Spinal cord injury (SCI) often results in permanent functional loss due to a series of degenerative events including cell death, axonal damage, and the upregulation of inhibitory proteins that impede regeneration. Repulsive Guidance Molecule A (RGMa) is a potent inhibitor of axonal growth that is rapidly upregulated following injury in both the rodent and human central nervous system (CNS). Previously, we showed that monoclonal antibodies that specifically block inhibitory RGMa signaling promote neuroprotective and regenerative effects when administered acutely in a clinically relevant rat model of thoracic SCI. However, it is unknown whether systemic administration of RGMa blocking antibodies are effective for SCI after delayed administration. Here, we administered elezanumab, a human monoclonal antibody targeting RGMa, intravenously either acutely or at 3 h or 24 h following thoracic clip impact-compression SCI. Rats treated with elezanumab acutely and at 3 h post-injury showed improvements in overground locomotion and fine motor function and gait. Rats treated 24 h post-SCI trended towards better recovery demonstrating significantly greater stride length and swing speed. Treated rats also showed greater tissue preservation with reduced lesion areas. As seen with acute treatment, delayed administration of elezanumab at 3 h post-SCI also increased perilesional neuronal sparing and serotonergic and corticospinal axonal plasticity. In addition, all elezanumab treated rats showed earlier spontaneous voiding ability and less post-trauma bladder wall hypertrophy. Together, our data demonstrate the therapeutic efficacy of delayed systemic administration of elezanumab in a rat model of SCI, and uncovers a new role for RGMa inhibition in bladder recovery following SCI.
Keywords: ABT-555; Axonal plasticity; Bladder function; Clip impact-compression; Elezanumab; Neuronal survival; Repulsive Guidance Molecule A (RGMa); Spinal cord injury.
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