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PubMed1996

Influence of a retinal pigment epithelial cell factor(s) on rat retinal progenitor cells.

Retinal development was studied by explant culture of retinas from embryonic and neonatal rats in response to medium conditioned (CM) by a transformed neonatal rat retinal pigment epithelial (tnrRPE) cell line. Retinal explants from embryonic days 16 and 18 and postnatal day 2 Long-Evans rats were cultured for over 3 weeks on a poly-D,L-ornithine-coated surface in RPE-CM only, 10% serum or a serum-free defined medium. By 2 days in vitro, round cells were seen emerging from both embryonic and neonatal retinal explants grown in tnrRPE-CM. With extended time in culture, these round cells had increased in number and were seen in large confluent clusters adjacent to the explants. After 2 weeks in culture, some of these cells had undergone a morphological differentiation as shown by process formation. Insignificant numbers of these same cells were seen in explant cultures grown in 10% serum or serum-free defined medium. When isolated and subcultured, approx. 80% of the round cells from embryonic and neonatal rat retinal explants were densely immunolabeled for opsin and arrestin, both photoreceptor cell markers and neuron-specific enolase, a marker for mature neurons. Cellular retinaldehyde-binding protein, a Müller cell marker, immunolabeled approx. 30% of the cells from embryonic and neonatal rat retinal explants. In addition, nestin, an intermediate filament protein found only in neuroepithelial cells, was present in approx. 70% of the embryonic cells, but in only less than 1% of the neonatal cells. Based on this immunocytochemical characterization, these round cells are termed retinal progenitor cells and because of their mitogenic capacity under these in vitro conditions, these cells appear to possess stem cell characteristics. Moreover, in a 3-day bioassay, tnrRPE-CM caused a twofold and greater increase in harvested progenitor cells from both neonatal and embryonic explants, while cell numbers in control and growth factor-supplemented cultures showed no increase above the initial plating density. In these studies, CM from cultures of transformed neonatal rat RPE cells promoted the production, survival, proliferation and maturation of retinal progenitor cells from neonatal and embryonic rat retinal explants.

Animals↗
PubMed1984

Hyperosmolarity response of ocular standing potential as a clinical test for retinal pigment epithelium activity. Rhegmatogenous retinal detachment.

The hyperosmolarity response of the ocular standing potential was recorded in unilateral rhegmatogenous retinal detachment (8 eyes) and in the fellow 'healthy' eye (8 eyes). The hyperosmolarity response was greatly suppressed (M-4 SD: M and SD indicate respectively the mean and the standard deviation in normal subjects) in all affected eyes (p less than 0.005), and slightly abnormal in 2 fellow eyes. The L/D ratio was normal in 2 affected eyes and in all fellow eyes. The hyperosmolarity response in the affected eyes was still greatly suppressed 14 months after successful surgical treatment.

Adolescent↗
PubMed1996

Retinal pigment epithelial debridement as a model for the pathogenesis and treatment of macular degeneration.

PURPOSE: To determine the effects of the absence of the retinal pigment epithelium on the choriocapillaris and outer retina by performing retinal pigment epithelial cell debridement with mitomycin C to inhibit cell proliferation pharmacologically in the porcine eye. METHODS: A pars plana vitrectomy was performed in 12 eyes, and two neurosensory retinal detachments per eye were created by injecting 10(-3) mg/ml mitomycin C and 0.25% edetic acid into the subretinal space. Twenty minutes later, the retinal pigment epithelium was debrided, and the retina was reattached with a fluid-gas exchange. RESULTS: Bruch's membrane was devoid of native retinal pigment epithelium, and the choriocapillaris was patent immediately after debridement. No proliferation of the retinal pigment epithelium occurred 1 week after debridement, and choriocapillaris atrophy was present beneath areas of Bruch's membrane that were devoid of retinal pigment epithelium. Four weeks postsurgery, choriocapillaris atrophy persisted in all debrided blebs, although unpigmented retinal pigment epithelium repopulated portions of Bruch's membrane in one of three blebs. Outer retinal atrophy was present in areas of Bruch's membrane with no retinal pigment epithelium and no choriocapillaris 4 weeks postsurgery. The choriocapillaris was patent in areas of mitomycin C injection without debridement. CONCLUSION: Absence of the retinal pigment epithelium leads to atrophy of the choriocapillaris within 1 week after surgery. This finding provides an animal model to study transplantation of retinal pigment epithelium onto bare patches of Bruch's membrane in age-related macular degeneration and other diseases and provides insight into the pathogenesis of nonexudative age-related macular degeneration.

