Dissecting Neural Circuits Involved in Musculoskeletal Pain

存在未满足的需求，以确定治疗方法来减轻与炎性关节炎相关的疼痛。 和骨关节炎（OA）关节病症。在美国，关节疼痛影响着超过5000万的成年人， 大约占人口的25%。严重的关节炎是导致慢性疼痛、残疾和减少的主要原因。 生活质量目前OA的治疗策略集中在通过减肥改善功能， 运动和用药理学镇痛剂如对乙酰氨基酚、非甾体类 抗炎药（NSAID）和阿片类药物。用于治疗OA的疾病修饰剂是有限的， 这些止痛剂的给药是治疗的主要手段。然而，与长期 长期使用NSAID（胃肠道出血）和阿片类药物（即滥用倾向）增加了对 确定替代镇痛药和缓解关节疼痛的方法。 该领域进展的一个关键障碍是缺乏关于感觉神经元亚群分布的知识。 以及在关节炎条件下这是如何变化的。这部分是由于困难 测量脱钙骨组织薄片内的神经支配模式。近年来，方法 已经被开发用于清除大脑中的大部分组织以更好地可视化神经回路;然而， 这些方法尚未广泛应用于检测分子的分布和形貌， 在骨骼组织内定义感觉神经元亚群。在目前的提案中，我们将改进以下方法： 小鼠骨骼和关节内神经纤维的分子定义子集的清除、成像和3D分析。 我们还将使用Flp/Cre驱动小鼠和病毒载体开发药理学和光遗传学方法 确定5-HT 3 R+传入对自发和运动诱发痛行为的贡献 与炎症和创伤后骨关节炎有关。 拟议的研究将提供一个前所未有的观点的密度，地形和分布， 正常和关节炎膝关节内感觉神经元的亚群。重要的是，这些研究将奠定 为未来研究感觉神经元亚群在驱动疼痛中的功能贡献奠定基础 相关的行为和疾病的发病机制在几个肌肉骨骼疼痛的条件。 1

There is an unmet need to identify therapeutic approaches to alleviate pain associated with inflammatory and osteoarthritic (OA) joint conditions. Joint pain affects over 50 million adults in the United States which is roughly 25% of the population. Severe arthritis is a leading cause of chronic pain, disability and reduced quality of life. Current treatment strategies for OA focus on improving function through weight loss and exercise and providing symptom relief with pharmacological analgesics such as acetaminophen, nonsteroidal anti-inflammatory drugs (NSAIDs) and opioids. Disease modifying agents for treating OA are limited so chronic administration of these analgesics is the mainstay for treatment. However, adverse outcomes related to long term use of NSAIDs (gastrointestinal bleeding) and opioids (i.e. abuse liability) increase the need for identification of alternative analgesics and approaches to alleviate joint pain. A critical barrier to progress in the field is lack of knowledge regarding the distribution of subsets of sensory neurons in bone and joints and how this changes under arthritic conditions. This is in part due to difficulty measuring patterns of innervation within thin sections of decalcified skeletal tissue. In recent years, methods have been developed to clear large sections of tissue in the brain to better visualize neural circuits; however, these approaches have not been applied extensively for examining distribution and topography of molecularly defined sensory neuron subsets within skeletal tissue. In the current proposal, we will refine methods for clearing, imaging and 3D analysis of molecularly defined subsets of nerve fibers within mouse bone and joints. We will also develop pharmacological and optogenetic approaches using Flp/Cre driver mice and viral vectors to determine the contribution of 5-HT3R+ afferents to spontaneous and movement evoked pain behaviors associated with inflammatory and post-traumatic osteoarthritis. The proposed studies will provide an unprecedented view of the density, topography and distribution of subsets of sensory neurons within the normal and arthritic knee joint. Importantly, these studies will lay the groundwork for future studies examining the functional contribution of subsets of sensory neurons in driving pain related behaviors and disease pathogenesis in several musculoskeletal pain conditions. 1