The use of interleukin-1 receptor-associated kinase 4 (IRAK4) inhibitor as a treatment for the inflammatory joint disease is a promising method. However, its underlying mechanism in osteoarthritis (OA) remains unclear. The purpose of this study is to look into the effects of adenovirus-mediated knockdown of IRAK4 on synovitis in the OA rabbit model. Ad-shIRAK4 was injected two weeks after anterior cruciate ligament resection. Six weeks later, the rabbits were killed. The expression of IRAK4, TNFR-associated factor 6(TRAF6), TGF-activated kinase 1(TAK1), p-IKB kinase (p-IKK), p-nuclear factor kappa-B (p-NFκB), p38, and p-p38 in the synovial membrane was detected by western blot, qRT-PCR, and immunohistochemistry analysis. Immunohistochemistry was to detect the expression of IRAK4 proteins in articular cartilage. H&E staining was to assess the pathological changes of synovium and cartilage. The levels of interleukin (IL)-1β, tumor necrosis factor-α(TNF-α), and MMP-13 in the synovial fluid were measured by ELISA. X-ray and micro-computerized tomography (μCT) scans were used to assess knee joint conditions and microstructure of subchondral bone. IRAK4 expression levels in synovial tissues of the OA model group exhibited a significant upward trend. Ad-shIRAK4 significantly reduced IRAK4 mRNA expression in synovium tissues. Notably, Ad-shIRAK4 suppressed the Toll-like receptor/interleukin-1 receptor (TLR/IL-1R) signaling. In addition, in the Ad-shIRAK4 treatment group, we can see less inflammatory cell infiltration and reduced hyperplasia and angiogenesis. The levels of IL-1β, TNF-α, and MMP-13 in the synovial fluid in the OA model group were significantly higher than that in the control group, which were reduced by Ad-shIRAK4 treatment. Finally, Results of HE stains, immunohistochemistry, and μCT showed that Ad-shIRAK4 treatment has a protective effect on cartilage damage. IRAK4 is significantly upregulated in the synovium from the osteoarthritis rabbit model. In addition, Ad-shIRAK4 reduced the expression of IRAK4 and suppressed TLR/IL-1R signaling in the synovium from the osteoarthritis rabbit model. Ad-shIRAK4 could alleviate synovitis and cartilage degradation in the osteoarthritis rabbit model, and thus alleviate the symptoms of OA and prevent the progression of OA.

中文翻译：

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腺病毒介导的 IRAK4 敲低对骨关节炎兔模型滑膜炎的影响

使用白细胞介素-1 受体相关激酶 4 (IRAK4) 抑制剂作为炎性关节病的治疗方法是一种很有前途的方法。然而，其在骨关节炎（OA）中的潜在机制仍不清楚。本研究的目的是研究腺病毒介导的 IRAK4 敲低对 OA 兔模型中滑膜炎的影响。Ad-shIRAK4 在前交叉韧带切除后两周注射。六周后，兔子被杀死。IRAK4、TNFR 相关因子 6 (TRAF6)、TGF 活化激酶 1 (TAK1)、p-IKB 激酶 (p-IKK)、p-核因子 kappa-B (p-NFκB)、p38 和 p 的表达通过蛋白质印迹、qRT-PCR 和免疫组织化学分析检测滑膜中的 -p38。免疫组化检测关节软骨中IRAK4蛋白的表达。H＆E染色用于评估滑膜和软骨的病理变化。ELISA法测定滑液中白细胞介素（IL）-1β、肿瘤坏死因子-α（TNF-α）和MMP-13的水平。X 射线和微型计算机断层扫描 (μCT) 扫描用于评估膝关节状况和软骨下骨的微观结构。OA模型组滑膜组织中IRAK4表达量呈明显上升趋势。Ad-shIRAK4 显着降低滑膜组织中 IRAK4 mRNA 的表达。值得注意的是，Ad-shIRAK4 抑制了 Toll 样受体/白细胞介素-1 受体 (TLR/IL-1R) 信号传导。此外，在 Ad-shIRAK4 治疗组中，我们可以看到炎症细胞浸润较少，增生和血管生成减少。IL-1β、TNF-α、OA模型组滑液中MMP-13和MMP-13明显高于对照组，经Ad-shIRAK4处理后降低。最后，HE染色、免疫组化和μCT结果显示Ad-shIRAK4处理对软骨损伤具有保护作用。IRAK4 在来自骨关节炎兔模型的滑膜中显着上调。此外，Ad-shIRAK4 降低了骨关节炎兔模型滑膜中 IRAK4 的表达并抑制了 TLR/IL-1R 信号传导。Ad-shIRAK4可以缓解骨关节炎兔模型中的滑膜炎和软骨退化，从而缓解OA症状，防止OA进展。μCT显示Ad-shIRAK4处理对软骨损伤有保护作用。IRAK4 在来自骨关节炎兔模型的滑膜中显着上调。此外，Ad-shIRAK4 降低了骨关节炎兔模型滑膜中 IRAK4 的表达并抑制了 TLR/IL-1R 信号传导。Ad-shIRAK4可以缓解骨关节炎兔模型中的滑膜炎和软骨退化，从而缓解OA症状，防止OA进展。μCT显示Ad-shIRAK4处理对软骨损伤有保护作用。IRAK4 在来自骨关节炎兔模型的滑膜中显着上调。此外，Ad-shIRAK4 降低了骨关节炎兔模型滑膜中 IRAK4 的表达并抑制了 TLR/IL-1R 信号传导。Ad-shIRAK4可以缓解骨关节炎兔模型中的滑膜炎和软骨退化，从而缓解OA症状，防止OA进展。