Animals↗
PubMed1999

Successful cotransplantation of intact sheets of fetal retina with retinal pigment epithelium.

PURPOSE: Many retinal diseases, such as macular degeneration, affect both retinal pigment epithelium (RPE) and photoreceptors. Therefore, retinal repair may require transplantation of both tissues together as a cograft. METHODS: As recipients of retina-RPE cografts, 7- to 10-week-old albino Royal College of Surgeons rats that lose their photoreceptors because of a pigment epithelium defect were used. Freshly harvested intact sheets of RPE with neural retina from pigmented normal rat fetuses were gel embedded for protection and transplanted into the subretinal space. RESULTS: After 6 to 7 weeks, with the support of the cografted RPE sheet, transplanted photoreceptors developed fully in organized parallel layers in the subretinal space. Immunohistochemistry for rhodopsin, rod alpha-transducin, and S-antigen and peanut agglutinin labeling for cone interphotoreceptor matrix domains suggested that the photoreceptors in the graft were capable of normal function. CONCLUSIONS: Freshly harvested intact sheets of fetal RPE and retina, transplanted together into the subretinal space, can develop a normal morphology. Such transplants have the potential to benefit retinal diseases with dysfunctional RPE and photoreceptors.

Animals↗
PubMed1990

Pigmented lesions of the retinal pigment epithelium and familial adenomatous polyposis.

Bilateral pigmented fundus lesions were found in 65 out of 72 patients with familial adenomatous polyposis, an additional five patients having unilateral lesions. With a family history of familial adenomatous polyposis, the occurrence of multiple bilateral fundus lesions indicates the presence of the abnormal gene, as does the occurrence of oval pigmented lesions with surrounding pale haloes. The absence of pigmented fundus lesions does not exclude the abnormal genotype, while the presence of occasional pigmented spots can be found in an appreciable percentage of the population. Ocular examination would, however, appear to be valuable in screening those at risk, with a positive yield in most carriers of the gene for familial adenomatous polyposis.

Adenomatous Polyposis Coli↗
PubMed1998

Verapamil inhibits proliferation, migration and protein kinase C activity in human retinal pigment epithelial cells.

The effects of three calcium channel blockers, verapamil, diltiazem and nifedipine, were examined on in vitro proliferation and migration of human retinal pigment epithelial cells. Human retinal pigment epithelial cells were seeded in Dulbecco's modified essential medium with 10% fetal bovine serum and different concentrations of the three calcium channel blockers. After 3 days of treatment, cell proliferation was determined by cell counting and by [3H]-thymidine uptake. Cell viability was determined with trypan blue exclusion. For determination of cell migration, retinal pigment epithelial cells were grown to confluence and then growth-inhibited with mitomycin C. After a 3 mm zone was denuded, the cells were treated with different concentrations of the calcium channel antagonists. After 24 hr, the cells that had migrated over the wound edge were counted. To determine the involvement of protein kinase C in the verapamil effect, its activity was measured in both verapamil-treated and untreated cells. Verapamil dose dependently inhibited serum-induced proliferation of retinal pigment epithelial cells, when measured by cell number (IC50 14.6 microM) or [3H]-thymidine incorporation (IC50 11.3 microM). At concentrations of 15 microM and below, there was no effect on cell viability, as determined by morphology and trypan blue exclusion. Diltiazem inhibited cell proliferation at a concentration of 100 microM; however, 100 microM nifedipine had no effect. Verapamil showed a significant inhibition of serum-induced migration in the range of 10 microM to 0.1 microM. The IC50 of the inhibition of retinal pigment epithelial cell proliferation and migration by verapamil is significantly higher than that seen for effects on calcium channel blockage. Eight micromolar verapamil reversibly inhibited total protein kinase-C activity in retinal pigment epithelial cells suggesting the possibility that the drug may act by inhibiting the protein kinase-C pathway. These data suggest the potential of the calcium channel blocker verapamil as a pharmacological modulator of disorders such as proliferative vitreoretinopathy in which there is increased retinal pigment epithelial cell proliferation and migration.

Calcium Channel Blockers↗
PubMedDate not supplied

Endophotocoagulation to retinal pigment epithelium as an adjuvant therapy in the management of retinal detachment caused by a highly myopic macular hole.

