SRT1720 Pretreatment Promotes Mitochondrial Biogenesis of Aged Human Mesenchymal Stem Cells and Improves Their Engraftment in Postinfarct Nonhuman Primate Hearts

Declined function of aged mesenchymal stem cells (MSCs) diminishes the benefits of cell therapy for myocardial infarction (MI). Our previous study has demonstrated that SRT1720, a specific SIRT1 activator, could protect aged human MSCs (hMSCs) against apoptosis. The purpose of the present study was to investigate the role of mitochondria in the antiapoptotic effects of SRT1720. In addition, we established a nonhuman primate MI model to evaluate cell engraftment of SRT1720-pretreated aged hMSCs (SRT1720-OMSCs). A hydrogen peroxide (H2O2)-induced apoptosis model was established in vitro to mimic MI microenvironment. Compared with vehicle-treated aged hMSCs (Vehicle-OMSCs), SRT1720-OMSCs showed alleviated apoptosis level, significantly decreased caspase-3 and caspase-9 activation, and reduced release of cytochrome c when subjected to H2O2 treatment. Mitochondrial contents were compared between young and aged hMSCs and our data showed that aged hMSCs had lower mitochondrial DNA (mtDNA) copy numbers and protein expression levels of components of the mitochondrial electron transport chain (ETC) than young hMSCs. Also, treatment with SRT1720 resulted in enhanced MitoTracker staining, increased mtDNA levels and expression of mitochondrial ETC components in aged hMSCs. Furthermore, SRT1720-OMSCs exhibited elevated mitochondrial respiratory capacity and higher mitochondrial membrane potential. In vivo study demonstrated that SRT1720-OMSCs had higher engraftment rates than Vehicle-OMSCs at 3 days after transplantation into the infarcted nonhuman primate hearts. Taken together, these results suggest that SRT1720 promotes mitochondrial biogenesis and function of aged hMSCs, which is involved in its protective effects against H2O2-induced apoptosis. These findings encourage further exploration of the optimization of aged stem cells function via regulating mitochondrial function.