switching" and "tip-switching." The phenomenon of rate acceleration due to an increase in the number of spiral arms possibly may underlie the acceleration of functional reentrant tachycardias paced by a clinician or an antitachycardia device.

Authors
Bursac, N; Aguel, F; Tung, L
MLA Citation
Bursac, N, Aguel, F, and Tung, L. "Multiarm spirals in a two-dimensional cardiac substrate." Proc Natl Acad Sci U S A 101.43 (October 26, 2004): 15530-15534.
PMID
15492227
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
101
Issue
43
Publish Date
2004
Start Page
15530
End Page
15534
DOI
10.1073/pnas.0400984101

Rotors and Spiral Waves in Two Dimensions

Authors
Tung, L; Bursac, N; Aguel, F
MLA Citation
Tung, L, Bursac, N, and Aguel, F. "Rotors and Spiral Waves in Two Dimensions." Cardiac Electrophysiology: Fourth Edition. June 1, 2004. 336-344.
Source
scopus
Publish Date
2004
Start Page
336
End Page
344
DOI
10.1016/B0-7216-0323-8/50040-3

Cultivation in rotating bioreactors promotes maintenance of cardiac myocyte electrophysiology and molecular properties.

We tested the hypothesis that cardiomyocytes maintained their phenotype better if cultured as three-dimensional tissue constructs than if cultured as confluent monolayers. Neonatal rat cardiomyocytes were cultured on biomaterial scaffolds in rotating bioreactors for 1 week, and resulting tissue constructs were compared with confluent monolayers and slices of native ventricular tissue with respect to proteins involved in cell metabolism (creatine kinase isoform MM), contractile function (sarcomeric myosin heavy chain), and intercellular communication (connexin 43), as well as action potential characteristics (e.g., membrane resting potential, maximum depolarization slope, and action potential duration), and macroscopic electrophysiological properties (maximum capture rate). The molecular and electrophysiological properties of cardiomyocytes cultured in tissue constructs, although inferior to those of native neonatal ventricles, were superior to those of the same cells cultured as monolayers. Construct levels of creatine kinase, myosin heavy chain, and connexin 43 were 40-60% as high as ventricle levels, whereas monolayer levels of the same proteins were only 11-20% as high. Construct action potential durations were 1.8-fold higher than those in ventricles, whereas monolayer action potential durations were 2.4-fold higher. Pharmacological studies using 4-aminopyridine showed that prolonged action potential duration and reduced maximum capture rate in tissue constructs as compared with native ventricles could be explained by decreased transient outward potassium current.

Authors
Bursac, N; Papadaki, M; White, JA; Eisenberg, SR; Vunjak-Novakovic, G; Freed, LE
MLA Citation
Bursac, N, Papadaki, M, White, JA, Eisenberg, SR, Vunjak-Novakovic, G, and Freed, LE. "Cultivation in rotating bioreactors promotes maintenance of cardiac myocyte electrophysiology and molecular properties." Tissue Eng 9.6 (December 2003): 1243-1253.
PMID
14670112
Source
pubmed
Published In
Tissue Engineering
Volume
9
Issue
6
Publish Date
2003
Start Page
1243
End Page
1253
DOI
10.1089/10763270360728152

Functional reentry in cultured monolayers of neonatal rat cardiac cells.

Previous studies of reentrant arrhythmias in the heart have been performed in computer models and tissue experiments. We hypothesized that confluent monolayers of cardiac cells can provide a simple, controlled, and reproducible experimental model of reentry. Neonatal rat ventricular cells were cultured on 22-mm-diameter coverslips and stained with the voltage-sensitive dye RH-237. Recordings of transmembrane potentials were obtained from 61 sites with the use of a contact fluorescence imaging system. An electrical field stimulus, followed by a point stimulus, induced 39 episodes of sustained reentry and 21 episodes of nonsustained reentry. Sustained reentry consisted of single-loop (n = 18 monolayers) or figure-of-eight (n = 4) patterns. The cycle length, action potential duration at 80% repolarization, and conduction velocity were (in means +/- SE) 358 +/- 33 ms, 118 +/- 12 ms, and 12.9 +/- 1.0 cm/s for single loop and 311 +/- 78 ms, 137 +/- 18 ms, and 7.8 +/- 1.3 cm/s for figure-of-eight, respectively. Electrical termination by 6- to 13-V/cm field pulses or 15- to 20-V point stimuli was successful in 60% of the attempts. In summary, highly stable reentry can be induced, sustained for extensive periods of time, and electrically terminated in monolayers of cultured neonatal rat cardiac myocytes.

