急性心肌梗死后Exosomes/miR-30a细胞间传递调节心肌自噬的机制研究

Autophagy is rapidly activated in cardiomyocytes after acute myocardial infarction (AMI) which could limit magnitude of the injury size. Autophagic activity diminished during later stage of AMI, contributing to cardiac remodeling. However, the exact mechanism needs further investigation. MiR-30a was found to regulate BECN1 and ATG5, both of which were involved in core autophagy pathway, leading to inhibition of autophagy. We found miR-30a was up-regulated obviously in myocardium of AMI mice accompanied by decreased activity of autophagy which showed miR-30a may be involved in autophagic regulation after AMI. In our preliminary experiment, miR-30a was found to be up-regulated and probably carried by exosomes in hypoxic cardiomyocytes. Therefore, we hypothesized that hypoxic cardiomyocytes secreted exosomes carrying miR-30a after AMI which targeted BECN1 and ATG5, leading to inhibition of myocardium autophagy and eventually contributing to adverse ventricular remodeling. We plan to study the dynamic alteration of miR-30a and autophagic level after AMI in mice, the effects of miR-30a on autophagy and ventricular remodeling after up-regulation or down-regulation of miR-30a. Transfer of exosomes/miR-30a was further verified between cardiomyocytes through transfection of pCT-CD63-GFP which could trace exosomes. Our study will clarify the mechanism of myocardium autophagy after AMI which could be regulated by exosomes/miR-30a transfer between cardiomyocytes and provide a new target of intervention of ventricular remodeling after AMI.

急性心肌梗死（AMI）后自噬迅速激活，限制心梗面积扩大，随着心梗时间延长，自噬下调，参与心室重构，其作用机制尚待进一步阐明。研究显示miR-30a调控自噬基因BECN1和ATG5而抑制自噬。我们预实验发现AMI小鼠心肌miR-30a上调，伴随自噬活性下降；离体缺氧心肌细胞表达miR-30a，miR-30a由exosomes运载。由此推测AMI后缺血心肌细胞分泌exosomes运载miR-30a，作用于心肌BECN1和ATG5基因，抑制心肌自噬，促进心室不良重构。本课题拟动态观察AMI小鼠miR-30a和自噬变化，增强或阻断miR-30a后自噬和心室重构变化，明确miR-30a对心肌自噬和心室重塑的调节作用，同时观察exosomes/miR-30a在离体细胞间传递及其对心肌自噬的影响。研究有助阐明exosomes/miR-30a细胞间传递对AMI后心肌自噬调节新机制，为靶向干预提供理论基础。

近期有研究表明，生理性自噬在缺血性心脏病中具有保护作用。然而，我们对缺血后自噬调控的基本机制知之甚少。Exosomes是由细胞释放的纳米颗粒，在细胞间通过传递miRNAs进行细胞通讯的过程中起关键作用。在这项研究中，我们观察到miR-30a高度集中在急性心肌梗死（AMI）患者血清中的Exosomes内，在缺氧刺激后的心肌细胞内和细胞培养基上清提取的Exosomes中也高表达。我们还发现，缺氧诱导因子（HIF）-a能够调节miR-30a，miR-30a在缺氧心肌细胞间通过Exosomes有效转运。抑制miR-30a和Exosomes的释放可以增加自噬核心调节蛋白beclin-1，Agt-12和LC3II/LC3I的表达水平，这有助于维持心肌细胞缺氧后的自噬应答水平。综上，目前的研究表明，来自缺氧心肌细胞的Exosomes通过旁分泌的方式转运miR-30a来调节自噬，它揭示了一种新的调节自噬途径，有可能为缺血性心肌病提供新的治疗靶点。