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

描述(由申请人提供)：骨性关节炎的疼痛(OA)是一种主要的未得到满足的医疗需求。我们对在骨性关节炎中产生和维持疼痛的途径的理解仍然很差。累积的数据表明，骨性关节炎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会放大疼痛并导致其慢性化。野生型C57BL/6小鼠内侧半月板(DMM)的不稳定提供了一个体内模型，在该模型中，关节病理进展缓慢，超过16周，从而能够研究与进行性关节病理相关的痛觉的时间变化。我们已经产生了令人信服的数据，DMM相关的疼痛行为呈现出两个阶段：机械性异位痛症早期开始，进展到4周，并在手术后持续16周；阶段2开始于第8周，变化表明持续性疼痛，包括运动减少(行走距离、攀登)。对支配背根神经节(DRG)分子变化的分析表明，DMM后8周，DRG中单核细胞趋化蛋白1(MCP-1)及其高亲和力受体CCR2表达显著上调。CCR2基因缺失的小鼠最初出现机械性痛觉异常，但在DMM后8周开始缓解。在这些小鼠中没有出现表明持续疼痛(活动减少)的疼痛行为，并且在DMM后16周，它们被部分保护而不受关节破坏。因此，这项提议的目的是检验中心假说：在DMM模型中，MCP-1/CCR2活性是维持疼痛和结构性损伤的关键驱动因素。目的1探讨单核细胞趋化蛋白-1(MCP-1)/CCR2在DMM后慢性骨性关节炎疼痛和关节病理改变中的作用。目的1a鉴定背根神经节中神经元、神经胶质细胞和巨噬细胞表达MCP-1和CCR2，并检测其下游功能。目的比较WT和CCR2基因敲除小鼠DMM后膝关节病理、细胞浸润和细胞因子表达的变化。目的2试图验证CCR2阻滞剂减少DMM手术后疼痛行为的假设。这一目的将检验CCR2受体拮抗剂的能力：1)对机械性异位痛症有即刻的止痛效果；2)从OA的早期或晚期开始进行长期干预，对持续性的OA疼痛行为和关节病理有改善作用。对疼痛行为的影响将每两周通过以下既定措施(机械性疼痛和运动)进行量化；对关节损伤的影响将通过组织病理学进行分析。

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.