Cx43半通道介导PGE2释放在异常咬合所致髁突软骨退变中的作用

Abnormal mechanical loading can induce articular cartilage degeneration including chondrocytes apoptosis, extracellular matrix degradation and so on, which is one of the main pathologic changes of osteoarthritis (OA). Based on a large number of clinical studies, we found that TMJ OA is related to malocclusion, but the mechanism remains unclear. Recently, we established unilateral anterior crossbite (UAC) rat and mouse models which indeed causes OA-like changes in TMJ. We observed the expression of Cx43 protein, and the production and release of PGE2 all increased in mandibular condylar cartilage of UAC rats. PGE2 is unsaturated fatty acid with small molecular which can efflux through Cx43 hemichannels and promote chondrocytes apoptosis, extracellular matrix degradation, inflammation factors and matrix-degrading enzymes production, angiogenesis and so on. In this study, we will use the inducible Cx43 knockout mouse, and isolated TMJ chondrocytes with in vitro biomechanical loading combined, to claim that UAC abnormal bite force leads to the opening of Cx43 hemichannels and increased PGE2 release, revealing the mechanism of UAC induced mandibular cartilage degeneration. By the above exploration, a new target for OA treatment will be provided.

骨关节炎（OA）软骨退变的主要病理改变包括细胞过度死亡和软骨基质降解，常与异常生物力作用有关。我们前期临床研究结果显示，颞下颌关节（TMJ）OA与咬合异常密切相关，但异常咬合导致TMJ软骨退变的分子机理尚不清楚。最近我课题组通过建立大鼠和小鼠单侧前牙反合（UAC）模型，成功诱导出TMJ OA样变，并发现在UAC大鼠TMJ退变软骨的细胞中，力敏感性Cx43半通道蛋白表达水平明显增高，PGE2含量明显增加。PGE2是影响软骨细胞代谢活动的一种小分子量不饱和脂肪酸，可经Cx43半通道释放到细胞外，刺激软骨细胞分泌炎性因子和基质降解酶，导致软骨细胞凋亡、软骨基质降解、血管生成增多。本项目拟以Cx43基因敲除小鼠为研究对象，并结合软骨细胞体外加载实验，以期论证UAC异常咬合力致髁突软骨细胞Cx43半通道开放、PGE2释放增加，是其所致髁突软骨OA样变的重要分子病理机理，为OA防治提供新思路。

针对异常生物力导致关节软骨退行性变的科学问题，围绕在Cx43半通道-PGE2在咬合异常导致TMJ髁突软骨退行性变中的重要作用，本项目主要进行了以下三个方面究：1. 构建单侧前牙反合（UAC）动物模型，发现UAC刺激可以诱导长期稳定的TMJ OA样退变，包括软骨细胞凋亡增加、软骨基质降解、炎性因子分泌增加、骨软骨交界明显增厚并硬化；并观察到UAC髁突软骨内Cx43表达升高、PGE2合成和分泌增多。2. 在液流剪切力作用下，体外培养的软骨细胞中Cx43表达升高，半通道活性增强， PGE2合成和分泌增多，且PGE2的分泌可被Cx43半通道抑制剂阻断。3. 对Cx43基因敲除小鼠施加UAC刺激，发现其髁突软骨退变较野生型小鼠明显缓解。综上，本项目证实：异常生物力作用下，软骨细胞膜上Cx43半通道活性增强，细胞内PGE2合成和分泌增加，造成关节软骨细胞凋亡、软骨基质丢失、软骨厚度变薄等OA样退行性变，阐述了 Cx43半通道-PGE2在异常生物力导致关节软骨退变中的力学-分子致病机制。