Ultrastructural and immunocytochemical changes in retinal pigment epithelium, retinal glia, and fibroblasts in vitreous culture.

Retinal pigment epithelial (RPE) cells, retinal glial, and fibroblasts, three cell types believed to play a role in the pathogenesis of epiretinal membrane formation, were maintained in vitreous culture to determine the influence of vitreous on their ultrastructure and expression of cytokeratin, glial fibrillary acidic protein (GFAP), vimentin, and glutamine synthetase (GS). Using a highly sensitive, preembedding technique for the immunolocalization of these antigens at the ultrastructural level, most RPE cells were found to lose cytokeratin and vimentin within 1 day after seeding on irradiated vitreous. The percentage of keratin-positive cells then increased with time in culture. If the vitreous was placed on RPE cells cultured in monolayer instead of placing the cells on the vitreous, keratin and vimentin were expressed these intermediate filament proteins diminished with time. Glutamine synthetase was found in RPE cells grown in monolayer with or without a vitreous overlay, but not in RPE cells grown on the surface of vitreous. Retinal glial grown on vitreous showed a time-dependent decrease in the number of cells expressing GFAP and a corresponding increase in cells expressing vimentin or GS. Some fibroblasts in vitreous culture expressed vimentin but not the other antigens evaluated. A substantial number of cells in each culture did not stain positively for cytokeratin, GFAP, vimentin, or GS. All three cell types showed phenotypic diversity at the ultrastructural level with each cell type being capable of assuming the same morphologic appearance under certain conditions. These results demonstrate the phenotypic plasticity of RPE cells, retinal glia, and fibroblasts when grown in contact with vitreous and provide further evidence that neither ultrastructure, intermediate filament protein expression, nor the presence of GS is sufficient to determine the cell type of origin of cells in epiretinal membranes.     

Co-cultivation of retinoblastoma with fibroblasts, iris pigment epithelium, and retinal pigment epithelium in tissue culture

Retinoblastoma cells of the Y79 line were co-cultivated with human fibroblasts and bovine iris and retinal pigment epithelium in tissue culture. The Y79 cells, which characteristically grow as a suspension culture, were found to attach directly to the fibroblasts and pigment epithelium on the flask surface. Electron microscopic examination of the fibroblast-retinoblastoma co-cultures revealed numerous pinocytotic vesicles lining the fibroblast cell borders that were in contact with the tumor cells. The retinoblastoma cells contained increased numbers of ribosomes, endoplasmic reticulum, and-mitochondria. Fibroblastic processes appeared to wrap around and engulf tumor cells. In both the iris and retinal pigment epithelium co-cultures with retinoblastoma cells, there were increased numbers of mitochondria in the tumor cells in areas adjacent to pigment epithelium but no pinocytotic vesicles were seen. The pigment epithelium attached to Y79 cells showed fewer processes than did the fibroblasts in co-culture. In summary, both fibroblast and pigment epithelium functioned as an effective carrier cell layer for retinoblastoma cells. In addition, we believe that the fibroblast layer removed substances secreted by the tumor cells via pinocytotic vesicles.     

Alcohol dehydrogenase and retinol dehydrogenase in bovine retinal pigment epithelium.

An NAD dependent alcohol dehydrogenase isolated from cytosol of bovine retinal pigment epithelium and catalysing ethanol oxidation, plays no role in the retinol-retinene interconversion.High retinol-retinene oxidoreductase activity was found in subcellular fractions of retinal pigment epithelium. This NADP-NADPH linked oxidoreductase, was extracted by sonication from mitochondria and microsomes and some catalytic properties were examined.The possible physiological significance of this enzyme in the metabolism of retinol and retinene in the pigment epithelium may be deduced by considering the participation of the pigment epithelium with regard to degradation of rod outer segments (ROS); the enzyme could be so located as to facilitate the reduction of the retinene, released by rhodopsin of phagocytosed ROS.Other physiological roles are discussed.     

