CD163+吞噬样软骨细胞的发现及其在TMJ OA中的作用

Osteoarthritis (OA) is one of the severe pathological changes that often occur in the temporomandibular joint (TMJ) of patients with severe statement of temporomandibular disorder (TMD), the disease with a frequency that ranked four in oral and maxillofacial regions. However, the pathological mechanism of OA is still not clear yet. After ten years research, we confirmed that the experimentally induced occlusal disorders could induce OA-like changes in the temporomandibular joint of rhesus monkey, rabbit, rat, and further observed the celluar phagocytosis and CD163 expression within mandibular condylar cartilage of the experimental rats. CD163 is one of the specific markers for macrophage. Using the flow cytometry analysis of CD163 and Col2, RNA interference and gene transfection, etc., the present project aimes to use our established TMJ OA rat model to demonstrate that there're CD163 expressing phagocytes within the mandibular condylar cartilage. Combined with the in vitro and in vivo experiments, we want to confirm that the CD163 expressing cells could be activated with increased phagocytosis by the local inflammatory factors secreted by chondrocytes. And by the immune TEM, we want to further verify that the CD163 expressing cells will eventually die in the form of autophagy because of the lack of nutrition caused by the local degradation of cartilage matrix which facilitates cell migration and phagocytosis. By the above exploration, we're aiming to claim that there're CD163 expressing phagocytes within the previous believed non-active joint cartilage, and they play important roles in the active clearance of inflammatory dead tissue and in localizing the expansion of inflammation in OA.

颞颌关节骨关节炎是口腔颌面部第四大疾病颞颌关节紊乱病的重症表现，骨关节炎的病理机制一直未能阐明。本课题组经十余年探索，证实所建独特的咬合紊乱可致恒河猴、兔、大鼠颞颌关节出现骨关节炎样变化，并在大鼠颞颌关节软骨中观察到细胞吞噬现象和CD163高表达。CD163是吞噬细胞的特异性标志物，本项目拟以所建咬合紊乱大鼠为实验对象，采用CD163和Col2流式双分选以及RNA干涉、基因转染等方法，论证颞颌关节髁突中存在CD163阳性的吞噬样软骨细胞；采用体内外实验相结合的方法证实，该类细胞可因关节软骨局部炎性因子的增加而被激活、吞噬活性增强；以免疫电镜等方法阐述，该类细胞多因局部软骨基质降解（以便细胞迁移、吞噬）、营养匮乏而最终以自噬样凋亡形式死亡的功能特点，以期阐述在过去认为惰性较强的关节软骨组织中存在CD163+吞噬样软骨细胞，在主动清理骨关节炎坏死组织、限制炎性扩散方面发挥着积极作用。

针对异常咬合导致颞下颌关节骨关节炎（TMJOA）、OA退变软骨中存在吞噬活动以及CD163阳性软骨细胞的吞噬功能活动问题，本项目主要进行了以下5个方面的研究：（1）构建了单侧前牙反合（UAC）导致大鼠/小鼠TMJ出现OA样变的动物模型，并通过喂以碎食的方式观察减轻异常咬合力刺激对TMJOA炎样变程度的影响，结果证实：UAC可以导致大鼠/小鼠TMJ出现明显的退行性变，表现为髁突软骨丢失，软骨下骨吸收活动增强。予以碎食喂养可以明显缓解关节软骨的退变程度。（2）为探索UAC导致TMJOA软骨退变的病理机理，本项目检测了UAC大鼠软骨细胞力敏感蛋白Cx43的表达水平以及Cx43半通道开放情况，结果表明，UAC大鼠TMJ软骨中Cx43表达水平增高，离体实验证实，软骨细胞表面的Cx43半通道可因力刺激而开放。因此，UAC通过开放髁突软骨细胞表面的Cx43半通道，导致细胞内生物活性物质（PGE2等）释放，从而产生相应的生物效应。（3）在渐进性咬合紊乱诱导的大鼠TMJ退变髁突软骨中，可见一定的细胞增殖反应，并且软骨中存活的软骨细胞高表达CD163，CD163+的软骨细胞表现出一定的吞噬能力，吞噬基质碎片和坏死细胞，发挥清道夫作用。但这种清道夫作用并不足以清理渐进性咬合紊乱所致的TMJ软骨中的退变组织，而只是试图包绕退变组织，将病变限制在一定范围内。（4）UAC刺激强于渐进性咬合紊乱，可导致软骨细胞损伤，继而出现软骨细胞终末分化增强和组织钙化，软骨组织钙化是软骨细胞应对异常生物力刺激的重要生物学行为，其结果是软骨组织钙化带增厚。（5）给UAC小鼠TMJ注射外源性干细胞，可延缓关节软骨的退变，而且这些外源性干细胞高表达CD163，通过吞噬活动清除退变软骨组织，为干细胞定植于退变软骨并分化为软骨细胞、分泌软骨基质、修复退变软骨组织创造了条件。总之，TMJ髁突软骨中存在CD163介导的吞噬活动，该吞噬活动可因异常咬合力刺激而增强，但CD163+软骨细胞的吞噬活动并不足以清除咬合紊乱所导致的TMJOA退变软骨组织，退变软骨最终通过软骨细胞死亡和过度分化而钙化。