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

描述（由申请方提供）：骨关节炎（OA）疼痛是一种主要的未满足的医疗需求。我们对OA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疼痛是通过关节局部机制产生的，而外周和中枢神经系统的致敏作用放大了疼痛并导致其慢性化。在野生型C57 BL/6小鼠中内侧半月板（DMM）的失稳提供了体内模型，其中关节病理学在16周内缓慢进展，从而使得能够研究与进行性关节病理学相关的疼痛感觉的时间变化。我们已经产生了令人信服的数据，即DMM相关的疼痛行为分为两个阶段：机械性异常性疼痛早期开始，进展长达4周，并在手术后维持16周;第二阶段从第8周开始，变化表明持续性疼痛，包括运动减少（移动距离，攀爬）。神经支配的背根神经节（DRG）的分子变化的分析表明，单核细胞趋化蛋白1（MCP-1）和其高亲和力受体，CCR 2，在DRG中高度上调DMM后8周。Ccr 2缺失小鼠最初发展机械性异常性疼痛，但在DMM后8周开始消退。在这些小鼠中不发生指示持续性疼痛的疼痛行为（运动减少），并且在DMM后16周，它们被部分保护免于关节破坏。因此，本提案的目标是测试中心假设：MCP-1/CCR 2活性是DMM模型中维持疼痛和结构损伤的关键驱动因素。目的1试图确定MCP-1/CCR 2在DMM后建立慢性OA疼痛和关节病理学中的功能。目的1a将鉴定DRG中神经元、神经胶质细胞和巨噬细胞的MCP-1和CCR 2表达，并检查下游功能效应。目的1b将比较DMM后WT和Ccr 2敲除小鼠膝关节中的病理学、细胞浸润和细胞因子表达的进展。目的2旨在检验CCR 2阻断可减少DMM手术后疼痛行为的假设。该目的将测试CCR 2受体拮抗剂1）对机械性异常性疼痛具有即时镇痛作用，和2）通过在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学具有疾病改善作用的能力。通过以下既定指标（机械性异常性疼痛和运动），每两周对疼痛行为的影响进行量化;通过组织病理学分析对关节损伤的影响。

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.