Abstract 3177: Ischemic Preconditioning Augments Survival of Stem Cells via miR-210 Expression by Targeting Caspase 8-Associated Protein 2
Background. MicroRNAs participate in most cellular functions by post-transcriptional regulation of their target gene expression. Nevertheless, little is known about their roles in apoptosis and survival of stem cells. We show that ischemic preconditioning (IPC) of bone marrow-derived mesenchymal stem cells (MSCs) with multiple cycles of brief ischemia/re-oxygenation (I/R) enhanced their survival upon subsequent exposure to lethal anoxia and following engraftment in the infarcted heart via miR-210 expression.
Methods and Results. IPC with two cycles of 30 min I/R significantly reduced apoptotic cell death in MSCs as evaluated by TUNEL staining and lactate dehydrogenase (LDH) leakage assay through upregulation of Akt, Erk1/2 and nuclear translocation of HIF-1α. Interestingly, we observed concomitant induction of miR-210 in the preconditioned MSCs (PCMSCs) as examined by qRT-PCR, and HIF-1α siRNA or miR-210 inhibitor significantly abrogated the cytoprotective effects of IPC. Computational prediction analysis and experimental data revealed functional participation of caspase 8-associated protein-2 (Casp8ap2) in PCMSCs survival. Induction of Casp8ap2 by miR-210 knockdown in PCMSCs increased LDH leakage and TUNEL positivity thus indicating Casp8ap2 as one of the miR-210 target genes during IPC of stem cells. Extrapolation of these data to in vivo studies in a rat model of acute myocardial infarction predominantly improved stem cell survival post-engraftment as determined by sry gene expression at 4 days after transplantation with a role for miR-210. Heart function indices including ejection fraction and fractional shortening at 6 weeks after transplantation were significantly improved in PCMSCs transplanted group (20.3±5.7 and 31.5±3.8 increases, p<0.05, respectively). Immunohistochemical analyses for myosin heavy chain, actinin, connexin 43 showed extensive engraftment and myogenic differentiation of PCMSCs. Moreover, PCMSCs increased blood vessel formation in infarcted region and markedly attenuated infarction size.
Conclusions. IPC by multiple short episodes of I/R is a powerful strategy to promote stem cell survival, and cytoprotection afforded by IPC is regulated by miR-210 induction via Casp8ap2 suppression.