Abstract: White matter injury is a key factor impacting stroke recovery. Physical exercise can promote white matter repair. Immune cells, especially regulatory T (Treg) cells, contribute to strengthening white matter integrity, yet little is known about the underlying mechanism. To examine this, we established a transient middle cerebral artery occlusion male mouse model. We found that physical exercise elevated brain Treg cells, thereby enhancing neurological recovery, reducing neuroinflammation, promoting myelin debris clearance, and accelerating white matter repair. Depletion of Treg cells caused a decrease in these positive effects of physical exercise. Mechanistically, the rise in osteopontin triggered by physical exercise is dampened when Treg cells are depleted. In addition, Treg-conditioned medium reduced oxygen–glucose deprivation/re-oxygenation-induced microglial inflammation and enhanced phagocytosis, which could be blocked by osteopontin antibodies. Importantly, although Treg infusion could mimic the protective effects of physical exercise, osteopontin blockade partially countered the effects of physical exercise and Treg cells. Finally, our sequencing data revealed a marked upregulation of C–X–C motif chemokine ligand 12 (CXCL12) mRNA expression subsequent to physical exercise, which was confirmed at the protein level. Stimulation of Treg cells with stroke brain lysates increased C–X–C motif chemokine receptor 4 (CXCR4) expression, indicating a potential role for the CXCL12–CXCR4 axis in recruiting Treg cells. These findings suggest that physical exercise promotes white matter repair after ischemic stroke by Treg cells. 

Key words: CXCL12, ischemic stroke, microglia, neuroinflammation, osteopontin, phagocytosis, physical exercise, transient middle cerebral artery occlusion, Treg cells, white matter injury