Smad4信号在骨诱导性仿生骨粉表面调控成骨的作用和机制研究

In our previous study, biomimetic calcium phosphate bone substitutes (BioCaP) and the biomimetic calcium phosphate coating by slowly releasing bone morphogenetic protein2 (BMP-2) can significantly induce bone formation. Thus BioCaP materials can obtain osteoinductivity. Moreover, BioCaP simultaneously releasing BMP-2 and icariin (ICA) can enhance the osteogenic effect of BMP-2. The synergistic effect of BMP-2 and ICA can regulate the osteogenesis, such as Smad4, Runx2, BMP-2, and OCN. The signals of Smad may be a critical factor in the regulation of osteogenesis. However, the mechanism and influence of Smad signals were unclear therein. This study proposes that the pathway of Smad signals could regular the osteogenesis on BioCaP materials, especially the Smad4 signal which could overlap or connect with independent Smad pathway. This study also will build up a virus carrier which could over-express or disturb Smad4, which transfects BMSCs, to explore the molecular mechanism. The mechanism and osteogenic effects were investigated in the orthotopic rabbit model. This study will contribute to the treatment of critical-sized bone defects and the improvement of bone substitutes.

前期实验发现，仿生骨粉BioCaP和仿生表面晶体涂层缓释骨形成蛋白2(BMP-2)能够显著诱导成骨，从而BioCaP骨粉获得骨诱导性。此外，BioCaP同时缓释BMP-2和淫羊藿苷(ICA)能够增强BMP-2的成骨效果，BMP-2与ICA的协同作用能够上调相关成骨基因表达，例如Smad4、Runx2、BMP-2、OCN等， Smad信号可能在其中起到调控和发挥关键作用，然而其中的分子机制尚不清楚。本课题提出假设Smad信号通路可能在BioCaP表面调控成骨，其中最关键的是Smad4，并且可能与Smad非依赖信号途径相联结、重叠，构建含有Smad4的过表达/干扰型慢病毒载体，转染BMSCs，探索分子机制，并在兔成骨模型上进行初步验证，为骨粉材料的改进和临界骨缺损的治疗提供理论和实践依据。

实验发现，仿生骨粉BioCaP和仿生表面晶体涂层缓释骨形成蛋白2(BMP-2)能够显著诱导成骨，从而BioCaP骨粉获得骨诱导性。此外，BioCaP同时缓释BMP-2和淫羊藿苷(ICA)能够增强BMP-2的成骨效果，BMP-2与ICA的协同作用能够上调相关成骨基因表达，例如Smad4、cbfa1、OPG等，证实 Smad信号在其中起到调控和发挥关键作用。Smad信号通路在BioCaP表面调控成骨，其中最关键的是Smad4。羊兔成骨模型上进行初步验证，BioCaP缓释BMP-2的成骨机制。仿生态BioCaP骨粉的研发基于仿生态磷酸涂层的研究，可以缓释BMP-2生长因子，亦可以作为携带释放其他因子（例如锶Sr）的载体，因为增加了含Sr涂层对BMSCs的研究，发现对BMSCs的迁徙、成骨分化有正性作用，促进快速骨整合。成骨需要BMP-2等活性因子，以及需要成血管/血管化，仿生态BioCaP骨粉缓释成骨或成血管活性因子，特别在骨质疏松Osteoporosis的情况下，其可能会发挥作用，其中发现血管紧张素II受体阻断剂（Angiotensin II Receptor Blockade）对骨质疏松的影响。仿生态BioCaP骨粉可以去携带释放血管紧张肽，在骨质疏松患者中发挥促进成骨作用。本课题已经证实了Smad4的调控和发挥关键作用，羊兔的临界骨缺损中BioCaP缓释BMP-2显著促进成骨抑制异物反应，为骨粉材料的改进和临界骨缺损的治疗提供理论和实践依据。