Characteristics Of Retinal Pigment Epithelium Research Articles

Морфофункциональные особенности пигментного эпителия сетчатки в норме и при возрастной макулярной дегенерации

Relevance. The retinal pigment epithelium performs a number of highly specialized functions. The relevance of studying morphological changes in the pigment epithelium is associated with an increased number of patients with age-related macular degeneration (AMD), polypoid choroidal vasculopathy, central serous retinopathy and retinitis pigmentosa. The increase in the number of patients with these pathologies is associated both with the general trend of aging of the world's population and with modern opportunities for mass diagnostics. Pathomorphological changes in the pigment layer are an important indicator of the development of AMD. Purpose. To analyze features of retinal pigment epithelium in normal and pathological conditions. Material and methods. The literature review was carried out using PubMed and Sochape Library. Results. Several authors present data about the complication of retinal detachment with development of the retinal pigment epithelium tear. The key criterion for tear treatment is the height of the pigment layer detachment. Violation of the integrity of the pigment layer in the long term is a factor in decrease or complete loss of vision. This is especially characteristic when a tear is formed in the central area of the retina. Also, visual impairment is observed in cases of submacular hemorrhage and fibrous scar formation. Conclusion. An important point, at present, is guidelines development for patients with pigment epithelium tears, it will allow to manage this condition on the background of concomitant disease. Key words: retinal pigment epithelium, age-related macular degeneration, pigment epithelium tear

Ultrasonographic features of retinal pigment epithelial adenoma

Objective: To investigate the ultrasonographic features of retinal pigment epithelium (RPE) adenoma. Methods: It was a retrospective case series study. The clinical clata of 15 patients (15 eyes) with pathologically confirmed RPE adenoma after local resection of intraocular tumor was collected at Beijing Tongren Hospital, Capital Medical University from November 2013 to October 2019. The general conditions of the patients and the location, size, shape, internal echo features of the lesions in the ocular ultrasound sonogram were analyzed, and the blood flow in the lesions was checked by color Doppler flow imaging (CDFI). Results: Of all the patients included in the study, 7 were male and 8 were female. Their age ranged from 25 to 58 years, with a mean age of (45.7±10.2) years. The most common symptom was vision loss or blurred vision (11 cases). Other symptoms included dark shadows or obscuration in front of the eyes (3 cases) and no symptoms (1 case). A history of previous ocular trauma was present in one case, and the rest of the patients had no history of ocular trauma.The location of tumor growth is scattered. The ultrasonographic features were as follows: the average maximum basal diameter was (8.07±2.75) mm and the average height was (4.02±1.81) mm; the ultrasonographic features mostly demonstrated abruptly elevated dome-shaped echo (6 cases); the lesion edge was not smooth, the internal echo was medium or low, and there could be hollow features (2 cases), with no choroidal depression; and the blood flow signal could be seen in the CDFI lesion, which could lead to retinal detachment and vitreous opacification. Conclusion: The ultrasound imaging features of RPE adenomas mostly demonstrate abruptly elevated dome-shaped echo, unsmooth lesion edge, with no choroidal depression, which may provide valuable evidence for clinical diagnosis and differentiation.

Intracerebral retina-like pigmented tissue in a stillborn fetus with holoprosencephaly

A stillbirth fetus with semilobar holoprosencephaly was induced at 24 weeks gestational age. While the eyes appeared unremarkable externally, there was an absence of optic nerves. At the ventral hypothalamicdiencephalic region there was an area of bilateral epithelioid cells containing melanin. Immunohistochemical characterization revealed the cells to be of neuroepithelial origin with features of retinal pigment epithelium. These findings reflect abnormalities in eye development in holoprosencephaly, especially when coupled with other structural defects in the visual system.

Development-related mitochondrial properties of retinal pigment epithelium cells derived from hEROs.

