Transforming growth factor-β3 promotes facial nerve injury repair in rabbits

The present study investigated the effects of transforming growth factor (TGF)-β3 on the regeneration of facial nerves in rabbits. A total of 20 adult rabbits were randomly divided into three equal groups: Normal control (n=10), surgical control (n=10) and TGF-β3 treatment (n=10). The total number and diameter of the regenerated nerve fibers was significantly increased in the TGF-β3 treatment group, as compared with in the surgical control group (P<0.01). Furthermore, in the TGF-β3 treatment group, the epineurial repair of the facial nerves was intact and the nerve fibers, which were arranged in neat rows, were morphologically intact with visible myelin swelling. However, in the surgical control group, the epineurial repair was incomplete, as demonstrated by: Atrophic nerve fibers, partially disappeared axons and myelin of uneven thickness with fuzzy borders. Electron microscopy demonstrated that the regenerated fibers in the TGF-β3 treatment group were predominantly myelinated, with clear-layered myelin sheath structures and axoplasms rich in organelles. Although typical layered myelin sheath structures were observed in the surgical control group, the myelin sheaths of the myelinated nerve fibers were poorly developed and few organelles were detected in the axoplasms. Neuro-electrophysiological examination demonstrated that, as compared with the surgical control group, the latency period of the action potentials in the TGF-β3 treatment group were shorter, whereas the stimulus amplitudes of the action potentials were significantly increased (P<0.01). The results of the present study suggest that TGF-β3 may improve the regeneration of facial nerves following trauma or injury.