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.