Transplantation of Human Embryonic Stem Cell-Derived Cardiomyocytes Improves Myocardial Performance in Infarcted Rat Hearts Oren Caspi, Irit Huber, Izhak Kehat, Manhal Habib, Gil Arbel, Amira ...Gepstein, Lior Yankelson, Doron Aronson, Rafael Beyar, Lior Gepstein The possible role of human embryonic stem cells (hESCs) for myocardial repair was assessed in the immunosupressed rat infarct model. Injection of undifferentiated hESCs resulted in formation of teratoma-like structures. Transplantation of ex vivo- differentiated human embryonic stem cell-derived cardiomyocytes (hESC-CMs) prevented this phenomenon. The grafted cardiomyocytes survived, proliferated, and integrated with host cardiac tissue. Echocardiography was used to assess the functional consequences of cell grafting. Control animals, injected with saline or nonmyocyte hESC derivatives, demonstrated significant left ventricular dilatation and functional deterioration, whereas grafting of hESC-CMs attenuated this remodeling process and resulted in improved function. These findings emphasize the potential of hESCs for myocardial repair.
The ability to derive human induced pluripotent stem (hiPS) cell lines by reprogramming of adult fibroblasts with a set of transcription factors offers unique opportunities for basic and ...translational cardiovascular research. In the present study, we aimed to characterize the cardiomyocyte differentiation potential of hiPS cells and to study the molecular, structural, and functional properties of the generated hiPS-derived cardiomyocytes.
Cardiomyocyte differentiation of the hiPS cells was induced with the embryoid body differentiation system. Gene expression studies demonstrated that the cardiomyocyte differentiation process of the hiPS cells was characterized by an initial increase in mesoderm and cardiomesoderm markers, followed by expression of cardiac-specific transcription factors and finally by cardiac-specific structural genes. Cells in the contracting embryoid bodies were stained positively for cardiac troponin-I, sarcomeric alpha-actinin, and connexin-43. Reverse-transcription polymerase chain reaction studies demonstrated the expression of cardiac-specific sarcomeric proteins and ion channels. Multielectrode array recordings established the development of a functional syncytium with stable pacemaker activity and action potential propagation. Positive and negative chronotropic responses were induced by application of isoproterenol and carbamylcholine, respectively. Administration of quinidine, E4031 (I(Kr) blocker), and chromanol 293B (I(Ks) blocker) significantly affected repolarization, as manifested by prolongation of the local field potential duration.
hiPS cells can differentiate into myocytes with cardiac-specific molecular, structural, and functional properties. These results, coupled with the potential of this technology to generate patient-specific hiPS lines, hold great promise for the development of in vitro models of cardiac genetic disorders, for drug discovery and testing, and for the emerging field of cardiovascular regenerative medicine.
Objectives The goal of this study was to establish a patient-specific human-induced pluripotent stem cells (hiPSCs) model of catecholaminergic polymorphic ventricular tachycardia (CPVT). Background ...CPVT is a familial arrhythmogenic syndrome characterized by abnormal calcium (Ca2+ ) handling, ventricular arrhythmias, and sudden cardiac death. Methods Dermal fibroblasts were obtained from a CPVT patient due to the M4109R heterozygous point RYR2 mutation and reprogrammed to generate the CPVT-hiPSCs. The patient-specific hiPSCs were coaxed to differentiate into the cardiac lineage and compared with healthy control hiPSCs-derived cardiomyocytes (hiPSCs-CMs). Results Intracellular electrophysiological recordings demonstrated the development of delayed afterdepolarizations in 69% of the CPVT-hiPSCs-CMs compared with 11% in healthy control cardiomyocytes. Adrenergic stimulation by isoproterenol (1 μM) or forskolin (5 μM) increased the frequency and magnitude of afterdepolarizations and also led to development of triggered activity in the CPVT-hiPSCs-CMs. In contrast, flecainide (10 μM) and thapsigargin (10 μM) eliminated all afterdepolarizations in these cells. The latter finding suggests an important role for internal Ca2+ stores in the pathogenesis of delayed afterdepolarizations. Laser-confocal Ca2+ imaging revealed significant whole-cell Ca2+ transient irregularities (frequent local and large-storage Ca2+ -release events, broad and double-humped transients, and triggered activity) in the CPVT cardiomyocytes that worsened with adrenergic stimulation and Ca2+ overload and improved with beta-blockers. Store-overload–induced Ca2+ release was also identified in the hiPSCs-CMs and the threshold for such events was significantly reduced in the CPVT cells. Conclusions This study highlights the potential of hiPSCs for studying inherited arrhythmogenic syndromes, in general, and CPVT specifically. As such, it represents a promising paradigm to study disease mechanisms, optimize patient care, and aid in the development of new therapies.
