Spared corticospinal neurons activate an endogenous plasticity program after partial CNS injury

Functional recovery after incomplete spinal cord injury depends substantially on the capacity of anatomically spared neurons to remodel their connections, yet the molecular programs underlying this endogenous plasticity remain poorly understood. To identify and validate these mechanisms, we combined retrograde labeling, unilateral corticospinal tract injury, spatial transcriptomics, and human stem cell-derived neurons. Injured corticospinal neurons exhibited widespread downregulation with remaining activated pathways dominated by stress, cell death, and degenerative programs. In contrast, spared corticospinal neurons activated a coordinated pro-plasticity program characterized by metabolic, immune, and cytoskeletal remodeling together with selective suppression of growth-inhibitory signaling. Network and drug perturbation analyses identified ARHGEF12 suppression and vorinostat treatment as complementary target- and state-based strategies to enhance neurite regeneration in human neurons. Together, these findings define key components of endogenous plasticity and provide a framework for discovering therapeutic targets for neural repair.