Newly repopulated spinal cord microglia exhibit a unique transcriptome and contribute to pain resolution (human)

Microglia contribute to the initiation of pain, however, a translationally viable approach addressing how or when to modulate these cells remains elusive. We used a targeted, inducible, genetic microglial depletion strategy at both acute and acute-to-chronic transition phases in the clinically-relevant tibial fracture/casting pain model to determine the contribution of microglia to the initiation and maintenance of pain. We observed complete resolution of pain which coincided with the timeframe of full repopulation of microglia after transient microglial depletion at the acute-to-chronic phase. These repopulated microglia were morphologically distinct from control microglia, signifying they may exhibit a unique transcriptome. RNA sequencing of repopulated spinal cord microglia identified genes of interest using weighted gene coexpression network analysis (WGCNA). We intersected these genes with a newly generated single nuclei microglial dataset from human spinal cord dorsal horn and identified human-relevant genes that may ultimately promote pain resolution after injury. This work presents a novel approach to gene discovery in pain and provides comprehensive datasets for the development of future microglial-targeted therapeutics. Overall design: Human lumbar spinal cords were collected from donors and used to generate a novel single-nuclei dataset to compare with our mouse transcriptomic data. The dataset allows us to confirm whether the gene candidates identified in our mouse work are expressed in human microglia, strenghtening the case for each gene to be considered a therapeutic target in our research moving forward.