OBJECTIVETo study the effects of glial cell derived neurotrophic factor (GDNF) on regeneration of facial nerve defects by autogenous facial vein conduit.

METHODSThirty-six rabbits were used in this study and 10 mm-length facial nerve defects were made on both sides of all animals. The nerve gaps were bridged using autogenous posterior facial vein graft of the same side. The animals received injection of either saline (group A, n=16) or GDNF (group B, n=16) into the veins. Nerve function was evaluated by evoking nerve action potential immediately after operation and 4, 8 and 16 weeks after operation. Regenerated nerve samples were harvested at 4, 8, and 16 weeks after operation and processed for histology and transmitting electron microscopic examination (TEM).

RESULTSAction potential did not exist immediately after operation but it was evoked at 4, 8, and 16 weeks in both groups. At 4 and 8 weeks after operation, the amplitude and width of action potential were significantly higher in group B than group A (P < 0.01), except wave width at 4 weeks, which showed no significant differences, while the latency period was significantly shorter in group B than that in group A (P < 0.01). At 16 weeks, action potential was similar between two groups, except wave amptitude, which was higher in group B than group A (P < 0.01). Morphologic and TEM examinations showed more matured myelinated nerve fibers and active Schwann's cells in group B when compared group A during the whole regeneration process.

CONCLUSIONGDNF can promote nerve regeneraat early stage during reconstruction of facial nerve defects by autogenous facial vein conduit and combination of GDNF and autogenous vein graft provides a valuable method for clinical reconstruction of facial nerve defects.