Regrowth of the rostral spinal axons into the caudal ventral roots through a collagen tube implanted into hemisected adult rat spinal cord.

Abstract

A collagen tube was used to guide axonal regrowth from the spinal cord to the periphery to contribute to improvement of paralysis after lower thoracic spinal cord injury. The spinal cords of adult male Sprague-Dawley rats were lesioned by removing the left hemicord from T12 to 5 mm below this level and additionally sectioning all left lumbar ventral roots. In experimental animals (n = 9), a collagen tube was inserted into this gap, spanning the rostral hemisected cord to the caudal sectioned lumbar ventral roots (gap, 7 mm). In control animals (n = 6), no treatment was performed. Six months after surgery, the return of some tension and resistance of the paralyzed hindlimb muscles was observed in all experimental rats except the untreated controls. Nine months postoperatively, muscle action potentials were recorded from the target muscles of the experimental animals while electrostimulating the tissue continuity within the collagen tube. Horseradish peroxidase retrograde labeling showed that the neurons in the rostral cord near the implantation site regrew into the reconnected lumbar ventral roots. Histological examination indicated numerous myelinated axons in the reconnected root pathways and newly formed endplates in the target muscles. No axonal regeneration was found in the control rats. These results indicate that the rostral spinal axons can regrow into the caudal sectioned and reconnected ventral roots through a collagen tube, thus innervating the denervated peripheral targets in adult rats after spinal cord injury. This surgical repair model also provides a means for testing the use of trophic factors that may further promote axonal regeneration.