mTORC1信号通路在骨折愈合中的作用及其调节机制

Osteoblast activity is a crucial factor in bone healing process and elucidation of the molecular signal mechanisms involved in regulating osteoblastic activity is considered as an essential scientific issue in bone field. Recently, it has been showed that mammalian target of rapamycin complex 1 (mTORC1) is probably a key modulator of osteoblast activity and increase of mTORC1 signaling activity could stimulate its proliferation and differentiation. However, the role and molecular mechanism of mTOC1 in osteoblast activity and bone fracture healing process are still unclear, which also need further confirmation in animal study. Our preliminary results suggest that mTORC1 signaling regulates osteoblast function and plays critical role in bone development and bone formation in cell-specific TSC1 gene knckout mice model. The current project aims to elucidate the roles and molecular and cellular mechanisms of mTOC1 signaling in bone fracture healing and osteoblastic proliferation and differentiation. The inducible and cell-specific knockout mice and cellular models will be used, in which the mTORC1 in osteoblast of mice could be specifically activated or inhibited. The effects of mTORC1 on osteoblast proliferation and differentiation and the expression of bone metabolic-related genes in these mice and cellular models will also be investigated. This study will identify novel function of mTORC1 in bone metabolism and provide novel mechanisms for bone healing and evidences for prevention and treatment of bone nonunion.

成骨细胞功能的激活对于骨折愈合至关重要，阐明调控成骨细胞增殖分化与功能的信号机制是骨科研究的关键科学问题。最近研究发现：雷帕霉素靶蛋白复合物1(mTORC1)通路可能调节成骨细胞增殖分化，但缺少体内直接证据，且其作用机制不清楚；成骨细胞mTORC1活性在骨折愈合中的作用也未见报道。我们前期工作中构建了成骨细胞特异敲除TSC1基因(mTORC1的上游抑制分子，敲除后mTORC1被活化)的小鼠模型，发现小鼠出现骨硬化表型。本课题拟构建可诱导、成骨细胞特异TSC1或Raptor（mTORC1特异组分）敲除的小鼠与细胞模型，在其骨折造模前后的不同时间，分别使其成骨细胞mTORC1被活化和抑制，观察其骨折愈合情况，从分子、细胞与整体水平阐明成骨细胞mTORC1活性对骨折愈合的作用及其调控成骨细胞增殖分化的细胞与分子机理，为骨代谢调节提供新机制，为预防和治疗骨不愈合提供新思路。

成骨细胞功能的激活对于骨折愈合至关重要，阐明调控成骨细胞增殖分化与功能的信号机制是骨科研究的关键科学问题。既往研究发现：雷帕霉素靶蛋白复合物1(mTORC1)通路可能调节成骨细胞增殖分化，但缺少体内直接证据，且其作用机制不清楚；成骨细胞mTORC1活性在骨折愈合中的作用也未见报道。我们前期工作中构建成骨细胞特异敲除TSC1基因的小鼠模型，发现小鼠出现骨硬化表型。本课题通过动物体内研究和体外细胞研究获得如下发现：1）证实雷帕霉素及成骨细胞mTORC1活性改变可影响骨折的愈合，且作用时期是骨折愈合的早期阶段；2）在研究过程中，我们惊喜的发现：雷帕霉素及mTORC1活性可调控骨折愈合的过程，此外还靶向破骨细胞的活性状态（M1和M2）发挥上述功能，这提示：雷帕霉素的靶向细胞同时涉及成骨细胞和破骨细胞（骨代谢的两种重要细胞）；3）初步明确柠檬酸促进成骨细胞分化作用和机制。上述研究成果为骨代谢调节提供新机制，为预防和治疗骨不愈合提供新思路。