滋养层干细胞源性的外泌体对心力衰竭心功能的影响及其机制研究

Chronic heart failure is the end stage of various cardiac disease with poor prognosis. Considering the main characteristic of heart failure is death or apoptosis of cardiomyocytes, functional deterioration of remaining cardiomyocytes, relative lack of blood supply, to retore the quantity of functional cardiomyocytes, induce its proliferation, inhibit its apoptosis, induce angiogenesis as well as ameliorate the microenvironment of cardiomyocytes would be the potential therapeutic strategy. Our previous researches have confirmed that trophoblast stem cells could reduce fibrosis and apoptosis of cardiomyocytes, induce angiogenesis, ameliorate cardiac function. As very few stem cells could differentiated into cardiomyocytes directly, we speculated the function is mainly mediated by paracrine effect mainly mediated by exosomes. In further research, we found miR-200b expression is obviously lower in TSCs-treated hearts compared to the MSCs-treated hearts. Down-regulation of MiR-200b has been reported to induce cell proliferation and angiogenesis, inhibit apoptosis in several cell lines. Thus, we propose that miRNA-200b may be involved in the mechanism underlying TSCs’ ameliorated cardiac function. So in this research, we tried to explore the effect of exosome originated from trophoblast stem cells on the animal model of dilated cardiomyopathy as well as if the miR-200b pathway is the main underlying mechanism so as to supply the theoretical and practical basis for clinical therapy.

慢性心力衰竭是各种心脏疾病的终末阶段，其预后不良。鉴于其主要特征为有功能心肌细胞的死亡或凋亡，残留心肌细胞功能恶化、血供的相对缺乏，因此尽可能恢复有功能的心肌细胞数量，促增殖，抗凋亡，促血管新生，改善心肌微环境就成为潜在的治疗策略。我们的前期研究发现滋养层干细胞在小鼠心肌梗死中可以改善心脏功能，但与既往干细胞移植类似的缺陷在于其同样只有非常小的比例可以直接分化为心肌细胞，提示其发挥有益的心脏保护作用可能更多由其分泌的外泌体介导。miR-200b在滋养层干细胞治疗组的心肌表达显著下调，而miR-200b低表达可抗细胞凋亡，促增殖及血管新生，可能在滋养层干细胞改善心脏功能的机制方面有着独特意义。因此，本项目拟在扩张型心肌病动物模型中通过直接心肌内注射或冠脉内注射滋养层干细胞源性的外泌体，观察其是否对于心力衰竭有重要作用及是否通过miR-200b通路介导，为临床心力衰竭的治疗提供理论和实践依据。

寻求更有效改善慢性心力衰竭预后的方法是目前的临床难点也是我们致力研究的方向。在我们前期研究发现滋养层干细胞可以改善心肌梗死小鼠心功能的基础上，鉴于干细胞直接分化成有功能心肌细胞的有限性，我们想到其发挥心脏保护作用更多是由其分泌的外泌体介导。我们通过提取滋养层干细胞源性的外泌体并构建阿霉素诱导的小鼠扩张型心肌病模型，通过体外和体内两部分实验，证实滋养层干细胞源性的外泌体可以改善扩张型心肌病小鼠的心脏功能，减轻心室重构，减少心肌细胞凋亡，减轻全身和心肌局部的炎症反应，减少心肌纤维化程度，减轻心肌细胞线粒体损伤，并通过信号通路检测证实滋养层干细胞源性的外泌体通过抑制miR-200b上调Zeb1、激活let-7i抑制YAP1信号通路、增加线粒体融合蛋白Mfn2的表达而发挥作用。该研究结果为临床应用滋养层干细胞来源的外泌体治疗心力衰竭、改善心功能提供理论和实践依据，有望成为心力衰竭治疗的新的靶点。