Abstract 16252: MiRNA-24 Over-Expression Potentiates Mesenchymal Stem Cells Survival in the Infarcted Myocardium Through Autophagy Activation via Targeting Rubicon
Objective: The efficacy of mesenchymal stem cells (MSCs)-based therapy for myocardial infarction (MI) is limited by the poor cells survival in the infarcted myocardium. We aimed to investigate the hypothesis that microRNA-24 (miR-24) protected MSCs against apoptosis in a hypoxic niche.
Methods and Results: Using miRNA microarrays and quantified-PCR, miR-24 was previously discovered to be highly expressed in human MSCs after 6-hour hypoxia exposure. Following the establishment of gain- and loss-of-function through lentivirus trans-infection, it was revealed that MSCsmiR-24, compared with MSCsnull, robustly decreased the cells apoptosis in a hypoxic condition, indicated as TUNEL [(35.5±3.63) % vs. (46.7±6.72) %, P<0.05], which was accompanied by the significant autophagy activation, shown as the increase in the conversion of LC3I to LC3II, the up-regulation of Beclin-1 expression, along with the promotion of autophagosome-fused lysosomes formation (all P<0.05). Administration of bafilomycin A1 or rapamycin were respectively observed to obviously attenuate or strengthen the above process. After bioinformaticly predicted as the putative target of miR-24, Rubicon, an inhibitor of autophagy, was evidenced to be suppressed by miR-24 via a luciferase reporter examination. Meanwhile, miR-24 over-expression was verified to reduce Rubicon, thus evoking subsequent hVps34 up-regulation, whereas miR-24 down-regulation reversed this process. Most importantly, the protective effect of miR-24 on MSCs apoptosis was observed to be abolished by Rubicon over-expression or hVps34 knockdown (both P<0.05). After MI rats model were developed (n=5, each group), it was validated that the survival rate of MSCsmiR-24, transplanted into the infarcted myocardium, significantly enhanced by 1.83 folds than that of MSCsnull on day four after transplantation; and that MSCsmiR-24 group exhibited a statistical improvement of cardiac function [LVEF: (50.2±3.9) % vs. (42.9±2.7) %, P<0.05] compared with MSCsnull one in a four-week follow-up.
Conclusions: MiR-24 promotes autophagy, suppressing Rubincon, therefore increases the viability of MSCs under hypoxia, suggesting that miR-24 might be developed as a novel target of cell-base therapy for MI.
- © 2013 by American Heart Association, Inc.