细胞间线粒体成分转移触发缺血性心肌纤维化

Intercellular mitochondrial component transfer triggers ischemic cardiac fibrosis

心肌纤维化是引发心源性猝死的重要原因.心肌缺血/再灌注(MI/R)损伤可导致心肌细胞损伤甚至死亡,而成纤维细胞却出现激活并导致纤维化.目前,导致这一矛盾现象的细胞间通讯机制仍不清楚.小细胞外囊泡(small extracellular vesicles,sEVs)在细胞间通讯中起重要作用.但是,sEVs是否介导以及如何介导MI/R后心肌细胞和成纤维细胞间的通讯尚不清楚.本研究通过在体MI/R模型和细胞学实验发现,MI/R损伤情况下存在一种心肌细胞来源的sEV(Myo-sEV^(I/R)),其内容物富含线粒体成分.Myo-sEV^(I/R)被成纤维细胞摄取并触发纤维化.通过生物信息学筛选和实验验证,新发现Ambra1是Myo-sEV^(I/R)中的关键组分和潜在标志物.并且证实,Ambra1+-Myo-sEVs的释放是由MI/R损伤后心肌细胞的分泌型自噬所驱动,而不是经典的降解型自噬.在缺血和缺血周边区域,Ambra1^(+)-Myo-sEVs被成纤维细胞内吞导致跨细胞线粒体成分传递;线粒体DNA(mtDNA)激活cGAS-STING通路,促进成纤维细胞的活化和增殖.此外,数据显示,Ambral定位于Myo-sEV^(I/R)表面,心脏特异性的下调Ambral可抑制Ambral^(+)-Myo-sEVs的释放和成纤维细胞摄取,有效抑制缺血后心肌纤维化.本研究新证实了心肌分泌型自噬可介导缺血后心肌纤维化发生过程中的细胞间通讯.Ambral是Myo-sEVs的潜在标志物和特征分子,并具有重要的生物活性.本研究为缺血后心脏重塑提供了新的治疗靶点.

Myocardial fibrosis is the villain of sudden cardiac death.Myocardial ischemia/reperfusion(MI/R)injury induces cardiomyocyte damage or even death,which in turn stimulates fibroblast activation and fibrosis,but the intercellular communication mechanism remains unknown.Recent studies have shown that small extracellular vesicles(sEVs)significantly contribute to intercellular communication.Whether and how sEV might mediate post-MI/R cardiomyocyte/fibroblasts communication remain unknown.Here,in vivo and in vitro MI/R models were established.We demonstrate that sEVs derived from cardiomyocyte(Myo-sEVs)carry mitochondrial components,which enter fibroblasts to initiate myocardial fibrosis.Based on bioinformatics screening and experimental verification,the activating molecule in Beclin1-regulated autophagy protein 1(autophagy/beclin-1 regulator 1,Ambra1)was found to be a critical component of these sEV and might be a new marker for Myo-sEVs.Interestingly,release of Ambra1+-Myo-sEVs was caused by secretory rather than canonical autophagy after MI/R injury and thereby escaped degradation.In ischemic and peripheral areas,Ambra1~+-Myo-sEVs were internalized by fibroblasts,and the delivered mtDNA components to activate the fibroblast cyclic GMP-AMP synthase(cGAS)-stimulator of interferon genes(STING)pathway to promote fibroblast activation and proliferation.In addition,our data show that Ambra1 is expressed on the EV surface and cardiac-specific Ambra1 down regulation inhibits the Ambra1+-Myo-sEVs release and fibroblast uptake,effectively inhibiting ischemic myocardial fibrosis.This finding newly provides the evidence that myocardial secretory autophagy plays a role in intercellular communication during cardiac fibrosis.Ambra1 is a newly characterized molecule with bioactivity and might be a marker for Myo-sEVs,providing new therapeutic targets for cardiac remodeling.