FGFR-p38α/βMAPK信号通路调控肌卫星细胞自我更新在肩袖撕裂后不可逆性肌萎缩中的作用及分子机制

Muscle atrophy after rotator cuff tears is commonly associated with poor clinical outcomes and failed rotator cuff repair. This atrophy is irreversible and dose not improve even after rotator cuff repair. The mechanisms underlying it are still unclear. We recently have observed that the number of human muscle satellite cells (MuSCs), the stem cells in muscle declined after rotator cuff tears. And the expression of proteins involved in FGFR-p38α/β MAPK signaling increased. Previous evidences suggested that FGFR-p38α/β MAPK signaling played very important roles in the self-renewal of MuSCs. Thus, We hypothesize that the activation of FGFR-p38α/β MAPK signaling after rotator cuff tears could induce obstructed self-renewal of MuSCs, which leads to the decreased number of stem cells and impaired ability of regenerative repair, finally resulting in the irreversible atrophy. To test this hypothesis, a clinical histopathologic experiment, an ex vivo cell experiment and a vivo mouse model experiment are successively designed. Lots of laboratory technologies such as immunofluorescence technique, Western blot, Real-time polymerase chain reaction technique will be used in this research project. This project will help us to delineate the cellular and molecular mechanisms underlying the irreversible rotator cuff atrophy after tears, providing potential therapeutic targets and shining new-lights on the prevention and treatment of it.

肩袖撕裂后常伴有不可逆的肌萎缩，但是其发生机制尚不清楚。我们前期研究发现，肩袖撕裂后肌卫星细胞（MuSCs）的自我更新能力下降，FGFR-p38α/β MAPK信号通路相关蛋白的表达增高。我们推测肩袖撕裂后MuSCs内FGFR-p38α/β MAPK通路被激活，自我更新能力下降，数量减少，再生修复能力下降，最终导致肌萎缩不可逆转。为了验证该假说，本课题拟从临床病理学、细胞实验和动物干预实验三个方面，利用基因沉默、免疫荧光、免疫印迹、RT-PCR、荧光示踪标记、激光共聚焦显微成像等技术，观察肩袖撕裂、MuSCs自我更新能力和FGFR-p38α/β MAPK通路三者之间的内在联系，明确其临床意义； 阐明肩袖撕裂后通过该通路导致MuSCs自我更新能力下降的机制；探索通过抑制该信号通路来提高MuSCs修复能力的方法，为该病的防治提供新的思路和治疗靶点。

肩袖撕裂后常伴有不可逆的肌萎缩，但是其发生机制尚不清楚。我们前期研究发现，肩袖撕裂后肌卫星细胞（MuSCs）的自我更新能力下降，FGFR-p38α/β MAPK信号通路相关蛋白的表达增高。我们推测肩袖撕裂后MuSCs内FGFR-p38α/β MAPK通路被激活，自我更新能力下降，数量减少，再生修复能力下降，最终导致肌萎缩不可逆转。为了验证该假说，我们完成了3部分内容：1）研究了人肩袖撕裂后 MuSCs 自我更新能力和 FGFR-p38α/β MAPK 信号通路的变化，结果显示肩袖撕裂患者冈上肌中， Pax7的表达显著降低，MuSCs的数量显著降低；肩袖撕裂组较对照组处于静止（Pax7+/MyoD-）和活化状态（Pax7+/MyoD+）的MuSCs的比例均降低；Pax7+的卫星细胞数量肩袖撕裂组也明显少于对照组，提示MuSCs的自我更新能力下降。此外，Western blotting结果显示肩袖撕裂后，MuSCs中p-p38α/β MAPK（B）和p38α/β MAPK的水平显著增高。本部分研究揭示了肩袖撕裂、 MuSCs 自我更新能力改变和 FGFR-p38α/β MAPK 通路变化三者之间的内在联系。2）细胞实验结果显示肩袖撕裂组Pax7的表达明显低于正常对照组，提示肩袖撕裂后处于静止状态的Pax7+的MuSCs数量显著减少；对照组和肩袖撕裂组加入SU5402（FGFR的拮抗剂）或SB203580（p38α/β MAPK 通路抑制剂）后Pax7+的MuSCs的数量增加，表明肩袖撕裂后通过FGFR-p38α/β MAPK 通路的影响MuSCs的自我更新能力。本部分研究明确了肩袖撕裂后肌卫星细胞的FGFR-p38α/β MAPK 通路上调，导致MuSCs自我更能能力下降这一机制的存在；3）动物实验结果显示肩袖撕裂后单纯修补+注射未经处理MuSCs后Pax7+的MuSCs数量以及myogenin的表达明显低于修补+注射经过SU5402和SB203580处理MuSCs，表明通过抑制FGFR-p38α/β MAPK 信号通路可以显著提高MuSCs分化形成成熟肌卫星细胞的能力。本部分研究表明）通过抑制 FGFR-p38α/β MAPK信号通路确实在一定程度上提高了MuSCs的自我更新能力，提高了其修复肌肉萎缩的能力。

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