Effects of IGF-I gene therapy on the injured rat pudendal nerve.

Injured nerves and their motor units may undergo enhanced recovery when exposed to recombinant human insulin-like growth factor-I (rhIGF-I). The external anal sphincter muscle in the female rat was denervated to model incontinence. The treatment-group muscle was injected with rhIGF-1 plasmid, whereas in the control group the plasmid lacked the cDNA insert and the normal group received neither surgery nor treatment. Electromyography data at 56 days post surgery indicated more reinnervation without fibrillation potentials in the treatment group (2 of 6) than in the control group (0 of 6). The histology of the regenerated axons in the pudendal nerve distal to the crush site also suggested an improved recovery in the treatment group. The number of motor neurons retrogradely labeled with horseradish peroxidase was decreased by 50% following pudendal nerve crush in both experimental groups compared to the normal group. We conclude from these preliminary results that rhIGF-I gene therapy may improve the distal recovery of structure and function.