Transplantation of a tissue-engineered heart muscle represents a novel experimental therapeutic paradigm for myocardial diseases. However, this strategy has been hampered by the lack of sources for ...human cardiomyocytes and by the scarce vasculature in the ischemic area limiting the engraftment and survival of the transplanted muscle. Beyond the necessity of endothelial capillaries for the delivery of oxygen and nutrients to the grafted muscle tissue, interactions between endothelial and cardiomyocyte cells may also play a key role in promoting cell survival and proliferation. In the present study, we describe the formation of synchronously contracting engineered human cardiac tissue derived from human embryonic stem cells containing endothelial vessel networks. The 3D muscle consisted of cardiomyocytes, endothelial cells (ECs), and embryonic fibroblasts (EmFs). The formed vessels were further stabilized by the presence of mural cells originating from the EmFs. The presence of EmFs decreased EC death and increased EC proliferation. Moreover, the presence of endothelial capillaries augmented cardiomyocyte proliferation and did not hamper cardiomyocyte orientation and alignment. Immunostaining, ultrastructural analysis (using transmission electron microscopy), RT-PCR, pharmacological, and confocal laser calcium imaging studies demonstrated the presence of cardiac-specific molecular, ultrastructural, and functional properties of the generated tissue constructs with synchronous activity mediated by action potential propagation through gap junctions. In summary, this is the first report of the construction of 3D vascularized human cardiac tissue that may have unique applications for studies of cardiac development, function, and tissue replacement therapy.
The ability to establish human induced pluripotent stem cells (hiPSCs) by reprogramming of adult fibroblasts and to coax their differentiation into cardiomyocytes opens unique opportunities for ...cardiovascular regenerative and personalized medicine. In the current study, we investigated the Ca(2+)-handling properties of hiPSCs derived-cardiomyocytes (hiPSC-CMs).
RT-PCR and immunocytochemistry experiments identified the expression of key Ca(2+)-handling proteins. Detailed laser confocal Ca(2+) imaging demonstrated spontaneous whole-cell Ca(2+)(i) transients. These transients required Ca(2+) influx via L-type Ca(2+) channels, as demonstrated by their elimination in the absence of extracellular Ca(2+) or by administration of the L-type Ca(2+) channel blocker nifedipine. The presence of a functional ryanodine receptor (RyR)-mediated sarcoplasmic reticulum (SR) Ca(2+) store, contributing to Ca(2+)(i) transients, was established by application of caffeine (triggering a rapid increase in cytosolic Ca(2+)) and ryanodine (decreasing Ca(2+)(i)). Similarly, the importance of Ca(2+) reuptake into the SR via the SR Ca(2+) ATPase (SERCA) pump was demonstrated by the inhibiting effect of its blocker (thapsigargin), which led to Ca(2+)(i) transients elimination. Finally, the presence of an IP3-releasable Ca(2+) pool in hiPSC-CMs and its contribution to whole-cell Ca(2+)(i) transients was demonstrated by the inhibitory effects induced by the IP3-receptor blocker 2-Aminoethoxydiphenyl borate (2-APB) and the phospholipase C inhibitor U73122.
