心肌肥厚新靶点-microRNA-25

Cardiac hypertrophy is a pathological characteristic common to numerous forms of heart disease, such as hypertension, ischemic myocardial injury and coronary heart disease, which can increase cardiovascular mortality and morbidity. It has important significance to alleviate and reverse myocardial hypertrophy. Nevertheless, the underlying molecular mechanisms for cardiac hypertrophy are still poorly understood. One study showed that the level of miR-25 was significantly elevated in a mouse model of hypertrophy, suggesting that miR-25 may be a potential therapeutic target for cardiac hypertrophy. It is well known that Ca2+-Calcineurin-NFATc3 signaling pathway plays a crucial role in the development of cardiac hypertrophy. On the basis of this point, we hypothesized that the expression of miR-25 is upregulated which in turn suppresses its target gene SERCA2a in cardiac myocytes. SERCA2a downregulation results in the activation of the calcineurin/NFATc3 signaling pathway, leading to cardiac hypertrophy. We propose to establish a mouse model of hypertrophy by thoracic aortic banding, observing miR-25 expression in hypertrophic heart. We further test the effect of miR-25 on cardiac hypertrophy as well as its mechanism in miR-25 transgenic mice and in cardiomyocytes transfected with miR-25. Meanwhile, we study that normalization of miR-25 level by LNA-antimiR-25 abolish this pro-hypertrophic effect of miR-25. Our study will indicate miR-25 as a new therapeutic target for this cardiac condition in clinic.

心肌肥厚是高血压、心肌梗死、冠心病等多种心血管疾病的共同病理改变，其可增加心血管疾病的发病率和致死率。减轻和逆转心肌肥厚具有重要意义，但其机制尚未完全阐明。据报道miR-25在肥厚心肌组织中高表达，提示miR-25可能成为心肌肥厚防治新靶点。基于Ca2+-Calcineurin-NFATc3信号通路在心肌肥厚发展中的重要作用，我们提出“miR-25心肌特异性高表达抑制其靶mRNA SERCA2a的蛋白表达，进而激活Ca2+-Calcineurin-NFATc3信号通路导致心肌肥厚发生”。本研究拟采用胸主动脉缩窄制备小鼠心肌肥厚模型，观察miR-25在肥厚心肌组织中的表达量；进一步采用心肌特异性过表达miR-25的转基因小鼠和转染miR-25的原代心肌细胞来研究miR-25过表达致心肌肥厚作用。同时，观察miR-25的反义寡核苷酸抑制心肌肥厚作用。本项目的完成将为临床防治心肌肥厚提供新靶点。

心肌肥厚是高血压、心肌梗死、冠心病等多种心血管疾病的共同病理改变，其可增加心血管疾病的发病率和致死率。减轻和逆转心肌肥厚具有重要意义，但其机制尚未完全阐明。据报道miR-25在肥厚心肌组织中高表达，提示miR-25可能成为心肌肥厚防治新靶点。.采用小鼠主动脉弓缩窄法（Transverse Aortic Constriction，TAC）制备压力后负荷心肌肥厚模型。在制备成功的小鼠心肌肥厚模型中检测miR-25的表达水平，Real-time PCR结果显示，与对照组相比，TAC组miR-25表达水平升高，此结果表明miR-25参与了心肌肥厚的过程。.为了验证miR-25的过表达可致心肌肥厚，在原代培养的心肌细胞上转染miR-25或antagomiR-25。结果显示过表达miR-25后心肌细胞面积明显增大, 心肌肥厚的标志物ANP、BNP、β-MHC mRNA表达水平显著升高；而共转染miR-25和antagomiR-25后，与Control组相比，心肌细胞面积和心肌肥厚的标志物均无明显变化；上述结果表明：在心肌细胞中外源性过表达miR-25可以引起心肌细胞肥大。.为了进一步探讨 miR-25 过表达致心肌细胞肥大的潜在作用机制，应用Targetscan 软件发现，miR-25 与小鼠 SERCA2a mRNA 3'UTR 端存在不完全互补结合位点，推测 SERCA2a 是 miR-25 的潜在作用靶点。Lucifrase结果显示与NC组相比，转染miR-25使生物荧光素酶活性明显降低；且过表达miR-25可以SERCA2a蛋白的表达下调。以上结果说明SERCA2a 是 miR-25 的作用靶点之一。由于SERCA2a靶蛋白表达下调，可导致细胞内钙水平升高，进而活化Calcineurin/NFATc3信号通路来引起心肌细胞肥大。.在ISO诱导的离体心肌细胞肥大模型中，miR-25 mRNA的表达水平增加，且SERCA2a靶蛋白下调，Calcineurin蛋白表达上调。然而，antagomiR-25可逆转上述指标的变化。.综上所述，MicroRNA-25过表达能够导致心肌细胞肥大，其主要通过靶向作用于SERCA2a，进而活化Calcineurin/NFATc3信号通路来导致心肌细胞肥大。本研究揭示了心肌细胞肥大的新机制，miR-25可能成为临床防治心肌肥厚的潜在治疗靶点。