Effects of nerve growth factor on nerve regeneration through a vein graft across a gap

The limited availability of donor sites for nerve grafts and their inherent associated morbidity continue to stimulate research toward finding suitabl e alternatives. In the following study, the effect of direct administration of nerve growth factor (NGF) into a nerve conduit across a gap was tested in a rat sciatic nerve model. A l-cm segment of the right sciatic nerve in Sprague-Dawley rats was resected, and the gap was then bridged using one of three methods: group I (NGF-treated group, n = 12), a vein graft filled wi th NGF (100 ng in 0.3-ml phosphate buffered saline); group II (control grou p, n = 12), a vein graft filled with phosphate buffered saline only; group III (standard nerve graft, n = 11), a resected segment of the sciatic nerve . All animals were evaluated at 3 and 5 weeks by behavioral testing and at 5 weeks by electrophysiologic testing. At 3 weeks, sensory testing showed t hat the latency to a noxious stimulus in group I animals (8.0 +/- 5.4 sec, mean +/- SD) was significantly lower than that of group II animals (13.2 +/ -: 6.5 sec), indicating that sensory recovery was superior in the animals r eceiving NGF. The mean latency of animals in group III was 12.9 +/- 6.5 sec , but the difference between the latencies of group I and group III did not reach statistical significance. At 5 weeks, there was no difference in sen sory testing between groups. Motor function in groups I and III as measured by walk pattern analysis was superior to that of group II at 5 weeks (toe spread ratios 0.66 +/- 0.09, 0.48 +/- 0.07, and 0.69 +/- 0.09 for groups I, II, and III, respectively). Mean motor conduction velocities across the l- cm gap were 8.6 +/- 4.7 m/sec, 2.5 +/- 0.7 m/sec, and 6.9 +/- 2.9 m/sec in groups I, II, and III respectively. The difference between groups I and III was not statistically significant, but the motor conduction velocity of gr oup II was significantly slower than that of either group I or III (p < 0.0 02). The positive effects of NGF on regeneration of nerves across a gap see n in this study suggest that it may be useful for treating peripheral nerve injuries in combination with autogenous vein grafts.