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

OBJECTIVE: A collagen tube was used to guide axonal regrowth from the spina l cord to the periphery to contribute to improvement of paralysis after low er thoracic spinal cord injury. METHODS: The spinal cords of adult male Sprague-Dawley rats were lesioned b y removing the left hemicord from T12 to 5 mm below this level and addition ally sectioning all left lumbar ventral roots. In experimental animals (n = 9), a collagen tube was inserted into this gap, spanning the rostral hemis ected cord to the caudal sectioned lumbar ventral roots (gap, 7 mm). In con trol animals (n = 6), no treatment was performed. RESULTS: Six months after surgery, the return of some tension and resistanc e of the paralyzed hindlimb muscles was observed in all experimental rats e xcept the untreated controls. Nine months postoperatively, muscle action po tentials were recorded from the target muscles of the experimental animals while electrostimulating the tissue continuity within the collagen tube. Ho rseradish peroxidase retrograde labeling showed that the neurons in the ros tral cord near the implantation site regrew into the reconnected lumbar ven tral roots. Histological examination indicated numerous myelinated axons in the reconnected root pathways and newly formed endplates in the target mus cles. No axonal regeneration was found in the control rats. CONCLUSION: 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 aft er spinal cord injury. This surgical repair model also provides a means for testing the use of trophic factors that may further promote axonal regener ation.