MRTF-A调控PAX7介导的肌肉再生及其机制研究

Muscular dystrophy affects human health seriously. Muscle regeneration is considered to be the important approach of muscle function reconstruction, and the regeneration process is closely related with satellite cell proliferation, differentiation and self-renewal. However, for muscular dystrophy patients, muscle regeneration is blocked due to satellite cell exhaustion. Thus, to promote the satellite cell differentiation and self-renewal is crucial for maintaining muscle regeneration and exploring clinical project of muscular dystrophy. Paired box 7 (PAX7) and myocardin related transcription factor A (MRTF-A) play important roles in muscle development and regeneration. Our previous study revealed that MRTF-A and PAX7 have protein interaction, and PAX7 is regulated by MRTF-A, but the molecular mechanisms are not completely understood. In this study, based on our previous results, we aim to investigate whether PAX7 influences the self-renewal of satellite cells by regulated by MRTF-A; further to determine the molecular mechanism of MRTF-A and PAX7 synergistically regulating satellite cell differentiation and muscle regeneration; to reveal the correlation of MRTF-A and PAX7 expression level with muscle regeneration through in vivo and in vitro experiments with various cellular and molecular biology techniques. All these investigations shall provide new approaches and methods for clinical prevention of the muscular dystrophy and exploitation of drug target.

肌肉萎缩严重危害人类身体健康。肌肉再生被认为是肌肉组织功能重建的重要途径，其再生过程与卫星细胞的增殖、分化和自我更新密切相关。然而，肌肉萎缩患者体内的异常调控导致卫星细胞耗竭，阻碍肌肉再生。因此，促进卫星细胞的分化和更新对维持肌肉再生以及临床治疗肌肉萎缩至关重要。PAX7以及新近发现的MRTF-A基因在肌肉发育和再生过程中发挥了重要作用。我们先前研究证明，MRTF-A与PAX7存在蛋白相互作用，且MRTF-A能够调控PAX7的表达，但确切的作用机制还不清楚。本研究此基础上，拟利用各种细胞与分子生物学技术，确定MRTF-A是否通过调控PAX7影响卫星细胞自我更新；深入探讨MRTF-A和PAX7协同调控卫星细胞分化和肌肉再生的分子机制；通过体内实验揭示MRTF-A和PAX7的表达水平与肌肉再生的相关性，最终为肌肉萎缩的临床防治及药物靶点的开发提供新的思路和方法。

肌肉萎缩是一种严重危害人类健康的疾病，目前尚无有效的治疗措施。由肌肉干细胞介导的肌肉再生被认为是肌肉组织功能重建的重要途径，配对盒7（Paired box 7, PAX7）是肌肉干细胞，即肌肉卫星细胞的标志基因，在卫星细胞增殖和自我更新过程中发挥了至关重要的作用。然而，PAX7参与卫星细胞调控的分子机制尚不十分明确。我们前期研究发现MRTF-A在卫星细胞中高表达，本研究在此基础上，利用各种细胞与分子生物学技术，旨在探讨MRTF-A调控PAX7的表达，进而影响肌肉细胞增殖和自我更新过程的分子机制，为肌肉萎缩的临床防治提供新思路。首先，本研究在原代肌肉卫星细胞和C2C12细胞的增殖和分化阶段检测MRTF-A和PAX7的表达情况，结果显示，二者的表达水平在增殖期逐渐上调，在分化期逐渐下调，说明 MRTF-A和PAX7可能参与肌肉细胞的增殖分化过程。进一步体内实验证实，在小鼠的肌肉损伤修复过程中，随着损伤的加剧，MRTF-A和PAX7的表达量显著上调，随着修复逐渐完成，二者恢复至正常水平，说明MRTF-A和PAX7参与肌肉再生。过表达/干扰MRTF-A可以促进/抑制肌肉细胞的增殖和自我更新，过表达或干扰MRTF-A不会引发肌肉细胞的凋亡。MRTF-A通过调控PAX7进而影响肌肉再生过程中相关基因及PAX7下游基因的表达。最重要的是，MRTF-A对PAX7的调控作用是通过直接结合在PAX7基因上游启动子区的CarG-box1位点来实现的。本研究结果将为肌肉萎缩的临床防治和药物靶点的选择提供重要的科学依据。