植入体表面微结构对细胞成骨相关行为的调控及分子机制

The attachment, spreading, and differentiation of cells affected by implant interface microtopography is closely related to the result of bone-implant integration. It was reported that osteogenic differentiation and bone regeneration can be enhanced when cells grow on a surface with topographies that can promote cells attachment and spreading. However, little is known about the signaling pathways and underlying intracellular mechanisms involved in the microtopography-mediated cell responses to different interfacial microstructures on implant materials. Hippo/YAP pathway has been found to play important roles in cell growth, differentiation and was one of the nuclear relays of mechanical signals exerted by ECM properties. Our preliminary work showed that the expression level and activity of YAP was increased in MC3T3-E1 cells grown on surface with specific microstructure that can promote cells spreading and osteogenesis. Also we found that YAP was mostly localized in nuclei at MC3T3-E1 cells with strong actomyosin contractility. There were also reports that cytoplasmic shuttling YAP can be as co-activator of Runx2 to regulate bone formation. These all remind us that YAP may be involved in the process of physical microtopography affecting the osteogenic differentiation of cells. Thus，this project intends to further research the optimal microstructure characteristics that promote osteogenic differentiation of cells by in situ construction of microstructure on implant surface, explore the mechanism of YAP/TAZ pathway sensing signals of microtopography to regulate osteogenesis. This work is expected to provide new ideas for novel biomimetic design and the optimization of orthopedic implant products.

植入体表面微结构对细胞粘附、分化的影响将直接关系到骨-植入体界面的骨整合效果。有报道易于细胞粘附铺展的界面微结构可促进成骨，提升骨再生效果，但成骨细胞响应微结构所涉及的信号转导机制仍不明确。Hippo/YAP通路在细胞生长、分化及胞外力学信号向胞内传递过程中扮演重要角色。我们前期结果也显示，在促进铺展的界面微结构上MC3T3-E1细胞YAP表达及活性升高，更易发生成骨向分化；且细胞骨架更有序排列时，YAP激活入核增加。也有报道YAP可作为成骨关键蛋白Runx2的共激活因子调节骨形成。这些都提示YAP很可能参与介导成骨细胞对界面微结构的响应。本项目拟在已有基础上通过在植入材料表面原位构建微结构，探究促细胞成骨向分化的最优微结构特征，对YAP/TAZ感应胞外力学信号，参与植入材料界面微结构促进细胞成骨向分化过程的机制问题进行探索，为植入体表现仿生技术的发展和骨科植入体产品性能优化提供新思路。

骨植入材料界面与在体组织的骨整合对植入体治疗成败有决定性作用。易于细胞粘附铺展的材料界面微结构可促进成骨，提升骨再生、骨整合的效果。然而，细胞响应不同界面微结构所涉及的信号转导机制仍不明确。深入系统地探讨内在机制可为植入材料表面微结构的优化设计提供分子水平的理论指导，为骨科植入物材料表面生物活化提供重要方法。本研究通过材料学、细胞及分子生物学、影像学等方法在常用骨植入材料钛合金表面原位构建微结构，以YAP/TAZ为切入点，对促细胞成骨向分化的微结构、植入材料界面微结构促进细胞成骨向分化过程的机制问题进行了深入的探索。项目主要完成了以下几部分的内容：1）利用飞秒激光技术在Ti6Al4V材料表面构建微结构，并探索了不同微结构对细胞成骨过程的影响；2）阐明Hippo通路在植入体表面微结构影响细胞成骨向分化过程中的作用、信号转导途径及响应机制；3）力学刺激对骨重建的影响机制；4）对非平面植入体材料表面微结构加工装置和力学加载细胞培养皿装置进行了研发。同时依托本项目，从骨修复骨整合的预防角度出发，拓展研究了异常骨结构的形态和力学性能。本项目已发表SCI收录论文5篇（其中Q1区3篇），中文核心期刊论文2篇，会议论文3篇；已授权国家发明专利1项并荣获第二十三届中国专利优秀奖。