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 (MSC)-M-PC 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 ((MSC)-M-miR) and functional recovery of the infarcted heart of rat transplanted with (MSC)-M-PC or (MSC)-M-miR was evaluated. Both (MSC)-M-PC and (MSC)-M-miR showed higher survival under lethal anoxia as compared to non-PCMSC and scramble-transfected MSC ((MSC)-M-Sc) controls with concomitantly lower CASP8AP2 expression. Similarly, both (MSC)-M-PC and (MSC)-M-miR 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 (MSC)-M-PC or (MSC)-M-miR (using non-PCMSC or (MSC)-M-Sc 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 (MSC)-M-PC was observed with concomitant expression of CASP8AP2 as compared to cardiomyocytes co-cultured with non-PCMSC 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 (MSC)-M-miR to host cardiomyocytes led to functional recovery of the ischemic heart.