WNT13调控Ⅱ型骨质疏松症骨髓基质干细胞分化的分子机制

Type II osteoporosis (OP) is related to aging directly, it is revealed that the patients were characterized by low bone mass and high fat capacity in the bone marrow. One of the mechanisms causing OP is the imbalance of osteocytogenic and adipocytogenic differentiation of mesenchymal stem cells (MSCs). Wnt signaling was demonstrated to be associated with aging and osteocytogenic-adipocytogenic differentiation of MSCs, suggesting that Wnt signaling pathways is associated with type II OP, however, the relationship of WNT members and type II OP is still poorly understood so far. Our previous studies have shown that WNT13 expression in MSCs was significantly lower in elder than in young subjects, and that WNT13 expression was reversely correlated with age. Our previous studies also have showed that WNT13 expression decreased in adipocytogenic differentiation of MSCs, suggesting that WNT13 gene may contribute to the occurrence of type II OP. The present study intends to explore the role of WNT13 in aging and osteocytogenic-adipocytogenic differentiation of MSCs by regulating the expression of WNT13 using gene overexpression, RNAi and other techniques in hMSCs from multiple subjects. By doing these, we aim to clarify the signal transduction mechanism of WNT13, and to reveal its role in the occurrence of type II OP. Results of our study will provide a theoretical basis and therapeutic strategies for the treatment of type II OP.

II型骨质疏松症(OP)与老龄化直接相关，患者在骨量减少的同时可见骨髓腔内脂肪容量升高，而骨髓基质干细胞(MSCs)的成骨－成脂分化失衡是其主要发生机制之一。Wnt信号与MSCs的老化、成骨－成脂分化关系密切，提示其是与II型OP发生相关的信号通路。但迄今对具体WNT成员在II型OP发生中的作用仍知之甚少。申请者前期研究显示，老年MSCs中的WNT13的表达较年轻者显著降低、WNT13的表达与年龄具有反向相关性；在MSCs向脂肪细胞分化的过程中，WNT13表达逐渐降低，提示其可能是与II型OP发生密切相关的WNT基因。本研究拟收集多样本来源的MSCs,用基因过表达、RNAi等方法调节WNT13信号的表达，探索WNT13对MSCs老化的影响和在MSCs向成骨细胞－脂肪细胞分化中的作用，并阐明其信号转导机制，揭示WNT13在II型OP发生中的作用，为II型OP的治疗提供理论基础及治疗策略。

人骨髓基质干细胞（hMSCs）向成骨细胞分化能力减弱、向脂肪细胞分化能力增强是II型骨质疏松症（OP）患者的骨－脂肪偶联失衡的主要机制之一。Wnt信号通路与老化和骨、脂肪分化密切相关，提示WNT信号通路有可能在hMSCs相关的II型OP中起着重要作用。研究者在既往建立的hMSCs分离平台的基础上，建立了hMSCs的培养体系，并且采用新的骨髓组织来源，获得了分化能力强的hMSCs。本项目将hMSCs分别进行成脂肪和成骨分化诱导，检测了在hMSCs成脂诱导分化的不同时间点的beta-cantenin蛋白的表达情况。发现在hMSCs向脂肪细胞分化过程中，beta-catenin的表达逐渐降低；在成骨和成脂肪的不同分化条件下，hMSCs中的WNT蛋白表达量呈现变强或者变弱的趋势。本项目采用基因过表达和RNAi等方法调控WNT信号的表达，研究WNT13和WNT14在hMSCs的老化和向成骨细胞－脂肪细胞分化中的作用，研究结果可以为开发针对WNT信号通路的模拟肽、抗体和小分子化合物等治疗OP的新药物提供靶点，为治疗II型OP提供理论基础及治疗策略。