AXONAL GROWTH WITHIN POLY(2-HYDROXYETHYL METHACRYLATE) SPONGES INFILTRATED WITH SCHWANN-CELLS AND IMPLANTED INTO THE LESIONED RAT OPTIC TRACT

Porous hydrophilic sponges made from 2-hydroxyethyl methacrylate (HEMA ) have a number of possible biomedical applications. We have investiga ted whether these poly(HEMA) hydrogels, when coated with collagen and infiltrated in vitro with cultured Schwann cells, can be implanted int o the lesioned optic tract and act as prosthetic bridges to promote ax onal regeneration. Nineteen rats (20-21 days old) were given hydrogel/ Schwann cell implants. No obvious toxic effects were seen, either to t he transplanted glia or in the adjacent host tissue. Schwann cells sur vived the implantation technique and were immunopositive for the low a ffinity nerve growth factor receptor, S100 and laminin. Immunohistoche mical studies showed that host non-neuronal cells (astrocytes, oligode ndroglia and macrophages) migrated into the implanted hydrogels. Astro cytes were the most frequently observed host cell in the polymer bridg es. RT97-positive axons were seen in about two thirds of the implants. The axons were closely associated with transplanted Schwann cells and , in some cases, host glia (astrocytes). Individual axons regrowing wi thin the implanted hydrogels could be traced for up to 900 mu m, showi ng that there was continuity in the network of channels within the pol ymer scaffold. Axons did not appear to be myelinated by either Schwann cells or by migrated host oligodendroglia. In three rats, anterograde tracing with WGA/HRP failed to demonstrate the presence of retinal ax ons within the hydrogels. The data indicate that poly(HEMA) hydrogels containing Schwann cells have the potential to provide a stable three- dimensional scaffold which is capable of supporting axonal regeneratio n in the damaged CNS.