Ph.D Thesis

Ph.D StudentCaspi Oren
SubjectStrategies for Myocardial Regeneration Using Human Embryonic
Stem Cell Derived Cardiomyocytes
DepartmentDepartment of Medicine
Supervisor PROF. Lior Gepstein
Full Thesis textFull thesis text - English Version


The study of human embryonic stem cells (hESC) has unleashed new avenues in the fields of developmental biology and regenerative medicine. Derivation of functional cardiac myocytes from hESC allows elucidation of the mechanisms involved in cardiac differentiation and maturation. One of the most attractive potential applications of hESC derived cardiomyocytes may be their use as a cell source for cell replacement therapy. Beyond the potential use for myocardial regeneration, the unique capability to reproducibly generate human cardiac tissue can potentially be employed for screening and predicting the adverse effects of drugs, developing novel anti-arrhythmic drugs and allowing better understanding of the delicate mechanism of cardiomyocyte interaction with adjacent cells.  In the present work, we studied the potential cues underlying hESCs differentiation to the cardiac lineage. Initially we demonstrated that the microenvironment of the neonatal, uninjured and injured adult rat heart does not provide the instructing signals allowing hESC differentiation to the cardiac lineage. Moreover, transplantation of undifferentiated cells results in the formation of teratomas. Hence, to allow cell transplantation we hypothesized that cells must be initially differentiated ex-vivo to the cardiac lineage. To this end we evaluated both a spontaneous differentiation system as well as directed system based on manipulation of the non-canonical Wnt signaling pathway. We then took advantage of the established in vitro cardiomyocyte differentiation system to assess the potential of the hESCs technology to serve as an in-vitro drug screening system. We next examined the fate of the transplanted hESC derived cardiomyocytes and demonstrated that the cells survived, integrated, and proliferated to a certain degree following engraftment to the adult rat myocardium. Moreover, transplantation of hESC derived cardiomyocytes to the infarcted rat myocardium was shown to favorably affect the remodeling process when compared to transplantation of non-cardiac cells or saline injection. Since cardiomyocyte cell transplantation is hampered by the limited long-term survival of the donor cell, we attempted to develop an alternating myocardial regenerative strategy. This approach aimed at engineering a three-dimensional vascularized cardiac tissue by seeding a cell mixture of hESC derived cardiomyocytes, endothelial cells, and embryonic fibroblasts on a polymeric scaffold.  Our results stress the importance of the embryonic fibroblasts for the vascularization process within the cardiac muscle tissue-construct. In summary, our results stress the potential of unique hESCs differentiation system for cardiovascular developmental biology, drug screening and target validation, and for the emerging field of regenerative medicine.