Our study establishes the presence of a functional, SERCA-sequestering, RyR-mediated SR Ca(2+) store in hiPSC-CMs. Furthermore, it demonstrates the dependency of whole-cell Ca(2+)(i) transients in hiPSC-CMs on both sarcolemmal Ca(2+) entry via L-type Ca(2+) channels and intracellular store Ca(2+) release.
Cell therapy is emerging as a promising strategy for myocardial repair. This approach is hampered, however, by the lack of sources for human cardiac tissue and by the absence of direct evidence for ...functional integration of donor cells into host tissues. Here we investigate whether cells derived from human embryonic stem (hES) cells can restore myocardial electromechanical properties. Cardiomyocyte cell grafts were generated from hES cells in vitro using the embryoid body differentiating system. This tissue formed structural and electromechanical connections with cultured rat cardiomyocytes. In vivo integration was shown in a large-animal model of slow heart rate. The transplanted hES cell-derived cardiomyocytes paced the hearts of swine with complete atrioventricular block, as assessed by detailed three-dimensional electrophysiological mapping and histopathological examination. These results demonstrate the potential of hES-cell cardiomyocytes to act as a rate-responsive biological pacemaker and for future myocardial regeneration strategies.
The advent of the human-induced pluripotent stem cell (hiPSC) technology has transformed biomedical research, providing new tools for human disease modeling, drug development, and regenerative ...medicine. To fulfill its unique potential in the cardiovascular field, efficient methods should be developed for high-resolution, large-scale, long-term, and serial functional cellular phenotyping of hiPSC-derived cardiomyocytes (hiPSC-CMs). To achieve this goal, we combined the hiPSC technology with genetically encoded voltage (ArcLight) and calcium (GCaMP5G) fluorescent indicators. Expression of ArcLight and GCaMP5G in hiPSC-CMs permitted to reliably follow changes in transmembrane potential and intracellular calcium levels, respectively. This allowed monitoring short- and long-term changes in action-potential and calcium-handling properties and the development of arrhythmias in response to several pharmaceutical agents and in hiPSC-CMs derived from patients with different inherited arrhythmogenic syndromes. Combining genetically encoded fluorescent reporters with hiPSC-CMs may bring a unique value to the study of inherited disorders, developmental biology, and drug development and testing.
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•Expression of genetically encoded voltage and calcium reporters in hiPSC-CMs•Analysis of the electrophysiological and calcium-handling properties of hiPSC-CMs•Drug screening using the optically derived action potentials and calcium transients•Modeling of inherited disorders with hiPSC-CMs expressing fluorescent reporters
To fulfill the potential of the hiPSC technology for several cardiovascular applications, methods should be developed for a large-scale, long-term, and functional analysis of hiPSC-derived cardiomyocytes. Gepstein and colleagues demonstrate the use of genetically encoded fluorescent voltage and calcium reporters for assessing changes in the electrophysiological and calcium-handling properties of hiPSC-CMs during drug screening and disease-modeling studies.
Human embryonic stem cells (hESC) are pluripotent lines that can differentiate in vitro into cell derivatives of all three germ layers, including cardiomyocytes. Successful application of these ...unique cells in the areas of cardiovascular research and regenerative medicine has been hampered by difficulties in identifying and selecting specific cardiac progenitor cells from the mixed population of differentiating cells. We report the generation of stable transgenic hESC lines, using lentiviral vectors, and single-cell clones that express a reporter gene (eGFP) under the transcriptional control of a cardiac-specific promoter (the human myosin light chain-2V promoter). Our results demonstrate the appearance of eGFP-expressing cells during the differentiation of the hESC as embryoid bodies (EBs) that can be identified and sorted using FACS (purity>95%, viability>85%). The eGFP-expressing cells were stained positively for cardiac-specific proteins (>93%), expressed cardiac-specific genes, displayed cardiac-specific action-potentials, and could form stable myocardial cell grafts following in vivo cell transplantation. The generation of these transgenic hESC lines may be used to identify and study early cardiac precursors for developmental studies, to robustly quantify the extent of cardiomyocyte differentiation, to label the cells for in vivo grafting, and to allow derivation of purified cell populations of cardiomyocytes for future myocardial cell therapy strategies.-- Huber, I., Itzhaki, I., Caspi, O., Arbel, G., Tzukerman, M., Gepstein, A., Habib, M., Yankelson, L., Kehat, I., Gepstein, L. Identification and selection of cardiomyocytes during human embryonic stem cell differentiation.