Authors
Iravanian, S; Nabutovsky, Y; Kong, C-R; Saha, S; Bursac, N; Tung, L
MLA Citation
Iravanian, S, Nabutovsky, Y, Kong, C-R, Saha, S, Bursac, N, and Tung, L. "Functional reentry in cultured monolayers of neonatal rat cardiac cells." Am J Physiol Heart Circ Physiol 285.1 (July 2003): H449-H456.
PMID
12623789
Source
pubmed
Published In
American journal of physiology. Heart and circulatory physiology
Volume
285
Issue
1
Publish Date
2003
Start Page
H449
End Page
H456
DOI
10.1152/ajpheart.00896.2002

Functional reentry in cultured monolayers of neonatal rat cardiac cells

Previous studies of reentrant-arrhythmias in the heart have been performed in computer models and tissue experiments. We hypothesized that confluent monolayers of cardiac cells can provide a simple, controlled, and reproducible experimental model of reentry. Neonatal rat ventricular cells were cultured on 22-mm-diameter coverslips and stained with the voltage-sensitive dye RH-237. Recordings of transmembrane potentials were obtained from 61 sites with the use of a contact fluorescence imaging system. An electrical field stimulus, followed by a point stimulus, induced 39 episodes of sustained reentry and 21 episodes of nonsustained reentry. Sustained reentry consisted of single-loop (n = 18 monolayers) or figure-of-eight (n = 4) patterns. The cycle length, action potential duration at 80% repolarization, and conduction velocity were (in means ± SE) 358 ± 33 ms, 118 ± 12 ms, and 12.9 ± 1.0 cm/s for single loop and 311 ± 78 ms, 137 ± 18 ms, and 7.8 ± 1.3 cm/s for figure-of-eight, respectively. Electrical termination by 6- to 13-V/cm field pulses or 15- to 20-V point stimuli was successful in 60% of the attempts. In summary, highly stable reentry can be induced, sustained for extensive periods of time, and electrically terminated in monolayers of cultured neonatal rat cardiac myocytes.

Authors
Iravanian, S; Nabutovsky, Y; Kong, C-R; Saha, S; Bursac, N; Tung, L
MLA Citation
Iravanian, S, Nabutovsky, Y, Kong, C-R, Saha, S, Bursac, N, and Tung, L. "Functional reentry in cultured monolayers of neonatal rat cardiac cells." American Journal of Physiology - Heart and Circulatory Physiology 285.1 54-1 (2003): H449-H456.
Source
scival
Published In
American Journal of Physiology - Heart and Circulatory Physiology
Volume
285
Issue
1 54-1
Publish Date
2003
Start Page
H449
End Page
H456

Cardiomyocyte cultures with controlled macroscopic anisotropy: a model for functional electrophysiological studies of cardiac muscle.

Structural and functional cardiac anisotropy varies with the development, location, and pathophysiology in the heart. The goal of this study was to design a cell culture model system in which the degree, change in fiber direction, and discontinuity of anisotropy can be controlled over centimeter-size length scales. Neonatal rat ventricular myocytes were cultured on fibronectin on 20-mm diameter circular cover slips. Structure-function relationships were assessed using immunostaining and optical mapping. Cell culture on microabraded cover slips yielded cell elongation and coalignment in the direction of abrasion, and uniform, macroscopically continuous, elliptical propagation with point stimulation. Coarser microabrasion (wider and deeper abrasion grooves) increased longitudinal (23.5 to 37.2 cm/s; r=0.66) and decreased transverse conduction velocity (18.1 to 9.2 cm/s; r=-0.84), which resulted in increased longitudinal-to-transverse velocity anisotropy ratios (1.3 to 3.7, n=61). A thin transition zone between adjacent uniformly anisotropic areas with 45 degrees or 90 degrees difference in fiber orientation acted as a secondary source during 2x threshold field stimulus. Cell culture on cover slips micropatterned with 12- or 25- micro m wide fibronectin lines and previously coated with decreasing concentrations of background fibronectin yielded transition from continuous to discontinuous anisotropic architecture with longitudinally oriented intercellular clefts, decreased transverse velocity (16.9 to 2.6 cm/s; r=-0.95), increased velocity anisotropy ratios (1.6 to 5.6, n=70), and decreased longitudinal velocity (36.4 to 14.6 cm/s; r=-0.85) for anisotropy ratios >3.5. Cultures of cardiac myocytes with controlled degree, uniformity and continuity of structural, and functional anisotropy may enable systematic 2-dimensional in vitro studies of macroscopic structure-related mechanisms of reentrant arrhythmias. The full text of this article is available at http://www.circresaha.org.

Authors
Bursac, N; Parker, KK; Iravanian, S; Tung, L
MLA Citation
Bursac, N, Parker, KK, Iravanian, S, and Tung, L. "Cardiomyocyte cultures with controlled macroscopic anisotropy: a model for functional electrophysiological studies of cardiac muscle." Circ Res 91.12 (December 13, 2002): e45-e54.
PMID
12480825
Source
pubmed
Published In
Circulation Research
Volume
91
Issue
12
Publish Date
2002
Start Page
e45
End Page
e54

Novel stable functional Reentrant patterns induced by rapid pacing in uniformly anisotorpic cardiomyocyte cultures

Authors
Bursac, N; Tung, L
MLA Citation
Bursac, N, and Tung, L. "Novel stable functional Reentrant patterns induced by rapid pacing in uniformly anisotorpic cardiomyocyte cultures." November 5, 2002.
Source
wos-lite
Published In
Circulation
Volume
106
Issue
19
Publish Date
2002
Start Page
304
End Page
304

Thrombendvenectomy for organized portal vein thrombosis at the time of liver transplantation.

