Molecular mechanism of temporomandibular joint osteoarthritis and gene therapy for degraded, cartilage

本研究旨在阐明骨关节炎（osteoarthritis，OA）软骨退化的机制，探讨结缔组织生长因子（connective tissue growth factor，CTGF）基因治疗关节软骨损伤的可能性。当用含有CTGF/Hcs 24基因的腺病毒感染RAC细胞时，RAC细胞表达CTGF/Hcs 24 mRNA并产生CTGF/Hcs 24蛋白。RAC细胞比对照细胞合成更多的蛋白多糖。这些结果提示CTGF是促进软骨修复的有效因子。第二，建立了机械应力诱导的兔颞下颌关节骨性关节炎模型。在实验兔中，施加重复的强制性下颌打开（RFJO）3小时/天，持续5天。TMJ关节组织的组织学评估，部分磨损的关节软骨，关节软骨软骨细胞的反应性边缘增殖和软骨下骨区域的软骨细胞巢状增殖观察后7天RFJO时期。此外，在RFJO期后7天，在软骨降解区域中观察到凋亡的软骨细胞。在软骨细胞凋亡明显的部位，观察到NO产生的标志物硝基酪氨酸和软骨ECM降解的关键因子MMP-3。这些结果表明，RFJO方案没有任何手术干预，可以诱导明显的OA样病变在兔TMJ，软骨退化，可能是通过软骨细胞凋亡诱导。该模型的建立对揭示关节软骨退化机制具有重要意义。

The purposes of this research are to clarify the mechanism of cartilage degradation in osteoarthritis (OA) and to investigate the possibility of gene therapy for articular cartlige restoration using connective tissue growth factor (CTGF).First, we investigated the effects of CTGF/Hcs24 transduced by recombinant adenoviruses on the rabbit articular cartilage (RAC) cells in vitro. When RAC cells were infected with adenoviruses containing the CTGF/Hcs24 gene, RAC cells expressed CTGF/Hcs24 mRNA and produced CTGF/Hcs24 protein. RAC cells synthesized more proteoglycan than the control cells. These results suggest that CTGF is useful factor for cartilage repair.Second, we establish a genuine mechanical-stress-induced OA model of the rabbit TMJ. In the experimental rabbits, repetitive forced jaw opening (RFJO) 3 hours/day for 5 days was applied. By histological assessment of the TMJ articular tissues, partial eburnation of the articular cartilage, reactive marginal proliferation of the articular cartilage chondrocytes and nested proliferation of chondrocytes in the subchondral bone area were observed at 7 days after the RFJO period. Furthermore, apoptotic chondrocytes were observed in the cartilage degradation area at 7 days after the RFJO period. And nitrotyrosine, a marker of NO production, and MMP-3, a key factor of cartilage ECM degradation, were observed where chondrocyte apoptosis was evident. These results suggest the RFJO protocol without any surgical intervention can induce evident OA-like lesions in the rabbit TMJ, and cartilage degradation in OA may be induced via chondrocytes apoptosis. This OA model may greatly contribute to the elucidation of the cartilage degradation mechanism in TMJ OA.