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

SUMMARY The dorsal root ganglion (DRG), a key site for the initiation and maintenance of neuropathic pain, was examined for sex-dependent phenotypes in sensory neurons, satellite glial cells (SGCs), and local macrophages following traumatic nerve injury and during natural pain resolution. Systematic analysis of 7,495 DRG immunofluorescence images and 62 transcriptomes revealed pronounced sex-specific, multicellular DRG phenotypes, especially during pain resolution. System parameters, including tissue size and neuron density also showed sex-dependent differences. Neuropathic pain resolved without tissue or sensory neuron loss. After injury, macrophages invaded the space between sensory neurons and satellite glial cells (SGCs); this was partially reversed during pain resolution, particularly in males. In females, immune-related gene expression and macrophage phenotypes persisted longer, while SGC activation and contact to sensory neurons was more persistent in males. During resolution, synaptic and excitability-related processes were pronounced in both sexes. However, while injury responses were largely shared between sexes, the resolution phase displayed distinctly sex-specific molecular and cellular signatures. GRAPHICAL ABSTRACT In brief Analysis of ∼7,500 bioimages and 62 transcriptomes reveals pronounced sex differences in rat dorsal root ganglia during pain resolution after peripheral nerve injury. Highlights In both female and male rats, peripheral nerve injury and subsequent pain resolution occur in the dorsal root ganglia (DRG) without neuronal or tissue loss. Sex influences DRG tissue size, neuron density, immune and glial phenotypes, and molecular-cellular responses to nerve injury and pain resolution. Following injury, macrophages infiltrate the space between sensory neurons and satellite glial cells (SGCs); this process reverses during pain resolution, particularly in males. In females, immune phenotypes remain more stable throughout pain resolution, while SGC contact is reduced. Pain resolution involves not only the reversal of injury-induced cell changes but also the activation of resolution-specific gene programs related to synaptic signaling, neuronal excitation, and cell–cell communication. Sex differences on the molecular-cellular level are less prevalent after nerve injury but become prominent during pain resolution.