Role of corticoids in retinal pigment epithelium physiopathology

Abstract

Purpose : Corticoids bind to glucocorticoid (GR) and mineralocorticoid receptor (MR), both expressed in the RPE but the transcriptional regulations induced by corticoids have not been fully explored.
The purposes are: - to analyzed corticoids-induced transcriptional regulations in human RPE derived from iPS (iRPE), - to measure corticoids in human ocular media, - to analyze the retinal phenotype of P1hMR mice that over express human MR.

Methods : GR and MR expression was analyzed in iRPE cells and corticoid-induced nuclear translocation was quantified. Corticoids were measured in human ocular media using a liquid chromatography-tandem mass spectrometry. iRPE cells were exposed to aldosterone, the MR-specific agonist, cortisol and cortisol + RU-486, a direct GR antagonist . Transcriptomic analysis identified genes differentially regulated at 24 hrs after stimulations. Validation was performed by RT-PCR, western-blots and immunohistochemistry. In order to evaluate the biological consequence of MR overactivation in the retina, the retinal phenotyping of mice overexpressing the human MR (P1hMR) was analyzed.

Results : iRPE cells stably express functional MR and GR. They do not produce or metabolize corticoids. In human aqueous humor and vitreous, cortisol and cortisone were measured at salivary levels but aldosterone was detected, suggesting that cortisol activates GR and MR in RPE cells. Genes regulated similarrly by aldosterone and by cortisol + RU-486 represent MR activated genes. They encodes proteins involved in extracellular matrix remodeling, epithelia-mesenchymal transition (EMT) and RPE cell migration (Itgb3, Plaur and Fosl1), immune balance (Tnfsf18, Ptrx3), and in RPE phagocytosis (Mrp3, Gfra2, Ptrx3). Down-regulated genes (Cnn1, Mgp, Amtn) encodes proteins involved in extracellular matrix remodeling and choroid innervation.
P1hMR mouse showed choroidal vasodilation, elongation of photoreceptors outer segments, focal alteration of the RPE/ choroid interface, migration of RPE cells and focal choroidal excavations, mimicking human pachychoroid phenotype

Conclusions : The human RPE is a mineralo-sensitive epithelium. Activation of MR pathway in the RPE induces the regulation of genes involved in RPE differentiation, immune regulation, synaptic transmission and angiogenesis, and extracellular matrix remodeling. P1hMR mouse confirmed the pathogenic role of MR overactivation and its possible link with pachychoroid epitheliopathy.

This is a 2021 ARVO Annual Meeting abstract.