Exosome-mediated Transfer Of MiR-133a From Mesenchymal Stromal Cells To Cardiomyocytes Contributes To Post-infarction Protection

Backgroud:Mesenchymal stromal cells（MSCs）take potential therapeutic effects on the treatment of cardiovascular diseases,including acute myocardial infarction（AMI）and dilated cardiomyopathy.In the event of AMI,transplanted MSCs can interact with damaged cardiomyocytes and influence many important signaling pathways through direct cell-cell communication and/or secretion of multiple paracrine factors,thereby promoting partial functional recovery of cardiomyocytes to achieve a protective effect.Numerous studies also showed that micro RNA-133a（mi R-133a）,a protective cardiac-specific micro RNA,was significantly decreased in infarcted area in patients with AMI and animal models.Method and result:In our study,we found that mi R-133a was significant increased in infarcted heart of rats with AMI after transplanting MSCs pretreated with rat infarcted heart tissue extracts.In vitro,after pretreating MSCs with rat infarcted heart tissue extracts,we found that mi R-133a was significant increased in those MSCs and exosomes.And we found that mi R-133a was also significantly increased in H9c2 cells when co-cultured with these MSC-derived mi R-133a-rich exosomes.To further validate this exosome-mediated intercellular communication,we constructed cel-mi R-67 luciferase reporter system and MSC-cardiomyocyte co-culture model.Results showed that cel-mi R-67 in MSCs transferred successfully into cardiomyocytes via exosomes through a fibrous membrane filter with a pore size of 150 nm but not 50 nm.Gap junction intercellular communication（GJIC）is a major way involved in intercellular molecular communication,including intercellular micro RNA communication.Carbenoxolone,a specific gap junction blocker,was used to block exosomal micro RNA communication between MSCs and H9c2 cells.Result showed that it inhibited both exosome release and intake.By knocking down mi R-133a in MSCs to further prove that the increased mi R-133a in H9c2 cells was transferred from MSCs via exosomes.MSCs were pretreated with infarct extracts 3 days post-infarction for 24 hours,then their exosomes were collected and injected into the AMI rat models.The results of HE staining,masson staining,and immunofluorescence antibody test（CD31 and Cx43）showed that in MSC^con-Exo group the infarct area of AMI rat heart was significantly reduced and the inflammatory response and fibrosis were decreased,while angiogenesis and Cx43 expression were increased,compared with MSCⁿ-Exo group and MSCⁱ-Exo group.Conclusion:This study demonstrates for the first time that mi R-133a-rich exosomes secreted by MSCs pretreated with rat infarct heart extracts can transferred into cardiomyocytes to repair their function in AMI and then exert a series of cardioprotective effects,part of which were achieved by targeting TAGLN2.