What does retinal pigment epithelium mean?
The retinal pigment epithelium (RPE) is a single layer of post-mitotic cells, which functions both as a selective barrier to and a vegetative regulator of the overlying photoreceptor layer, thereby playing a key role in its maintenance.
What causes pigmentation of the retina?
retinal pigmentation
- Stickler Syndrome, Type I. High myopia and vitreous degeneration dominate the ocular manifestations of Stickler syndrome, type I.
- Abetalipoproteinemia. ...
- Retinoschisis, Juvenile. ...
What is the retinal pigment epithelium (RPE) in the eye?
The role of the retinal pigment epithelium: Topographical variation and ageing changes
- Abstract. The retinal pigment epithelium (RPE) is a single layer of post-mitotic cells, which functions both as a selective barrier to and a vegetative regulator of the overlying photoreceptor layer, ...
- Author information. Correspondence to Mike Boulton.
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- About this article. Boulton, M., Dayhaw-Barker, P. ...
What is retinal pigment epithelial atrophy?
Retinal pigment epithelial atrophy. An extensive area of geographic, submacular pigment atrophy involves the entire posterior retina between the temporal retinal vascular arcades. The underlying choroidal vasculature is more prominent when the pigment epithelium is absent or atrophic.
What is the function of the retinal pigment epithelium?
The retinal pigment epithelium (RPE) is a monolayer of highly pigmented cells that form the outer blood–retina barrier and performs many critical functions that support photoreceptor health and integrity (reviewed in (Strauss, 2005)).
Where is vitamin A stored in the eye?
The retinal pigment epithelium (RPE) is considered to be the principal storage depot for vitamin A in the eye. The vitamin reaches this cell layer from two principal sources: (a) it flows in from the retina during light adaptation (Dowling, 1960 ), and (b) it is taken up from the blood ( Young and Bok, 1970; Hall and Bok, 1974 ), where it circulates as a 1:1 molar complex with retinol binding protein pre-albumin. The circulating vitamin that enters the pigment epithelial cell from the blood is in the form of the alcohol; yet, inside the cell, about 92% of it is in the ester form. Cell fractionation studies have shown that the principal storage site of retinyl ester in cattle RPE is in the microsomes ( Berman, Segal and Feeney, 1979 ). A second, smaller, storage pool for the ester in mammalian RPE appears to be lipid droplets in the cytoplasm ( Hirosawa and Yamada, 1976; Robison and Kuwabara, 1977; Berman and co-workers, 1979 ). On the other hand, unesterified retinol (vitamin A alcohol) of the RPE is localized exclusively in the soluble portion of the cell, all of it bound to cytosol retinol binding protein (MW ≃ 17,000). Metabolic transformations of these different forms of vitamin A within the RPE are poorly understood. We have recently confirmed the early observation of Krinsky (1958) showing a very active esterifying enzyme for retinol; it is concentrated mainly in the microsomes of the RPE cell ( Berman and co-workers, 1980 ). The present report describes three different aspects of retinol metabolism in bovine RPE which, taken together, suggest the possible existence of a vitamin A cycle in cattle RPE.
What is the function of Bruch membrane?
Bruch membrane in conjunction with the RPE plays a compartmental function between the retina and choroid, and this function is of vital importance because any defect in both layers can be a place to grow vessels from the choroid to the retina or vice versa.
What is the RPE cell?
Like choroid plexus cells, RPE cells (1) are in close apposition to many blood vessels, (2) are specialized for transmembrane transport, and (3) form the blood–cerebrospinal (or, in this case, blood-retinal) fluid barrier by tight junctions ( Fig. 16.6 ).
What is the role of EGCG in the retina?
Experiments have shown that EGCG plays a role in protecting irradiated cells against free-radical DNA damage.39 The protective effect of green tea polyphenols ...
What is the role of RPE cells in the cell cycle?
However, by re-entering the cell cycle, RPE cells can initiate proliferation and migration and induce the secretion of extracellular matrix proteins in diseases such as proliferative diabetic retinopathy, proliferative vitreoretinopathy, and AMD. 42.
What is the function of RPE?
One of the major functions of the RPE is the transport and recycling of retinoids. Following light exposure, photoreceptors must replenish 11-cis retinal, the chromophore required for light detection. This process takes place via a series of enzymes that are expressed by the RPE.