Differential changes in spinal motor neurons innervating paretic upper limb flexors and extensors after stroke

Post-stroke hemiplegia often leads to a slower and less complete recovery of the paretic upper limb's extension compared to its flexion. The mechanisms underlying this disparity remain unclear. This study investigated the effects of unilateral photothrombotic stroke on forelimb flexor and extensor muscles in adult mice, with a focus on differential changes in spinal motor neurons. Our comparative analysis demonstrated a significantly greater reduction in the number of motor neurons innervating the extensor muscles post-stroke. Bioinformatics analysis of the transcriptome revealed that genes associated with inflammatory responses and cell chemotaxis were upregulated in the spinal segment innervating the extensors, whereas genes related to cellular repair were upregulated in the segment innervating the flexors. These findings offer insights into the differential recovery of paretic upper limb flexion and extension following stroke.