Laminin and optic nerve regeneration in the goldfish.

Previous work from our laboratory had shown that goldfish retinal fragments explanted onto a polylysine substratum 1 to 2 weeks following optic nerve crush exhibit a striking clockwise pattern of neuritic outgrowth. In the present study, however, when the basal lamina component laminin was used as a substratum, neurites grew out as uncurved spokes, were less fasciculated, and had an increased rate of elongation. When laminin was combined with polylysine in the substratum, the degree of fasciculation and rate of elongation were similar to those seen on laminin alone, whereas the tendency for clockwise outgrowth was even more pronounced than that observed with polylysine alone. These results suggest that regenerating neurites have an affinity for laminin. Using an antibody to murine Engelbreth-Holm-Swarm sarcoma laminin, which cross-reacted with basal lamina in goldfish tissue sections, we studied the histochemical distribution of laminin in the goldfish visual system. Immunoperoxidase staining for laminin showed a characteristic scalloped pattern of staining in cross-sections of optic nerve bundles. Following optic nerve crush, the reaction product became much more diffuse and intense, especially distal to the crush site. When the retinal ganglion cell bodies were eliminated by removing the eye, the degenerating optic nerve stump still showed the intensive staining. We interpret these results to indicate that optic nerve glia are responsible in large part for the formation of laminin. Taken together, these in vivo and in vitro findings suggest that laminin plays a role in nerve regeneration in the goldfish central nervous system.