Hedgehog信号途径调控BMP9诱导的间充质干细胞成骨分化

The treatment of bone defect is still a major clinical problem. BMP9 has strong potential to induce osteogenic differentiation of Mesenchymal Stem Cells (MSCs), and brings hope to the MSCs-based bone defect treatment. However, the precise molecular mechanism involved in BMP9-induced osteogenic differentiation of MSCs remains to be fully elucidated. Our recent preliminary results showed that Hedgehog signal pathway is likely to regulate BMP9-induced osteogenic differentiation of MSCs. Based on these results, we will firstly try to validate if BMP9 can activate Hedgehog signal pathway in MSCs. Secondly we will analyze and characterize the effect of Hedgehog signal pathway on BMP9-induced osteogenic differentiation of MSCs. Subsequently, we will investigate the molecular mechanisms through which Hedgehog signal pathway to regulate BMP9-induced osteogenic differentiation of MSCs. Finally, we will explored the feasibility of using Shh, a Hedgehog family member, to enhance BMP9-induced osteogenic differentiation of MSCs, thus to promote fracture healing and to accelerate bone defect repairing. Collectively, this project will further enrich our understanding of the complex signal network involved in BMP9-induced osteogenic differentiation of MSCs, and will provide a theoretical and experimental basis for the use of BMP9 in clinical treatment of fracture and bone defect in the future.

骨缺损修复是临床一大难题。BMP9具有强效诱导间充质干细胞（Mesenchymal Stem Cells，MSCs)成骨分化的能力，这为以MSCs为基础的骨缺损修复带来希望。但目前对BMP9诱导MSCs成骨分化分子机制的理解，仍不够深入。课题组前期发现Hedgehog信号途径可能对BMP9诱导MSCs成骨分化有调控作用。在此基础上，本项目首先确认BMP9是否可活化MSCs中Hedgehog信号；随后分析Hedgehog信号对BMP9诱导MSCs成骨分化的调控作用及特点，并解析Hedgehog信号调控BMP9诱导的MSCs成骨分化分子机制；最后探索利用Hedgehog家族成员Shh来增强BMP9诱导的MSCs成骨分化，从而促进骨折愈合和骨缺损修复的可行性。研究结果将进一步丰富对BMP9调控MSCs成骨分化复杂信号网络的认识和理解，并为BMP9将来在临床用于骨折和骨缺损治疗提供理论和实验依据。

BMP9调控MSCs成骨分化的分子机制一直尚未阐明。本项目的主要研究内容为：利用PCR和Western证实BMP9可激活MSCs中的Hedgehog；深入分析Hedgehog信号对BMP9诱导MSCs成骨分化的影响，并初步解析Hedgehog信号调控BMP9诱导的MSCs成骨分化分子机制，包括Hedgehog信号对BMP9下游成骨相关信号途径的影响，以及Hedgehog信号下游重要转录因子Gli1和Gli2在其中的关键作用。在大骨缺损模型中，探索利用Hedgehog家族成员Shh来增强BMP9诱导的MSCs成骨分化，从而更有效促进骨折愈合和加速骨缺损修复的可行性。通过体外成骨分化实验和裸鼠皮下MSCs异位移植模型证实了Hedgehog途径对BMP9诱导的MSCs成骨分化的调控作用，即：激活Hedgehog信号，BMP9诱导的MSCs成骨分化进一步增强；抑制Hedgehog信号，BMP9诱导的MSCs成骨分化相应受到抑制。初步解析了Hedgehog信号调控BMP9诱导的MSCs成骨分化分子机制，即：Hedgehog信号可影响BMP9下游Smad/1/5/8等成骨相关信号途径；转录因子Gli1和Gli2在Hedgehog信号调控BMP9诱导MSCs成骨分化中具有关键作用。证实了Shh对BMP9成骨的增强作用，与单一BMP9相比，BMP9联合Shh，可以获得更强的体外促成骨效果，并且可以可更有效促进裸鼠皮下异位成骨和骨缺损修复。本项目的完成将完善和丰富目前了解较少的BMP9诱导MSCs成骨分化相关信号转导体系，为进一步深入揭示BMP9诱导成骨的机理提供新的理论依据，由此得到的结果可有助于BMP9的基础和应用研究。而且， BMP9和Shh联合使用有可能在将来为骨组织工程提供一种更有效的促进种子细胞成骨分化的策略，有利于提高临床对骨缺损、骨不连等疾病的治疗效果。