Stem cell-based delivery of Hypoxamir-210 to the infarcted heart: implications on stem cell survival and preservation of infarcted heart function

This study seeks to test our hypothesis that transgenic induction of miR-210 in mesenchymal stem cells (MSC) simulates the pro-survival effects of ischemic preconditioning (IPC) and that engraftment of PC MSC helps in the functional recovery of ischemic heart by miR-210 transfer to host cardiomyocytes through gap junctions. miR-210 expression in MSC was achieved by IPC or nanoparticle-based transfection of miR-210 plasmid ( miR MSC) and functional recovery of the infarcted heart of rat transplanted with PC MSC or miR MSC was evaluated. Both PC MSC and miR MSC showed higher survival under lethal anoxia as compared to non-PC MSC and scramble-transfected MSC ( Sc MSC) controls with concomitantly lower CASP8AP2 expression. Similarly, both PC MSC and miR MSC survived better and accelerated functional recovery of ischemic heart post-transplantation. To validate our hypothesis that MSC deliver miR-210 to host cardiomyocytes, in vitro co-culture between cardiomyocytes and PC MSC or miR MSC (using non-PC MSC or Sc MSC as controls) showed co-localization of miR-210 with gap-junctional connexin-43. miR-210 transfer to cardiomyocytes was blocked by heptanol pretreatment. Moreover, higher survival of cardiomyocytes co-cultured with PC MSC was observed with concomitant expression of CASP8AP2 as compared to cardiomyocytes co-cultured with non-PC MSC thus suggesting that miR-210 was translocated from MSC to protect host cardiomyocytes. Induction of miR-210 in MSC promoted their survival post-engraftment in the infarcted heart. Moreover, direct transfer of pro-survival miR-210 from miR MSC to host cardiomyocytes led to functional recovery of the ischemic heart.