KLF4-RANK轴调控BMSCs成骨分化机制及其在骨骼衰老中的作用

Osteoporosis is a degenerative bone disease caused by aging, characterized by reduced bone mass, changes in the microstructure and patients are prone to fractures. BMSC is a precursor stem cell of osteoblasts and adipocytes in bone marrow. In osteoporosis, the decreased differentiation of BMSC into osteoblasts and the increase of adipogenic differentiation is an important reason for the imbalance of bone formation and bone resorption. RANK is highly expressed in osteoclast precursors and activated by RANKL, which can promote osteoclast survival, proliferation and differentiation. It is the most important receptor for osteoclast differentiation. However, its function in BMSC has not been reported yet. The applicant found that BMSC highly expressed RANK receptor, and the expression of RANK was down-regulated rapidly after the osteogenesis was induced. Osteogenic differentiation was significantly inhibited with overexpression of RANK. It is speculated that RANK can inhibit the osteogenic differentiation of BMSC, and it is expected to be a new target for the research and development of drugs for promoting bone formation. Through a series of experiments in vivo and in vitro, we will determine the expression of RANK and describe the changes; clarify the overexpression/knockdown effect on differentiation of BMSC in vitro; explore the molecular mechanisms of its regulation on osteogenic differentiation; construct rank flox/flox-prx-1 cre mice in vivo; isolate BMSC from patients and analyze the relationship between the expression level of RANK and bone density and fracture risk. The study is aimed to clarify the roles of KLF4-RANK in regulating BMSC differentiation in bone aging.

骨质疏松症(OP)是一种衰老所致的骨骼退行性疾病，表现为骨量降低、骨组织显微结构改变，患者易发生骨折。BMSC是骨髓中成骨和脂肪细胞的前体干细胞，在骨骼衰老过程中BMSC向成骨细胞分化减少，向成脂分化增多，是骨形成与骨吸收失衡的重要原因。RANK高表达于破骨前体细胞，RANKL激活后可促进破骨细胞存活、增殖和分化，但其在BMSC中的功能尚不明确。申请人发现BMSC细胞高表达RANK；成骨分化时RANK受体表达迅速下调；过表达时成骨分化显著抑制；预测KLF4转录因子能够转录RANK，调控BMSC成骨分化。我们拟通过体内外实验，明确RANK受体时空表达及变化特征；研究体外过表达、敲减对BMSC分化的作用；阐明RANK调控成骨分化的分子机制；构建条件敲除小鼠观察体内作用；分析BMSC中RANK表达水平与骨密度、骨折风险关系，以期阐明KLF4-RANK轴调控BMSC分化及在骨骼衰老过程中的作用。

RANKL 信号对破骨细胞生成至关重要，在成骨细胞分化和骨形成中的作用尚不清楚。通过本项目研究，我们证明 RANK 在小鼠和人骨髓间充质干细胞成骨分化过程中的早期阶段表达，并迅速下降。 RANKL 信号通过促进 β-连环蛋白降解并抑制其合成来抑制成骨。相反，RANKL 信号对 BMSC 脂肪形成没有显着影响。使用 Prx1-Cre 小鼠条件性敲除 BMSCs 中的RANK会促进骨形成，表现为骨小梁增多和骨密度升高。rank flox/flox: Prx1-Cre 小鼠抵抗卵巢切除术 (OVX) 引起的骨丢失。本研究结果表明，RANKL 信号通过抑制 BMSC 成骨分化和促进破骨细胞生成来调节破骨和成骨代谢平衡。.本项目揭示了骨质疏松症发病新机制和干预新靶点，构建了骨靶向外泌体改善微环境，筛选了破骨靶向药物调控细胞分化，获得了一系列原创成果。近五年来，负责人以第一作者和通讯作者在Science Advances (2020, IF:14.116)、Cell Reports Medicine (2023, IF: 16.988)、Bone Research (2021, IF: 12.354)、EMBO Reports (2021, IF: 9.071)、Chemical Engineering Journal (2022, IF: 16.744)、Bioactive Materials (3篇, 2021, 2022, 2022 IF: 14.593)、Acta Pharmaceutica Sinica B (2020, IF: 14.911)、Drug Discovery Today (2篇，2020, 2022, IF: 8.369)等国际知名学术期刊发表学术论文30篇，累计引用次数2200余次，累计影响因子273.57分，H指数27，其中影响因子>10分11篇，获国家发明专利授权6项，主编专著6部，包括Wiley旗下国际英文专著《Biomaterials Effect on the Bone Microenvironment》一部。