The Retinal Pigment Epithelium Chemical Composition and Structure

Investigative ophthalmology 10/1974; 13(9):675-87.
Source: PubMed

ABSTRACT Chemical and morphologic studies were carried out on bovine retinal pigment epithelial (RPE) cells that were free of contamination by outer segments or other tissues. Both melanotic and amelanotic cells were present, the latter originating from areas overlying the tapetum lucidum. Cells near the tapetum lucidum contain large melanolysosomes suggesting that melanin produced in this marginal area is destroyed by autophagy. Otherwise, bovine RPE cells resemble those of other species. The protein content of RPE was somewhat lower than that of whole retina, and both in turn contained less than half of that in rat liver. RPE has about the same lipid content as whole retina and in both tissues, 55 to 60% of the total lipids are phospholipids. While both phosphatidyl ethanolamine and phosphatidyl choline (PC) were readily identified in retina and liver, only PC could be detected in pigment cells. The fatty acids of RPE phospholipids consisted of 16:0 (31%), 20:4 (17%), and 18:0, 18:1, and 18:2 (each approximately 14%). Long chain polyenoates such as 22:5 and 22:6, which comprise a major portion of retinal phospholipid fatty acids were not clearly detectable in RPE. The content of retinol plus retinyl ester in pigment cells was 1.9 μg per eye, or 481 μg per g of wet tissue. The latter value is about 5 times higher than bovine liver and 70 times higher than whole retina. The DNA content of RPE is about the same as that of whole retina, and both are approximately 3 times higher than liver. Cytophotometric analyses showed, however, that RPE nuclei are diploid.

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    • "Lipofuscin is a heterogeneous material composed of a mixture of lipids and different fluorescent compounds, the main fluorophore of which has been identified as the pyridinium bis-retinoid, N -retinylidene-N -retinylethanolamine (A2E), a derivative of vitamin A. RPE lipofuscin is unique because it originates mainly from the phagocytosed photoreceptor outer segments as was demonstrated in early studies. For instance, analysis of the chemical composition of RPE cells revealed that it is different from the photoreceptor outer segments (Berman et al 1974). In addition, investigations undertaken on the Royal College of Surgeons (RCS) rats showed that in this strain, which fails to phagocytose shed outer segments, lipofuscin is significantly diminished (Katz et al 1986; Eldred and Lasky 1993). "
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    ABSTRACT: As the retinal pigment epithelium (RPE) ages, a number of structural changes occur, including loss of melanin granules, increase in the density of residual bodies, accumulation of lipofuscin, accumulation of basal deposits on or within Bruch's membrane, formation of drusen (between the basal lamina of the RPE and the inner collagenous layer of Bruch's membrane), thickening of Bruch's membrane, microvilli atrophy and disorganization of the basal infoldings. Although these changes are well known, the basic mechanisms involved in them are frequently poorly understood. These age-related changes progress slowly and vary in severity in different individuals. These changes are also found in age-related macular degeneration (AMD), a late onset disease that severely impacts the RPE, but they are much more pronounced than during normal aging. However, the changes in AMD lead to severe loss of vision. Given the many supporting functions which the RPE serves for the retina, it is important to decipher the age-related changes in this epithelium in order to understand age-related changes in vision.
    Clinical ophthalmology (Auckland, N.Z.) 07/2008; 2(2):413-24. DOI:10.2147/OPTH.S2151
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    • "Infirmary, Glasgow G1l 6NT Fig. 1 The optic cup in a human embryo to show acquiredjuxtaposition of anterior and posterior hemispheres of the optic vesicle systems needed to produce pigment, so that embryonic synthesis of pigment may be a once-for-all event on this tissue (Feeney, 1973b, Berman et al., 1974). "
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    ABSTRACT: The interdependence of the outer retina and pigment epithelium is illustrated by the functional changes and structural alterations which occur in each in response to choroidal ischaemia, retinal detachment, vitamin A deficiency, and other causes. The pluripotential role of the pigment epithelium is stressed, particularly in relation to the phagocytosis of outer segment material and the ability of this layer to undergo metaplasia into a variety of different cell types. Similarities of all disturbances of the retinal-pigment epithelial interface to retinitis pigmentosa are pointed out, and the significance of the findings in relation to this disease is discussed.
    British Journal of Ophthalmology 03/1979; 63(2):71-84. DOI:10.1136/bjo.63.2.71 · 2.98 Impact Factor
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    ABSTRACT: The effects of vitamins E and A derivatives on proliferation and migration of fibroblasts in cell culture were compared. In vitro wound repair was determined. Treatment was divided by group: 0.1% ethanol (group 1), α-tocopherol succinate (50 μM) dissolved in ethanol (final concentration 0.1%; group 2), and 13-cis retinol (10 μM; group 3). There were no differences among the groups within the first 24 hours. At 48 hours, α-tocopherol succinate demonstrated inhibitory effects on wound repair.
    Annals of Ophthalmology 06/2002; 34(2):108-112. DOI:10.1007/s12009-002-0037-1 · 0.17 Impact Factor
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