Lithium chloride and chondroitinase ABC promote axonal regeneration of rubrospinal neurons after spinal cord injury

Abstract

Axons in the spinal cord fail to regenerate spontaneously after injury. We examined whether chondroitinase ABC (ChABC) promote the axonal regeneration of rubrospinal tract (RST) neurons following injury of the spinal cord. We also assessed the effect of lithium chloride (LiCl) on the regeneration of RST neurons in the injured spinal cord. Adult female Sprague–Dawley rats were used in this study. Under anesthesia with ketamine and xylazine, the animals received a unilateral hemisection at the seventh cervical spinal cord segment (C7). Four weeks after the injury, regeneration of RST axons across the lesion scar was examined by injection of Fluoro-Gold at spinal segment T2. The recovery of motor function was studied on a test of forelimb usage. RST neurons did not regenerate their axons after spinal cord injury. Intraperitoneal injection of LiCl alone did not promote the axonal regeneration of RST neurons. Administration of ChABC at the lesion site promoted the regeneration of RST axons by 20%. Combined treatment of LiCl together with ChABC significantly increased the regeneration of RST axons to 42%. Animals receiving the combined treatment used both forelimbs together more often than animals received sham or single treatment. Immunoblotting and immunohistochemical analysis revealed that administration of LiCl induced the expression of inactive GSK-3 and the upregulation of Bcl-2 in RST neurons after spinal cord injury. These results suggest that LiCl inhibits GSK-3 and reinforces the regeneration-promoting effect of ChABC through a Bcl-2 dependent mechanism. Combined use of LiCl together with ChABC could be a potential treatment for spinal cord injury. Acknowledgment: This study was supported by the University of Hong Kong.