This experimental study defined the influence of photoreceptor degeneration on retinal ganglion cell (RGC) survival, showing that an ongoing retinal degenerative process can delay axotomy-induced RGC loss.
Investigators assessed the potential influence of photoreceptor degeneration on RGC survival in wild-type and retinal degeneration 1 mice that underwent optic nerve section. To assess retinal function in wild-type animals, electroretinograms were recorded on the injured eyes and compared with the contralateral eyes. Similar labeling experiments were carried out on retinal degeneration 1 mice. Surviving RGCs were counted 21 days after axotomy and compared with wild-type mice.
A significant decrease in RGC density was observed six days after axotomy in the wild-type mice. When comparing RGC densities in wild-type and retinal degeneration 1 mice, significantly greater survival was observed in the latter.
The authors note that electroretinographical recordings exhibited a progressive decrease in the amplitude of the positive scotopic threshold response wave, reflecting ganglion cell loss. This highly significant difference in amplitude found three weeks after axotomy with respect to control eyes, in coincidence with the remarkable decrease of RGC density, suggests the importance of RGCs in the generation of positive scotopic threshold response.
They conclude that rod degeneration seems to protect RGCs from axotomy-driven damage.