Cartilage Innate Immunity in Osteoarthritis

摘要 项目总结： 原始Toll样受体(TLR)介导的先天免疫反应触发和塑造了许多炎性和 免疫紊乱。IL-1诱导软骨细胞TLR2和TLR4的表达及在骨性关节炎软骨中的表达 在原地。此外，微生物TLR2和TLR4配体刺激软骨细胞的分解代谢反应。我们的 初步数据显示，共有的TLR和IL-1受体适配器蛋白MyD88(但不是可溶性IL-1 受体拮抗剂)钝化所有炎症诱导的软骨分解代谢和分化反应 组织块和培养的软骨细胞。我们进一步观察到TLR2、TLR4双基因敲除(TLR2/4 dKO) 小鼠软骨外植体和软骨细胞保持IL-1反应性，但对低反应性丧失反应 分子量透明质酸低聚糖(LMW-HA)和HMGB1，两个内源TLR2和TLR4 配体存在于骨性关节炎关节中。此外，TLR2/4 dKO小鼠软骨细胞失去了装载 软骨细胞的分解代谢反应不仅与透明质酸酶-2的表达增加有关，透明质酸酶-2是一种催化 LMW-HA形成，也有HMGB1。这一提议的中心和翻译假设是抑制 TLR2和TLR4信号在体外和体内都具有软骨保护作用，并提供了新的手段 开发疾病修饰性骨关节炎疗法。我们将进行软骨移植的体外反应研究和 用LMW-HA和HMGB1标记软骨细胞确定TLR2和TLR4信号对软骨细胞的促进作用 不仅使用MyD88，而且使用选择性需要的TIRAP/MAL进行肥大和软骨分解代谢 用于TLR2和TLR4信令。我们还将使用外科手术不稳定导致的膝骨性关节炎进行体内研究。 评估TLR2和TLR4的双重敲除是否抑制骨性关节炎进展的模型，或者通过 TIRAP/MAL的单一敲除，MyD88的敲除比IL-1的敲除具有更好的保护作用 OA抑制受体。这些研究的完成将为了解先天免疫机制提供新的见解 软骨中的炎症反应促进了骨关节炎的进展，并提供了至少一种潜在的可用药 有效的骨关节炎疾病改进的目标。 相关性： 骨关节炎(OA)是最常见的与衰老有关的关节疾病。低成本促进了办公自动化的进步 软骨炎症分级。白介素1(IL-1)是一种炎症介质，它促进了骨关节炎的进展， 但通过抑制IL-1抑制骨性关节炎的研究结果并不完整。迫切需要找出 IL-1以外的介质推动骨性关节炎进展，以开发真正有效的疾病修改 治疗这种疾病的方法。

Abstract Project Summary: Primitive Toll-like receptor (TLR)-mediated innate immune responses trigger and shape many inflammatory and immune disorders. IL-1 induces TLR2 and TLR4 in chondrocytes and both TLRs are increased in OA cartilage in situ. Moreover, microbial TLR2 and TLR4 ligands stimulate catabolic responses in chondrocytes. Our preliminary data reveal that the shared TLR and IL-1 receptor adaptor protein MyD88 (but not soluble IL-1 receptor antagonist) blunts all inflammation-induced catabolic and differentiation responses tested in cartilage explants and cultured chondrocytes. We further observe that TLR2, TLR4 double knockout (TLR2/4 dKO) mouse cartilage explants and chondrocytes retain IL-1 responsiveness, but lose responsiveness to low molecular weight hyaluronan oligosaccharides (LMW-HA) and HMGB1, two endogenous TLR2 and TLR4 ligands present in OA joints. In addition, TLR2/4 dKO mouse chondrocytes lose the capacity to mount a catabolic response in chondrocytes with increased expression of not only hyaluronidase-2 which catalyzes LMW-HA formation but also HMGB1. The central and translational hypothesis of this proposal is that inhibition of both TLR2 and TLR4 signaling is chondroprotective both in vitro and in vivo and offers novel means to develop disease-modifying OA therapy. We will perform in vitro studies on responses of cartilage explants and chondrocytes to LMW-HA and HMGB1 to determine how TLR2 and TLR4 signaling promotes chondrocyte hypertrophy and cartilage catabolism using not only MyD88, but also TIRAP/Mal which is selectively required for TLR2 and TLR4 signaling. We will also perform in vivo studies using a surgical instability-induced knee OA model to assess if OA progression is suppressed by dual knockout of TLR2 and TLR4, and alternatively by single knockout of TIRAP/Mal, and if knockout of MyD88 has superior protective effects than knockout of IL-1 receptor for OA suppression. Completion of these studies will provide new insights into how innate immune inflammatory responses in cartilage promote OA progression and provide at least one potentially druggable target for effective OA disease modification. Relevance: Osteoarthritis (OA) is the most common joint disease related to aging. Progression of OA is promoted by low- grade inflammation in cartilage. Interleukin-1 (IL-1), an inflammatory mediator, promotes the progression of OA, but results have been incomplete for suppression of OA via IL-1 inhibition. There is a pressing need to identify mediators beyond IL-1 that drive OA progression, in order to develop true and effective disease modifying treatment of this disease.