骨细胞直接参与并促进弥散性微损伤的结构和力学性能修复的研究

Physiological wear and tear cause bone microdamage at several hierarchical levels, and these have different biological consequences. Bone remodeling is widely held to be the mechanism by which bone microdamage is repaired. However, recent studies showed that unlike linear microcracks, diffuse damage does not activate remodeling. Interestingly, diffuse damage structurally and mechanically repaired in cortical bone in vivo over time. Our preliminary study shows diffuse matrix damage elevates solute transport in lacunar-canalicular system in bovine cortical bone. In view of recent discoveries, we proposed that the osteocytes, within the damage sites, directly mediate the repair of small crack by production of such protein, with combination of the physicochemical process. To examine this, we induce selectively diffuse damage in mouse ulnae in vivo by using end-load ulnar bending creep model. Changes in damage content were assessed by histomorphometry and mechanical testing. (1) Firstly, we will test the physicochemical process of repair without living osteocytes, to indirectly show the role of osteocyte in the direct repairing process. (2) Secondly, we will observe the changes in the expression of local mineralization regulating molecules by osteocytes within diffuse damages sites, and investigate the influence of the expression of DMP1 (the matrix protein produced by osteocytes) on the self-repair in diffuse damage. (3) Last, we will investigate fluid and solute transport in osteocyte lacunar-canalicular system for each group in vivo. This study will provide some new information on the repair of bone matrix damage, open up a broad area of research into the mechanisms that allow for repair of our bone at the submicron level.

弥散性微损伤是骨疲劳引发的主要骨微损伤之一。研究发现：与线性裂痕不同，弥散性微损伤的骨细胞未凋亡，损伤区在“无骨重建过程”下进行了直接修复。我们前期研究发现弥散性微损伤后骨陷窝-骨小管内的物质输运增强。综合文献和前期数据，本研究设想：弥散性微损伤位点，未凋亡骨细胞“直接”通过自分泌矿化蛋白，与物理修复联合调控微损伤修复。为验证此观点，本研究将建立单纯弥散损伤小鼠模型，以结构和力学性能修复为考察指标，设立以下内容。首先对损伤后无活性骨细胞（冷冻处理）的微损伤自修复考察，间接说明骨细胞在损伤修复中的作用；其次检测弥散性微损伤对骨细胞矿化蛋白表达的影响，然后考察骨细胞表达矿化蛋白DMP1对弥散性微损伤修复的影响；最后考察弥散损伤对在体骨细胞微环境的物质输运影响。本研究可能为骨损伤修复的研究提供一个新视角；并为临床治疗骨折、骨质疏松等骨组织疾病提供新思路，为开展以靶点骨细胞自体治疗提供的理论支持。

骨细胞作为自环境调节因子的作用机制得到了越来越多的关注。本研究基于前期研究发现“弥散性微损伤的骨细胞未凋亡，损伤区在无骨重建过程下进行了直接修复”的现象，提出了研究构想：弥散性微损伤位点，未凋亡骨细胞“直接”通过自分泌矿化蛋白，与物理修复联合调控微损伤修复。为验证此观点，本项目从组织和细胞水平分别进行了考察研究。首先通过建立单纯弥散损伤模型，以骨细胞微环境输运、损伤位点结构和力学性能修复为考察指标，检测并部分验证了骨细胞通过动态微环境的变化参与弥散性微损伤位点的自修复过程；其次通过体外细胞实验，就剪切力对骨细胞自噬的影响，验证了骨细胞力诱自噬影响骨细胞的ATP代谢及细胞活性；间接说明了弥散损伤位点骨细胞微环境的应力改变将参与骨细胞的自修复调节过程。总之，本研究结果揭示了骨细胞在其流体微环境内参与密质骨内弥散性基质微损伤自修复。本项目开展为骨损伤修复的研究提供一个新视角；并为临床治疗骨折、骨质疏松等骨组织疾病提供新思路。