Local administration of neurotrophic growth factor in subcutaneous silicon chambers enhances the regeneration of the sensory component of the rat sciatic nerve.

An experimental model for local administration of neurotrophic growth factor (NGF) in peripheral nerve lesions is tested. The model consists of a subcutaneous reservoir connected to the sciatic nerve neurorrhaphy. The right sciatic nerves were exposed, severed, and repaired at a level 1.5 cm proximal to their trifurcation. Then, a dome-shaped silicone reservoir connected to the proximal end of a silicone tube was placed subcutaneously in the dorsum of the experimental animal. The distal end of the connecting tube was located in the nerve neurorrhaphy. Two experimental groups were made: Group A (n = 90) received daily doses of a solution containing NGF-7S during the first 4 weeks after surgery and a single weekly dose thereafter. Within this group, three subgroups of 30 rats each were made: A-4 sacrificed 4 weeks after surgery, A-8 sacrificed after 8 weeks, and A-12 after 12 weeks. Group B (n = 90) received the same vehicle solution without NGF under the same schedule and volume as in Group A. Three subgroups were also made as in Group A depending on the survival period. In order to locate the neurons in the dorsal root ganglia, the retrograde tracer horseradish peroxidase was administered at the proximal stump of the sciatic nerve (tibialis branch), which was severed 1 cm distal to the sciatic trifurcation. In respect of the nonoperated side, the percentage between the number of dorsal root ganglia neurons in the NGF-treated group was significantly higher than in the control group (P < 0.001). These results demonstrate that percutaneous administration of multiple doses of NGF in this model enhances sensory nerve regeneration after sciatic lesions evaluated by horseradish peroxidase labeling of dorsal root ganglia neurons.