Sex differences define the molecular and cellular phenotypes of pain resolution in dorsal root ganglia

Neuropathic pain, affecting 10% of the general population, poses a significant socioeconomic burden that current treatment options cannot sufficiently cover. While pain naturally resolves in some patients, the mechanisms driving this process remain elusive. we hypothesized that pain resolution modulates multicellular interactions of neurons, satellite glial cells (SGCs), and local macrophages within the dorsal root ganglia (DRGs). Therefore, we aimed to identify molecular and cellular processes that characterize ongoing pain resolution. With behavioral tests, we determined a 50% improvement of the pain phenotype to capture ongoing mechanisms of pain resolution. We expect to see dysregulated signaling mediators in the DRG, as well as channels and components influencing hypersensitivity, as well as regulation of an immune and inflammatory phenotype. Comparing the ipsilateral sides during hypersensitvity and pain resolution, we aim to elucidate pathways that characterize the resolution phase. Based on prior knowledge and imaging data, we expected to initially see a strong immune phenotype, with differences between male and female rats during pain resolution, potentially reflecting a difference in pain prevalence between sexes in the clinic. Pathway analysis of the bulk RNA data confirmed an ongoing immune phenotype in female rats as opposed to males. Top regulated factors after CCI, include many mediators such as NPY, VIP, Gal, IL24 and IL6. Biological processes associated with pain resolution included G-protein coupled receptor signaling, synaptic transmission and regulation of the membrane potential.神经性疼痛（Neuropathic Pain）影响全球10%的普通人群，当前治疗方案无法充分覆盖其所带来的沉重社会经济负担。尽管部分患者的疼痛可自然缓解，但驱动这一过程的分子机制仍不明晰。我们提出假说：疼痛缓解过程会调控背根神经节（dorsal root ganglia, DRGs）内神经元、卫星胶质细胞（satellite glial cells, SGCs）与局部巨噬细胞之间的多细胞相互作用。因此，本研究旨在鉴定表征持续性疼痛缓解过程的分子与细胞事件。通过行为学实验，我们将疼痛表型改善50%作为观测节点，以捕捉疼痛缓解的动态机制。我们预期在背根神经节中可观察到信号介质的失调表达、参与疼痛超敏反应的离子通道及相关组分，同时还会涉及免疫与炎症表型的调控过程。通过对比痛觉超敏期与疼痛缓解期的损伤同侧样本，我们旨在阐明表征疼痛缓解阶段的核心通路。基于既往研究与成像数据，我们最初预期在疼痛缓解阶段可观察到显著的免疫表型特征，且雌雄大鼠间存在差异，这或可反映临床中不同性别人群的疼痛患病率差异。对批量RNA转录组数据的通路分析证实，与雄性大鼠相比，雌性大鼠在疼痛缓解阶段呈现持续活跃的免疫表型。慢性压迫性损伤（Chronic Constriction Injury, CCI）后差异表达最为显著的因子包括多种信号介质，如神经肽Y（Neuropeptide Y, NPY）、血管活性肠肽（Vasoactive Intestinal Peptide, VIP）、甘丙肽（Galanin, Gal）、白细胞介素24（Interleukin 24, IL24）与白细胞介素6（Interleukin 6, IL6）。与疼痛缓解相关的生物学过程包括G蛋白偶联受体信号通路、突触传递以及膜电位调控。