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J. Ding, L. V. Johnson, C. Bowes Rickman; Immunohistochemical Analysis of Drusen-Associated Proteins in RPE and Bruch’s Membrane (BM) of Apolipoprotein E4 (APOE4) Targeted Replacement (TR) Mouse. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1932.
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The retina and RPE of aged, APOE4 TR mice fed a high fat and cholesterol enriched (HFC) diet exhibit pathological changes similar to those found in age-related macular degeneration (AMD). AMD is marked by sub-RPE deposits comprised of proteins and lipidssome of which are precursors to and by-products of inflammation and oxidative stress, including complement components, cholesterol, apolipoproteins, and amyloid beta (Aβ). We analyzed APOE4 TR mouse RPE and BM for the extent of overlap of these molecules in deposits that form in this mouse model of AMD.
APOE4 TR mice over 65 weeks old were fed a HFC diet for 8 weeks before sacrifice. Immunohistochemistry was performed for ApoE, vitronectin, activated fragments of complement (C3b/iC3b/C3c) and Aβ on ocular tissue sections. Some subcellular localization was further confirmed with immunoelectron microscopy.
Vitronectin was found uniformly in BM. ApoE was also localized to BM, with strong patchy immunolabeling associated with the basal side of the RPE. EM immunogold labeling revealed RPE-associated ApoE to be intracellular or associated with basal infoldings. Anti-mouse C3b/iC3b/C3c immunolabeling exhibited a small linear patchy pattern on basal side of the RPE. These patches are often localized adjacent to a single RPE cell. Aβ is also localized in the deposits near RPE basal infoldings. The subcellular distribution of the latter two proteins was also analyzed.
Four proteins that are commonly found in human drusen are also found in RPE- and BM-associated deposits in APOE4 TR mice fed a HFC diet. These proteins have distinct distributions and are not necessarily co-localized.
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