BMP-2诱导破骨细胞活化导致骨溶解的Smad与JNK信号通路研究

The use of recombinant human bone morphogenetic protein-2 (BMP-2) to enhance lumbar spine fusion and repair bone defect has gained popularity after Food and Drug Administration of the United States approved its use in 2002. However, the development of vertebral osteolysis was found by many retrospective studies and still unresolved. Recent study showed the vertebral osteolysis might have a relationship with the abnormal activities of osteoclast by BMP-2. Nevertheless，the mechanism and pathway of osteoclast abnormal activiating by BMP-2 is still unknown, so this impetus us to intensive this study. The initial study of us found expression P-Smad and P-JNK in activating osteoclast treated by high concentrated BMP2. Based on this study, we build hypothesis that high concentrated BMP-2 can activate osteoclast directly through BMPR and Smad signal pathway, which was regulate by JNK signal pathway. JNK activation may affect the binding of Smad6 and Smad1 to the BMP receptor, which resulting in increased levels of phosphorylated Smad1 and increased the expression of the mature osteoclast. This study will utilize the multiple techniques，such as RNA interference and gene transfection to verify our hypothesis. Investigate the novel pathway and mechanism of osteoclast activity and regulation will benefit to clinical use of BMP-2 and helpful to find a new solution for avoiding vertebrae osteolysis.

利用基因重组BMP-2提高脊柱手术植骨融合率及修复缺损的骨组织是近年来骨科领域研究的重点和热点，但其应用后出现的骨溶解现象一直亟待解决。目前研究认为骨溶解的发生可能与BMP-2对破骨细胞的活化有关，但具体的途径和机制并不清楚。我们前期研究工作发现BMP-2诱导破骨细胞活化的同时伴有Smad和JNK的磷酸化水平升高，提示Smad通路和JNK通路可能参与了破骨细胞的活化。为此，我们提出假说：BMP-2可能通过上调JNK的表达，调控Smad6和Smad1与BMPR竞争性结合实现Smad1磷酸化进而促进破骨细胞的活化。本实验将采用real time PCR、Western blot、腺病毒载体转染、RNA干扰等手段，探讨破骨细胞活化的途径及调控机制。研究结果对于阐明骨溶解发生的机制具有重要意义，为临床上合理的使用BMP2提供重要的理论依据。

利用基因重组骨形态发生蛋白2（Bone Morphogenetic Protein 2，BMP-2）提高脊柱手术植骨融合率及修复缺损的骨组织是近年来骨科领域研究的重点和热点，但其应用后出现的骨溶解现象一直亟待解决。目前研究认为骨溶解的发生可能与BMP-2促进破骨细胞活化有关，但具体的途径和机制并不明确。我们通过向小鼠胫骨髓腔注射能过表达BMP-2的慢病毒来观察体内BMP-2对骨骼的影响，在体外通过培养骨髓来源巨噬细胞（Bone Marrow-derived Macrophages，BMMs），在使用M-CSF和RANKL诱导BMMs分化为破骨细胞的同时加入不同浓度的rhBMP-2（0、30、60、90ng/ml），观察破骨细胞的骨吸收功能，检测破骨细胞活化的相关标志基因表达，分析Smad和NF-κB信号通路相关蛋白的翻译情况，最后探索BMP受体在rhBMP-2调节破骨细胞分化中的作用。结果表明在体内BMP-2能诱导小鼠胫骨出现显著的骨吸收现象，使得骨体积分数、骨小梁数量和骨小梁厚度明显下降，在体外rhBMP-2能促进RANKL诱导的破骨细胞分化，增强破骨细胞骨吸收功能。rhBMP-2通过激活Smad信号通路，使磷酸化Smad增多，协同促进IκBα的降解，释放NF-κB，随后加速p65磷酸化并进入细胞核内，调节破骨细胞分化。同时BMP受体，特别是BMP 2型受体与RANK的协同作用在这个过程中也起到重要作用。我们的研究结果初步明确了rhBMP-2导致骨溶解的机制，为临床上合理使用rhBMP-2提供了重要的理论依据。