Abstract
Transplants of fetal spinal cord support regeneration of severed dorsal root axons and allow synapse formation. To analyze the components of the transplants that provide this favorable environment, we studied whether or not 1) the embryonic spinal cord transplants contain Schwann cells, a major producer of laminin, and 2) whether dorsal roots regenerate into transplants of immature astrocytes. We used calcitonin gene-related peptide (CGRP), laminin and glial fibrillary acidic protein (GFAP) immunocytochemistry to identify regenerated axons, Schwann cells and astrocytes, respectively. CGRPimmunoreactive axons regenerated into embryonic day 14 fetal spinal cord transplants, but the transplant did not contain laminin. Dorsal roots immunoreactive for CGRP also regenerated into suspensions of cultured astrocytes. The transplanted astrocytes also favored the expression of laminin and GFAP. CGRP-labeled axons regenerated and distributed widely into the polycarbonate tubes coated with poly L-lysine and containing medium with or without cultured astrocytes. These results indicate that Schwann cells are not likely to account for dorsal root regeneration into transplants of fetal spinal cord and that astrocytes may in fact induce regeneration. Regeneration may also take place in response to various environments.
