FNDC5促进骨骼肌再生及保护失神经支配肌萎缩的分子机制研究

The skeletal muscle presents the pathological state of atrophy and regeneration disorder after denervation, since the muscle homeostasis is disturbed. The treatment strategy of denervated muscle atrophy mainly focuses on preventing the progress of atrophy, but the efficacy is not satisfactory. Therefore, the enhancement of muscle regeneration is supposed to be a new strategy of muscle atrophy therapy. However, the molecular mechanism of muscle regeneration remains unclear. In our pilot study, FNDC5 was found markedly upregulated both in vitro (the differentiation of C2C12 cells) and in vivo (induction of CTX) models of muscle regeneration. Furthermore, overexpression of FNDC5 could promote muscle regeneration in vitro, whereas knockdown of FNDC5 could inhibit that. In addition, myostatin might be a downstream gene of FNDC5. Based on the results above, functional experiments will be performed first in vitro and in vivo to clarify the relationship between FNDC5 and muscle regeneration. The mechanism of muscle regeneration mediated by the progress that FNDC5 regulated myostatin will be illuminated subsequently. Finally, the protective function of FNDC5 against denervated muscle atrophy will be confirmed via overexpression of FNDC5. This study could provide the experimental evidence and a novel target for denervated muscle atrophy therapy.

骨骼肌失神经支配后，肌肉内环境稳态随之失衡，呈现肌小管萎缩与再生障碍为主导的病理状态。当前治疗策略主要是围绕干预肌小管萎缩进程而展开，但效果不理想。因此，提高肌肉再生能力可能是治疗肌萎缩的新策略，但肌肉再生的分子机制尚不清楚。本项目前期研究发现，FNDC5在细胞水平（C2C12细胞分化）和动物水平（心脏毒素诱导）的肌肉再生模型中表达均升高；进一步在C2C12细胞过表达FNDC5能促进肌肉再生，而敲降FNDC5能抑制肌肉再生；myostatin可能是FNDC5的潜在下游基因。基于该研究基础，本项目首先在细胞和动物水平明确FNDC5与肌肉再生的关系；然后阐明FNDC5通过调控myostatin介导肌再生的机制；最后基于FNDC5过表达手段，明确FNDC5通过促进肌再生保护失神经所致肌萎缩的机理。本研究将为治疗失神经所致肌萎缩提供实验依据和干预新靶点。

促进肌肉再生是治疗某些肌肉疾病的潜在方法。FNDC5 (Fibronectin type III domain containing 5)是一种糖基化I型膜蛋白，在肌肉、脑和心脏中大量存在。FNDCs有促进心肌细胞分化、脂肪源性干细胞、成骨细胞、脂肪生成的作用。然而，FNDC5在肌肉再生中的作用尚不清楚。在此，我们通过体外和体内实验评估了FNDC5对骨骼肌再生的影响。我们发现在体外C2C12成肌细胞分化过程中FNDC5的表达增加。过表达FNDC5促进细胞分化，低表达FNDC5抑制细胞分化。在体内，我们发现FNDC5在心脏毒素(CTX)诱导的肌肉再生模型中表达增加。敲低和敲除FNDC5小鼠骨骼肌再生能力下降。我们发现FNDC5通过抑制肌肉生长抑制素介导肌源性分化。总之，这些结果表明FNDC5是骨骼肌分化和再生的重要调节因子。