Abstract 36: Cardiac Progenitor Cell Lineage Tracing During Embryonic Cardiomyogenesis

Abstract

Introduction: Stem cell therapy represents great promises to myocardium regeneration. Multipotent c-Kit pos cardiac progenitor cells (CPCs) are able to differentiate into endothelial cells, smooth muscle cells, and cardiomyocytes. However, fundamental knowledge of CPC biology remains incomplete. Studies in rodent myocardial infarction model revealed that CPCs have poor long-term survival and engraftment after adoptive transfer, perhaps due to the severely damaged host environment. Therefore, it is critical to understand how CPCs interface with the recipient environment following transfer in order to enhance their true regenerative potentials. Hypothesis: Adoptively transferred stem cells are thought to survive and engraft best in an environment closely resembling their original habitat. Thus, we hypothesized that the embryonic environment provides the optimal spatiotemporal conditions to promote CPCs engraftment and commitment to cardiac fate. Methods: CPCs isolated from adult mouse hearts were expanded, fluorescence-tagged, and injected into blastocysts at E3.75 and in utero at E15.5. Embryos were analyzed following cardiogenesis by immunofluorescence for presence of CPC-derived tissues. Additionally, CPCs were injected intramyocardially at various stages from P0 to P7, to follow long-term adoptive transfer and assess CPCs lineage commitment. Results and Conclusions: At 48 hours post injection, donor CPCs were found anchoring in blastocoel and trophoblasts at E5.5, and were detected within the host myocardium at E17.5 predominantly at perivascular regions (n=4). Interestingly, CPCs also integrated into aminochorionic sac, indicating a novel non-cardiogenic fate of CPCs (n=5). CPCs injected at P3 stably engrafted into left ventricular myocardium by 14 days post injection (n=4), sharing gap junction proteins (ZO-1, Connexin-43) with neighboring cells. In conclusion, this study provides vivid evidence for the first time of CPC engraftment and survival in vivo under homeostasis during cardiogenesis. Future studies will assess the permissive environmental conditions, which may optimize their use in therapeutic applications, and the cardiogenic potential of CPCs in order to provide fundamental insights on CPCs biology.