HDAC5调控肌卫星细胞PGC-1α基因低表达抑制DMD模型小鼠骨骼肌再生的机制研究

Muscle satellite cell dysfunction exacerbates progression of Duchenne muscular dystrophy (DMD). PGC-1α is considered as the key regular of mitochondrial function . We have firstly shown earlier that PGC-1α expression was significantly decreased in muscle satellite cells of mdx mouse (a model of DMD), and was critically involved in the mitochondrial dysfunction and regenerative dysfunction of satellite cells. Whereas under dystrophic ambience, the under regulatory mechanisms of PGC-1α gene expression and the precise role of in muscle regeneration is still unclear. Chromatin modification by histone acetylation has been proved to play a key role in regulating PGC-1α gene expression. Our preliminary experiment indicated that HDAC5 was highly expressed in mdx-derived satellite cells, and more importantly, the histone deacetylase inhibitor Trichostatin A (TSA) restored PGC-1α gene expression. We speculate that regenerative dysfunction of mdx-derived satellite cells results from HDAC5-mediated decreased PGC-1α expression by mitochondrial dysfunction by impairing mitochondrial function. By using molecular-biological technologies in vitro and in mdx mice, we aim to investigate the under regulatory mechanisms of PGC-1α gene expression and its role of in dystrophic muscle regeneration. The long-term goal is to unveil a new mechanism of regenerative dysfunction of satellite cells in dystrophic muscle mediated by mitochondria, and provide a novel therapeutic target for the treatment of DMD.

肌卫星细胞再生功能障碍加剧杜氏肌营养不良症（DMD）病情进展。PGC-1α是调节线粒体功能的关键蛋白。前期研究中我们首次发现mdx小鼠（DMD疾病模型）肌卫星细胞PGC-1α异常低表达损害线粒体功能并导致细胞增殖和成肌分化障碍，但PGC-1α低表达的机制及其对mdx小鼠骨骼肌再生的影响尚不清楚。组蛋白乙酰化调控基因转录表达，我们预实验发现mdx小鼠肌卫星细胞组蛋白去乙酰化酶5（HDAC5）表达异常增高，抑制去乙酰化酶活性可促进PGC-1α基因表达，我们推测mdx小鼠骨骼肌再生障碍可能与HDAC5调控PGC-1α基因低表达介导的肌卫星细胞线粒体功能障碍有关。本项目拟采用分子生物学技术，观察肌卫星细胞HDAC5对PGC-1α基因的调控作用，从体内体外两个层次探讨PGC-1α低表达的调控机制及其对mdx小鼠骨骼肌再生的影响，从线粒体的角度揭示DMD骨骼肌再生障碍的新机制，为防治DMD提供新思路。

杜氏肌营养不良症（DMD）是一种致死性X-连锁隐性遗传性肌肉疾病，目前尚无可治愈该疾病的治疗方法。肌卫星细胞（MuSC）再生功能障碍加剧DMD病情进展。PGC-1α蛋白是调节线粒体功能的关键蛋白。本项目采用分子生物学技术，观察MuSC组蛋白去乙酰化酶5（HDAC5）对PGC-1α基因的调控作用，从体内体外两个层次探讨PGC-1α低表达的调控机制及其对mdx小鼠骨骼肌再生的影响。我们的结果发现：（1）和正常C57小鼠骨骼肌MuSC相比较，mdx小鼠骨骼MuSC线粒体功能（包括生物合成、能量代谢和膜电位等）和成肌分化能力（包括增殖和成肌分化）明显受损；（2）mdx小鼠骨骼肌MuSC PGC-1α 基因异常低表达，PGC-1α 基因异常低表达损害线粒体功能并导致MuSC再生能力障碍，体外PGC-1α过表达可明显改善细胞线粒体功能并促进细胞体外增殖和成肌分化；（3）mdx小鼠骨骼肌MuSC异常高表达的 HDAC5 通过去乙酰化作用抑制 MEF2 的转录活性而降低PGC-1α 基因转录，进而影响肌卫星细胞线粒体功能并损害并损害细胞再生分化能力。本项目从MuSC线粒体功能的角度探讨肌营养不良症骨骼肌再生功能障碍的潜在病因，从组蛋白乙酰化修饰调控基因表达的角度深入研究 mdx-MuSC PGC-1α 基因异常表达的分子机制，并分析PGC-1α 基因异常表达对 MuSC 再生能力的影响，从而可望阐明 DMD 骨骼肌再生功能障碍的新机制，为 DMD 的防治提供新的思路和策略。