MCP-1/CCR2 Signaling in the Maintenance of OA Pathology and Associated Pain

描述（由申请人提供）：骨关节炎（OA）疼痛代表了一个主要的未满足的医疗需求。我们对骨关节炎中产生和维持疼痛的途径的理解仍然很差。累积数据表明，OA疼痛是通过关节的局部机制产生的，而外周和中枢神经系统的敏感化放大了疼痛并导致其慢性。野生型C57BL/6小鼠内侧半月板失稳（DMM）提供了一个体内模型，其中关节病理在16周内缓慢进展，从而能够研究疼痛感觉的时间变化与进行性关节病理的关系。我们已经产生了令人信服的数据，dmm相关的疼痛行为表现为两个阶段：机械性异常性疼痛早期开始，进展至4周，并在手术后维持16周；第2阶段开始于第8周，变化表明持续疼痛，包括运动减少（行走距离，攀爬）。神经支配背根神经节（DRG）的分子变化分析显示，单核细胞化学引诱蛋白1 （MCP-1）及其高亲和力受体CCR2在DMM后8周的DRG中高度上调。Ccr2缺失小鼠最初出现机械异常性疼痛，但在DMM后8周开始消退。这些小鼠没有出现表明持续疼痛（运动减少）的疼痛行为，并且在DMM后16周，它们部分保护关节免受破坏。因此，本提案的目标是验证中心假设：MCP-1/CCR2活性是DMM模型中疼痛和结构损伤维持的关键驱动因素。目的1旨在确定MCP-1/CCR2在慢性OA疼痛和DMM后关节病理中的作用。Aim 1a将鉴定DRG中神经元、胶质细胞和巨噬细胞中MCP-1和CCR2的表达，并将检测下游功能影响。Aim 1b将比较DMM后WT和Ccr2缺失小鼠膝关节的病理进展、细胞浸润和细胞因子表达。目的2旨在验证CCR2阻断减少DMM手术后疼痛行为的假设。这一目的将测试CCR2受体拮抗剂的能力：1)对机械性异痛症有立即的镇痛作用；2)通过从OA早期或晚期开始的长期干预，对持续性OA疼痛行为和关节病理有疾病改善作用。对疼痛行为的影响将通过以下既定措施（机械异常性疼痛和运动）每两周量化一次；对关节损伤的影响将通过组织病理学分析。

DESCRIPTION (provided by applicant): Pain in osteoarthritis (OA) represents a major unmet medical need. Our understanding of the pathways that generate and maintain pain in OA remains poor. Cumulative data suggest that OA pain is generated through local mechanisms in the joint, while sensitization of the peripheral and central nervous system amplifies the pain and contributes to its chronicity. Destabilization of the medial meniscus (DMM) in wild-type C57BL/6 mice provides an in vivo model where joint pathology progresses slowly over 16 weeks, thus enabling the study of temporal changes in pain sensation in association with progressive joint pathology. We have generated compelling data that DMM-associated pain behavior presents in two stages: mechanical allodynia begins early, progresses up to 4 weeks, and is maintained for 16 weeks after surgery; stage two begins at week 8, with changes indicative of persistent pain, including decreased locomotion (distance traveled, climbing). Analysis of molecular changes in the innervating dorsal root ganglia (DRG) shows that monocyte chemoattractant protein 1 (MCP-1) and its high affinity receptor, CCR2, are highly upregulated in the DRG 8 weeks post DMM. Ccr2 null mice initially develop mechanical allodynia, but it begins to resolve 8 weeks post DMM. Pain behaviors indicative of persistent pain (decreased locomotion) do not occur in these mice, and they are partially protected from joint destruction by 16 weeks post DMM. Therefore, the goal of this proposal is to test the Central Hypothesis: MCP-1/CCR2 activity is a key driver for the maintenance of pain and structural damage in the DMM model. Aim 1 seeks to determine the function of MCP-1/CCR2 in establishing chronic OA pain and joint pathology post DMM. Aim 1a will identify expression of MCP-1 and CCR2 by neurons, glia, and macrophages in the DRG and will examine downstream functional effects. Aim 1b will compare the progression of pathology, cellular infiltration, and cytokine expression in the knee joint of WT and Ccr2 null mice after DMM. Aim 2 seeks to test the hypothesis that CCR2 blockade reduces pain behavior following DMM surgery. This aim will test the ability of a CCR2 receptor antagonist to 1) Have an immediate analgesic effect on mechanical allodynia, and 2) Have disease-modifying effects on persistent OA pain behaviors and joint pathology by long-term intervention beginning at early or late stages of OA. Effects on pain behavior will be quantified on a bi-weekly basis by the following established measures (mechanical allodynia and locomotion); Effects on joint damage will be analyzed by histopathology.