Abstract
Abstract: :
Purpose: To correlate the size of surviving RGCs and their spatial relationship to other RGCs in rats with induced IOP elevation and glaucomatous DBA/Nnia mice. To evaluate whether a topographical relationship between cell size and survival of RGCs in glaucomatous rats and DBA/Nnia mice exists. Methods: 7 retinas obtained from 15 month old DBA/Nnia mice and one retina from a rat subjected to episcleral vein cauterization with partial RGC loss were used for this study. RGCs were retrogradely labeled with 5% Flurogold. The animals were sacrificed 7 days later and their retinas were prepared as wholemounts. The entire retina was imaged with a fluorescent microscope equipped with an automated stage and a digital camera. Digital images were used to generate multidimensional color–coded retinal maps for all the retinas, depicting the topographic coordinates, distance to the closest cell (nearest neighbor distance –NND) and cell size. Results: The total number of RGCs in the mouse retinas ranged from 22,330 to 92,150 cells per retina while for the rat retina was 28,498 cells. Mean equivalent cell diameter (+/– SD) measured 5.99 (+/–0.48) µm for the mice and was 12.7 (+/–4.4) µm for the rat. Comparison of digital maps of NND and cell size in DBA/Nnia mice revealed that larger cells were predominantly identified within patches of high RGC cell density (where cells were more preserved). The same was true for the one glaucomatous rat retina studied. Conclusions: Comparatively larger cells are topographically associated with areas of cell preservation. Whether this finding is due to preferential loss of small cells, cellular swelling with age or glaucoma, or preferential loss of larger cells in areas of greater damage needs to be further investigated.
Keywords: ganglion cells • apoptosis/cell death • aging