Structural and functional mapping of visceral pain afferent neurocircuitries of the colorectum and bladder in preclinical models

摘要 肠易激综合征（IBS）和间质性膀胱炎/膀胱疼痛综合征（IC/PBS）是常见的慢性炎症， 分别影响结肠和膀胱的内脏疼痛疾病。这两种情况都对健康 和经济负担。值得注意的是，IBS和IC/PBS存在相当多的重叠症状，而 个别患者可能同时患有这两种疾病。结肠和膀胱交叉致敏， 共享脊髓神经然而，尽管人们对它们的生殖学和生殖系统的作用有了更多的了解， 疼痛传入在其病理生理学，没有有效的治疗方法。为数不多的药物 包括阿片类药物具有显著的副作用。目前开发有效疗法的障碍 IBS和IC/PBS包括：a）对二分背侧肌的结构和功能知识不足， 远端结肠和膀胱的根神经节（DRG）神经元。B）缺乏对性别的充分调查 在跨器官敏感性方面存在差异，尽管这两种情况在妇女中的患病率高于 在男性中（女性与男性的比例：IBS为2：1，IC/PBS为5-10：1） 神经支配和跨器官致敏的物种与人类具有较高的翻译相关性。我们 我建议通过同时监测两个国家的结肠和膀胱疼痛回路来解决这些差距。 临床前模型和3个特定目标。1）：结肠和膀胱疼痛传入的结构映射 神经回路：二分法和非二分法神经元，它们的空间分布和连接。2）、 急性和慢性跨器官模型中结肠和膀胱传入神经的功能特征 致敏和3）：映射结肠和膀胱疼痛的脊柱部位，并通过 神经调节我们将使用急性和慢性跨器官致敏模型，最先进的高- 分辨率成像，3D标测，膀胱和结肠感觉神经元的双重逆行追踪， 二分神经元的体内DRG Ca 2+成像，来自膀胱的离体电生理记录， 结肠传入神经和经皮脊髓刺激（TSCS）方法。小鼠模型将揭开 肠-膀胱和膀胱-肠急性疼痛传入/神经元的类别及其功能回路 和慢性疼痛交叉致敏。猪的研究将提供新的信息结构图 结肠和膀胱的二分神经元及其连接以及疼痛的交叉敏化 应答它还将使我们能够深入了解使用TSCS映射脊髓回路和回溯 结肠和膀胱疼痛回路及其用于人类的转化可行性。联合多学科 这些方法将填补目前关于结肠/膀胱二分DRG神经元、空间 分布和连接以及致敏后疼痛回路的可塑性。我们的发现将 有助于了解结肠和膀胱神经回路的基础，这将是至关重要的迫切 所需的药物和/或神经调节剂治疗慢性内脏疼痛综合征，如IBS和IC/PBS。

ABSTRACT Irritable Bowel Syndrome (IBS) and interstitial cystitis/painful bladder syndrome (IC/PBS) are common chronic visceral pain disorders that affect the colon and bladder respectively. Both conditions pose significant health and financial burden. Notably, IBS and IC/PBS present with considerable overlapping symptoms, whilst individual patients can suffer from both disorders concurrently. The colon and bladder cross-sensitize and share spinal innervations. However, despite increased understanding of their symptomatology and the role of pain afferents in their pathophysiology, there are no effective therapies. The few pharmacological drugs including opioids have significant adverse effects. Current barriers to the development of effective therapies for IBS and IC/PBS include: a) Inadequate structural and functional knowledge on the dichotomizing dorsal root ganglia (DRG) neurons of the distal colon and bladder. b) The lack of adequate investigation on sex differences in cross-organ sensitization, despite the prevalence of both conditions being higher in women than in men (female to male ratio: 2:1 for IBS, 5-10:1 for IC/PBS) c) Lack of knowledge of the sensory afferent innervation and cross-organ sensitization in species with higher translational relevance to humans. We propose to address these gaps through concurrent monitoring of the colon and bladder pain circuitries in two pre-clinical models and under 3 specific aims. 1): Structural mapping of colon and bladder pain afferent neurocircuits: Dichotomizing and non-dichotomizing neurons, their spatial distribution and connectivity. 2): Functional characterization of colon and bladder afferents in acute and chronic models of cross-organ sensitization and 3): Map spinal sites of colon and bladder pain and cross-organ sensitization through neuromodulation. We will use acute and chronic cross-organ sensitization models, state-of-the-art high- resolution imaging, 3D mapping, dual retrograde tracing of bladder and colon sensory neurons, CLARITY, ex vivo DRG Ca2+ imaging of dichotomizing neurons, ex vivo electrophysiological recordings from bladder and colon afferents and transcutaneous spinal stimulation (TSCS) approaches. The murine model will unravel the classes of pain afferents/neurons and their functional circuits in bowel-to-bladder and bladder-to-bowel acute and chronic pain cross sensitization. The porcine studies will provide novel information on the structural map of the colon and bladder dichotomizing neurons and their connections as well as cross sensitization of pain responses. It will also allow us to gain insight on the use of TSCS to map spinal cord circuits and backtrack colon and bladder pain circuits and its translational feasibility for human use. The combined multidisciplinary approaches will fill the gaps in current knowledge on the colon/bladder dichotomizing DRG neurons, spatial distribution and connections as well as the plasticity in the pain circuitries post sensitization. Our findings will contribute to the foundation for understanding colon and bladder neurocircuitries that will be critical for urgently needed drugs and/or neuromodulator therapies for chronic visceral pain syndromes such as IBS and IC/PBS.