IschemicPreconditioningAugmentsSurvivalofStemCellsvia miR-210ExpressionbyTargetingCaspase-8-associatedProtein2 *□

MicroRNAs (miRs) participate in most cellular functions by posttranscriptional regulation of gene expression albeit with little information regarding their role in ischemic preconditioning (IP) of stem cells. We report that IP of bone marrow-derived mesenchymal stem cells (MSCs) with two cycles of 30-min ischemia/reoxygenation (I/R) supported their survival under subsequent longer exposure to anoxia and following engraftment in the infarcted heart. IP significantly reduced apoptosis in MSCs through activation of Akt (Ser 473 ) and ERK1/2 (Thr 202 / Tyr 204 ) and nuclear translocation of hypoxia-inducible factor-1 (HIF-1). We observed concomitant induction of miR210 in the preconditioned MSCs ( PC MSCs). Inhibition of HIF-1 or of miR-210 abrogated the cytoprotective effects of preconditioning. Extrapolation of these data to in vivo studies in a rat model of acute myocardial infarction predominantly improved stem cell survival after engraftment with a role for miR-210. Notably, multiple I/R cycles more effectively regulated the miR-210 and hence promoted MSC survival compared with single-cycle hypoxia of an equal duration. Real time PCR array for rat apoptotic genes, computational target gene analyses, and luciferase reporter assay identified FLICE-associated huge protein (FLASH)/caspase-8-associated protein-2 (Casp8ap2 )i n PC MSCs as the target gene of miR-210. Induction of FLASH/ CASP8AP2 in miR-210 knocked-down PC MSCs resulted in increased cell apoptosis. Taken together, these data demonstrated that cytoprotection afforded by IP was regulated by miR210 induction via FLASH/Casp8ap2 suppression. These results highlighted that IP by multiple short episodes of I/R is a novel strategy to promote stem cell survival.