OBJECTIVE: To determine the efficacy of portal thrombendvenectomy in cases of portal vein thrombosis at the time of orthotopic liver transplantation. SUMMARY BACKGROUND DATA: Portal vein thrombosis (PVT) has been reported to have an incidence of 2% to 39% in end-stage liver disease. Multiple techniques have been suggested to treat this finding. Several reports have suggested suboptimal results after liver transplantation in recipients with PVT. METHODS: The authors prospectively collected data on 1,546 patients who underwent an initial orthotopic liver transplant at the authors' institution between December 1984 and October 1999. There were 820 male patients and 726 female patients. All recipients received either cyclosporine or tacrolimus immunosuppression. Intraoperative flows of the portal vein and hepatic artery were routinely measured. Duplex sonography was routinely performed on the first postoperative day and routinely 1, 2, 5, and 10 years after transplantation. Eighty-five patients underwent thrombendvenectomy for organized thrombus partially or completely occluding the portal vein. Postoperative treatment included low-molecular-weight dextran for 48 hours and daily aspirin for 3 months. There were 53 male patients and 32 female patients. The PVT group was compared with a control group consisting of transplant recipients without PVT. RESULTS: When compared with the control group, PVT patients were older at the time of transplantation and had a higher incidence of liver disease secondary to cryptogenic cirrhosis and Laennec's cirrhosis. There were no significant differences among both groups for 1-, 3-, and 6-year patient and graft survival rates. CONCLUSIONS: Thrombendvenectomy provides a rapid resolution of an otherwise complex problem. It is the authors' procedure of choice in cases of organized PVT at the time of transplantation. Operative time and length of stay in the intensive care unit are not prolonged, and patient and graft survival rates are not compromised.

Authors
Molmenti, EP; Roodhouse, TW; Molmenti, H; Jaiswal, K; Jung, G; Marubashi, S; Sanchez, EQ; Gogel, B; Levy, MF; Goldstein, RM; Fasola, CG; Elliott, EE; Bursac, N; Mulligan, D; Gonwa, TA; Klintmalm, GB
MLA Citation
Molmenti, EP, Roodhouse, TW, Molmenti, H, Jaiswal, K, Jung, G, Marubashi, S, Sanchez, EQ, Gogel, B, Levy, MF, Goldstein, RM, Fasola, CG, Elliott, EE, Bursac, N, Mulligan, D, Gonwa, TA, and Klintmalm, GB. "Thrombendvenectomy for organized portal vein thrombosis at the time of liver transplantation." Ann Surg 235.2 (February 2002): 292-296.
PMID
11807371
Source
pubmed
Published In
Annals of Surgery
Volume
235
Issue
2
Publish Date
2002
Start Page
292
End Page
296

Optical maps of reentrant activity in cultured monolayers of neonatal rat cardiac myocytes

Authors
Iravanlan, S; Nabutovsky, Y; Saha, S; Bursac, N; Tung, L
MLA Citation
Iravanlan, S, Nabutovsky, Y, Saha, S, Bursac, N, and Tung, L. "Optical maps of reentrant activity in cultured monolayers of neonatal rat cardiac myocytes." CIRCULATION 104.17 (October 23, 2001): 108-108.
Source
wos-lite
Published In
Circulation
Volume
104
Issue
17
Publish Date
2001
Start Page
108
End Page
108

System identification of dynamic closed-loop control of total peripheral resistance by arterial and cardiopulmonary baroreceptors.

Prolonged exposure to microgravity in space flight missions (days) impairs the mechanisms responsible for defense of arterial blood pressure (ABP) and cardiac output (CO) against orthostatic stress in the post-flight period. The mechanisms responsible for the observed orthostatic intolerance are not yet completely understood. Additionally, effective counter measures to attenuate this pathophysiological response are not available. The aim of this study was to investigate the ability of our proposed system identification method to predict closed-loop dynamic changes in TPR induced by changes in mean arterial pressure (MAP) and right atrial pressure (RAP). For this purpose we designed and employed a novel experimental animal model for the examination of arterial and cardiopulmonary baroreceptors in the dynamic closed-loop control of total peripheral resistance (TPR), and applied system identification to the analysis of beat-to-beat fluctuations in the measured signals. Grant numbers: NAG5-4989.

