AXONAL GROWTH INTO TUBES IMPLANTED WITHIN LESIONS IN THE SPINAL-CORDSOF ADULT-RATS

Cultured Schwann cells were implanted into the thoracic spinal cords o f adult rats inside thin tubes made of polycarbonate film coated with poly-L-lysine. Additional control tubes were implanted which did not c ontain cultured Schwann cells. Some of the control tubes were coated w ith poly-L-lysine and others were not. One week to 2 months later the animals were perfused with fixatives and the tubes were prepared for l ight or electron microscopy. Immunocytochemical studies of the Schwann cell tubes reveal that they contain axons. Most of these axons are gr ouped in fascicles that run longitudinally through the tubes. The dist ribution of these axons matches precisely the distribution of basal la mina within the tubes as displayed by immunolabeling with an antibody to laminin. Surprisingly, the same patterns of labeling are seen in th e control tubes, although they contain fewer axons. Control tubes lack ing poly-L-lysine contain the fewest. Electron microscopy verifies tha t the tubes, including control tubes, contain Schwann cells and axons of different diameters. Furthermore, the Schwann cells ensheathe and m yelinate the axons. These results strengthen the hypothesis that Schwa nn cells can support axonal growth in the spinal cords of adult animal s. They also demonstrate that these Schwann cells can be implanted or they can be derived from the host animal. This finding raises the poss ibility that therapies could be devised for bridging spinal cord lesio ns that are based on maximizing migration of endogenous host cells int o the sites of lesions. (C) 1996 Academic Press, Inc.