HDAC4-MYOG抑制对失神经肌萎缩的保护作用及机制

Denervation-induced muscle atrophy is a difficult clinical problem, and it is a complex process involving multiple genes and signals. Studying the mechanism and drug targets of denervation-induced muscle atrophy is of great significance to the treatment of muscle atrophy. Our previous study discovered that miR-124-3p and early triggers HDAC4-MYOG might play an important role in denervation-induced muscle atrophy through gene chip, miRNA chip and bioinformatics analysis. However, the regulatory mechanism of denervation-induced muscle atrophy is still unclear. This project intends to elucidate the regulatory mechanism of HDAC4-MYOG on muscle atrophy through the experiments in vitro and in vivo, to clarify the protective effect and mechanism of miR-124-3p targeting HDAC4-MYOG on muscle atrophy, to further investigate the protective effect and mechanism of miR-124-3p targeting HDAC4-MYOG on denervation-induced muscle atrophy in vivo through inhibiting HDAC4 or inhibiting MYOG, or overexpression of miR-124-3p and HDAC4 with lentiviral vector, and finally to explore the value of HDAC4-MYOG as a new target for the prevention and treatment of denervation-induced muscle atrophy.

失神经肌萎缩是临床难题，是涉及多基因、多信号的复杂过程，研究失神经肌萎缩的机制及药物靶点对治疗该疾病具有重要意义。本课题组前期通过基因芯片、miRNA芯片及生物信息学分析发现miR-124-3p和早期促发因子HDAC4-MYOG在失神经肌萎缩过程中可能发挥重要作用，但有关其对肌萎缩的调控仍然不清楚。本项目拟通过体内外实验阐明HDAC4-MYOG对肌萎缩的调节作用，明确miR-124-3p靶向抑制HDAC4-MYOG对肌萎缩的保护作用及机制；进而利用病毒干扰失神经支配靶肌中HDAC4或MYOG的表达、或过表达miR-124-3p及HDAC4，在体观察miR-124-3p靶向HDAC4-MYOG对失神经肌萎缩的保护作用及机制，探讨HDAC4-MYOG作为失神经肌萎缩防治新靶点的应用价值。

失神经支配会引起骨骼肌分解代谢途径的激活，导致骨骼肌发生进行性萎缩。目前针对肌萎缩，尚无有效的治疗手段。Histone deacetylase 4 (HDAC4)最近被发现与肌萎缩密切相关，但有关HDAC4在失神经骨骼肌萎缩过程中潜在作用机制仍然不清楚。本研究构建ICR小鼠坐骨神经离断模型，靶向干扰胫前肌（tibialis anterior, TA）中HDAC4的表达，结合转录组测序和生物信息学分析来探究HDAC4在失神经肌萎缩过程中作用机制。研究发现HDAC4在失神经肌萎缩过程中表达显著升高，干扰HDAC4的表达可有效延缓失神经引起的骨骼肌萎缩，抑制肌肉特异性E3泛素连接酶（MuRF1和MAFbx）和自噬相关蛋白（ATG7, LC3B, PINK1 and BNIP3）的表达，抑制Ⅰ型纤维向Ⅱ型纤维的转变，增强SIRT1和PGC-1α表达。为了进一步探究HDAC4在失神经肌萎缩过程中的作用机制，采用转录组测序和生物信息学分析发现HDAC4可能通过调节以下生物过程参与失神经诱导的肌肉萎缩，包括参与肌肉适应调节的去神经反应、细胞分裂、细胞周期、凋亡过程、骨骼肌萎缩，细胞分化等。STRING分析表明，HDAC4可能通过直接调节肌生成素（myogenin，MYOG）、细胞周期抑制蛋白p21（CDKN1A）和盐诱导激酶1（salt induced kinase 1, SIK1）参与肌肉萎缩过程。进一步研究显示，MYOG在失神经支配骨骼肌中表达显著升高，抑制MYOG表达可显著缓解失神经支配引起的骨骼肌萎缩，同时伴随着MuRF1 and MAFbx表达下调；与单独抑制HDAC4相比，抑制HDAC4表达的同时过表达MYOG会降低肌肉质量、减小肌纤维截面积、增加线粒体自噬，这一结果表明，过表达MYOG会降低HDAC4 抑制对失神经肌萎缩的保护效果。由此可见，HDAC4和MYOG在失神经支配骨骼肌中高表达，HDAC4抑制可通过降低MYOG表达来延缓失神经支配引起的骨骼肌萎缩。这一结果既丰富了失神经肌萎缩的分子调控机制，又为HDAC4-MYOG轴作为肌萎缩防治的新靶点提供实验依据。