Exosomes Pinched from Mesenchymal Stem Cells Overexpressing GATA‐4 Serve as Reservoir for Anti‐apoptotic miRs for Cardioprotection (LB524)

Abstract

There is an abundant evidence that exosomes play an important role in intracellular signaling and exert regulatory function through carrying bioactive molecules. This study is aimed to determine whether cardioprotection by mesenchymal stem cells (MSCs) overexpressing GATA‐4 (MSCGATA‐4) is initiated by exosomes which deliver anti‐apoptotic miRs to regulate the target proteins in recipient cells. Exosomes were isolated and purified from MSCGATA‐4 and the control MSCs (MSCNull). The cell injury was investigated in primary cultured rat neonatal cardiomyocytes (CM) and in rat heart. CM were incubated with exosomes from MSCGATA‐4 (ExoGATA‐4) and MSCNull (ExoNull) under hypoxic environment for 48 hrs. CM survival was significantly increased; the cell apoptosis and LDH release were reduced in CM treated with ExoGATA‐4 compared to ExoNull. ExoGATA‐4 maintained the mitochondrial membrane potential (ΔΨm) CM. Real‐time PCR indicated that the anti‐apoptotic miRs (e.g. miR‐19a and miR‐451) were highly expressed in MSCGATA‐4 and in ExoGATA‐4. Si‐miR‐19a transfection significantly abolished ExoGATA‐4 mediated cardioprotection. Furthermore, miR‐19 was upregulated and BIM and PTEN were decreased in ExoGATA‐4 treated CM. A rapid internalization of ExoGATA‐4 by CM was observed via time‐lapse images. Direct transplantation of ExoGATA‐4 into the boarder of ischemic myocardium following ligation of left anterior descending coronary artery (LAD) significantly improved cardiac contractile function and reduced infarct size. ExoGATA‐4 were detected inside damaged cells where the expression of miR‐19a was the highest. It is concluded that ExoGATA‐4 mediated cardioprotection through anti‐apoptotic miRs which reduced apoptosis in the ischemic cells.Grant Funding Source: Supported by National Institutes of Health grants HL105176 and HL114654 (M. Xu).