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Carly Lewis, Adam Hedberg-Buenz, Michael G Anderson; Retinal ganglion cell density and vascular proximity in a mouse model of glaucoma. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2436.
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© ARVO (1962-2015); The Authors (2016-present)
Multiple lines of evidence support vascular influences to glaucomatous neurodegeneration. The purpose of these experiments was to test whether proximity to the major superficial retinal vessels influences retinal ganglion cell layer cellularity in the nee mouse model of glaucoma versus strain-matched controls.
H&E stained retinal flat mounts were collected from 12-week-old B6 congenic (N10) mice homozygous for the nee mutation and healthy C57BL/6J controls. Photomicrograph montages following retinal vessels (from 200µm extending to 3200µm distal to optic nerve head) were collected from 6-7 vessels per genotype (2-4 vessels per mouse, 2 mice). Retinal ganglion cell layer cellularity was quantified in three 30-µm wide zones parallel to each vessel (1, nearest vessel; 2, middle; 3 furthest) using custom macros in Image J and compared to regional averages of cellularity in the central, mid-central, mid-peripheral, and peripheral areas of the same retinas.
As expected for mice with glaucoma, retinal cellularity was decreased in nee mice compared to healthy controls (7142 + 1258 vs 9162 + 686 cells/mm2, P=0.005). As also predicted, cellularity was highest in the central retina and lowest in the peripheral retina of both healthy and glaucomatous mice. Across all areas, zone 1 had a significantly higher density of cells than either zone 2 or 3 in both nee (9306+838 cells/mm2, P=0.03) and control mice (10945+544 cells/mm2, P=0.005), while the densities of zones 2 and 3 were indistinguishable. There was a trend for preferential sparing of cells in zone 1 in the glaucomatous nee mice, but statistical significance was not met.
These results indicate that there is an increased density of retinal ganglion cell layer cells immediately adjacent to the major vessels. Because this was observed in both healthy and glaucomatous mice, the phenomenon appears to be developmental in origin. In ongoing work, we are classifying the identity of cells in zone 1 and further testing whether zone 1 cells may be preferentially spared in glaucoma.
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