Myocardial regeneration strategies have been hampered by the lack of sources for human cardiomyocytes (CMs) and by the significant donor cell loss following transplantation. We assessed the ability ...of a three-dimensional tissue-engineered human vascularized cardiac muscle to engraft in the in vivo rat heart and to promote functional vascularization. Human embryonic stem cell-derived CMs alone or with human endothelial cells (human umbilical vein endothelial cells) and embryonic fibroblasts (triculture constructs) were seeded onto biodegradable porous scaffolds. The resulting tissue constructs were transplanted to the in vivo rat heart and formed cardiac tissue grafts. Immunostaining studies for human-specific CD31 and alpha-smooth muscle actin demonstrated the formation of both donor (human) and host (rat)-derived vasculature within the engrafted triculture tissue constructs. Intraventricular injection of fluorescent microspheres or lectin resulted in their incorporation by human-derived vessels, confirming their functional integration with host coronary vasculature. Finally, the number of blood vessels was significantly greater in the triculture tissue constructs (60.3 +/- 8/mm(3), p < 0.05) when compared with scaffolds containing only CMs (39.0 +/- 14.4/mm(3)). In conclusion, a tissue-engineered human vascularized cardiac muscle can be established ex vivo and transplanted in vivo to form stable grafts. By utilizing a multicellular preparation we were able to increase biograft vascularization and to show that the preexisting human vessels can become functional and contribute to tissue perfusion.
Myocardial cell replacement therapies are hampered by a paucity of sources for human cardiomyocytes and by the expected immune rejection of allogeneic cell grafts. The ability to derive ...patient-specific human-induced pluripotent stem cells (hiPSCs) may provide a solution to these challenges. We aimed to derive hiPSCs from heart failure (HF) patients, to induce their cardiomyocyte differentiation, to characterize the generated hiPSC-derived cardiomyocytes (hiPSC-CMs), and to evaluate their ability to integrate with pre-existing cardiac tissue.
Dermal fibroblasts from two HF patients were reprogrammed by retroviral delivery of Oct4, Sox2, and Klf4 or by using an excisable polycistronic lentiviral vector. The resulting HF-hiPSCs displayed adequate reprogramming properties and could be induced to differentiate into cardiomyocytes with the same efficiency as control hiPSCs (derived from human foreskin fibroblasts). Gene expression and immunostaining studies confirmed the cardiomyocyte phenotype of the differentiating HF-hiPSC-CMs. Multi-electrode array recordings revealed the development of a functional cardiac syncytium and adequate chronotropic responses to adrenergic and cholinergic stimulation. Next, functional integration and synchronized electrical activities were demonstrated between hiPSC-CMs and neonatal rat cardiomyocytes in co-culture studies. Finally, in vivo transplantation studies in the rat heart revealed the ability of the HF-hiPSC-CMs to engraft, survive, and structurally integrate with host cardiomyocytes.
Human-induced pluripotent stem cells can be established from patients with advanced heart failure and coaxed to differentiate into cardiomyocytes, which can integrate with host cardiac tissue. This novel source for patient-specific heart cells may bring a unique value to the emerging field of cardiac regenerative medicine.
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