Abstract 16426: Transfer of miRNAs Through Exosomes Excreted by Stem Cells Regulates an Epigenetic Regulator in Cardiomyocytes for Reprogramming and Cytoprotection
Background and Objectives: Stem cell transplantation is a promising strategy to treat ischemic heart diseases. In addition to the ability of transplanted stem cells to engraft and differentiate, these cells secrete factors to reduce heart injury and/or enhance heart repair. In this study, we examined the role of microRNAs(miRs) excreted by exosomes in stem cell-mediated cardioprotection.
Methods and Results: Exosomes collected from the conditioned media of ischemic and non-ischemic precondioned MSC(IPMSC, non-IPMSC) exhibited cup-shaped morphology and measured 50[[Unable to Display Character: –]]100 nm in diameter under the electron microscope. These exosomes were positive for exosome-marker protein CD63 as determined by western blot and free of cellular contamination in RNA extracted from exosomes (lack of 18S and 28S). Then miR microarray was applied to profile exosomal miRs. The results showed miR-22 upregulation in IPMSC exosomes(accompanied with other reported prosurvival miRs, such as, miR-21, miR-24, miR-210). Bioinformatics predicted MeCP2(methyl CpG binding protein 2), a critical epigenetic regulator, to be conserved target gene of miR-22. Overexpression of miR-22 reversed the upregulation of MeCP2 in ischemic cardiomyocytes(CM) and improved survival of CM. However, inhibition of miR-22 upregulated MeCP2 and sensitize CM to cell death. Further, luciferase assay confirmed the interaction of miR-22 and 3’UTR of MeCP2. Excitingly, after transfection miR-22 mimic (green) and lentiviral overexpression of fusion protein CD63-RFP (red, pCT-CD63-RFP) in MSC, by time lapse confocal imaging, we for the first time captured the.
dynamic shedding of exosomes containing miR-22, which was characterized by overlapping of miR mimic (green) and exosome (red). Later, in transwell co-culture system (top: MSC transfected with green miR-22 and pCT-CD63-RFP,bottom: CM) we observed significant transfer of miR-22 from exosomes into CM.
Conclusions: Our findings unveil a mechanism of exosome-mediated miRs transfer from stem cells to regulate the epigenetic process in cardiomyocytes. It may prove to be a promising strategy that transfer of miRs from exosomes excreted from stem cells may reprogram cardiomyocytes/fibroblasts to repair damaged hearts and mediate cardioprotection.
- © 2012 by American Heart Association, Inc.