Age- and sex-dependent proteome dynamics of nerve injury-induced neuropathic pain in mice

Neuropathic pain (NeuP) is a global health problem, with clinical manifestations including spontaneous (non-evoked) chronic pain (i.e. burning sensation) and altered somatosensory perception. To date, we still lack a detailed understanding of the molecular mechanisms driving NeuP. In preclinical mouse studies of NeuP, the main behaviour endpoints often fail to reflect typically observed patient symptoms, and the routine use of male subjects across diverse age ranges likely masks potential age- and sex-dependent variations. We aim to investigate the impact of age and sex on pain-related behaviours and proteome dynamics in a longitudinal study in mice with NeuP, induced by the spared nerve injury model. Adolescent and adult mice of both sexes were investigated for evoked and non-evoked pain-related behaviours, followed by proteome profiling of peripheral sensory neurons from dorsal root ganglia (DRG). While pain-related behaviours only exhibited marginal alterations across age and sex, we see prominent differences at the protein level. Several proteins of well-known pain genes (e.g. the cation channel TRPM8) exhibited a previously unknown age-dependent expression profile upon NeuP. Global analysis of altered protein networks and biological pathways revealed pronounced age-and sex-dependency. For example, proteins implicated in “synapse pruning” being downregulated in adolescent mice but overtly upregulated in adult male mice upon NeuP. With this study, we provide novel and comprehensive insights into molecular changes associated with NeuP. Our data reveal hitherto unknown spatio-temporal dynamics of DRG proteomes while integrating age and sex as biological variables – a prerequisite to foster effective forward translation of preclinical pain research.