Rapamycin-Preactivated Autophagy Enhances Survival and Differentiation of Mesenchymal Stem Cells After Transplantation into Infarcted Myocardium.

Stem cell transplantation has been limited by poor survival of the engrafted cells in hostile microenvironment of the infarcted myocardium. This study investigated cytoprotective effect of rapamycin-preactivated autophagy on survival of the transplanted mesemchymal stem cells (MSCs). MSCs isolated from rat bone marrow were treated with 50 nmol/L rapamycin for 2 h, and then the cytoprotective effect of rapamycin was examined. After intramyocardial transplantation in rat ischemia/reperfusion models, the survival and differentiation of the rapamycin-pretreated calls were accessed. After treatment with rapamycin, autophagic activities and lysososme production of the cells were increased significantly. In the condition of short-term or long-term hypoxia and serum deprivation, the apoptotic cells in rapamycin-pretreated cells were less, and secretion of HGF, IGF-1, SCF, SDF-1 and VEGF was increased. After transplantation of rapamycin-pretreated cells, repair of the infarcted myocardium and restoration of cardial function were enhanced dramatically. Expression of HGF, IGF-1, SCF, SDF-1, VEGF, HIF-1α and IL-10 in the myocardium was upregulated, while expression of IL-1β and TNF-α was downregulated. Tracing of GFP and Sry gene showed that the survival of rapamycin-pretreated cells was increased. Cardiomyogenesis and angiogenesis in the infarcted myocardium were strengthened. Some rapamycin-pretreated cells differentiated into cardiomyocytes or endothelial cells. These results demonstrate that moderate preactivation of autophagy with rapamycin enhances the survival and differentiation of the transplanted MSCs. Rapamycin-primed MSCs can promote repair of the infarcted myocardium and improvement of cardiac function effectively. [ABSTRACT FROM AUTHOR]