Fetal spinal cord homografts ameliorate the severity of lesion-induced hind limb behavioral deficits.

Fetal spinal cord grafts survive for long periods in host spinal cord. We explored the ability of such grafts into a lesion in C3 fasciculus gracilis to influence the expected deterioration of hind limb performance following this lesion. Ten adult Sprague-Dawley rats were placed on a schedule of 23 h off and 1 h on water. These subjects were then trained to traverse a narrow platform for a water reward. Criterion was established as 10 trials/day completed in 15 s a trial for 2 consecutive days. Animals were ranked for hind limb and forelimb performance utilizing slips, recovery, and manner of traversing the platform. In a triple-blind experimental design, the animals' identification was coded and laminectomy performed at C3. The fasciculus gracilis was bilaterally transected at the rostral and caudal borders of the segment and aspirated. Five subjects were chosen at random immediately after the lesion was made for the implantation of two 1-mm segments of E14 spinal cord from fetuses of timed pregnant Sprague-Dawley dams at the time of the lesion. Coded lesion and lesion-transplant animals were then tested after 21, 30, 45, 60, and 90 days until criterion or for 4 days. Hind limb performance of the lesion-only (ANOVA chi 2 = 13.04, df 5; P less than 0.05) and lesion-transplant groups (ANOVA chi 2 = 11.82, df 5; P less than 0.05) showed that the C3 fetal transplants significantly decreased (P less than 0.05) the severity of hind limb deficit at 21 days postlesion and significantly (P less than 0.05) decreased the expected foot slips and limb recovery to the platform that was expected and did develop in lesion-only animals at 90 days. There were no significant differences in forelimb performance (ANOVAs P greater than 0.05). There were few small-caliber nerve fibers in the fasciculus gracilis at the level of C1 indicating that reinnervation was not a major factor in the reduction of the deficit.