MicroRNA-451通过心肌自噬调控心肌重构的功能和机制研究

Basal autophagy plays a critical role in maintaining cardiac homeostasis and dysfunctional autophagy induces cardiac remodeling. It is remained to be clarified how cardiac autophagy is regulated in both physiological and pathological conditions. Our previous study found that miR-451 was significantly down-regulated in the myocardium of patients with hypertrophic cardiomyopathy. In vitro studies showed that miR-451 might regulate cardiac autophagy and cardiac remodeling. In the present project: 1) In order to evaluated the roles of miR-451 in the regulation of cardiac autophagy and cardiac remodeling, we will generate miR-451 knockout mice and cardiac-specific transgenic mice to observe the effect of depletion and overexpression of miR-451 on cardiac autophagy and cardiac remodeling in vivo. Furthermore, mice models with cardiac remodeling induced by pressure-overload will be generated based on the genetic modified mice, to investigate whether intervention on miR-451 can inhibit cardiac remodeling and autophagic dysfunction. 2) In order to reveal the role of cardiac autophagy in the miR-451-induced cardiac remodeling, we will rescue the dysfunction of autophagy with drugs in the above mice models or in cultured neonatal rat cardiomyocytes with miR-451 knockdown or overexpression, to measure whether cardiac remodeling can be antagonized both in vivo and in vitro. 3) Our previous study indicated that TSC1 was a novel target of miR-451. TSC1 is a known regulator of autophagy by interacting with RHEB and thereby regulating the activity of mTORC1. In the present project, we will knockdown TSC1 and express active RHEB in cultured cardiomyocytes with miR-451 knockdown, to test whether they can abolish the dysfunction of autophagy and cardiac remodeling induced by miR-knockdown. Through the present project, we hope to clarify the roles of miR-451 in cardiac autophagy and cardiac remodeling, and get a deep insight on how microRNAs contribute to the maintaining of cardiac autophagic homeostasis.

心肌自噬紊乱会导致心肌重构，但其发生机制尚不清楚。我们前期研究发现miR-451在患者肥厚心肌中显著降低，体外实验显示miR-451参与调控心肌重构和心肌自噬。本课题中，1）我们将构建miR-451敲除和心肌特异转基因小鼠，建立压力超负荷诱导的心肌重构模型，体内实验明确miR-451对心肌自噬和心肌重构的调控作用；2）在上述小鼠模型中以及敲低或过表达miR-451的心肌细胞中，药物干预逆向改变心肌自噬，观察能否对抗miR-451的调控，明确心肌自噬在miR-451诱导心肌重构中的作用； 3）通过逆向干预TSC1、RHEB等我们前期发现的miR-451靶基因及其通路关键因子，明确TSC1/RHEB/mTOR是否为miR-451调控心肌自噬和心肌重构的主要信号转导通路。我们期望通过本研究，为解开心肌自噬调控机制提供新视角，并为干预心肌重构提供新的潜在靶点。

心衰是各种心血管疾病的终末表现，也是心血管疾病致死致残的最主要原因。心肌重构是心衰发生的先决条件，延缓和阻断心肌重构过程可以治疗心衰。但由于心肌重构机制复杂，我们对其机制理解尚不充分，仍缺少特异有效的干预手段。MicroRNA是具有重要生物学功能的非编码RNA，在疾病发生发展中具有重要作用。本课题发现miR-451在肥厚心肌中显著下调，体外实验发现miR-451可以调控心肌细胞肥大，进一步研究发现可能与心肌自噬和凋亡相关。在miR-451敲除大鼠模型中，阿霉素诱导的心衰被抑制，并加剧了AngII诱导的心肌肥厚。我们的结果提示miR-451是心肌重构调控因子，miR-451下调能够促进代偿性心肌肥厚，保障机体对心脏功能需求，延缓心衰。