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. Overall design: We analyzed L4 rat DRG, that were harvested and snap frozen in liquid nitrogen after chronic constriction injury (CCI). Experimental groups were male and female rats at 1 week or 5 weeks after CCI, with investigation of both the injured, ipsilateral side and the contralateral side as control.