Partial functional recovery of paraplegic rat by adenovirus-mediated gene delivery of constitutively active MEK1

Spinal cord injury in adult mammals results in little axonal regeneration, although the mechanism of regeneration failure still remains elusive. Recen t research has revealed that activation of the extracellular-signal-regulat ed kinases (ERKs) plays an important role in the neurite outgrowth. In the present study, we constructed a replication-defective adenovirus vector car rying mutated form of MEK1 (CA-MEK virus), which constitutively activate ER K pathway, and investigated its effect on thoracic spinal cord injury model in young adult rats as well as neurite outgrowth in vitro. In rat pheocrom ocytoma cell line PC12 cells, CA-MEK virus infection induced sustained acti vation of ERKs and stimulated neurite outgrowth in the absence of neurotrop hic factors. In rat spinal cord transection model, injection of CA-MEK viru s into the completely transected spinal cord efficiently activated ERKs in the supraspinal neurons and induced axonal regeneration across the transect ion site, which was confirmed by anterograde labeling with wheat-germ-agglu tinin conjugated peroxidase (WGA-HRP). Spinal cord evoked potentials (SCEP) showed that these regenerated axone were electroconductive. Most important ly, CA-MEK virus-treated rats showed significant recovery of hind limb func tion 2 weeks after operation compared to the control rats treated with no v irus or LacZ virus. These results suggest that adenovirus-mediated CA-MEK g ene transduction offers a novel strategy for the gene therapy of spinal cor d injury. (C) 2000 Academic Press.