Ascorbate peroxidase in bovine retinal pigment epithelium and choroid

Peroxidase, catalyzing hydrogen peroxide reduction concurrent with ascorbate oxidation, was demonstrated in the extract of retinal pigment epithelium and choroid. The peroxidase in the choroid, RPE, and retina are 236.1, 25.1, and 0.5 units/mg protein respectively. Ammonium sulfate fractionation and high pressure liquid chromatography showed that the peroxidase in the RPE-choroid is associated with a group of heme proteins with absorption maxima at 410 nm, and optimal activity at pH 4.5. The high peroxidase activity in the RPE-choroid explains the observation of dehydroascorbate in these tissues and indicates a possible role of this enzyme in the removal of H2O2.     

Efficient gene transfer to retinal pigment epithelium cells with long-term expression

PURPOSE: To evaluate the safety and efficiency of feline immunodeficiency virus (FIV) vectors for gene delivery into the mammalian retina. METHODS: A first-generation FIV vector was constructed and administered into rabbit eyes at two different concentrations by intravitreal or subretinal routes. A second-generation FIV vector was also constructed and administered subretinally into both rabbit and rat eyes at the same concentration. After vector administration, eyes were monitored using slit-lamp biomicroscopy, indirect ophthalmoscopy, fundus photography, and electroretinogram. After the rabbits were killed, eye tissues were processed for light microscopy and immunohistochemical analysis. RESULTS: Administration of both first- and second-generation FIV vectors produced transient vitritis and/or papillitis in rabbits, without other pathologic abnormalities. Retinal pigment epithelium (RPE) cells were the predominant cell type transduced in rabbit eyes, but ganglion cells and Muller cells were also transduced. Transduction was confined to the retinal bleb area. The second-generation FIV vector transduced RPE cells much more efficiently than the first-generation vector (95% vs. 4.5%, respectively; P = 0.0015) in rabbit eyes. In contrast, no toxicity was evident over a 24- to 25-month follow-up period after injection of the second-generation FIV vector into rat eyes. Tropism in the rat eye was similar, including RPE and ganglion cells, and the RPE transduction rate was also high (50%). Transgene expression was persistent in both species over the duration of the experiment. CONCLUSION: Second-generation FIV vectors can efficiently transfer genes into RPE cells with resulting long-term expression, properties potentially valuable to gene therapy approaches to some retinal diseases.     

bFGF对体外培养牛RPE细胞特异性吞噬功能的影响

目的:探讨碱性成纤维细胞生长因子(basicfibrob-lastgrowthfactor,bFGF)对体外培养牛视网膜色素上皮(retinalpigmentepithelium,RPE)细胞特异性吞噬功能的影响及实验方法的选择。方法:采用辣根过氧化物酶Ⅱ型(horseradishperoxi-diase,HRP)示踪法测定不同bFGF浓度及作用时间对体外培养单层牛RPE细胞吞噬HRT量的影响。结果:不同bFGF浓度及作用时间各组光吸收值差异均不显著。结论:bFGF对体外培养牛RPE细胞特异性吞噬功能无明显影响。     

UV irradiation causes multiple cellular changes in cultured human retinal pigment epithelium cells

Background The retinal pigment epithelium maybe causally involved in the development and progression of age-related macula degeneration; however, the mechanisms leading to the development of age-related macula degeneration remain largely unknown. The purpose of this study was to examine cellular changes in the retinal pigment epithelium induced by direct irradiation with UV light in culture.Methods Retinal pigment epithelium cells from post-mortem human retinas were used to obtain dissociated cultures with cells retaining the ability to differentiate in vitro. These cells were cultured over several days to weeks. The UV radiation (UV-A and UV-B) occurred under sterile conditions with a 100 HBO/mercury bulb attached to a dissecting microscope, delivering co-axial illumination. The time dependence of irradiation effects was analysed using morphometric, immunohistochemical, functional and apoptosis-detecting techniques.Results Vital and proliferating retinal pigment epithelium cell cultures could be prepared consistently. The cells showed tissue-specific morphologies in vitro for several days to weeks. Pigment epithelium-derived factor was detected in these cells using immunocytochemistry and Western blots. The UV irradiation but not white light resulted in measurable alterations of cell shape and size. The irradiated cells showed partial swelling and shrinkage reminiscent of progressing apoptotic degeneration. TUNEL staining revealed that apoptosis was induced by UV light, but not detectably by white light. The phagocytosis of fluorescent micro-particles diminished after irradiation. These effects were dependent on the duration of irradiation.Conclusions Cultures of retinal pigment epithelium are suitable and sensitive models to study cell damage and may contribute to unravelling the pathogenetic mechanisms of retinal degeneration.     

