Reinnervation of denervated lumbar ventral roots and their target muscle by thoracic spinal motoneurons via an implanted nerve autograft in adult rats after spinal cord injury

Intraspinally implanting a nerve autograft (NAG) to promote axonal regenera tion toward periphery was investigated as a surgical treatment for spinal c ord injury in adult rats. Fifteen animals underwent a left hemisection of t he spinal cord at T12 level and an intradural section of all ipsilateral lu mbar ventral roots. In repaired animals (n = 9), the electrophysiologically selected left L3 and L4 lumbar ventral roots supplying the quadriceps musc le were anastomosed to a NAG. The NAG was taken from the right peroneal ner ve and then ventrolaterally implanted into the cord at a level 7 mm rostral to the hemisection. In the control group (n = 6), sectioned lumbar ventral roots were left unrepaired, Nine months later, the animals were assessed w ith clinical, electrophysiological, and histological examinations. Muscle a ction potential and motor evoked potential were obtained from the denervate d/reinnervated quadriceps in all repaired animals, with a mean amplitude of 918.3 +/- 328.9 mu V and 215.8 +/- 39.7 mu V, respectively. Horseradish pe roxidase retrograde labeling from the denervated/repaired lumbar ventral ro ots, performed in five repaired animals, showed that the mean of labeled ne urons, ipsilaterally located in the thoracic ventral horn near the implanta tion site, was 145.8 +/- 111.7. Histological analysis showed numerous myeli nated axons in the NAG and denervated/repaired lumbar ventral roots of all repaired animals. The study of neuromuscular junctions furthermore confirme d numerous newly formed endplates appearing in the denervated/reinnervated quadriceps, These changes were absent in the control animals. These data in dicate that the rostral thoracic spinal motoneurons can innervate the cauda l denervated/repaired lumbar ventral roots and the target quadriceps via an implanted NAG, thereby inducing some functional recovery in adult rats aft er lower thoracic spinal cord injury. (C) 1999 Wiley-Liss, Inc.