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George Inana, Chris Murat, Weijun An, Ian Harris, Jing Cao; Phagocytosis Activity is Reduced in AMD Retinal Pigment Epithelium in Vitro. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2290.
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© ARVO (1962-2015); The Authors (2016-present)
Diurnally regulated phagocytosis of the outer tips of photoreceptor outer segments (POS) is a critically important function of the retinal pigment epithelium (RPE). Its importance is well demonstrated in the RCS rat model in which the retina degenerates as a result of a genetic defect in POS phagocytosis and in retinitis pigmentosa in humans who have the same genetic defect. Since age-related macular degeneration (AMD) is a disease that is characterized by slow RPE degeneration with accumulation of intra- and extra-cellular deposits, phagocytosis may be involved in its pathogenesis. In order to investigate this hypothesis we had set up an in vitro phagocytic function assay of human RPE. We have now used this assay system to compare phagocytosis in the normal and AMD RPE obtained from post-mortem eyes.
Harvesting of human RPE, culture, isolation of rod outer segments (ROS) and labeling with fluorescein, and phagocytosis assay were mostly based on the methods used for rat RPE phagocytosis. RPE was obtained from 4 post-mortem human AMD eyes in addition to 8 normal eyes. ROS was prepared from human retinas.
Feeding of fluorescently labeled ROS to cultured AMD RPE demonstrated phagocytosis as we have previously shown with normal human RPE with the same appearance and kinetics. When the levels of phagocytosis in the 4 AMD RPE cultures were compared to those of 8 human normal RPE cultures, a decrease in the phagocytosis level was seen in the AMD RPE to 50-75% of normal RPE. The level of decrease was approximately the same in the dry and wet forms of AMD. The reduction in phagocytosis level was consistent in more than 20 total experiments.
The finding that phagocytosis level is reduced in AMD RPE is significant in that it is consistent with our long-standing hypothesis that RPE phagocytosis activity may be involved in the pathogenesis of AMD.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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