To explore the temporal mitochondrial characteristics of retinal pigment epithelium (RPE) cells obtained from human embryonic stem cells (hESC)-derived retinal organoids (hEROs-RPE), to verify the optimal period for using hEROs-RPE as donor cells from the aspect of mitochondria and to optimize RPE cell-based therapeutic strategies for age-related macular degeneration (AMD). RPE cells were obtained from hEROs and from spontaneous differentiation (SD-RPE). The mitochondrial characteristics were analyzed every 20d from day 60 to 160. Mitochondrial quantity was measured by MitoTracker Green staining. Transmission electron microscopy (TEM) was adopted to assess the morphological features of the mitochondria, including their distribution, length, and cristae. Mitochondrial membrane potentials (MMPs) were determined by JC-1 staining and evaluated by flow cytometry, reactive oxygen species (ROS) levels were evaluated by flow cytometry, and adenosine triphosphate (ATP) levels were measured by a luminometer. Differences between two groups were analyzed by the independent-samples t-test, and comparisons among multiple groups were made using one-way ANOVA or Kruskal-Wallis H test when equal variance was not assumed. hEROs-RPE and SD-RPE cells from day 60 to 160 were successfully differentiated from hESCs and expressed RPE markers (Pax6, MITF, Bestrophin-1, RPE65, Cralbp). RPE features, including a cobblestone-like morphology with tight junctions (ZO-1), pigments and microvilli, were also observed in both hEROs-RPE and SD-RPE cells. The mitochondrial quantities of hEROs-RPE and SD-RPE cells both peaked at day 80. However, the cristae of hEROs-RPE mitochondria were less mature and abundant than those of SD-RPE mitochondria at day 80, with hEROs-RPE mitochondria becoming mature at day 100. Both hEROs-RPE and SD-RPE cells showed low ROS levels from day 100 to 140 and maintained a normal MMP during this period. However, hEROs-RPE mitochondria maintained a longer time to produce high levels of ATP (from day 120 to 140) than SD-RPE cells (only day 120). hEROs-RPE mitochondria develop more slowly and maintain a longer time to supply high-level energy than SD-RPE mitochondria. From the mitochondrial perspective, hEROs-RPE cells from day 100 to 140 are an optimal cell source for treating AMD.

Fundus Autofluorescence and Optical Coherence Tomography Characteristics in Different Stages of Central Serous Chorioretinopathy.

Objective To describe the morphological changes on fundus autofluorescence (FAF) and spectral-domain optical coherence tomography (SD-OCT) imaging at different chronicity of central serous chorioretinopathy (CSC). Methods This cross-sectional study included patients with CSC of different chronicity. Changes in FAF scans and morphological changes on SD-OCT were evaluated and compared at different stages of CSC. Results Sixty-nine patients were enrolled in the study, with a mean age of 52.1 ± 11.8 years. A distinct hypoautofluorescence (AF) pattern was observed at the leakage point in acute CSC (100%). The leakage site was indistinguishable in 48% of the patients with late-chronic CSC. The majority of acute CSC patients showed hyper-AF in the area of serous retinal detachment (SRD), which persisted in the early-chronic stage of CSC. In late-chronic CSC, many cases of hypo-AF (22.2%) and mixed-pattern AF (14.8%) were observed. SD-OCT revealed evolving features of retinal pigment epithelium (RPE) abnormalities in a time-dependent manner: from peaked PEDs in acute CSC to low-lying PEDs in early-chronic CSC and, eventually, flat, irregular PEDs in late-chronic CSC. The average thickness of the photoreceptor layer (inner and outer segment; IS/OS) was 79 μm in the acute group and 55.2 μm in the chronic group. The photoreceptor layer (IS/OS) height was positively associated with visual acuity (p=0.002). Conclusion Different stages of CSC present different patterns on FAF and SD-OCT imaging. Chronicity of CSC can be estimated using specific features in these images. Photoreceptor layer (IS/OS) height acts as a good and objective predictor of visual outcomes in CSC patients.

Retinal Pigment Epithelium Responses to Selective Retina Therapy in Mouse Eyes.

To investigate the characteristics of retinal pigment epithelium (RPE) and retinal damage induced by selective retina therapy (SRT) in mice, and to elucidate longitudinal changes in RPE cells. C57BL/6J mice received SRT and continuous-wave laser photocoagulation (cwPC). The cell death pattern was evaluated using TUNEL assay, and proliferative potential of the RPE cells was evaluated using 5-ethynyl-2'-dexoyuridine (EdU) assay. To investigate the cell-cell integrity of RPE cells, β-catenin staining was performed. The number and hexagonality of RPE cells in the SRT-treated area were estimated using a Voronoi diagram with time periods of 3 hours to 14 days. Antibodies to microphthalmia-associated transcription factor (MiTF) and orthodenticle homeobox 2 (Otx2) were used to confirm the specific characteristics of RPE cells in the SRT-treated area. The number of TUNEL-positive cells located in the neural retina was significantly lower in lesions treated with SRT compared to those treated with cwPC. EdU-positive RPE cells were first detected 3 to 12 hours after SRT, and increased until 3 to 7 days after SRT. β-catenin staining showed that hexagonality was compromised and subsequently, RPE cells expanded in size within the targeted location. The number of RPE cells in SRT lesions decreased gradually until 12 hours after SRT and recovered by 14 days. Upregulated expression of MiTF and Otx2 was observed for 2 weeks in the SRT lesions. Selective retina therapy seems to induce selective RPE damage without collateral thermal injury in the neural retina. Furthermore, SRT-treated lesions recovered by proliferation of RPE cells that were present in the treated lesions and by expansion of adjacent RPE cells.

