Abstract 553: Human Embryonic Stem Cell-Derived Cardiomyocytes Form Human Myocardium and Improve Cardiac Function in Infarcted Rat Hearts
Human embryonic stem cells (hESCs) represent an attractive source for deriving large numbers of definitive and rapidly proliferating human cardiomyocytes for cell-based cardiac repair. Successful application of this cell type will require development of strategies to ensure a sufficiently pure cardiac preparation and to improve cell survival following implantation, and here we report significant progress toward both. Efficient cardiogenesis was achieved by differentiating H7 hESCs under serum-free conditions for 10 days following serial application of activin A and BMP-4, and the cells then were further enriched by Percoll gradient centrifugation. The resultant preparations were demonstrated to be >95% cardiac by β-myosin heavy chain (β-MHC) immunostaining. To test the capacity of these highly purified hESC-derived cardiomyocytes to regenerate myocardium after infarction, we implanted 10 million cells into previously infarcted (60 min ischemia + reperfusion) athymic rats in the presence of a previously reported combinatorial anti-death cocktail (Matrigel supplemented with ZVAD-FMK, Bcl-XL BH4, cyclosporine A, IGF-1, and pinacidil). Histologic analysis 4 weeks later revealed the formation of large human myocardial implants within the infarct, evidenced by staining for human-specific β-MHC and human-specific genomic in situ probes. No surviving non-cardiac human elements were identified. Functional evaluation by MRI at this same timepoint indicated a beneficial effect of cell implantation on left ventricular ejection fraction (mean LVEF of 57.3 ± 2.7 % for cell-treated group vs. 48.3 ± 1.9 % for recipients of anti-death vehicle alone, p= 0.05). These findings demonstrate that hESC-derived cardiomyocytes can mediate the remuscularization of infarcted hearts and that this intervention improves ventricular function.