胰岛素样生长因子2介导远隔缺血适应心肌保护作用及机制研究

It has been demonstrated that limb remote ischemic conditioning(RIC）is a promising adjunctive treatment during early reperfusion therapy in patients with acute myocardial infarction. RIC cardioprotection involves the release of humoral factors (3.5-15 kDa), which is carried by the blood from skeletal muscle to the heart. To identify the cardioprotective humoral factors produce by RIC has become an important research area in cardiovascular medicine. Our previous and pilot studies showed microRNA-Let-7 expression in plasma or skeletal muscle was reduced after RIC while the expression of Let-7 upstream RNA binding protein Lin28 and its downstream non-Let-7 dependent target,insulin-like growth factor 2(IGF2） was increased. Thus, the hypothesis is RIC cardioprotection can be mediated by increased IGF2, which is released into humoral pathway. Myocardial ischemia/reperfusion model will be made with wild rats and muscle-specific IGF2 Knock-out rats and remote ischemic postconditioning was performed immediately after reperfusion. The mechanisms and cardoprotection of IGF2 as a humoral factor produced by RIC will be established using such molecular biological techniques as Western blot,RT-PCR and immunohistochemistry. The initiating effects of increased Lin28 expression in skeletal muscle will be further confirmed with muscle-specific Lin28 Knock-out rats.

研究证实，肢体远隔缺血适应（RIC）可望成为急性心肌梗死早期再灌注治疗的辅助治疗措施。RIC心脏保护作用的主要机制是通过体液途径将骨骼肌释放的体液因子传送至心脏发挥作用，识别具有心脏保护作用的体液因子是一个重要研究领域。我们前期研究和预实验结果显示，RIC使血浆和骨骼肌microRNA-Let-7表达下调，而Let-7上游负性调控蛋白Lin28及其非Let-7依赖性下游靶点IGF2表达上调，由此提出假说：RIC使IGF2合成增加并释放入血，成为具有心脏保护作用的重要体液因子。本研究拟在野生型大鼠和骨骼肌特异的IGF2或Lin28敲除大鼠缺血再灌注模型上实施肢体RIC，采用Western blot, RT-PCR,免疫组化等分子生物学技术，并通过细胞学实验，探讨IGF2作为RIC体液因子的心肌保护作用和分子机制，并进一步证实骨骼肌组织Lin28表达上调在肢体RIC心肌保护作用中的始动作用。

远隔缺血适应（RIC）可望成为急性心肌梗死早期再灌注治疗的辅助治疗措施。RIC心脏保护作用的主要机制是通过体液途径将骨骼肌释放的体液因子传送至心脏发挥作用，识别具有心脏保护作用的体液因子是一个重要研究领域。我们前期研究和预实验结果显示，RIC使血浆和骨骼肌microRNA-Let-7表达下调，而Let-7上游负性调控蛋白Lin28及其非Let-7依赖性下游靶点IGF2表达上调，由此提出假说：RIC使IGF2合成增加并释放入血，成为具有心脏保护作用的重要体液因子。研究结果首先证实远隔缺血适应大鼠肢体骨骼肌组织Lin28和IGF2表达水平增高，同时检测到血浆IGF2水平升高及其在心肌发挥保护作用的下游信号通路。然后，在野生型大鼠和骨骼肌特异的IGF2或Lin28敲除大鼠在体缺血再灌注模型上实施肢体RIC，采用Western blot, RT-PCR,免疫组化等分子生物学技术，进一步探讨IGF2作为RIC体液因子的心肌保护作用和分子机制，并证实了骨骼肌组织Lin28表达上调在肢体RIC心肌保护作用中的始动作用。为研究远隔缺血适应心肌保护的体液途径开辟了一个新的视角，为心肌保护药物的研发提供了重要的实验依据。