基于GSK3β/Rac1/NF-κB通路的骨折血肿微环境中MFG-E8促骨愈合机制研究

Microenvironment of fracture hematoma plays an important role in the regulation of bone healing, but the mechanisms of promoting bone healing have not been elucidated yet. Our preliminary study found that the expression of the milk fat globule-derived epidermal growth factor 8 protein (MFG-E8) in the inflammation of fracture hematoma was significantly increased and the osteogenic differentiation of the bone marrow mesenchymal stem cells (BMSCs) was promoted. Further exploration found that MFG-E8 can up-regulate the phosphorylation of GSK3β and downregulate the Rac1 and p-IκBα level，influencing the osteogenic differentiation of BMSCs. Accordingly, we hypothesize that MFG-E8 promotes osteogenic differentiation of BMSCs through regulation of p-GSK3β, Rac1 levels and NF-κB pathway in the inflammatory microenvironment of fracture hematoma. Based on the above studies, this study intends to explore the possible molecular mechanisms of MFG-E8 in promoting the osteogenic differentiation of BMSCs in the inflammatory microenvironment of fracture hematoma, and provides an academic basis for the treatments of fracture nonunion and bone defects.

骨折血肿微环境对骨愈合具有重要的调控作用，但其促进骨愈合的机制尚未阐明。申请者前期研究发现乳脂肪球表皮生长因子8蛋白（MFG-E8）在骨折血肿炎症微环境中表达显著升高，并可促进骨髓间充质干细胞（BMSCs）成骨分化。进一步探索发现外源性MFG-E8可上调GSK3β磷酸化水平，同时下调Rac1水平和p-IκBα水平从而影响BMSCs成骨分化。据此，我们提出假说：在血肿炎症微环境中，MFG-E8通过调控p-GSK3β、Rac1水平和NF-κB信号通路促进BMSCs成骨分化。本课题拟在上述研究基础上，从整体、细胞和分子水平，探讨MFG-E8促进血肿炎症微环境中BMSCs成骨分化的可能分子机制，为丰富骨折不愈合和骨缺损的治疗提供学术依据。

骨折或大段骨缺损导致的骨折血肿微环境对骨愈合具有重要的调控作用，但其促进骨愈合的机制尚未阐明。MFG-E8作为一种分泌性糖蛋白几乎表达于所有细胞中，能够介导凋亡细胞清除，肠上皮功能的维护和修复，抗炎作用和血管生成的调节等，因而在调节多种细胞的生物学功能上起着重要作用。本项目从细胞、分子和体内体外多角度探究了MFG-E8对于骨微环境中成骨的作用和机制，发现MFG-E8能够通过GSK3β信号通路促进骨髓间充质干细胞成骨分化，能够通过NF-κB信号通路改善TNF-α诱导的炎症环境，从而促进BMSC成骨分化，此外我们也进一步从体外证实了外源性重组MFG-E8蛋白可以显著促进骨缺损的修复和愈合，本项目较为全面和深入的探究了MFG-E8这个重要的促成骨分子，本研究可以为临床中多发伤、多发骨折患者的治疗和改善预后提供一定的理论和实验依据。