Repopulating Microglia Suppress Peripheral Immune Cell Infiltration to Promote Poststroke Recovery.

AIMS: Sustained neuroinflammation following ischemic stroke impedes post-injury tissue repairment and neurological functional recovery. Developing innovative therapeutic strategies that simultaneously suppress detrimental inflammatory cascades and facilitate neurorestorative processes is critical for improving long-term rehabilitation outcomes. METHODS: We employed a microglia depletion-repopulation paradigm by administering PLX5622 for 7 days post-ischemia; followed by a 7-day withdrawal period to allow microglia repopulation. Single-cell transcriptomics, behavioral testing, cytokine arrays, flow cytometry, and immunofluorescence were used to assess the effects of microglia repopulation and delineate the transition of reshaped immune microenvironment. RESULTS: PLX5622 administration reshaped the poststroke immune microenvironment, promoting neurofunctional recovery. Repopulated microglia adopted a homeostatic phenotype, increasing homeostatic states by ~14.36% and reducing pro-inflammatory states by ~20.17%. This reshaped environment suppressed T cell exhaustion, limited neutrophil terminal differentiation, and promoted a phagocytic macrophage phenotype. Furthermore, we identified that these transitions in infiltrating immune cells may be driven by reduced chemokine production, enhanced blood-brain barrier (BBB) integrity, and transcriptional reprogramming. CONCLUSION: Transient microglial depletion and repopulation via PLX5622 during the acute phase post stroke facilitate the recovery of neurological function. This immunomodulatory strategy offers a promising and clinically translationally relevant approach to enhance functional recovery following ischemic brain injury.