Department of Oral and Maxillofacial Surgery, Stomatological Hospital, Southern Medical University, Guangzhou, China.
Department of Oral and Maxillofacial Surgery, Stomatological Hospital, Southern Medical University, Guangzhou, China.
Int Immunopharmacol. 2023 Nov;124(Pt B):111014. doi: 10.1016/j.intimp.2023.111014. Epub 2023 Oct 11.
Previous studies have demonstrated that PPARγ deficiency is associated with osteoarthritis in the knee joint. However, whether epigenetic PPARγ dysregulation has any effect on temporomandibular joint osteoarthritis (TMJOA) is unknown. This study aims to determine the role and mechanism of epigenetic PPARγ dysregulation in TMJOA.
Partial TMJ discectomy was performed to induce TMJOA in rat. Primary condylar chondrocytes were isolated, and TNF-α-induced inflammatory condition was created in vitro. The expressions of PPARγ and DNA methyltransferase were investigated in vivo and in vitro. The association of PPARγ and DNA methylation was further studied by treating chondrocytes with DNA demethylation agent 5-Aza-2'-deoxycytidine (5Aza) and transfecting with siRNA of DNA methyltransferase (DNMT)1 and DNMT3a, and the methylation level of PPARγ promoter was evaluated by Bisulfite-sequencing PCR. The chondroprotective effects of 5Aza were explored in vitro and in vivo.
PPARγ suppression and upregulated DNMT1/DNMT3a expression exist in TMJOA cartilage in vivo and primary condylar chondrocytes under TNF-α-induced inflammatory conditions in vitro. DNMT1 and DNMT3a elevation contributes to PPARγ-promoter hypermethylation in TMJ chondrocytes under TNF-α-induced inflammation conditions. DNA demethylation intervention by 5Aza protects chondrocytes from inflammation response in vitro. Mechanistically, 5Aza reversed the hypermethylation of the PPARγ promoter and subsequently resulted in PPARγ restoration and decreased expression of cartilage-catabolic factors in chondrocytes. Rat TMJOA model revealed that 5Aza, by reversing PPARγ suppression, effectively attenuated cartilage degeneration and stabilized cartilage homeostasis by balancing anabolic factor and catabolic factor expression.
Epigenetic PPARγ suppression may play a causal role in TMJOA pathogenesis, which can be alleviated by DNA demethylation with 5Aza treatment. This study provides new insights into the pathogenic mechanism and therapeutic strategy of TMJOA.
先前的研究表明，过氧化物酶体增殖物激活受体γ（PPARγ）缺失与膝关节骨关节炎有关。然而，表观遗传 PPARγ 失调是否对颞下颌关节骨关节炎（TMJOA）有影响尚不清楚。本研究旨在确定表观遗传 PPARγ 失调在 TMJOA 中的作用和机制。
通过对大鼠进行部分颞下颌关节盘切除术来诱导 TMJOA。分离原代髁状突软骨细胞，并在体外建立 TNF-α诱导的炎症状态。在体内和体外研究 PPARγ 和 DNA 甲基转移酶的表达。通过用 DNA 去甲基化剂 5-氮杂-2'-脱氧胞苷（5Aza）处理软骨细胞和转染 DNA 甲基转移酶（DNMT）1 和 DNMT3a 的 siRNA，进一步研究 PPARγ 和 DNA 甲基化的关联，并通过亚硫酸氢盐测序 PCR 评估 PPARγ 启动子的甲基化水平。在体外和体内探索 5Aza 的软骨保护作用。
在体内 TMJOA 软骨和体外 TNF-α诱导的炎症条件下的原代髁状突软骨细胞中存在 PPARγ 抑制和上调的 DNMT1/DNMT3a 表达。DNMT1 和 DNMT3a 的升高导致 TNF-α诱导的炎症条件下 TMJ 软骨细胞中 PPARγ 启动子的过度甲基化。5Aza 的 DNA 去甲基化干预可在体外保护软骨细胞免受炎症反应。在机制上，5Aza 逆转了 PPARγ 启动子的过度甲基化，随后导致 PPARγ 恢复和软骨细胞中软骨分解因子的表达减少。大鼠 TMJOA 模型表明，5Aza 通过逆转 PPARγ 抑制，通过平衡合成代谢因子和分解代谢因子的表达，有效减轻软骨退变，稳定软骨内稳态。
表观遗传 PPARγ 抑制可能在 TMJOA 的发病机制中起因果作用，5Aza 的 DNA 去甲基化治疗可缓解这种作用。本研究为 TMJOA 的发病机制和治疗策略提供了新的见解。