Authors
Aljuri, AN; Bursac, N; Marini, R; Cohen, RJ
MLA Citation
Aljuri, AN, Bursac, N, Marini, R, and Cohen, RJ. "System identification of dynamic closed-loop control of total peripheral resistance by arterial and cardiopulmonary baroreceptors." Acta Astronaut 49.3-10 (August 2001): 167-170.
PMID
11669106
Source
pubmed
Published In
Acta Astronautica
Volume
49
Issue
3-10
Publish Date
2001
Start Page
167
End Page
170

Tissue engineering of functional cardiac muscle: molecular, structural, and electrophysiological studies.

The primary aim of this study was to relate molecular and structural properties of in vitro reconstructed cardiac muscle with its electrophysiological function using an in vitro model system based on neonatal rat cardiac myocytes, three-dimensional polymeric scaffolds, and bioreactors. After 1 wk of cultivation, we found that engineered cardiac muscle contained a 120- to 160-microm-thick peripheral region with cardiac myocytes that were electrically connected through gap junctions and sustained macroscopically continuous impulse propagation over a distance of 5 mm. Molecular, structural, and electrophysiological properties were found to be interrelated and depended on specific model system parameters such as the tissue culture substrate, bioreactor, and culture medium. Native tissue and the best experimental group (engineered cardiac muscle cultivated using laminin-coated scaffolds, rotating bioreactors, and low-serum medium) were comparable with respect to the conduction velocity of propagated electrical impulses and spatial distribution of connexin43. Furthermore, the structural and electrophysiological properties of the engineered cardiac muscle, such as cellularity, conduction velocity, maximum signal amplitude, capture rate, and excitation threshold, were significantly improved compared with our previous studies.

Authors
Papadaki, M; Bursac, N; Langer, R; Merok, J; Vunjak-Novakovic, G; Freed, LE
MLA Citation
Papadaki, M, Bursac, N, Langer, R, Merok, J, Vunjak-Novakovic, G, and Freed, LE. "Tissue engineering of functional cardiac muscle: molecular, structural, and electrophysiological studies." Am J Physiol Heart Circ Physiol 280.1 (January 2001): H168-H178.
PMID
11123231
Source
pubmed
Published In
American journal of physiology. Heart and circulatory physiology
Volume
280
Issue
1
Publish Date
2001
Start Page
H168
End Page
H178

Tissue engineering of functional cardiac muscle: Molecular, structural, and electrophysiological studies

The primary aim of this study was to relate molecular and structural properties of in vitro reconstructed cardiac muscle with its electrophysiological function using an in vitro model system based on neonatal rat cardiac myocytes, three-dimensional polymeric scaffolds, and bioreactors. After 1 wk of cultivation, we found that engineered cardiac muscle contained a 120- to 160-μm-thick peripheral region with cardiac myocytes that were electrically connected through gap junctions and sustained macroscopically continuous impulse propagation over a distance of 5 mm. Molecular, structural, and electrophysiological properties were found to be interrelated and depended on specific model system parameters such as the tissue culture substrate, bioreactor, and culture medium. Native tissue and the best experimental group (engineered cardiac muscle cultivated using laminin-coated scaffolds, rotating bioreactors, and low-serum medium) were comparable with respect to the conduction velocity of propagated electrical impulses and spatial distribution of connexin43. Furthermore, the structural and electrophysiological properties of the engineered cardiac muscle, such as cellularity, conduction velocity, maximum signal amplitude, capture rate, and excitation threshold, were significantly improved compared with our previous studies.

Authors
Papadaki, M; Bursac, N; Langer, R; Merok, J; Vunjak-Novakovic, G; Freed, LE
MLA Citation
Papadaki, M, Bursac, N, Langer, R, Merok, J, Vunjak-Novakovic, G, and Freed, LE. "Tissue engineering of functional cardiac muscle: Molecular, structural, and electrophysiological studies." American Journal of Physiology - Heart and Circulatory Physiology 280.1 49-1 (2001): H168-H178.
Source
scival
Published In
American journal of physiology. Heart and circulatory physiology
Volume
280
Issue
1 49-1
Publish Date
2001
Start Page
H168
End Page
H178

Three-dimensional cultures of cardiomyocytes for electrophysiological studies of cardiac muscle

It was hypothesized that 3D cultures of cardiac myocytes consisting of multiple layers of interconnected cells would better mimic the structure and function of native tissue. Dissociated neonatal rat ventricular myocytes were seeded on 3D biodegradable polymer scaffolds and cultivated in a rotating tissue culture bioreactor for 7 days. In general, significant data was obtained.

Authors
Bursac, N; Papadaki, M; White, J; Eisenberg, S; Freed, L
MLA Citation
Bursac, N, Papadaki, M, White, J, Eisenberg, S, and Freed, L. "Three-dimensional cultures of cardiomyocytes for electrophysiological studies of cardiac muscle." Annals of Biomedical Engineering 28.SUPPL 1 (2000): 54-. (Academic Article)
Source
manual
Published In
Annals of Biomedical Engineering
Volume
28
Issue
SUPPL 1
Publish Date
2000
Start Page
54

Three-dimensional cultures of cardiomyocytes for electrophysiological studies of cardiac muscle

It was hypothesized that 3D cultures of cardiac myocytes consisting of multiple layers of interconnected cells would better mimic the structure and function of native tissue. Dissociated neonatal rat ventricular myocytes were seeded on 3D biodegradable polymer scaffolds and cultivated in a rotating tissue culture bioreactor for 7 days. In general, significant data was obtained.