Cultivation and differentiation characteristics of human limbal progenitor cells

Background The aim of this study was to investigate whether limbal progenitor cells can be cultured, expanded and differentiated in vitro not only to enter corneal differentiation but also towards RPE (retinal pigment epithelium) characteristics. Methods A 3 mm broad strip of human corneoscleral limbal tissue was digested enzymatically and cells were set into cell culture. Differentiation status and characteristics, proliferation and phagocytotic activity were assessed by immunocytochemical staining in combination with digital and confocal microscopy. Results Immunocytological analysis revealed expression of Nestin and p63 marker suggesting progenitor cell properties. Mitotic activity was demonstrated by BrdU (bromodesoxyuridine) uptake. Upon consecutive passages, corneal differentiation markers were predominantly expressed. Phagocytotic activity was demonstrated via uptake of FITC (fluorescein isothiocyanate) labelled latex beads. RPE markers Bestrophin and Cytokeratin 8/18 as well as glial marker GFAP and neuronal marker MAP with respective controls were negative indicating no differentiation towards characteristics of retinal pigment epithelium or neural and glial lineage. Conclusions The results suggest that isolation and cultivation of proliferating and phagocytotic cells from the human corneal limbus was achieved which showed characteristics of both progenitor and differentiated corneal cells. No evidence was found for the hypothesis of spontaneous differentiation potential towards RPE lineage or neuronal characteristics, providing evidence of the inherent directional capacity of limbal progenitor cells.

The retinal pigment epithelium of the teleost Notopterus notopterus (Pallas): appearance of basal infoldings during prolonged dark-adaptation.

In teleosts, the basal part of the retinal pigment epithelium (RPE) is relatively smooth, i. e., it is free of basal membrane infoldings. In the featherback, Notopterus notopterus, whereas this is the situation in light adaptation, during dark-adaptation, especially when kept for prolonged periods (6-9 hour), numerous infoldings appear at the basal region, as found uniquely by transmission electron microscopy. In this teleost, during retinomotor movements, the rods move vitreally during dark-adaptation, while the cones do not elongate, and remain stationary in both light- and dark-adaptation. The significance of the appearance of basal infoldings in dark-adapted RPE is explained in terms of the pattern of retinomotor responses and the features of RPE and photoreceptors in this species. It is suggested that (1) the thick, impervious tapetal layer present in the RPE, (2) the unusual position of the photoreceptors in the visual cell layer of dark-adapted retina, and (3) the presumably high demand for glucose and O2 of the outer retina during dark-adaptation might contribute to cause this phenomenon in this species. The available evidence tend to associate this phenomenon with the involvement of the RPE in nutrient and O2 delivery to the photoreceptors via the basal infoldings of the RPE in dark-adapted state in this species. This has not been reported for any other teleosts to date.

The organization of human retinal pigment epithelium in vitro

The in vitro growth characteristics of retinal pigment epithelium from post mortem human eyes have been described. Our studies demonstrated that only a small percentage of the RPE cells initially plated out enter the division phase 12–21 days after plating and give rise to confluent cultures. The duration of the initial lag phase and the size of the proliferative fraction are age-dependent; cultures established from younger donor eyes have a larger fraction of proliferating cells and enter the division phase earlier than those from older donor eyes. Using the melano-lipofuscin granules as cell markers, we identified two distinct cell populations in the confluent cultures. One population consisted of small, diploid, non-pigmented cells that were undergoing division; the second, larger, densely pigmented cells that appeared stationary. Electron microscopy studies confirmed that both cell populations are epithelial-like in ultrastructure and that the RPE cells in vitro retain many of their in vivo ultrastructural characteristics.