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Tomas L. White, Ula V. Jurkunas; UV-A irradiation and 4-hydroxyestradiol induce endothelial-mesenchymal transition in human corneal endothelial cells. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2269.
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Fuchs endothelial corneal dystrophy (FECD) is an age-related and female predominant disorder. Given that endothelial-mesenchymal transition (EMT) has recently been implicated in the pathogenesis of FECD, the aim of this study was to investigate whether oxidative stress and estrogen metabolism, induced by UV-A light and 4-hydroxyestradiol (4-OHE(2)) respectively, cause EMT during rosette formation in human corneal endothelial cells (HCEnCs).
Immortalized HCEnCs were cultured until 90% confluency, before being subjected to varying fluences of UV-A light, using a fluorescent UV-A broadband lamp, followed by a recovery period of up to 24 hours in reduced serum opti-MEM. Additionally, HCEnCs were treated with 4-OHE(2) for 24 hours, with and without prior UV-A irradiation. Cellular morphology was observed using phase-contrast microscopy, cell viability assessed with trypan blue dye exclusion assay, and gene expression analysis carried out using RT-PCR. Statistical significance was assessed using one-way ANOVA with Tukey's post-hoc test.
UV-A irradiation of HCEnCs resulted in characteristic FECD rosette formation, with junctional disruption, loss of hexagonality, and the formation of elongated cellular processes. These morphological changes were more severe following longer post-UV-A recovery times, and were mirrored by a sequential increase in Snail1 expression. 4-OHE(2) treatment produced similar morphological changes, which were enhanced when combined with UV-A light, resulting in reduced cell viability. UV-A irradiation (25j/cm2 with 24 hours recovery) caused an upregulation in markers associated with EMT (fibronectin, vimentin, COL4A1; p < 0.05) and FECD (clusterin, TGFβI; p < 0.05). A combination of both UV-A and 4-OHE2 potentiated Snail1, clusterin, and TGFβI expression (p < 0.01) compared to UV-A light alone.
In response to UV-A-light and 4-OHE(2)-induced oxidative stress, HCEnCs undergo morphological changes that mirror those seen in FECD. Furthermore, UV-A light irradiation induced EMT, which was enhanced by 4-OHE2, as seen by the upregulation of Snail1, the main transcriptional modulator of EMT. Given that the corneal endothelium is exposed to a lifetime of direct sunlight, and that FECD is a female predominant disorder, these findings suggest that there is interplay between UV-A irradiation and estrogen metabolism in FECD pathogenesis.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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