Authors
Bursac, N; Papadaki, M; White, J; Eisenberg, S; Freed, L
MLA Citation
Bursac, N, Papadaki, M, White, J, Eisenberg, S, and Freed, L. "Three-dimensional cultures of cardiomyocytes for electrophysiological studies of cardiac muscle." Annals of Biomedical Engineering 28.SUPPL. 1 (2000): S-54.
Source
scival
Published In
Annals of Biomedical Engineering
Volume
28
Issue
SUPPL. 1
Publish Date
2000
Start Page
S
End Page
54

Cardiac tissue engineering: cell seeding, cultivation parameters, and tissue construct characterization.

Cardiac tissue engineering has been motivated by the need to create functional tissue equivalents for scientific studies and cardiac tissue repair. We previously demonstrated that contractile cardiac cell-polymer constructs can be cultivated using isolated cells, 3-dimensional scaffolds, and bioreactors. In the present work, we examined the effects of (1) cell source (neonatal rat or embryonic chick), (2) initial cell seeding density, (3) cell seeding vessel, and (4) tissue culture vessel on the structure and composition of engineered cardiac muscle. Constructs seeded under well-mixed conditions with rat heart cells at a high initial density ((6-8) x 10(6) cells/polymer scaffold) maintained structural integrity and contained macroscopic contractile areas (approximately 20 mm(2)). Seeding in rotating vessels (laminar flow) rather than mixed flasks (turbulent flow) resulted in 23% higher seeding efficiency and 20% less cell damage as assessed by medium lactate dehydrogenase levels (p < 0.05). Advantages of culturing constructs under mixed rather than static conditions included the maintenance of metabolic parameters in physiological ranges, 2-4 times higher construct cellularity (p &le 0.0001), more aerobic cell metabolism, and a more physiological, elongated cell shape. Cultivations in rotating bioreactors, in which flow patterns are laminar and dynamic, yielded constructs with a more active, aerobic metabolism as compared to constructs cultured in mixed or static flasks. After 1-2 weeks of cultivation, tissue constructs expressed cardiac specific proteins and ultrastructural features and had approximately 2-6 times lower cellularity (p < 0.05) but similar metabolic activity per unit cell when compared to native cardiac tissue.

Authors
Carrier, RL; Papadaki, M; Rupnick, M; Schoen, FJ; Bursac, N; Langer, R; Freed, LE; Vunjak-Novakovic, G
MLA Citation
Carrier, RL, Papadaki, M, Rupnick, M, Schoen, FJ, Bursac, N, Langer, R, Freed, LE, and Vunjak-Novakovic, G. "Cardiac tissue engineering: cell seeding, cultivation parameters, and tissue construct characterization." Biotechnol Bioeng 64.5 (September 5, 1999): 580-589.
PMID
10404238
Source
pubmed
Published In
Biotechnology & Bioengineering
Volume
64
Issue
5
Publish Date
1999
Start Page
580
End Page
589

Cardiac muscle tissue engineering: toward an in vitro model for electrophysiological studies.

The objective of this study was to establish a three-dimensional (3-D) in vitro model system of cardiac muscle for electrophysiological studies. Primary neonatal rat ventricular cells containing lower or higher fractions of cardiac myocytes were cultured on polymeric scaffolds in bioreactors to form regular or enriched cardiac muscle constructs, respectively. After 1 wk, all constructs contained a peripheral tissue-like region (50-70 micrometer thick) in which differentiated cardiac myocytes were organized in multiple layers in a 3-D configuration. Indexes of cell size (protein/DNA) and metabolic activity (tetrazolium conversion/DNA) were similar for constructs and neonatal rat ventricles. Electrophysiological studies conducted using a linear array of extracellular electrodes showed that the peripheral region of constructs exhibited relatively homogeneous electrical properties and sustained macroscopically continuous impulse propagation on a centimeter-size scale. Electrophysiological properties of enriched constructs were superior to those of regular constructs but inferior to those of native ventricles. These results demonstrate that 3-D cardiac muscle constructs can be engineered with cardiac-specific structural and electrophysiological properties and used for in vitro impulse propagation studies.

