Stem Cells in Cardiac Repair and Angiogenesis

The overall aim of this Award was to test the central hypothesis that bone marrow derived stem cells have the ability to differentiate and adopt cardiac phenotype when transplanted in young as well as aging hearts with experimental myocardial infarction. To support this hypothesis, the initial studies were designed and conducted to understand the basic properties of BMSCs and compare them in vitro from young and aging donor animals. Furthermore, we have elucidated that cardiac transdifferentiation of BMSCs can be achieved in vitro under specific set of cell culture conditions. The second phase of experiments was performed in vivo in experimental animal models to extrapolate our in vitro findings and observe that the transplanted BMSCs are able to achieve cardiomyocytes phenotype and integrate with the host myocardium. To accomplish these aims, state of the art integrated approaches including our well-established co-culture conditions, in vivo experimental animal model, histological studies combined with confocal microscopy and ultra-structure analysis by transmission electron microscopy, molecular studies by western blotting, fluorescent in situ hybridization, real time and classical PCR, siRNA techniques, and heart function studies using Pressure- volume loops and echocardiography were employed. Aging significantly affected the stem cells which were slower in their proliferation and propagation ability in vitro. Similarly when subjected to anoxia, younger MSCs showed more resistance and survived better as indicated by low level LDH release (an indicator of cellular injury) and reduced TUNEL positivity. Genetic modulation of the cells with AKT and angiopoietinl or their pharmacological preconditioning prior to transplantation promoted their survival as well as angiogenic and myogenic potential in young and aging animal hearts