Changchen Xiao1,2, Kan Wang1,2, Yinchuan Xu1,2, Hengxun Hu1,2, Na Zhang1,2, Yingchao Wang1,2, Zhiwei Zhong1,2, Jing Zhao1,2, Qingju Li1,2, Dan Zhu1,2, Changle Ke1,2, Shuhan Zhong1,2, Xianpeng Wu1,2, Hong Yu1,2, Wei Zhu1,2, Jinghai Chen1,3,2, Jianyi Zhang4, Jian'an Wang1,2, Xinyang Hu1,2. 1. From the Department of Cardiology, Second Affiliated Hospital, College of Medicine (C.X., K.W., Y.X., H.H., N.Z., Y.W., Z.Z., J.Z., Q.L., D.Z., C.K., S.Z., X.W., H.Y., W.Z., J.C., J.W., X.H.). 2. Zhejiang University, Hangzhou, China; Cardiovascular Key Laboratory of Zhejiang Province, Hangzhou, China (C.X., K.W., Y.X., H.H., N.Z., Y.W., Z.Z., J.Z., Q.L., D.Z., C.K., S.Z., X.W., H.Y., W.Z., J.C., J.W., X.H.). 3. Institute of Translational Medicine (J.C.). 4. Department of Biomedical Engineering, University of Alabama at Birmingham (J.Z.).
Abstract
RATIONALE: Autophagy can preserve cell viability under conditions of mild ischemic stress by degrading damaged organelles for ATP production, but under conditions of severe ischemia, it can promote cell death and worsen cardiac performance. Mesenchymal stem cells (MSCs) are cardioprotective when tested in animal models of myocardial infarction, but whether these benefits occur through the regulation of autophagy is unknown. OBJECTIVE: To determine whether transplanted MSCs reduce the rate of autophagic degradation (autophagic flux) in infarcted hearts and if so, to characterize the mechanisms involved. METHODS AND RESULTS: Treatment with transplanted MSCs improved cardiac function and infarct size while reducing apoptosis and measures of autophagic flux (bafilomycin A1-induced LC3-II [microtubule-associated protein 1 light chain 3] accumulation and autophagosome/autolysosome prevalence) in infarcted mouse hearts. In hypoxia and serum deprivation-cultured neonatal mouse cardiomyocytes, autophagic flux and cell death, as well as p53-Bnip3 (B-cell lymphoma 2-interacting protein 3) signaling, declined when the cells were cultured with MSCs or MSC-secreted exosomes (MSC-exo), but the changes associated with MSC-exo were largely abolished by pretreatment with the exosomal inhibitor GW4869. Furthermore, a mimic of the exosomal oligonucleotide miR-125b reduced, whereas an anti-miR-125b oligonucleotide increased, autophagic flux and cell death, via modulating p53-Bnip3 signaling in hypoxia and serum deprivation-cultured neonatal mouse cardiomyocytes. In the in vivo mouse myocardial infarction model, MSC-exo, but not the exosomes obtained from MSCs pretreated with the anti-miR-125b oligonucleotide (MSC-exoanti-miR-125b), recapitulated the same results as the in vitro experiments. Moreover, measurements of infarct size and cardiac function were significantly better in groups that were treated with MSC-exo than the MSC-exoanti-miR-125b group. CONCLUSIONS: The beneficial effects offered by MSC transplantation after myocardial infarction are at least partially because of improved autophagic flux through excreted exosome containing mainly miR-125b-5p.
RATIONALE: Autophagy can preserve cell viability under conditions of mild ischemic stress by degrading damaged organelles for ATP production, but under conditions of severe ischemia, it can promote cell death and worsen cardiac performance. Mesenchymal stem cells (MSCs) are cardioprotective when tested in animal models of myocardial infarction, but whether these benefits occur through the regulation of autophagy is unknown. OBJECTIVE: To determine whether transplanted MSCs reduce the rate of autophagic degradation (autophagic flux) in infarcted hearts and if so, to characterize the mechanisms involved. METHODS AND RESULTS: Treatment with transplanted MSCs improved cardiac function and infarct size while reducing apoptosis and measures of autophagic flux (bafilomycin A1-induced LC3-II [microtubule-associated protein 1 light chain 3] accumulation and autophagosome/autolysosome prevalence) in infarctedmouse hearts. In hypoxia and serum deprivation-cultured neonatal mouse cardiomyocytes, autophagic flux and cell death, as well as p53-Bnip3 (B-cell lymphoma 2-interacting protein 3) signaling, declined when the cells were cultured with MSCs or MSC-secreted exosomes (MSC-exo), but the changes associated with MSC-exo were largely abolished by pretreatment with the exosomal inhibitor GW4869. Furthermore, a mimic of the exosomal oligonucleotidemiR-125b reduced, whereas an anti-miR-125b oligonucleotide increased, autophagic flux and cell death, via modulating p53-Bnip3 signaling in hypoxia and serum deprivation-cultured neonatal mouse cardiomyocytes. In the in vivo mousemyocardial infarction model, MSC-exo, but not the exosomes obtained from MSCs pretreated with the anti-miR-125b oligonucleotide (MSC-exoanti-miR-125b), recapitulated the same results as the in vitro experiments. Moreover, measurements of infarct size and cardiac function were significantly better in groups that were treated with MSC-exo than the MSC-exoanti-miR-125b group. CONCLUSIONS: The beneficial effects offered by MSC transplantation after myocardial infarction are at least partially because of improved autophagic flux through excreted exosome containing mainly miR-125b-5p.