Cellular organization in retinal transplants using cell suspensions or fragments of embryonic retinal tissue

We have investigated the cellular organization in two different types of retinal transplants using cell type-specific monoclonal antibodies. Both fragments and cell suspensions of E17-E19 Sprague-Dawley rat retina were transplanted to a subretinal site in congenic adult rat hosts. After a survival time of 28 days, the transplants were stained by immunocytochemistry with antibodies against rhodopsin, which stained rods; with antibodies against HPC-1, which stained amacrine cells and outer and inner plexiform layers; and with antibodies against vimentin, which stained Müller cell fibers and horizontal cells. In the host retina, the distribution of immunocytochemical staining was similar, irrespective of transplantation technique. In the transplants, the anti-rhodopsin staining showed that fragment transplants developed photoreceptors in rosettes, whereas in cell suspension transplants, this staining showed a scattered distribution of photoreceptors. The HPC-1 staining showed that regions corresponding to the inner nuclear layer surrounded both types of transplants and made large invaginations into them. In one case, using the cell suspension technique, fibres were found to run from the inner plexiform layer of the transplant to the outer plexiform layer of the host. The vimentin staining revealed a disorganized array of Müller cell fibres in both types of transplants, but with some concentration to the regions corresponding to the inner plexiform layer.