Remodeling processes during neural retinal regeneration in adult urodeles: an immunohistochemical survey

Dynamic features of neural retina regeneration in the adult newt Pleurodeles waltl were analyzed using immunohistochemical studies. Antibody to Glial Fibrillary Acidic Protein (GFAP) was used as a marker of the retinal glial supportive system in order to obtain an overview of the retinal reorganization pattern. Unexpectedly, retinal progenitor cells displayed GFAP staining, as did later Müller glial processes and astrocytes supporting ganglional axons. To study changes of plasticity during retinal restoration, the expression patterns of highly- (PSA) and weakly-sialylated N-CAM were examined by double staining. In the retina of adult newts, a sustained expression of total-N-CAM and PSA-N-CAM was detected. However, while an intense distribution of N-CAM was observed throughout the retina, PSA labeling was especially seen in the outer retinal layers. During retinal regeneration, similar widespread staining patterns were observed with the two antibodies, but labeling appeared higher with anti-total-N-CAM antibody than with anti-PSA-N-CAM antibody. On the other hand, tenascin (Tn) expression was analyzed for the first time during retinal regeneration. At the early stages, brightly stained matrix fibers of abundant Tn accumulating in the eye cavity were seen close to the retinal rudiment cells, which suggested that Tn was secreted from these cells. Tn expression was seen nearly throughout the retinal regenerate during neurite migration and then became restricted to the plexiform layers. In the light of the functions attributed to N-CAM and Tn in histogenetic events, the putative roles played by these morphoregulatory molecules in adult newt retinal regeneration were discussed.