Inflammatory Mechanisms in Traumatic Joint Injury and Repair

描述（由申请人提供）： 创伤性关节损伤是许多退伍军人和平民所遭受的，并且经常导致数年后创伤后骨关节炎（OA）的发展。目前，没有干预措施可以预防创伤性关节损伤后OA的发展，而用于治疗OA的干预措施侧重于疼痛控制和关节置换，所有这些都针对晚期疾病的症状，而不是疾病的潜在机制。虽然OA长期以来被认为是“磨损”的结果，但越来越多的证据表明，炎症反应有助于OA的发病机制。我们已经确定炎症性补体系统是OA的关键参与者。我们发现补体级联反应在OA滑膜关节中过度活化，这种局部过度活化可能是由于滑膜组织中补体编码基因的失调和软骨分解产物对补体的激活。在OA的内侧半月板切除术（MM）小鼠模型中，发现缺乏中心补体成分C5或补体效应物MAC（膜攻击复合物）的一种成分的小鼠可免受OA样关节病理学和步态功能障碍的发展。用中和性抗C5抗体治疗野生型小鼠也能提供保护。相反，缺乏C4（经典补体途径的一种成分）的小鼠出现了更严重的OA样病理。我们现在建议使用两种创伤后OA的小鼠模型，以及来自创伤后OA患者和健康个体的生物样品，以进一步剖析补体在创伤后OA中的作用。将在遗传缺陷小鼠中手术诱导内侧半月板（DMM）和创伤后OA的MM模型的不稳定性，这些小鼠遗传缺陷如下：（i）所有三种补体途径共有的中心补体成分;（ii）旁路途径的补体成分;（iii）经典途径的补体成分;或（iv）MAC效应子途径的补体成分或抑制剂。我们将通过监测这些小鼠的功能障碍（通过客观步态分析评估）和评价小鼠关节中的软骨降解（通过组织学分析）来评估对OA样病理的保护或恶化。为了确定OA关节组织中MAC沉积是否是创伤后OA特有的异常，我们将对不同持续时间和病因的OA患者以及受伤但健康的个体的软骨和滑膜组织进行免疫组织化学分析。MAC介导的致病性和经典补体介导的保护机制将在一系列原位和体外实验中进行研究，旨在确定MAC是否能诱导关节组织产生炎症和降解介质，以及经典补体是否能促进炎症软骨碎片的吞噬清除。将通过将OA滑液的分级分离和蛋白质组学研究与体外补体激活试验相结合来检查补体在OA中是如何激活的。最后，我们将测试补体抑制剂（临床开发或FDA批准）预防和治疗小鼠创伤后OA的能力。这一建议的成功可能会导致创伤后OA的疾病修饰治疗干预措施的发展。

DESCRIPTION (provided by applicant): Traumatic joint injuries are incurred by many Veterans and civilians, and frequently lead to the development of post-traumatic osteoarthritis (OA) years later. At present, there are no interventions that can prevent the development of OA following traumatic joint injury, while interventions used to treat OA focus on pain control and joint replacement, all of which target the symptoms of advanced disease rather than the mechanisms underlying the disease. Although OA has long been viewed as the result of "wear and tear", accumulating evidence suggests that inflammatory responses contribute to the pathogenesis of OA. We have identified the inflammatory complement system as a key player in OA. We found that the complement cascade is hyperactivated in OA synovial joints, and that this local hyperactivation may result both from dysregulation of complement-encoding genes in synovial tissues and from activation of complement by cartilage-breakdown products. In the medial meniscectomy (MM) mouse model of OA, mice deficient in the central complement component C5 or in a component of the complement effector MAC (membrane attack complex) were found to be protected against the development of OA-like joint pathology and gait dysfunction. Treatment of wild-type mice with a neutralizing anti-C5 antibody conferred protection, too. In contrast, mice deficient in C4, a component of the classical complement pathway, developed more severe OA-like pathology. We now propose to use two mouse models of post-traumatic OA, as well as biological samples from post-traumatic OA patients and healthy individuals, to further dissect the role of complement in post-traumatic OA. The destabilization of the medial meniscus (DMM) and the MM models of post-traumatic OA will be surgically induced in mice genetically deficient in (i) central complement components common to all three complement pathways; (ii) complement components of the alternative pathway; (iii) complement components of the classical pathway; or (iv) complement components or inhibitors of the MAC effector pathway. We will assess protection from or exacerbation of OA-like pathology by monitoring functional disturbances (as assessed by objective gait analysis) in these mice and evaluating cartilage degradation in mouse joints (by histologic analysis). To determine whether MAC deposition in OA joint tissues is an aberration specific to post-traumatic OA, we will perform immunohistochemical analysis of cartilage and synovial tissue from patients with OA of different duration and causation, as well as from injured but otherwise healthy individuals. The mechanisms of MAC-mediated pathogenicity and of classical-complement-mediated protection will be investigated in a series of in situ and in vitro experiments aimed at determining whether MAC acts to induce the production of inflammatory and degradative mediators by joint tissues and whether classical complement facilitates the phagocytic clearance of inflammatory cartilage debris. How complement is activated in OA will be examined by combining fractionation and proteomic survey of OA synovial fluids with in vitro complement activation assays. Finally, we will test the ability of complement inhibitors (that are in clinical development or FDA-approved) to prevent and treat the development of post-traumatic OA in mice. Success of this proposal could lead to the development of disease-modifying therapeutic interventions for post-traumatic OA.