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Lionel Bretillon, Emilie Simon, Bernadette Kantelip, Joël Michel, Niyazi Acar, Alain M. Bron, Jeannine Lherminier, Catherine P. Creuzot-Garcher; Ultrastructural Changes In The Outer Retina And Retinal Pigment Epithelium Of The ApoB100,LDLR-/- Mouse, A Murine Model Of Aging Of The Human Retina. Invest. Ophthalmol. Vis. Sci. 2011;52(14):957.
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Age-related Macular Degeneration (AMD) is the leading cause of visual impairment after the age of 50 years in Western countries. Deposition of lipids including cholesteryl esters within Bruch’s membrane (BrM) is a hallmark of aging of the human retina and is observed in eyes of patients with maculopathies and AMD. We previously demonstrated that the ApoB100,LDLR-/- mouse exhibits deposits of cholesteryl esters in BrM, fundus autofluorescence and reduced electroretinographic response, making it a relevant model of aging of the human retina. In order to better characterize its phenotype, we aimed to evaluate the ultrastructural changes in the retina of the ApoB100,LDLR-/- mouse.
In vivo fundus autofluorescence of aged ApoB100,LDLR-/- mice was evaluated using a confocal scanning laser ophthalmoscope. Mices were enucleated and the ocular globes were immediately fixed with 2.5% glutaraldehyde prepared in 0.1M phosphate buffer pH7.2 for 20h, postfixed with 0.5% buffered osmium tetroxide for 1h, dehydrated through a graded ethanol series and propylene oxide, and embedded in Epon resin. Semithin sections (0.5µm) were stained with 0.2% toluidine blue pH11 prior to examination by bright field microscopy with a Leica DRMB microscope. Ultrathin sections (90nm) were counterstained with 3% (w/v) uranyl acetate and lead citrate and examined with a Hitachi H7500 transmission electron microscope operating at 80kV and equipped with an AMT camera.
ApoB100,LDLR-/- mice showed punctuated fundus autofluorescence at 488nm, consistent with the accumulation of lipid-rich lipofuscin material. ApoB100,LDLR-/- mice exhibited irregular disk arrangement of the outer segments of photoreceptors. Accumulation of remnants of incomplete phagocytosis of photoreceptor outer segments was visible in the RPE. Vacuoles were observed in the cytoplasm and mitochondria of the RPE. Electron-dense material accumulated in the RPE. Enlarged basal infoldings were found in ApoB100,LDLR-/- mice, and material with amorphous deposits can be seen between basal infoldings in the mouse RPE.
Our data on ultrastructural changes in the outer retina and RPE of aged ApoB100,LDLR-/- mice support further investigations on the use of the ApoB100,LDLR-/- mouse as a relevant model for dry AMD.
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