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Emily L. Hughes, John G. Browne, Deborah M. Wallace, John K. Crean, Colm J. O'Brien; The Retinal Pigment Epithelial Cell: Potential Mediator of Lamina Cribrosa Extracellular Matrix Remodelling and Optic Disc Cupping in Glaucoma?. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2826.
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© ARVO (1962-2015); The Authors (2016-present)
There is a well established link between peripapillary atrophy (PPA) and glaucoma, but it’s aetiology is unknown. Histologically, the beta zone- that adjacent to the optic disc, is bare of retinal pigment epithelial (RPE) cells. Epithelial cells in other organs have been shown to differentiate to a fibroblast-like phenotype through the process of epithelial to mesenchymal transition (EMT) in response to a variety of stimuli in vitro, including stretch, hypoxia and transforming growth factor beta (TGFß), a growth factor known to be elevated in the optic nerve head in glaucoma. The purpose of this work is to examine the possibility that these stimuli may induce EMT in the RPE cell, thus inferring a potential role for PPA in lamina cribrosa extracellular matrix (ECM) remodelling and optic disc cupping.
The human retinal pigment epithelial cell line, ARPE-19, was treated with TGFß, (10ng/ml) and connective tissue growth factor (CTGF, 25ng/ml) in serum free media. Post-treatment analysis included real time polymerase chain reaction (qPCR), western blotting, microarray analysis and immunocytochemistry. Results were considered to be significant (p<0.05).
Treatment of ARPE-19 cells in culture with TGFß or CTGF induced an EMT change from a cobblestone morphology to a more elongated swirl pattern indicating a mesenchymal phenotype. Western blot analysis and immunofluorescence of cells post-treatment showed a loss of epithelial markers (Zona Occludins-1), and a gain of mesenchymal markers (alpha smooth muscle actin and vimentin). There was also an increased migratory ability of the cells on scratch assay. Microarray analysis and differential gene expression analysis demonstrated an upregulation of genes associated with cytoskeletal structure and motility, and downregulation of genes associated with cell adhesion (p<0.05). This was further confirmed by qPCR.
ARPE-19 cells were shown to change from an epithelial to a mesenchymal phenotype after exposure to glaucoma-like stimuli in-vitro. This transdifferentiation to a fibroblast-like cell indicates a potential role for the RPE cell in the ECM remodelling of the lamina cribrosa seen in glaucoma. Possible therapeutic benefit may arise from the role of EMT inhibitors in this process.
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