Wnt11/Ca2+信号通路下SPA对BM-MSCs成骨分化的影响及其在感染性骨不连中的作用

Infected nonunion is a knotty disease in orthopaedic department and insufficent bone formation is its essential characteristics.Up to now,the pathogenic mechanism causing infected nonunion is still unclear.Staphylococcus aureus (SA) are the main pathogenic bacterium of infected nonunion,but it is still unknown how does it cause bone nonunion.Our previous studies demonstrated staphylococal protein A(SPA) could significantly down-regulate the osteogenic potential of BM-MSCs when the expression level of Wnt11 desend significantly. Studies reported that wnt11 play an importment role in body development and osteogenic differentiation of stem cells via non-canonial wnt/Ca2+ signaling pathway.Furthermore,bioinformatics analysis demonstrated the promoter of wnt11 existing the potential binding site for SPA.Therefore,we speculate SPA might significant down-regulate the osteogenic potential of BM-MSCs resulting in difficient bone formation, the appearance might be one of the important causes for bone nonunion.This study will take the somatic protein of staphylococcus aureus as the new key point of breaking through to reveal the osteogenic potential variation of BM-MSCs and the signal transduction mechanism under infectious condition,the study will present the possible occurrence mechanism of bone nonuion from a new point, it will still provide experiment basis and new idea for prevention and treatment for infected nonunion.

感染性骨不连是骨科难题，骨生成不足是骨不连的本质特征。迄今为止，感染性骨不连的发病机制仍然不是很清楚。金黄色葡萄球菌(SA)是感染性骨不连的主要致病菌，但其如何引起骨不连则仍然不清楚。课题组前期发现SA菌体A蛋白(SPA)在体外能降低BM-MSCs的wnt11表达并显著下调其成骨分化能力；有研究报道Wnt11 主要通过非经典的Wnt/Ca2+信号通路对机体发育以及干细胞分化起重要的调节作用。课题组通过生物信息学分析提示Wnt11启动子区存在与SPA潜在结合位点。因此，我们 推测SPA可能通过Wint11/Ca2+信号显著下调BM-MSC的成骨分化能力，引起骨生成不足，该现象可能是引起感染性骨不连的重要因素之一。本实验以SA菌体成分作为新突破点，揭示感染条件下BM-MSCs成骨分化能力的变化及其信号转导机制，从新角度阐述感染性骨不连的可能机理，以期为其防治提供实验依据和新思路。

感染性骨不连是骨科的难题之一，很难彻底治愈，给患者及社会带来了严重的身心健康损害和经济负担。本题组发现SPA浓度梯度在体外界能不同程度影响hMSCs的成骨分化能力，在100ng/mL浓度时开始显现显著影响，并随着浓度增加而增加，并能够下调WNT11介导的非经典β-catenin信号通路；WNT11能够一定程度抑制NF-κB的表达。同时，通过WNT11过表达组hMSCs与PHA/FN/ALG复合支架构建的组织工程骨在修复感染性骨缺损动物模型中，发现其具有更好的修复能力，具有临床应用的潜在应用价值。我们研究结果提示WNT11可以作为一个潜在的调节靶点，发挥增强成骨分化的能力。SPA毒力因子刺激炎症条件下，在hMSCs体外成骨分化过程中，非经典Wnt信号通路与经典Wnt/β-catenin信号通路相互关联，具有一定的协同作用, 并且具有抑制NF-κB的作用。