A novel clinically- relevant mouse model of chronic overlapping pain conditions for screening analgesics

慢性重叠疼痛状况（COPC）影响超过1亿人，主要是女性。但他们 在很大程度上，由于缺乏具有转化相关性的有效动物模型，因此仍然没有得到有效治疗。在 作为对FOA PAR-18-763的回应，该提案旨在开发一种新的COPC小鼠模型， 外部有效性，以促进发现具有镇痛和抗炎作用的神经治疗剂。我们 该模型将纳入已知的导致COPC病因学的关键遗传和环境因素 通过增强胆碱能神经张力。估计66%的COPC患者，如纤维肌痛， 在编码儿茶酚-O-甲基转移酶（COMT;一种普遍表达的 代谢儿茶酚胺的酶），这导致低COMT活性。COMT基因型对 疼痛会因压力和受伤而减轻。例如，具有“低活性”COMT基因型的个体报告 压力事件（例如，机动车碰撞和心理紧张）后疼痛增强， 外科手术（如拔牙和乳房切除术）。低COMT、压力和损伤可通过以下方式产生疼痛： 增加致敏伤害感受器的促炎细胞因子的产生。此前，我们的实验室 采用药理学方法来研究驱动COMT依赖性疼痛的机制和靶点，然而， 这种方法不能充分模拟COPC的复杂临床病因。因此，这一目标 一项建议是开发和验证一种新的COPCS小鼠模型，其中遗传易感性 COMT+/-小鼠经历应激和损伤事件。我们的中心假设是COMT+/-小鼠， 尤其是女性，经历短暂的压力和伤害性事件， 身体部位和增加的临床相关细胞因子生物标志物水平，这些生物标志物将被现有FDA- 批准的止痛药。初步数据显示，表现出正常基线疼痛行为的COMT+/-小鼠， 接受游泳压力和磨牙拔除手术的患者在多个身体部位出现夸大的长期疼痛 部位（后爪、背部和腹部）。此外，经历游泳应激和磨牙拔除的COMT+/-小鼠 表现出增加的伤害感受器活性。本文提出的研究将扩展这项工作。在1.5年期间， R61阶段，我们将确定几个身体部位疼痛的幅度和持续时间，原发性致敏 神经支配这些身体部位的传入伤害感受器，以及与疼痛相关的抑郁和焦虑样行为， 我们的COPC小鼠模型在满足“进展里程碑”后：COMT+/- vs WT小鼠经历应激+损伤 在1）多个身体部位的机械性疼痛和2）伤害感受器方面表现出显著增加（效应量>3） 活动，我们将进入R33阶段。在1.5年的R33阶段，我们将评估临床相关性 细胞因子生物标志物以确定构建有效性，临床使用的镇痛剂以确定预测性 我们模型的有效性。如果成功，我们将开发一种新的COPCS小鼠模型，其有效性得到提高， 将对有效发现具有翻译相关性的镇痛药产生重大影响。

Chronic overlapping pain conditions (COPCs) affect over 100 million people, predominantly women. Yet, they remain ineffectively treated due, in large part, to lack of valid animal models with translational relevance. In response to FOA PAR-18-763, this proposal seeks to develop a new mouse model of COPCs with improved external validity to facilitate discovery of neurotherapeutics with analgesic and anti-inflammatory effects. Our model will incorporate key genetic and environmental factors known to contribute to the etiology of COPCs through enhancing catacholaminergic tone. An estimated 66% of patients with COPCs such as fibromyalgia have functional variants in the gene encoding catechol-O-methyltransferase (COMT; a ubiquitously expressed enzyme that metabolizes catecholamines), that result in low COMT activity. The effect of COMT genotype on pain is modified by stress and injury. For example, individuals with the ‘low activity’ COMT genotype report enhanced pain following stressful events (eg, motor vehicle collision and psychological strain) and injurious surgical procedures (eg, molar extraction and mastectomy). Low COMT, stress, and injury can produce pain by increasing the production of pro-inflammatory cytokines that sensitize nociceptors. Previously, our lab employed a pharmacologic approach to study mechanisms and targets driving COMT-dependent pain, yet this approach does not adequately mimic the complex clinical etiology of COPCs. Thus, the objective of this proposal is to develop and validate a novel mouse model of COPCS in which genetically predisposed COMT+/- mice undergo stressful and injurious events. Our central hypothesis is that COMT+/- mice, especially females, undergoing transient stressful and injurious events will develop chronic pain at multiple body sites and increased levels of clinically-relevant cytokine biomarkers that will be reduced by existing FDA- approved analgesics. Preliminary data show that COMT+/- mice, which exhibit normal baseline pain behavior, undergoing swim stress and molar extraction surgery develop exaggerated long-lasting pain at multiple body sites (hindpaw, back, and abdomen). Further, COMT+/- mice undergoing swim stress and molar extraction exhibit increased nociceptor activity. The studies proposed herein will extend this work. During the 1.5-year R61 phase, we will establish the magnitude and duration of pain at several body sites, sensitization of primary afferent nociceptors innervating those body sites, and pain-related depressive- and anxiety-like behaviors in our COPC mouse model. Upon meeting the ‘go milestones’: COMT+/- vs WT mice undergoing stress+injury exhibit significant increases (effect size >3) in 1) mechanical pain at multiple body sites and 2) nociceptor activity, we will move to the R33 phase. During the 1.5-year R33 phase, we will evaluate clinically-relevant cytokine biomarkers to determine construct validity and clinically-used analgesics to determine predictive validity of our model. If successful, we will develop a novel mouse model of COPCS with improved validity that will have a significant impact on effective discovery of analgesics with translational relevance.