Authors
Bursac, N; Papadaki, M; Cohen, RJ; Schoen, FJ; Eisenberg, SR; Carrier, R; Vunjak-Novakovic, G; Freed, LE
MLA Citation
Bursac, N, Papadaki, M, Cohen, RJ, Schoen, FJ, Eisenberg, SR, Carrier, R, Vunjak-Novakovic, G, and Freed, LE. "Cardiac muscle tissue engineering: toward an in vitro model for electrophysiological studies." Am J Physiol 277.2 Pt 2 (August 1999): H433-H444.
PMID
10444466
Source
pubmed
Published In
The American journal of physiology
Volume
277
Issue
2 Pt 2
Publish Date
1999
Start Page
H433
End Page
H444

Cardiac muscle tissue engineering: toward an in vitro model for electrophysiological studies

Authors
Bursac, N; Papadaki, M; Cohen, RJ; Schoen, FJ; Eisenberg, SR; Carrier, R; Vunjak-Novakovic, G; Freed, LE
MLA Citation
Bursac, N, Papadaki, M, Cohen, RJ, Schoen, FJ, Eisenberg, SR, Carrier, R, Vunjak-Novakovic, G, and Freed, LE. "Cardiac muscle tissue engineering: toward an in vitro model for electrophysiological studies." AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY 277.2 (August 1999): H433-H444.
Source
wos-lite
Published In
American journal of physiology. Heart and circulatory physiology
Volume
277
Issue
2
Publish Date
1999
Start Page
H433
End Page
H444

Cardiac tissue engineering: Cell seeding, cultivation parameters, and tissue construct characterization

Cardiac tissue engineering has been motivated by the need to create functional tissue equivalents for scientific studies and cardiac tissue repair. We previously demonstrated that contractile cardiac cell-polymer constructs can be cultivated using isolated cells, 3-dimensional scaffolds, and bioreactors. In the present work, we examined the effects of (1) cell source (neonatal rat or embryonic chick), (2) initial cell seeding density, (3) cell seeding vessel, and (4) tissue culture vessel on the structure and composition of engineered cardiac muscle. Constructs seeded under well-mixed conditions with rat heart cells at a high initial density ((6-8) x 10 6 cells/polymer scaffold) maintained structural integrity and contained macroscopic contractile areas (approximately 20 mm 2 ). Seeding in rotating vessels (laminar flow) rather than mixed flasks (turbulent flow) resulted in 23% higher seeding efficiency and 20% less cell damage as assessed by medium lactate dehydrogenase levels (p < 0.05). Advantages of culturing constructs under mixed rather than static conditions included the maintenance of metabolic parameters in physiological ranges, 2-4 times higher construct cellularity (p ≤ 0.0001), more aerobic cell metabolism, and a more physiological, elongated cell shape. Cultivations in rotating bioreactors, in which flow patterns are laminar and dynamic, yielded constructs with a more active, aerobic metabolism as compared to constructs cultured in mixed or static flasks. After 1-2 weeks of cultivation, tissue constructs expressed cardiac specific proteins and ultrastructural features and had approximately 2-6 times lower cellularity (p < 0.05) but similar metabolic activity per unit cell when compared to native cardiac tissue.

Authors
Carrier, RL; Papadaki, M; Rupnick, M; Schoen, FJ; Bursac, N; Langer, R; Freed, LE; Vunjak-Novakovic, G
MLA Citation
Carrier, RL, Papadaki, M, Rupnick, M, Schoen, FJ, Bursac, N, Langer, R, Freed, LE, and Vunjak-Novakovic, G. "Cardiac tissue engineering: Cell seeding, cultivation parameters, and tissue construct characterization." Biotechnology and Bioengineering 64.5 (March 20, 1999): 580-589.
Source
scopus
Published In
Biotechnology & Bioengineering
Volume
64
Issue
5
Publish Date
1999
Start Page
580
End Page
589
DOI
10.1002/(SICI)1097-0290(19990905)64:5<580::AID-BIT8>3.0.CO;2-X

Cardiac muscle tissue engineering: Toward an in vitro model for electrophysiological studies

The objective of this study was to establish a three-dimensional (3-D) in vitro model system of cardiac muscle for electrophysiological studies. Primary neonatal rat ventricular cells containing lower or higher fractions of cardiac myocytes were cultured on polymeric scaffolds in bioreactors to form regular or enriched cardiac muscle constructs, respectively. After 1 wk, all constructs contained a peripheral tissue-like region (50-70 μm thick) in which differentiated cardiac myocytes were organized in multiple layers in a 3-D configuration. Indexes of cell size (protein/DNA) and metabolic activity (tetrazolium conversion/DNA) were similar for constructs and neonatal rat ventricles. Electrophysiological studies conducted using a linear array of extracellular electrodes showed that the peripheral region of constructs exhibited relatively homogeneous electrical properties and sustained macroscopically continuous impulse propagation on a centimeter-size scale. Electrophysiological properties of enriched constructs were superior to those of regular constructs but inferior to those of native ventricles. These results demonstrate that 3-D cardiac muscle constructs can be engineered with cardiac-specific structural and electrophysiological properties and used for in vitro impulse propagation studies.