Retinal detachment secondary to a highly myopic macular hole remains a particular surgical challenge. Pars plana vitrectomy, endophotocoagulation at the base of a macular hole in conjunction with fluid-gas exchange was performed in 4 consecutive patients with a mean refraction of -13.8D (range, -8D-(-)18D). Mean axial length was 27.5 mm (range, 26.0-29.0 mm). Mild atrophy of the retinal pigment epithelium was present in 3 patients while 1 patient had moderate atrophy. The mean follow-up period was 12 months (range, 6-18 months). The overall primary anatomical success rate was 75%. All 3 eyes with mild retinal pigment epithelium atrophy had retinal reattachment after one operation.

Adult↗
PubMed1998

Morphogenesis of the retinal pigment epithelium: toward understanding retinal degenerative diseases.

The phenotype of an epithelial cell is defined by a unique combination of morphology, gene and protein expression, and protein localization. Results indicate that the terminal differentiation of the RPE cell can be described in part by changes in the polarity of its surface proteins alpha v beta 5 integrin, Na,K-ATPase, N-CAM, and EMMPRIN. Changes in protein/gene expression and protein localization in late stages of RPE development identify alpha v beta 5 integrin as a key player in RPE phagocytosis, and N-CAM and EMMPRIN as potentially important molecules in other RPE functions necessary for photoreceptor survival. By studying the trafficking of the later two proteins it is shown that entry into an apical or basolateral pathway in RPE cells cannot be predicted by the distribution of a given protein in other epithelial cells, and that this distribution may change through the course of RPE development. The mechanisms used by RPE and other epithelia to establish and maintain their specific polarity properties are fundamental to the formation and maintenance of their specific epithelial phenotype. The ability to therapeutically direct molecules incorporated into RPE by gene therapy into apical or basal surfaces requires an understanding of protein localization and expression. Furthermore, evidence is provided that assays capitalizing on changes in gene/protein expression and protein localization during the late stages of RPE development can prove a productive way of identifying proteins used by RPE for photoreceptor support. This approach can continue to be exploited to identify other proteins essential for the mission of the RPE cell, that may thus be likely candidates for participation in retinal degenerative disease.

Aging↗
PubMed2000

Retinal pigment epithelial autotransplantation: morphological changes in retina and choroid.

BACKGROUND: Replacement of degenerating retinal pigment epithelial (RPE) cells has been proposed to promote photoreceptor survival in retinal pigment epithelial disease. However, allografts of RPE have a higher rate of immunological rejection. The investigators studied the effects of autotransplantation of RPE on the morphological changes in photoreceptors and choriocapillaris. METHODS: RPE autotransplantation (wound type 1) was performed in 25 rabbits and compared with wounds following debridement of the RPE (wound type 2). Light and electron microscopy and scanning electron microscopy of choroidal vascular casts were performed at 3, 7, 14 and 30 days after surgery. Quantitative analysis of the choriocapillaris bed area was performed by automated image analysis and the results were analyzed by paired Student's t-test. RESULTS: Retinal pigment epithelium was found to be monolayered and ill-differentiated at day 7. Differentiation occurred at day 30, with preservation of photoreceptors and other layers of the neurosensory retina in type 1 wounds. Type 2 wounds showed atrophy of the regenerating retinal pigment epithelium at day 14 and day 30 with loss of overlying photoreceptor cell layer. There was significant choriocapillaris regeneration in type 1 wounds compared to the type 2 wounds at day 7 (P=0.045), day 14 (P=0.028) & day 30 (P=0.06). CONCLUSIONS: Retinal pigment epithelial autotransplantation significantly reduced photoreceptor degeneration and choriocapillaris atrophy associated with loss of retinal pigment epithelium. This procedure supports the hypothesis that RPE autotransplantation may be helpful in geographic atrophy and conditions requiring submacular surgery.

Animals↗
PubMed1977

Defective phagocytosis of isolated rod outer segments by RCS rat retinal pigment epithelium in culture.

Retinal pigment epithelium cultured from normal rats phagocytizes large amounts of rod outer segment fragments isolated from normal rats and from RCS rats with inherited retinal degeneration. Cultured RCS rat pigment epithelium rarely ingests outer segment material, although the cells extend cellular processes around fragments of either type. Both normal and RCS pigment epithelium phagocytize polystyrene spheres. This demonstrates that RCS rat pigment epithelial cells contain a defect in the mechanism for phagocytizing outer segments.

Animals↗
PubMed1989

DNA synthesis in human retinal pigment epithelium in organ culture.

