Progressive optic axon dystrophy and vascular changes in rd mice

PURPOSE. TO examine how the vascular plexuses in the rd mouse retina are af fected by the loss of photoreceptors and how this compares with the Royal C ollege of Surgeons (RCS) rat. To examine whether the profound effects of va scular pathology on retinal ganglion cells (RGCs) and their axons seen in R CS rats are also found in rd mice. METHODS. Vascular patterns were studied in flatmounted and sectioned retina s using either nicotinamide adenine dinucleotide phosphate(NADPH)-diaphoras e histochemistry or vessel filling with horseradish peroxidase, Optic axons were visualized using RT97 (an antibody against the 200-kDa neurofilament subunit), and RGCs were labeled by retrograde transport of fluorescence lab el, the Fluorogold, applied to the superior colliculus. RESULTS. The present study showed that in the rd mouse, similar to the RCS rat, vascular complexes developed in association with retinal pigment epith elial cells at the outer border of the retina. The number and distribution of complexes were very different from the rat? but as in the rat, progressi ve axonal dystrophy was seen in the optic fiber layer. RGC loss, rather tha n being local was more broadly distributed, but some, at least, appeared to be secondary to axonal dystrophy caused by vessels supplying vascular form ation. CONCLUSIONS. Photoreceptor loss in the rd mouse leads to RGC axonal dystrop hy and loss. The lesser degree and different distribution of RGC loss cause d by abnormal vasculature associated with vascular formations in the outer retina in the rd mouse may be due to the early atrophy of the deep vascular plexus in this animal.