Authors
Bursac, N; Papadaki, M; Cohen, RJ; Schoen, FJ; Eisenberg, SR; Carrier, R; Vunjak-Novakovic, G; Freed, LE
MLA Citation
Bursac, N, Papadaki, M, Cohen, RJ, Schoen, FJ, Eisenberg, SR, Carrier, R, Vunjak-Novakovic, G, and Freed, LE. "Cardiac muscle tissue engineering: Toward an in vitro model for electrophysiological studies." American Journal of Physiology - Heart and Circulatory Physiology 277.2 46-2 (1999): H433-H444.
Source
scival
Published In
American journal of physiology. Heart and circulatory physiology
Volume
277
Issue
2 46-2
Publish Date
1999
Start Page
H433
End Page
H444

Cardiac tissue engineering: Cell seeding, cultivation parameters, and tissue construct characterization

Cardiac tissue engineering has been motivated by the need to create functional tissue equivalents for scientific studies and cardiac tissue repair. We previously demonstrated that contractile cardiac cell-polymer constructs can be cultivated using isolated cells, 3-dimensional scaffolds, and bioreactors. In the present work, we examined the effects of (1) cell source (neonatal rat or embryonic chick), (2) initial cell seeding density, (3) cell seeding vessel, and (4) tissue culture vessel on the structure and composition of engineered cardiac muscle. Constructs seeded under well-mixed conditions with rat heart cells at a high initial density ((6-8) x 106 cells/polymer scaffold) maintained structural integrity and contained macroscopic contractile areas (approximately 20 mm2). Seeding in rotating vessels (laminar flow) rather than mixed flasks (turbulent flow) resulted in 23% higher seeding efficiency and 20% less cell damage as assessed by medium lactate dehydrogenase levels (p < 0.05). Advantages of culturing constructs under mixed rather than static conditions included the maintenance of metabolic parameters in physiological ranges, 2-4 times higher construct cellularity (p ≤ 0.0001), more aerobic cell metabolism, and a more physiological, elongated cell shape. Cultivations in rotating bioreactors, in which flow patterns are laminar and dynamic, yielded constructs with a more active, aerobic metabolism as compared to constructs cultured in mixed or static flasks. After 1-2 weeks of cultivation, tissue constructs expressed cardiac specific proteins and ultrastructural features and had approximately 2-6 times lower cellularity (p < 0.05) but similar metabolic activity per unit cell when compared to native cardiac tissue.

Authors
Carrier, RL; Papadaki, M; Rupnick, M; Schoen, FJ; Bursac, N; Langer, R; Freed, LE; Vunjak-Novakovic, G
MLA Citation
Carrier, RL, Papadaki, M, Rupnick, M, Schoen, FJ, Bursac, N, Langer, R, Freed, LE, and Vunjak-Novakovic, G. "Cardiac tissue engineering: Cell seeding, cultivation parameters, and tissue construct characterization." Biotechnology and Bioengineering 64.5 (1999): 580-589.
Source
scival
Published In
Biotechnology & Bioengineering
Volume
64
Issue
5
Publish Date
1999
Start Page
580
End Page
589
DOI
10.1002/(SICI)1097-0290(19990905)64:5<580::AID-BIT8>3.0.CO;2-X

Three-dimensional environment promotes in vitro differentiation of cardiac myocytes

Previous studies demonstrated that three-dimensional (3D) engineered cardiac muscle tissue can be created in vitro with structural and functional properties resembling those of native cardiac muscle. In this study, we investigated the effect of 3D vs. two-dimensional (2D) culture environment on cell differentiation. Primary ventricular cardiac muscle cells were cultivated in a 3D (on fibrous polymer scaffolds to form an engineered cardiac muscle) or a 2D culture system (in Petri dishes to form confluent cell monolayers) under otherwise identical conditions. Cell size was similar for 2D and 3D cultures. The amounts of gap junctional protein connexin-43 (an index of electrical coupling) and creatine kinase-MM (differentiation marker) were significantly higher in 3D than in 2D cultures, suggesting that the 3D environment promoted cell differentiation, probably due to increased cell-cell communication and more physiological cell shape. Similar trends were observed for tissue electrophysiological properties, where it was shown that in contrast to 2D cultures, cardiac myocytes in 3D cultures did not beat spontaneously but were readily excitable.

Authors
Bursac, N; Papadaki, M; Langer, R; Eisenberg, SR; Vunjak-Novakovic, G; Freed, LE
MLA Citation
Bursac, N, Papadaki, M, Langer, R, Eisenberg, SR, Vunjak-Novakovic, G, and Freed, LE. "Three-dimensional environment promotes in vitro differentiation of cardiac myocytes." Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings 1 (1999): 128--.
Source
scival
Published In
Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings
Volume
1
Publish Date
1999
Start Page
128-

Towards a functional tissue engineered cardiac muscle

Previous studies showed that engineered cardiac muscle with features resembling those of native cardiac tissues can be designed in vitro. In the present study, laminin coating of the polymer scaffolds was used in conjunction with cultivation in low serum medium, in order to improve tissue properties. Primary ventricular cardiac muscle cells were seeded onto polymer scaffolds, laminin coated or not, and cultured at low or high serum concentration. Positive immunofluorescence staining for the gap junctional protein connexin-43 provided evidence that cells in the engineered tissues were electrically coupled. Low serum increased the amount of myosin heavy chain, while laminin increased the amount of creatine kinase isoform MM. Electrophysiological properties for the laminin-low serum group, such as conduction velocity, approached the levels of neonatal ventricles; the maximum capture rate and maximum amplitude were also significantly improved.

