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Gillian J McLellan, Sara Adelman, Leandro B C Teixeira, Kazuya Oikawa, Matthew Ellinwood; Retinal ganglion cell (RGC) somas persist after loss of axons in a spontaneous feline glaucoma model. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2539.
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© ARVO (1962-2015); The Authors (2016-present)
To establish the sequence and timeline for RGC axon and soma loss in cats with feline congenital glaucoma (FCG).
RGC somas and axons were quantified and topographic maps of RGC density were constructed for 7 cats (Felis catus: 4 homozygous for the LTBP2 mutation responsible for recessively inherited FCG; 3 unaffected control cats) of ages ranging from 10 mths to 8yrs. Cresyl violet stained retinal whole-mounts were prepared from one eye of each cat for light microscopy, and images focused on the ganglion cell layer at 20x magnification acquired using a motorized stage and automated image stitching software (Cellsens, Olympus) with manual correction as needed. RGC somas were manually identified in the resulting images on the basis of cell morphology and soma size and then quantified automatically (ImageJ). RGC axons were quantified using a semi-automated targeted counting method in p-phenylenediamine stained optic nerve sections as previously described (Teixeira, LBC at al, 2014; PMC3976691). RGC topographic isodensity maps were created using open source software (R package Retina and ImageJ).
RGC soma counts were within the normal range in 3/4 adult cats with FCG (115,000-173,000) but optic nerve axon counts were significantly lower than normal in all cats with FCG. The oldest FCG cat had a>60% reduction in number of both RGC axons AND presumed RGC somas (30,370 and 43,890, respectively). Feline RGC distribution was characterized by a steep drop-off from a peak (104 cells/mm2) in the area centralis. Patterns of reduced RGC density were variable between individual cats with FCG.
We present evidence that RGC somas appear to persist for years beyond loss of their axons in FCG. Patterns of loss of neuronal cells from the ganglion cell layer of the retina in FCG varied between individuals.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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