Intramiocardial administration of resident c-kit+ cardiac progenital cells activates epicardial progenitor cells and promotes myocardial vascularation after the infarction

Abstract

Resident cardiac progenitor cells reside in the adult heart and govern myocardial homeostasis and repair after injury. Many experimental and clinical studies are being completed with encouraging results. However, the mechanisms of the therapeutic action of CPC remain poorly understood. Initially they were explained by the ability of CPC to differentiate into cardiomyocytes and vascular cells, recently their regenerative effects are mainly explained by secretion biologically active molecules and the release of exosomes, which promote activation of the regenerative program in the heart cells. The aim of the present study is to assess the effect of intramyocardial CPC transplantation on the activation of the vasculogenic pool of epicardial cells. In our study we ligated the anterior descending coronary artery in the hearts of male Wistar rats and intramyocardial injections of a fluorescently labeled (CM-DIL+) CPC or control medium were performed. Fourteen days after transplantation, CPC retained viability, proliferation properties and some cells showed signs of vasculogenic differentiation. We did not find significant differences in the infarct size between two groups assessed by morphometric studies. However, CPC transplantation attenuated adverse remodeling: we found reduction in left ventricular dilatation, severity of transmural injury and activation of arteriogenesis in the border zone. By immunofluorescence staining of myocardial sections, obtained after CPC transplantation, we found a significant increase the number of Wt1+ cells in the epicardium, indicating activation of the epithelial-mesenchymal transition and the formation of epicardial progenitor cells (EPC). EPC migrated to the myocardium, some of them coexpressed markers CD31 (Pecam), alpha-smooth muscle actin (a-SMA), and participated in the new vessels formation. Thus, intramyocardial CPC transplantation increased the vascularization of the myocardium by differentiation of the transplanted cells, as well as the activation of vasculogenic epicardial cells, which can contribute the reduction of negative cardiac remodeling.