Mechanism of retinal ganglion cell loss in inherited retinal dystrophy

To study the inner retinal layers in RCS rats, which suffer major loss of retinal photoreceptors during the first 3 months of life, retinal ganglion cells (RGC) were labelled with fluorogold and their axons were immunoreacted with an antibody against neurofilaments. The retinal vessels were stained with horeseradish peroxidase and the RGC layer was stained with methylene blue. Animals more than 6 months of age showed areas devoid of fluorogold-labelled cells that extended from the optic disc to the periphery. The course of the RGC axons was also abnormal and showed tortuosities, dilatations and signs of abortive regeneration at sites where most inner retinal vessels cross the axons. We conclude that some months after photoreceptor degeneration has concluded in dystrophic animals, some retinal vessels compress the RGC axons and cause retrograde degeneration of their parent cells.