Demonstration of tyrosinase in the adult bovine uveal tract and retinal pigment epithelium.

Modern techniques offer an opportunity for a more complete evaluation of melanin production in the uvea and retinal pigment epithelium (RPE). By measuring the release of tritium from tritiated tyrosine in homogenized samples of adult bovine RPE as well as iris and choroid, tyrosinase activity could be demonstrated in both the uveal tract and the RPE. Phenylthiourea, a specific tyrosinase inhibitor, markedly decreased tyrosinase activity, whereas 3-iodo-tyrosine, a tyrosine hydroxylase inhibitor, had no effect. These techniques indicate tyrosinase activity in the uveal tract and the RPE of adult cattle. This is the first biochemical demonstration of tyrosinase in adult RPE.     

Experimental eye enlargement in mature animals changes the retinal pigment epithelium.

Form deprivation has been shown to result in myopia in a number of species such that the eye enlarges if one eye is permanently closed at the time of eye opening. In the quokka wallaby, the eye grows slowly throughout life. After form deprivation, the eye enlarges by 1-1.5 years of age to the size of that in a 4-6-year-old animal and the number of multinucleated retinal pigment epithelial (RPE) cells in the enlarged retina remains much lower than would be expected in eyes of comparable size. Here we have repeated the experiment but examined animals at 4 years of age. The sutured eye grew significantly larger than did its partner. Numbers of RPE cells were comparable between sutured and partner eyes but were lower than in normal animals of similar age. Reductions in RPE cell density were greater in nasal than in dorsal or ventral retina and were not seen in temporal retina. The distribution of multinucleated cells was quite different in the sutured and open eyes. As in normal eyes, partner eyes had most multinucleated cells in ventral retina, while in the sutured eyes such cells were located mainly in the far periphery. In conclusion, the RPE is significantly changed by the eye enlargement process. However, it is not known whether this change results from an active part played by the RPE in the retinal expansion process or whether the changes are simply a result of a passive increase in area of the RPE.     

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.     

Neoplasia versus hyperplasia of the retinal pigment epithelium. A comparison of two cases.

PURPOSE: To present the clinical and histopathological characteristics of two different tumor-like lesions of the retinal pigment epithelium (RPE). METHODS: Two cases of tumor-like lesions of the RPE were identified in the files of the Eye Pathology Institute. The clinical characteristics and the light- and electron microscopical morphology of the lesions were compared and the diagnoses were re-evaluated applying modern immunostainings. RESULTS: Clinically, both adenoma and tumor-like hyperplasia of the RPE may present with prominent retinal feeder arterioles. The lesions are hypofluorescent in the filling phases and have multiple hyperfluorescent zones in the late phase in fluorescein angiography. They show high internal reflectivity by A-scan and appear as solid tumors by B-scan ultrasonography. Histologically, the two presented lesions of the RPE are different. The first is an adenoma of the vacuolated subtype. The other lesion is a hyperplasia of the RPE disclosing a tubular morphology. The pathologically active cells in both cases were positive for the reaction with antibodies against: cytokeratin, NSE, vimentin, S-100, HMB-45, desmin and SMA. However, only the adenoma was sporadic melan-A positive. CONCLUSION: Adenomas and tumor-like hyperplastic lesions of the RPE are very rare lesions. They share many morphological and immunohistological characteristics. Of the presented cases only the RPE adenoma is sporadic melan-A positive.     

