Cortical visual functions can be preserved by subretinal RPE cell grafting in RCS rats

Photoreceptor loss in the Royal College of Surgeons (RCS) rat is limited by transplantation of retinal pigment epithelial cell lines into the subretinal space prior to the onset of major photoreceptor loss. The purpose of this study was to examine to what extent visual cortical function was rescued by such transplantation and how the degree of rescue correlated with threshold responses recorded in the superior colliculus. To achieve this, single unit responses were recorded from the supragranular layers of cortical area, V1, at 7 months of age at a time when the cortex in these animals is normally non-responsive to specific visual stimulation. The best animals gave cortical responses that were very little different from normal. For the whole group studied, of the eight parameters measured for each cell, only three were significantly less well tuned than in normal non-dystrophic rats. In general, better single unit responses in the cortex were obtained with more photoreceptor rescue and this correlated with better threshold responses. These results indicate that discrete central visual responses can be preserved by subretinal transplantation of a cell line which limits chronic loss of input signal associated with progressive photoreceptor loss.