Clonal cardiac stem cell lines develop into cardiomyocytes in a Bmp2 and Nkx2.5 dependent manner

Somatic stem cells of the heart have been isolated in past years by several groups using different strategies. These cell populations had different morphology but in common that they differentiate only to cells residing in the heart and that they could not be maintained as clonal stable cell lines so far. We have isolated and cloned stable cardiac stem cell lines from murine hearts and demonstrated that they express sternness genes such as Oct4, Nanog, Sox2, and Tert1, and marker genes for primitive mesoderm and early cardioblasts, such as Bra-chyury, Mesp1, Desmin, Nkx2.5, Mef2C, and Isl1 at the same time. They self-renew in a LIF dependent manner for at least 87 passages without loosing their potential to spontaneously differentiate to cardiomyocytes, smooth muscle cells and endothelial cells. Cardiomyocytes develop to mature pacemaker cells and atrial and ventricular cardiomyocytes expressing Connexin 43. Bmp2 promotes early cardiomyogenesis via activation of the Nkx2.5 gene, whereas LIP inhibits cardiomyogenesis in cardiovascular progenitor cells. Our results demonstrate successful isolation and long-term culture of donal cardiovascular progenitor cells within a micro-environment accurately recapitulating a minimal stem cell niche.