兔虹膜色素上皮细胞和视网膜色素上皮细胞血管内皮生长因子及其受体FLK-1 mRNA表达的对比研究

目的　研究血管内皮生长因子 (VEGF)及其受体 (FLK 1)mRNA在健康兔眼虹膜色素上皮 (IPE)细胞和视网膜色素上皮 (RPE)细胞中的表达特征 ,探讨IPE细胞代替RPE细胞用于自体移植治疗年龄相关性黄斑变性 (ARMD)及RPE异常相关疾病的可行性。方法　分离成年健康有色家兔的IPE细胞和RPE细胞 ,采用逆转录聚合酶链反应 (RT PCR)检测其VEGF及其受体FLK 1mRNA的表达情况。结果　兔眼IPE细胞和RPE细胞均可表达VEGF和FLK 1mRNA。IPE细胞的VEGF和FLK 1mRNA含量低于RPE细胞。IPE细胞的VEGFmRNA的表达量约为RPE细胞的 4 4 6 2 % ,FLK 1mRNA的表达量约为RPE细胞的 5 2 36 % ,差异均有显著意义 (P <0 0 0 1)。结论IPE细胞VEGF及其受体FLK 1mRNA的表达水平比RPE细胞低 ,IPE细胞代替RPE进行细胞移植可能更为有利。     

Localization of cellular retinal-binding protein in bovine retina and retinal pigment epithelium, with a consideration of the pigment epithelium isolation technique

Bovine RPE was isolated by commonly used brushout procedures and analyzed by light and electron microscopy. The preparation was found to consist almost entirely of cells with retained organelles (mitochondria, pigment, and other granules) but with broken surface membranes and extracted cytoplasm. In keeping with this, the wash obtained by sedimenting these broken cells contained approximately 97 percent of the cellular retinol-binding protein present in the suspension. Cellular retinoic acid-binding protein, present in bovine retinal extracts, was found in low amounts in the wash from RPE. The cellular retinol-binding protein present in the RPE wash was of high specific activity and similar in properties to that obtained from bovine retina. Supernatant obtained from sonicated rod outer segments contained approximately 10 percent of the retinol-binding protein of the retina. No retinoic acid-binding protein was found. The relatively large amount of cellular retinol-binding protein present in the RPE (more than is found in the retina) is consistent with a functional role of this protein in uptake and transport of retinol by the RPE.     

Drusen are associated with local and distant disruptions to human retinal pigment epithelium cells

Drusen are extra-cellular deposits that form between the retinal pigment epithelium (RPE) and Bruch's membrane (BM). Numerous and/or confluent drusen are a significant risk factor for age-related macular degeneration (AMD). Here, using whole mounted human RPE preparation we show that RPE cell morphology changes in association with drusen. These changes included an increase in cell size and distortion in the regularity of their distribution. Further, although binucleation is relatively rare in human RPE, there was a marked increase in the number of binucleated RPE cell associated with individual druse. Surprisingly many of these changes were found at distances up to 400 μm from drusen.     

The retinal pigment epithelium induces fenestration of endothelial cells in vivo.

Rodent photoreceptor dystrophies are characterized by late stage ingrowth of retinal blood vessels into the retinal pigment epithelium (RPE) where they proliferate. Some of these vessels develop the fenestrated phenotype of the choriocapillaris (CC). To determine if development of fenestrae in these endothelial cells is a function of the duration of time the endothelial cell had been encapsulated by the RPE, we did an ultrastructural morphometric study of these vessels in urethane induced photoreceptor degeneration in Long-Evans rats. Retinas of animals aged 20, 24, 40 and 56 weeks were studied. The fraction of vessel profiles within the RPE that had fenestrated endothelial cells increased from 10% to 90% between 20 to 56 weeks. The average number of fenestrae per vessel increased approximately 25 fold between 20 and 24 weeks but stabilized after that, despite a decrease in the number of vessels present at 56 weeks. A large number of degenerated retinal vessel profiles were seen in the RPE at 40 weeks. These facts support the idea that the presence of the RPE induces endothelial cell fenestrae, and also show that a complex process of remodelling including proliferation and degeneration is occurring in these vessels. Analogies between the basic cell biology of neovascularization occurring in these rodent models and that of proliferative diabetic retinopathy and age-related macular degeneration are discussed.