Juvenile idiopathic arthritis can affect the temporomandibular joint (TMJ) can cause growth disturbances of the lower jaw (mandible). The collagen-induced arthritis (CIA) juvenile rat model may be an appropriate model for studying how juvenile arthritis affects this joint during growth. However, studies using this animal model to investigate TMJ arthritis are limited. To validate an animal model for studying TMJ arthritis in growing rats, our study aimed to investigate the changes in mandibular growth and expression of proteins and cytokines in the mandibular condyle of CIA juvenile rat TMJs. A total of 27 male Wistar rats (3 weeks old) were scanned with microcomputed tomography (MicroCT) and divided into three groups (n = 9); CIA was induced in each TMJ in the CIA group, the Saline group received saline injections (sham injections) into their TMJs, and the Healthy group remained untreated (no TMJ injections) as negative controls. After 4 weeks, our results show that mandibular growth was significantly reduced in the CIA group compared with the Saline group (p < 0.01). There was no difference in mandibular growth between the two control groups (Saline and Healthy). Inflamed synovial tissue, cartilage invaginations, and lipid accumulation were observed in the CIA TMJs. Toluidine blue staining revealed decreased proteoglycan production in the CIA cartilage. In addition, immunohistochemistry revealed that type II collagen expression decreased, interleukin-1β expression increased, and matrix metalloproteinase-13 expression increased in the CIA TMJs in comparison with the two control groups (Saline and Healthy). Immunostaining of tumor necrosis factor-α (TNF-α) was quantified and we showed that TNF-α expression was significantly greater in the CIA cartilage compared with both control groups (p < 0.05), and there was no difference in TNF-α expression between the Saline and Healthy groups. This CIA juvenile rat model of TMJ juvenile arthritis shows that CIA reduced mandibular growth and induced degenerative changes in TMJ condylar cartilage. This new information will help to understand the pathogenesis involved in CIA in juvenile rat TMJs for this animal model to be used in research investigating new therapeutics to treat TMJ juvenile arthritis.

中文翻译：

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胶原诱导颞下颌关节关节炎幼鼠动物模型

幼年特发性关节炎可影响颞下颌关节 (TMJ)，可引起下颌（下颌骨）的生长障碍。胶原诱导关节炎 (CIA) 幼年大鼠模型可能是研究幼年关节炎在生长过程中如何影响该关节的合适模型。然而，使用这种动物模型来研究 TMJ 关节炎的研究是有限的。为了验证用于研究生长大鼠 TMJ 关节炎的动物模型，我们的研究旨在调查下颌骨生长的变化以及 CIA 幼鼠 TMJ 下颌骨髁中蛋白质和细胞因子的表达。共27只雄性Wistar大鼠（3周龄）用显微计算机断层扫描（MicroCT）扫描并分为三组（n = 9); 在 CIA 组的每个 TMJ 中诱导 CIA，盐水组在其 TMJ 中接受盐水注射（假注射），健康组保持未经治疗（未注射 TMJ）作为阴性对照。4 周后，我们的结果显示，与生理盐水组相比，CIA 组的下颌生长显着降低（p < 0.01)。两个对照组（盐水组和健康组）的下颌骨生长没有差异。在 CIA TMJ 中观察到发炎的滑膜组织、软骨内陷和脂质堆积。甲苯胺蓝染色显示 CIA 软骨中蛋白聚糖的产生减少。此外，免疫组织化学显示，与两个对照组（盐水组和健康组）相比，CIA TMJ 中 II 型胶原蛋白表达减少，白细胞介素-1β 表达增加，基质金属蛋白酶-13 表达增加。肿瘤坏死因子-α（TNF-α）的免疫染色被量化，我们发现与两个对照组相比，CIA 软骨中 TNF-α 的表达显着增加（p < 0.05)，并且生理盐水组和健康组之间的 TNF-α 表达没有差异。这种 TMJ 幼年关节炎的 CIA 幼年大鼠模型表明，CIA 减少了下颌骨的生长并诱导了 TMJ 髁突软骨的退行性变化。这一新信息将有助于了解幼年大鼠 TMJ 中 CIA 的发病机制，该动物模型将用于研究治疗 TMJ 幼年关节炎的新疗法。