Effect of nerve growth factor and Schwann cells on axon regeneration of distracted inferior alveolar nerve following mandibular lengthening

Objective:To study the effect of nerve growth f actor (NGF) and Schwann cells on axon regeneration of the inferior alveolar nerv e following mandibular lengthening with distraction osteogenesis. Methods:Unilateral mandibular osteodistraction was performed i n 9 healthy adult male goats with a distraction rate of 1 mm/d. Every 3 goats we re killed on days 7, 14 and 28 after mandibular lengthening, respectively. The i nferior alveolar nerves in the distraction callus were harvested and processed f or ultrastructural and NGF immunohistochemical study. The inferior alveolar nerv es from the contralateral side were used as controls. Results:On day 7 after distraction, axon degeneration and Schw ann cell proliferation were observed, and very strong staining of NGF in the dis tracted nerve was detected. On day 14 after distraction, axon regeneration and r emyelination were easily observed, and NGF expression started to decline. On day 28 after distraction, the gray scale of NGF immunoreactivity recovered to the n ormal value and the Schwann cells almost recovered to their normal state. Conclusions:Gradual mandibular osteodistraction can result in mild or moderate axon degeneration of the inferior alveolar nerve. Nerve trauma may stimulate the proliferation of Schwann cells and promote the synthesis and s ecretion of NGF in the Schwann cells. Schwann cells and NGF might play important roles in axon regeneration of the injured inferior alveolar nerve following man dibular lengthening.