Retinal pigment epithelium from human eyes was maintained in organ culture, and DNA synthesis was visualized by autoradiography of cultures exposed to labelled thymidine. In Ham's F10 medium, labelling of cells was observed after 7 as well as after 14 days in vitro. At both stages the labelled cells were characteristically located adjacent to areas of epithelial damage. Cells remote from such areas did not incorporate thymidine, This pattern was observed in epithelia removed from the posterior pole as well as from the periphery of the fundus. Several types of routine media and media with human as well as foetal bovine serum (FBS) were found to support DNA synthesis in the cultured epithelium, labelled cells were not observed in epithelium maintained in Ham's F10 without serum, or with low serum concentration. Our study demonstrates, that DNA synthesis does take place in organ cultured human retinal pigment epithelium when the appropriate culture conditions are used. Our findings indicate that induction of DNA synthesis in the cells is not promoted by an indiscriminate effect of the medium but related to the presence of epithelial damage.

Culture Media↗
PubMed1976

Retinal vascular changes in congenital hypertrophy of the retinal pigment epithelium.

The overlying retinal blood vessels were abnormal in five cases of congenital hypertrophy of the retinal pigment epithelium. This illustrated the well-recognized association between outer retinal degeneration and obliteration of the overlying retinal vasculature. The proposed pathophysiological mechanisms, however, seem inadequate to explain completely the morphological changes of the retinal blood vessels in the presence of atrophy of the outer retina.

Adult↗
PubMed2000

Acquired tumors arising from congenital hypertrophy of the retinal pigment epithelium.

BACKGROUND: Congenital hypertrophy of the retinal pigment epithelium (CHRPE) is widely recognized to be a flat, stationary condition. Although it can show minimal increase in diameter, it has not been known to spawn nodular tumor that is evident ophthalmoscopically. OBJECTIVES: To report 5 cases of CHRPE that gave rise to an elevated lesion and to describe the clinical features of these unusual nodules. METHODS: Retrospective medical record review. RESULTS: Of 5 patients with a nodular lesion arising from CHRPE, there were 4 women and 1 man, 4 whites and 1 black. Three patients were followed up for typical CHRPE for longer than 10 years before the tumor developed; 2 patients were recognized to have CHRPE and the elevated tumor concurrently. Visual acuity was decreased in 3 patients, mainly due to cystoid macular edema. The tumor was located between the equator and ora serrata in all 5 patients. There was no predilection for quadrant of the fundus. The flat part of the lesion was black and had visible lacunae in all 5 patients. The CHRPE ranged in basal diameter from 3 x 3 mm to 13 x 11 mm. The size of the elevated lesion ranged from 2 x 2 x 2 mm to 8 x 8 x 4 mm. The nodular component in all cases was supplied and drained by slightly prominent, nontortuous retinal blood vessels. Yellow retinal exudation occurred adjacent to the nodule in all 5 patients and 1 patient developed a secondary retinal detachment. Two tumors that showed progressive enlargement, increasing exudation, and progressive visual loss were treated with iodine 125-labeled plaque brachytherapy, resulting in deceased tumor size but no improvement in the visual acuity. CONCLUSIONS: Congenital hypertrophy of the retinal pigment epithelium can spawn a nodular growth that slowly enlarges, attains a retinal blood supply, and causes exudative retinopathy and chronic cystoid macular edema. Although no histopathologic evidence is yet available, we believe that the tumor probably represents either an acquired adenoma or a reactive proliferation of the retinal pigment epithelium. The best treatment of these lesions is not yet established.

Adenoma↗
PubMed1991

[Peripheral retinal streaks. Linear depigmentation of the peripheral retinal pigment epithelium].

An unusual peripheral depigmented streak lesion of the retina is described in three patients. This depigmented line is located in the equatorial region running parallel to the ora serrata and seems to result from a focal reduction or loss of pigmentation in the retinal pigment epithelium. Similar lesions have been reported as a symptom of the presumed ocular histoplasmosis syndrome (POHS) called linear streaks of the equator. As we did not find any additional symptoms of POHS in our patients, the aetiology of this peripheral depigmented streaks remains unclear.

Aged↗
PubMed1987

Dietary vitamins A and E influence retinyl ester composition and content of the retinal pigment epithelium.

