2 research outputs found
Anatomie de la rétine
La neurorĂ©tine est une unitĂ© fonctionnelle du systĂšme nerveux central assurant la conversion dâun signal lumineux en un influx nerveux. Dâorigine neuroectodermique, dĂ©rivĂ©e du diencĂ©phale, la neurorĂ©tine est un tissu stratifiĂ©, composĂ© de six types de cellules neuronales (deux types de photorĂ©cepteurs : les cĂŽnes et les bĂątonnets ; les cellules horizontales, bipolaires, amacrines et ganglionnaires) et de trois types de cellules gliales (les cellules gliales de MĂŒller, les astrocytes et les cellules microgliales). La neurorĂ©tine repose sur lâĂ©pithĂ©lium pigmentaire rĂ©tinien, lâensemble constituant la rĂ©tine. Lâexistence des barriĂšres hĂ©mato-rĂ©tiniennes interne et externe et des jonctions intra-rĂ©tiniennes rend compte de la finesse de la rĂ©gulation des Ă©changes de la rĂ©tine avec la circulation et au sein de la rĂ©tine elle-mĂȘme. La zone centrale de la rĂ©tine humaine, la macula, zone hautement spĂ©cialisĂ©e pour assurer lâacuitĂ© visuelle, prĂ©sente des spĂ©cificitĂ©s anatomiques. Les mĂ©thodes dâimagerie rĂ©centes permettent dâenrichir nos connaissances sur les caractĂ©ristiques anatomiques et fonctionnelles de la rĂ©tine, qui restent encore imparfaitement dĂ©crites
Pathogenic Effects of Mineralocorticoid Pathway Activation in Retinal Pigment Epithelium
International audienceGlucocorticoids are amongst the most used drugs to treat retinal diseases of various origins. Yet, the transcriptional regulations induced by glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) activation in retinal pigment epithelium cells (RPE) that form the outer bloodâretina barrier are unknown. Levels of endogenous corticoids, ligands for MR and GR, were measured in human ocular media. Human RPE cells derived from induced pluripotent stem cells (iRPE) were used to analyze the pan-transcriptional regulations induced by aldosteroneâan MR-specific agonist, or cortisol or cortisol + RU486âa GR antagonist. The retinal phenotype of transgenic mice that overexpress the human MR (P1.hMR) was analyzed. In the human eye, the main ligand for GR and MR is cortisol. The iRPE cells express functional GR and MR. The subset of genes regulated by aldosterone and by cortisol + RU-486, and not by cortisol alone, mimics an imbalance toward MR activation. They are involved in extracellular matrix remodeling (CNN1, MGP, AMTN), epithelialâmesenchymal transition, RPE cell proliferation and migration (ITGB3, PLAUR and FOSL1) and immune balance (TNFSF18 and PTX3). The P1.hMR mice showed choroidal vasodilation, focal alteration of the RPE/choroid interface and migration of RPE cells together with RPE barrier function alteration, similar to human retinal diseases within the pachychoroid spectrum. RPE is a corticosteroid-sensitive epithelium. MR pathway activation in the RPE regulates genes involved in barrier function, extracellular matrix, neural regulation and epithelial differentiation, which could contribute to retinal pathology