干细胞exosomes通过传递STAT3蛋白修复梗死心脏的作用及机制

Myocardial infarction is a leading cause for death and heart failure in patients with coronary heart disease. It was well known that stem cell-derived exosomes could repair the infarct heart through transferring therapeutic microRNAs. However, it remains unclear whether exosomes from stem cells provide cardioprotective effects via delivery of proteins. As a vital signal sensor, signal transductor and transcriptor 3 (STAT3) protects the heart against ischemic injury. Recently, proteomic analysis revealed that STAT3 protein is highly enriched in bone marrow-derived mesenchymal stem cells (BMSCs). We also detected STAT3 expression in rat BMSCs by using a method of western blot and found that injection with such exosomes transvenously can improve left ventricular wall motion, up-regulate expression of STAT3, Bcl-xL and Ang-2 in a rat model of myocardial infarction. So, we speculate that exosomes secreted from stem cells may repair the infarct heart via transporting STAT3 into cardiac cells to upregulate expression of protective factors. In order to test this hypothesis, we will use BMSCs from rats as resource of exosomes to assess their cardioprotective effects, BMSCs-derived exosomes intaked by cardiac cells, position of STAT3 protein in cardiac cells, and expression of protective factors by using a variety of different technologies (such as molecualr biological, RNA interference and molecualr microscopic imaging) in vitro and in vivo. Our project will be helpful to explore the novel mechanism that stem cell-derived exosomes repair the infarct heart from the perspective of protein delivery, and to provide more experimental evidences for clinical application of such exosomes in the future.

心肌梗死是冠心病患者死亡和心力衰竭的主要原因。干细胞exosomes(外泌体)可通过传递MicroRNAs修复梗死心脏，但能否经传递蛋白发挥心脏保护效应仍然未知。信号转导与转录因子3（STAT3）作为重要的胞内信号传感器，参与缺血心肌保护性调节。我们预实验发现大鼠骨髓间充质干细胞（BMSCs）外泌体富含STAT3蛋白，并可改善心肌梗死大鼠心室壁运动、上调STAT3、Ang-2和Bcl-xL表达。因而推测，干细胞外泌体可通过传递STAT3蛋白至心脏细胞、诱导下游保护性基因表达进而修复梗死心脏。为证明该假说，我们以大鼠BMSCs为种子细胞获取外泌体，应用分子生物学、RNA干扰和分子显微成像等技术，从细胞和动物两个水平，观察干细胞外泌体的心脏保护效应、心脏细胞吸纳外泌体、STAT3蛋白定位和相关保护性基因表达，以期从传递蛋白角度揭示干细胞外泌体修复梗死心脏的新机制，为其将来临床应用提供更多依据。

心肌梗死是冠心病患者死亡和心力衰竭的主要原因。干细胞exosomes(外泌体)可通过传递 MicroRNAs修复梗死心脏，但能否经传递蛋白发挥心脏保护效应仍然未知。信号转导与转录因 子3(STAT3)作为重要的胞内信号传感器，参与缺血心肌保护性调节。我们发现大鼠骨髓间充质干细胞(BMSCs)外泌体富含STAT3蛋白,干细胞外泌体可以通过传递STAT3蛋白减轻心肌细胞、血管内皮细胞缺氧复氧损伤，并抑制体外胶原合成，在细胞水平证实了干 细胞外泌体通过传递stat3蛋白修复梗死心脏的作用。在体心肌梗死大鼠动物模型实验发现BMSCs来源外泌体干预后28天，明显改善梗死后心脏功能、减轻心肌纤维化、促进新生血管形成，上调ang-2和BCL-XL等基因表达。进一步构建STAT3-RFP融合蛋白表达载体转染至大鼠骨髓间充质干细胞后分类获得外泌体，再加入心脏靶细胞培养上清中培养12h，发现细胞散发红色荧光，证实BMSCs来源外泌体可通过传递STAT3蛋白发挥心肌保护作用。