Synapse formation of the cortico-spinal axons is enhanced by RGMa inhibition after spinal cord injury.

Several proteins have been identified as inhibitors of axonal regeneration following injury of the adult vertebrate central nervous system. The repulsive guidance molecule (RGMa) is considered a potent myelin-derived neurite outgrowth inhibitor. In rats, RGMa inhibition enhances the growth of injured axons and promotes functional recovery after spinal cord injury (SCI). Here, we demonstrate that RGMa inhibition induces synaptic rearrangements of spared axonal projections after SCI. Intrathecal administration of a function-blocking antibody to RGMa enhances anatomical synapse formation of the corticospinal tract in the cervical region of rats with thoracic spinal cord hemisection. These findings suggest that the suppression of synaptic rearrangements as well as axon growth inhibition in the adult spinal cord may contribute to the limitation of functional recovery after SCI.