Abstract 11266: Murine Adult Epicardium Requires Hypoxia for Progenitor and Multipotency Ability

Introduction: The epicardium is a source of the coronary vasculature and stroma during heart development. Although quiescent in the physiological adult heart, increasing evidences indicate the potential epicardium activation and differentiation into its progeny after cardiac injury; however, this remains debated. Hypothesis: We hypothesize that in vivo hypoxia exposure can mimic the embryonic cardiac profile and prime the adult epicardial progenitor cell to a more immature profile. Methods: Perinatal and adult BL6 and Pw1 nLacz hearts were used to track the expression of PW1 - progenitor cell marker - together with cell surface proteins. In vivo hypoxia (10% O 2 ) exposure was used to stimulate the adult heart. Histology, protein expression profiles and single cell analysis were assessed. Freshly FACS isolated Gp38 + PW1 + epicardial cells were cultured to determine their progenitor cell potential (clonogenicity, self-renewal and cell fate potential). Results: Here, we report that PW1 expression decreases during postnatal life, but is maintained in the cardiac hypoxic niche epicardium and subepicardium. Adult mice exhibit increased PW1 expression in epicardial/subepicardial cells and endothelial cells in response to hypoxia. The epicardium and subepicardium are activated to undergo cell proliferation and re-express a subset of embryonic genes in response to hypoxia. We established a new in vitro model to study purified PW1 + /Gp38 + epicardial cells, and we found properties of clonogenicity, self-renewal and multipotency (fibroblast, smooth muscle and endothelial cells) at single cell level in the developing epicardial cells. Cell fate potential towards an endothelial profile is dependent upon low levels of oxygen, and the in vitro ability to grow in culture is restore after in vivo priming of the adult heart. Conclusions: In conclusion our data support that the resident PW1 + /Gp38 + epicardial cells are a reminiscent progenitor population in adult mammalian heart that can be reactivated by exposure to hypoxia, highlighting the potential therapeutic role of hypoxia in regenerative medicine.