Pathologic Stimulus Determines Lineage Commitment of Cardiac c-Kit + Cells. Mus musculus

Although cardiac c-kit+ cells are being tested in clinical trials, the circumstances that determine lineage differentiation of c-kit+ cells in vivo are unknown. Recent findings suggest endogenous cardiac c-kit+ cells rarely contribute cardiomyocytes to the adult heart. We assessed if various pathological stimuli affect the eventual cell fates of c-kit+ cells differently. We employed single cell sequencing and genetic lineage tracing of c-kit+ cells to determine if various pathologic stimuli would result in different fates of c-kit+ cells. Single cell sequencing of cardiac CD45-c-kit+ cells showed innate heterogeneity, indicative of the existence of vascular and mesenchymal c-kit+ cells in normal hearts. Cardiac pressure overload resulted in a modest increase in c-kit derived cardiomyocytes with significant increases in the numbers of endothelial cells and fibroblasts. Doxorubicin-induced (DOX) acute cardiotoxicity did not increase c-kit derived endothelial cell fates but instead induced cardiomyocyte differentiation. Mechanistically, DOX induced DNA damage in c-kit+ cells resulted in expression of p53. Inhibition of p53 blocked cardiomyocyte differentiation in response to DOX, while small molecule RITA induced stabilization of p53 was sufficient to induce c-kit derived cardiomyocyte differentiation. These results demonstrate that different pathologic stimuli induce different cell fates of c-kit+ cells in vivo. We show that p53 is central to the ability of c-kit+ cells to adopt cardiomyocyte fates, which could lead to the development of strategies to preferentially generate cardiomyocytes from c-kit+ cells.