BMPRIA介导的信号通路在调控成骨细胞数量及其终末分化中的作用及机制研究

Differentiation of bone marrow-derived mesenchymal stem cells to osteoblasts and the terminal differentiation of osteoblasts to osteocytes participate in many physiopathological processes such as bone development, bone remodeling, osteoporosis and bone-related tumor, however, the mechanisms regulating these processes are now unclear. Our previous studies showed that deletion of type IA receptor for bone morphogenic protein (BMPR1A) in mice led to massive bone formation in long bone, significant increase of the number of ostoeblasts and no significant changes of the proliferation ability of osteoblasts, apoptosis of osteoblasts and the number of osteoclasts. BMPR1A knockout also resulted in lowered bone intensity and decreased bone collage. These results indicated that BMPR1A played an important role in regulating the differentiation of bone marrow-derived mesenchymal stem cells to osteoblasts and the terminal differentiation of osteoblasts to osteocytes. Based on these findings, the involved signaling pathway and the possible mechanisms of BMPR1A in regulating the number and terminal differentiation of osteoblasts will be investigated in this project by means of gene deletion, gene rescue and Real-time PCR, et al. Related research will tell preliminarily the mechanisms of BMPR1A in regulating the differentiation of mesenchymal stem cells and osteoblasts, shed light on the mechanism of the development of ostroporosis and bone-related tumor, and enrich the basic theory of stem cell differentiation.

骨髓间充质干细胞向成骨细胞分化及成骨细胞向骨细胞的终末分化参与骨发育与重塑、骨质疏松和骨肿瘤等多种生理病理过程，但其调控机制尚不明了。前期实验中我们发现敲除小鼠骨形态发生蛋白IA型受体（BMPRIA）后，在长骨中出现大量松质骨，组织学检测显示成骨细胞数量明显增加，而成骨细胞的增殖活性、凋亡率及破骨细胞数量没有明显变化，即敲除BMPRIA主要通过增加增加间充质细胞向成骨细胞分化而促进成骨；但在骨量增加的同时，骨强度和骨中胶原蛋白含量下降。这些结果提示BMPRIA在调控成骨细胞数量及其终末分化中起到关键作用。本项目将在此基础上，通过基因敲除和挽救、实时定量PCR等方法，探讨BMPRIA在调控成骨细胞数量及其终末分化中的下游信号通路及其作用机制。相关研究将初步阐明BMPRIA调控骨髓间充质干细胞和成骨细胞分化的机制，有助于了解骨质疏松和骨肿瘤等发生机制，并丰富干细胞分化的基础理论。

成骨细胞终末分化参与骨发育与重塑、骨质疏松和骨肿瘤等多种生理病理过程，但其调控机制尚不明了。本项目通过基因激活和敲除、细胞培养、实时定量PCR和免疫荧光组织化学等方法观察发现BMPRIA 在成骨细胞中敲除后，Wnt/β-catenin信号通路相关因子以及Osterix表达升高，小鼠虽然骨量增加，但骨质量下降，而在成骨细胞和骨细胞中持续激活β-catenin后同样观察到骨量增加伴骨矿化、骨强度水平下降，进一步研究发现这与成骨细胞滞留于细胞增殖周期，终末分化受阻相关，下调的DKK1在这一过程中起到重要作用。另外Wnt/β-Catentin相关信号通路活性以及骨重塑水平在小鼠皮质骨和松质骨呈现不同的变化规律，松质骨的骨重塑水平更容易受Wnt/ß-catenin信号通路的影响。上述研究结果证实 BMPR1A 及其介导的信号通路在调控成骨细胞数量和成骨细胞的终末分化中起到关键作用，下游的Wnt/β-Catentin 信号通路需要精确调控才能保证其对成骨效应的积极作用，同时也为进一步应用于临床治疗骨质疏松等疾病做出有益的探索。