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

本研究旨在阐明骨关节炎软骨退化的机制，探讨结缔组织生长因子(CTGF)基因治疗关节软骨修复的可能性。首先，我们研究了重组腺病毒转导CTGF/Hcs24基因对兔关节软骨细胞的影响。当携带CTGF/Hcs24基因的腺病毒感染RAC细胞时，RAC细胞表达CTGF/Hcs24基因，并产生CTGF/Hcs24蛋白。RAC细胞比对照细胞合成更多的蛋白多糖。这些结果表明CTGF是软骨修复的有用因子。其次，我们建立了真正的机械应力诱导的兔TMJ骨关节炎模型。实验兔采用重复强迫张口(RFJO)，每天3小时，连续5天。关节组织学观察，术后7d关节软骨部分脱落，关节软骨细胞反应性边缘增生，软骨下骨区软骨细胞嵌套性增殖。此外，在RFJO术后7天，软骨退变区可见软骨细胞凋亡。在软骨细胞凋亡明显的部位，观察到NO生成的标志物硝基酪氨酸和软骨ECM降解的关键因子--基质金属蛋白酶-3。这些结果提示，RFJO方案在不需要任何手术干预的情况下，可以在兔TMJ诱导明显的骨性关节炎样病变，骨关节炎的软骨退化可能是通过软骨细胞的凋亡来诱导的。该模型对阐明TMJ骨关节炎的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.