Experiments were conducted to determine the influence of dietary levels of vitamin A and alpha-tocopherol on the amounts and composition of retinyl esters in the retinal pigment epithelium of light-adapted albino rats. Groups of rats were fed diets containing alpha-tocopherol and either no retinyl palmitate, adequate retinyl palmitate, or excessive retinyl palmitate. Other groups of rats received diets lacking alpha-tocopherol and containing the same three levels of retinyl palmitate. Retinoic acid was added to diets lacking retinyl palmitate. After 27 weeks, the animals were light-adapted to achieve essentially total visual pigment bleaches, and the neural retinas and retinal pigment epithelium-eyecups were then dissected from each eye for vitamin A ester determinations. Almost all of the retinyl esters were found in the retinal pigment epithelium-eyecup portions of the eyes, mainly as retinyl palmitate and retinyl stearate. Maintaining rats on a vitamin A-deficient, retinoic acid-containing diet led to significant reductions in retinal pigment epithelial retinyl ester levels in rats fed both the vitamin E-supplemented and vitamin E-deficient diets; contrary to expectations, the effect of dietary vitamin A deficiency was more pronounced in the vitamin E-supplemented rats. Vitamin A deficiency in retinoic acid-maintained animals also led to significant reductions in retinyl palmitate-to-stearate ester ratios in the retinal pigment epithelia of both vitamin E-supplemented and vitamin E-deficient rats. Excessive dietary intake of vitamin A had little, if any, effect on retinal pigment epithelial retinyl ester content or composition. Vitamin E deficiency resulted in significant increases in retinal pigment epithelial retinyl palmitate content and in palmitate-to-stearate ester ratios in rats fed all three levels of vitamin A, but had little effect on retinal pigment epithelial retinyl stearate content. In other tissues, vitamin E deficiency has been shown to lower vitamin A levels, and it is widely accepted that this effect is due to autoxidative destruction of vitamin A. The increase in retinal pigment epithelial vitamin A ester levels in response to vitamin E deficiency indicates that vitamin E does not regulate vitamin A levels in this tissue primarily by acting as an antioxidant, but rather may act as an inhibitor of vitamin A uptake and/or storage. The effect of vitamin E on pigment epithelial vitamin A levels may be mediated by the vitamin E-induced change in retinyl palmitate-to-stearate ratios.

Animals↗
PubMed1997

Indocyanine green videoangiography after acute retinal pigment epithelial tears in age-related macular degeneration.

PURPOSE: To determine the features of combined fluorescein and indocyanine green videoangiography after acute retinal pigment epithelial tears associated with age-related macular degeneration. METHODS: We performed combined fluorescein and indocyanine green videoangiography in three eyes of three patients 2 days to 2 months after the development of tears of the retinal pigment epithelium. RESULTS: The area of exposed choroid in a retinal pigment epithelial tear shows intense hyperfluorescence in fluorescein videoangiography; in contrast, this area demonstrates near-normal choroidal fluorescence on an indocyanine green videoangiogram. The folded and retracted flap of retinal pigment epithelium in a retinal pigment epithelial tear discloses marked hypofluorescence on the fluorescein videoangiogram; in contrast, this flap of retinal pigment epithelium displays varying degrees of hyperfluorescence on the indocyanine green videoangiogram. CONCLUSIONS: The angiographic differences between fluorescein and indocyanine green result from the distinct biophysical properties of these two dyes as well as from the differential penetration of their fluorescence through such pigmented structures as retinal pigment epithelium. Compared with fluorescein videoangiography, indocyanine green videoangiography allows better visualization of choroidal neovascular membranes within the rolled-up and retracted flap of the retinal pigment epithelial tear.

Acute Disease↗
PubMed2003

The effect of intraoperative retinal manipulation on the underlying retinal pigment epithelium: an experimental study.

PURPOSE: Retinal pigment epithelial changes described after vitreoretinal surgery may result from localized compression injury caused by intentional or inadvertent contact with vitreoretinal instruments. The authors evaluated these changes resulting from manipulation of the retina without frank retinal injury. METHODS: One eye each of six pigmented rabbits underwent surgery during which the inner retinal surface was touched at several points with a 20-gauge silicone-tipped subretinal fluid cannula without causing a retinal break or subretinal hemorrhage. The rabbits were followed-up with indirect ophthalmoscopy, fundus photography, and fluorescein angiography, and were killed at 1 hour, 1 week, or 2 weeks. Light microscopy was used for histopathologic evaluation. RESULTS: On fluorescein angiography, diffuse leakage noted at the injury sites significantly decreased by the fourth day and almost completely disappeared by the second week. Disruption of photoreceptor outer segments and retinal pigment epithelium in the early specimens, and irregular pigmentation, proliferation, and migration of the retinal pigment epithelium at 1 and 2 weeks were the prominent features on histopathologic examination. CONCLUSIONS: Intraoperative manipulation of the attached retina may cause significant pigment epithelium displacement and proliferation and varying degrees of disorganization of normal retinal architecture in the absence of clinically evident retinal breaks and subretinal hemorrhages.

Animals↗