AXONAL REGENERATION INTO SCHWANN CELL-SEEDED GUIDANCE CHANNELS GRAFTED INTO TRANSECTED ADULT-RAT SPINAL-CORD

Schwann cells (SC) have been shown to promote regeneration in both the peripheral and central nervous systems. In this study we tested the a bility of SC to enhance axonal regeneration in adult rat spinal cord b y grafting SC-seeded guidance channels into transected cords. SC were purified in culture from adult inbred rat sciatic nerves, suspended in Matrigel, and seeded into semipermeable PAN/PVC channels (2.6 mm I.D. x 10 mm long) at a final density of 120 x 10(6) cells/ml. Channels fi lled with Matrigel alone served as controls. Adult isologous rat spina l cords were transected at the T8 level, and segments T9-T11 were remo ved. The rostral stump was inserted 1 mm into channels with capped dis tal ends. One month after grafting, a vascularized tissue cable was pr esent within the channel in all animals. In SC-seeded channels (n = 14 ), a mean of 501 myelinated axons was found in the cable, and many axo ns extended 9-10 mm. Electron microscopy revealed typical SC ensheathm ent and myelination of axons with four times more unmyelinated than my elinated axons. Control channels (n = 8) contained fewer myelinated ax ons (mean = 71). When SC were prelabeled in culture with a nuclear dye , labeled nuclei were observed at 30 days, confirming SC survival. Ast rocytes identified by glial fibrillary acidic protein staining did not migrate far into the cable, and prelabeled SC did not enter the cord. Lack of immunostaining for serotonin and dopamine beta-hydroxylase in dicated that supraspinal axons did not regenerate into the cable. Fast Blue injections into the middle of the cable (n = 3) marked spinal co rd interneurons (mean = 306) as far as nine segments rostral (25 mm, C 7) extending axons into the graft; fewer dorsal root ganglion neurons were retrogradely labeled. In conclusion, purified populations of SC t ransplanted within channels promote both propriospinal and sensory axo nal regeneration in the adult rat thoracic spinal cord. (C) 1995 Wiley -Liss, Inc.