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Anupama Tiwari, Imran Ahmed Bhutto, Malia Michelle Edwards, Rhonda Grebe, Gerard A Lutty; Increased expression of epithelial-to-mesenchymal transition markers in geographic atrophy. Invest. Ophthalmol. Vis. Sci. 2020;61(7):2273.
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Previous studies suggest that RPE migration occurs at the border of atrophy in geographic atrophy (GA), an advanced form of dry age related macular degeneration (AMD). However, our understanding of RPE migration and epithelial-to-mesenchymal transition (EMT) in AMD is limited.The purpose of this study is to determine if RPE migration is associated with EMT and if there is increased expression of EMT markers in RPE-choroid complex of GA subjects compared to aged control human subjects.
Cryosections from GA and aged control subjects were processed for immunohistochemistry and imaged using a Zeiss confocal microscope. RPE migration was observed in neighboring sections by periodic acid-schiff-hematoyxylin (PAS-H) staining. Localization of various EMT markers in RPE-choroid complex was observed by immunofluorescence. These markers included cytoskeletal proteins such as N- cadherin (cell-cell adhesion), vimentin (intermediate filament), β catenin (EMT modulator that detaches from cell membrane and translocates into nucleus affecting cell migration related gene expression ), α-smooth muscle actin (α-SMA-myofibroblast marker), transcription factors that repress E-cadherin and induce EMT such as Zeb1 and SNAIL, Sox2 (binds to SNAIL and SLUG), enzymatic EMT inducers such as matrix metallo protease MMP2 (degrades extracellular matrix components), Endoglin/CD105 (TGFβ receptor and EMT modulator) and fibroblast specific protein 1 (FSP-1- EMT fibroblast marker).
PAS-H staining demonstrated migration of RPE from Bruchs membrane (BrMb). RPE cells were present in various shapes and sizes throughout retina, a characteristic feature of EMT. Normal RPE did not show these changes. Most of the EMT markers were expressed in migrating RPE and in drusen. FSP1 and Sox 2 were expressed in RPE basement membrane adjacent to drusen. MMP2 and β catenin were observed in drusen and choroidal cells. Migrating RPE cells expressed Zeb1 and SNAIL. Endoglin was expressed at the base of some drusen. Vimentin expression was significantly increased in drusen, basement membrane around drusen, choroidal stroma and several choroidal cells. N-cadherin expression was expressed in RPE around drusen .
Our data suggest migration of RPE cells from BrMb and increased expression of several EMT markers in RPE-choroid complex in GA subjects compared to aged control human subjects.
This is a 2020 ARVO Annual Meeting abstract.
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