肌脂蛋白介导的肌细胞转分化在老年肌肉减少症骨骼肌纤维化中的作用及机制研究

Sarcopenia is a geriatric syndrome in elder people, characterized by loss of muscle mass and function with aging, and skeletal muscle fibrosis is a key pathological change during muscle aging. Under oxidative stress and chronic inflammatory status, the myoblasts with muscle regenerative function may transdifferentiate to myofibroblasts, which secrete a large amount of collagen to promote skeletal muscle fibrosis. In our previous work, we have observed increased expression of Sarcolipin (SLN) in the muscle of sarcopenic rats. And recent studies have reported that SLN is closely associated with atrial muscle fibrosis. Therefore, we speculate that SLN plays an important role in the pathogenesis of skeletal muscle fibrosis in sarcopenia through SLN-mediated cell transdifferentiation. In this study, sarcopenic aged rats and C2C12 cell lines are used to discuss the possible mechanism of SLN in the skeletal muscle fibrosis in sarcopenia. Methods like adeno-associated virus (AAV) transfection are adopted both in vivo and in vitro studies to validate the correlation between SLN-induced calcium overload and skeletal muscle fibrosis. We focus on the role of myocyte transdifferentiation, aim to clarify the molecular mechanisms of SLN in the pathogenesis of sarcopenia, and hope to provide new insights into the prevention of sarcopenia in elder population.

肌肉减少症（肌少症）是衰老过程中以骨骼肌质量减少及功能减退为特征的老年综合征，骨骼肌纤维化是肌肉衰老过程中重要的病理改变。氧化应激、慢性炎症等状态下，具有肌肉组织再生功能的成肌细胞向肌成纤维细胞转分化，后者可分泌大量的胶原蛋白促进骨骼肌纤维化。我们的前期工作观察到肌少症大鼠骨骼肌中肌脂蛋白表达明显升高，既往研究还发现肌脂蛋白与心房肌纤维化密切相关，由此我们推测肌脂蛋白参与了老年肌少症骨骼肌纤维化的发生，其机制可能与肌脂蛋白介导的肌细胞转分化密切相关。本项目以老年肌少症大鼠和体外衰老肌细胞模型为研究对象，首次探讨肌脂蛋白在肌少症骨骼肌纤维化中的作用。采用腺相关病毒转染等方法在体内-体外研究中明确肌脂蛋白引起的肌细胞钙超载与骨骼肌纤维化的相关性。从肌细胞转分化角度入手，进一步探讨肌少症的可能分子机制，以期探寻肌少症骨骼肌纤维化新的发病机制和防治策略。

肌肉减少症是衰老过程中以骨骼肌质量减少及功能减退为特征的老年综合征，增加老年人失能的风险。骨骼肌纤维化是肌肉衰老过程中重要的病理改变，促进肌少症的发生。肌脂蛋白是新近发现存在于肌浆网中的小分子膜蛋白，能显著抑制肌浆网钙泵活性，造成细胞内钙超载。本研究探讨肌脂蛋白在肌少症骨骼肌纤维化改变中的作用。D半乳糖成功诱导C2C12成肌细胞衰老，CCK8与流式细胞术检测发现D-gal浓度在20g/L时细胞增殖活性下降明显，且晚期凋亡细胞数增多，总细胞存活数目尚可,β半乳糖苷酶染色显示衰老细胞数明显增多，且衰老相关因子P16与P53蛋白表达增加；衰老组纤维化相关指标TGF-β1和Col-1，Col-3mRNA与蛋白表达水平升高，肌脂蛋白表达也明显升高，细胞内钙离子浓度增加；Ad-SLN成功转染C2C12细胞后，肌脂蛋白表达被抑制，成纤维细胞标志蛋白α-SMA表达明显降低，纤维化指标TGF-β1和胶原蛋白表达也降低。肌脂蛋白通过调节细胞转分化促进衰老成肌细胞纤维化改变。成功构建了衰老相关的肌少症小鼠模型，同时发现肌少症小鼠骨骼肌纤维化水平明显升高。本研究结果表明，肌脂蛋白可能是未来防治肌少症骨骼肌纤维化病变的新靶点。