Authors
Papadaki, M; Bursac, N; Gupta, P; Langer, R; Vunjak-Novakovic, G; Freed, LE
MLA Citation
Papadaki, M, Bursac, N, Gupta, P, Langer, R, Vunjak-Novakovic, G, and Freed, LE. "Towards a functional tissue engineered cardiac muscle." Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings 1 (1999): 125--.
Source
scival
Published In
Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings
Volume
1
Publish Date
1999
Start Page
125-

Post-LSD hallucinosis is associated with decrease in flicker-fusion sensitivities

Authors
VanToi, V; Abraham, H; Bursac, N
MLA Citation
VanToi, V, Abraham, H, and Bursac, N. "Post-LSD hallucinosis is associated with decrease in flicker-fusion sensitivities." INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE 37.3 (February 15, 1996): 3307-3307.
Source
wos-lite
Published In
Investigative Ophthalmology and Visual Science
Volume
37
Issue
3
Publish Date
1996
Start Page
3307
End Page
3307

Post-LSD hallucinosis is associated with decrease in flicker-fusion sensitivities

Purpose. LSD and similar agents may alter visual perceptions continuously and permanently in certain users resulting in hallucinogen persisting perceptual disorder (HPPD)1. In the present study, the psychophysical De Lange curves (TMTF curves) were established to determine how HPPD affected former LSD abusers. Methods. Sinusoidal waveform stimulation was used and generated by a visual stimulator2. The stimuli were achromatic, with 200 troland luminance, 50° field size, and were seen under a Maxwellian view. Nine flicker frequencies were tested. At each frequency, the measurement was triplicated using the "fusion to flicker with preview" method3 and the results were averaged. The examiner was blinded to the diagnostic status of the subjects. Eighteen subjects participated in the study. They formed three equal number groups: LSD naive controls (age: 25±2.9 years), post-LSD subjects without HPPD (age: 27.2±8.5) and post-LSD subjects with HPPD (age: 22.4±4.2). The LSD groups had a history of LSD use 2-3 years prior to the study. At the time of testing, subjects were drug-free verified by toxicological screening. Binocular corrected visual acuity was normal in all subjects. Results. The De Lange curves were established in 10-15 minutes for each subject. Among the three groups: 1) The difference in high frequency sensitivities (> 30 Hz) was not statistically significant; 2) By contrast, the sensitivities at lower frequencies differed markedly: the lower the frequencies, the greater the difference, e.g., at 5 Hz the sensitivities of the control group were more than 3 times those of the LSD subjects without HPPD, and 5 times those of LSD with HPPD; and 3) The differences of the CFF values were statistically significant using an ANOVA (p<0.001). Conclusions. 1) LSD reduces sensitivities to the flicker at frequencies less than 30 Hz; 2) Patients with post-LSD hallucinations have the least sensitivity to the flicker perception, followed by asymptomatic LSD users, followed by LSD naive controls; 3) The De Lange curve is a sensitive, specific and reliable method to determine this; 4) Decreased sensitivity to flicker is consistent with the hypothesis that HPPD is associated with disinhibition of visual information processing.

Authors
Toi, VV; Abraham, H; Bursac, N
MLA Citation
Toi, VV, Abraham, H, and Bursac, N. "Post-LSD hallucinosis is associated with decrease in flicker-fusion sensitivities." Investigative Ophthalmology and Visual Science 37.3 (1996): S723-.
Source
scival
Published In
Investigative Ophthalmology and Visual Science
Volume
37
Issue
3
Publish Date
1996
Start Page
S723
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Research Areas:

  • Action Potentials
  • Anisotropy
  • Arrhythmias, Cardiac
  • Biomedical Engineering
  • Bioreactors
  • Cardiomyopathies
  • Connexin 43
  • Electrophysiological Processes
  • Electrophysiology
  • Fibroblasts
  • HEK293 Cells
  • Hydrogels
  • Induced Pluripotent Stem Cells
  • Microtechnology
  • Muscle, Skeletal
  • Muscle, Striated
  • Myoblasts, Skeletal
  • Myocardial Infarction
  • Myocytes, Cardiac
  • Pluripotent Stem Cells
  • Regenerative Medicine
  • Satellite Cells, Skeletal Muscle
  • Stem Cell Transplantation
  • Stem Cells
  • Tissue Engineering
  • Tissue Scaffolds
  • Voltage-Sensitive Dye Imaging