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Praveena Gupta, Valentina Reffatto, doris Amaro, Edward Kraft, Marjan Afrouzian; Histochemical Characterization of Drusen Related Pathology in Age Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1219. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Age related macular degeneration (AMD) is the leading cause of irreversible vision loss among the elderly in developed nations. Dry AMD, a subtype of advanced-stage AMD, is distinguished by deposits of extracellular deposits called drusen and subsequent atrophy of the retinal pigment epithelium (RPE) and photoreceptor layer (PR). Drusen is a complex molecule, comprised of mucopolysaccharides, lipids, proteins, and inflammation-related molecules. Although pathways leading to drusen formation is unknown, detailed review of pathological features can shed some insight in its biogenesis.
Human age matched AMD and non-AMD eyes were processed for cryo/paraffin sections containing the sclera, choroid, and Bruch’s membrane. These sections were either left unstained or stained with H&E, Congo red, Oil red O, Periodic Schiff’s, and 8-oxo-dG staining. Unstained slides were analyzed under fluorescence microscope as well. Images were taken under a bright field and/or confocal fluorescence microscope.
In the AMD eyes, a chain of drusen bodies were found to be seated on the inner collagenous layer of the Bruch's membrane (BM). Also, small round or large dome shaped drusen bodies were unevenly interspaced from each other, suggesting a secondary mechanism in drusen biogenesis. Almost every drusen had positive eosinophilic material inside, while a few had melanin granules and an occasional whole cell. Molecular composition of drusen included amyloids (positive Congo red), glycoproteins and glycolipids (positive PAS staining) and DNA oxidative stress products. Also, drusen seemed to fluoresce in both green and red channels without bleaching. Age matched control eyes had rare basal laminal deposit when stained with PAS. Pronounced thickening of the BM in the AMD eyes was also noted with uneven distribution of amorphous collagen that appeared as outward notching towards the choroidal face. Oil red O staining of the AMD-BM showed presence of neutral lipids in the elastin layer, which may lead to a hindrance in nutrient exchange between RPE and choroid.
Drusen accumulation may lead to the dysregulation of homeostatic equilibrium between the Bruch’s membrane and RPE. Histopathology of drusen showed that it is composed of mucopolysaccharides and complex lipoprotein molecules. Profiling the key molecular components of drusen can help facilitate our understanding in the pathogenesis of AMD.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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