微小RNA-222（miR-222）是介导生理性心肌肥大发生的关键微小RNA，然而其对病理性心肌肥厚和心力衰竭的保护作用及分子基础尚不清楚。我们前期研究发现，miR-222在苯肾上腺素（PE）诱导的肥大心肌细胞中显著下调，过表达miR-222可以抵抗病理性心肌肥大，还鉴定出TIMP3是miR-222的一个新靶基因。在本项目中，拟基于原代心肌细胞，采用PE、异丙肾上腺素（ISO）和血管紧张素II（AngII）诱导的三种病理性心肌肥大模型，行miR-222的功能获得/缺失性实验，并基于心肌特异性miR-222过表达或敲除小鼠，行主动脉弓缩窄术，明确miR-222与病理性心肌肥厚和心力衰竭的关系。其后，通过功能挽救实验，明确miR-222的靶基因。本项目将明确miR-222对病理性心肌肥厚和心力衰竭的保护作用及分子基础,过表达miR-222有望成为防治心力衰竭的新方法。

miR-222 is a key regulator of exercise induced physiological hypertrophy, however, its protective role in pathological myocardial hypertrophy and heart failure is unclear. Our preliminary data demonstrated that miR-222 was significantly downregulated in phenylephrine (PE)-stimulated hypertrophic cardiomyocytes, while miR-222 overexpression prevented this in vitro. Moreover, TIMP3 was suggested as a novel target gene of miR-222. In this project, we aim to conduct miR-222 gain-of-function and loss-of-function assays in the neonatal rat cardiomyocytes treated with PE, isoprenaline (ISO), or angiotensin II (AngII). Also, the myocardial miR-222 transgenic or knockout mice will be subjected to transverse aortic constriction (TAC) experiment to further clarify the role of miR-222 in pathological cardiac hypertrophy and heart failure. Moreover, rescue experiments will be performed both in vitro and in vivo to identify the target gene(s) of miR-222, including Hmbox1, P27, HIPK1, HIPK2, and TIMP3. Among them, TIMP3 was a new target gene of miR-222 that we have identified in our preliminary study while the rest four were reported by our collaborative group in Cell Metabolism. Our project will clarify the potential protective effect and associated mechanisms of miR-222 in pathological hypertrophy and heart failure. Overexpression of miR-222 might be considered as a novel therapeutic strategy for heart failure.