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1
Kuznetsova, Alla V., Alexander M. Kurinov, and Maria A. Aleksandrova. "Cell Models to Study Regulation of Cell Transformation in Pathologies of Retinal Pigment Epithelium." Journal of Ophthalmology 2014 (2014): 1–18. http://dx.doi.org/10.1155/2014/801787.
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The retinal pigment epithelium (RPE) plays a key role in the development of many eye diseases leading to visual impairment and even blindness. Cell culture models of pathological changes in the RPE make it possible to study factors responsible for these changes and signaling pathways coordinating cellular and molecular mechanisms of cell interactions under pathological conditions. Moreover, they give an opportunity to reveal target cells and develop effective specific treatment for degenerative and dystrophic diseases of the retina. In this review, data are presented on RPE cell sources for culture models, approaches to RPE cell culturing, phenotypic changes of RPE cellsin vitro, the role of signal pathways, and possibilities for their regulation in pathological processes.
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Marrs, J. A., C. Andersson-Fisone, M. C. Jeong, L. Cohen-Gould, C. Zurzolo, I. R. Nabi, E. Rodriguez-Boulan, and W. J. Nelson. "Plasticity in epithelial cell phenotype: modulation by expression of different cadherin cell adhesion molecules." Journal of Cell Biology 129, no. 2 (April 15, 1995): 507–19. http://dx.doi.org/10.1083/jcb.129.2.507.
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A primary function of cadherins is to regulate cell adhesion. Here, we demonstrate a broader function of cadherins in the differentiation of specialized epithelial cell phenotypes. In situ, the rat retinal pigment epithelium (RPE) forms cell-cell contacts within its monolayer, and at the apical membrane with the neural retina; Na+, K(+)-ATPase and the membrane cytoskeleton are restricted to the apical membrane. In vitro, RPE cells (RPE-J cell line) express an endogenous cadherin, form adherens junctions and a tight monolayer, but Na+,K(+)-ATPase is localized to both apical and basal-lateral membranes. Expression of E-cadherin in RPE-J cells results in restriction and accumulation of both Na+,K(+)-ATPase and the membrane cytoskeleton at the lateral membrane; these changes correlate with the synthesis of a different ankyrin isoform. In contrast to both RPE in situ and RPE-J cells that do not form desmosomes, E-cadherin expression in RPE-J cells induces accumulation of desmoglein mRNA, and assembly of desmosome-keratin complexes at cell-cell contacts. These results demonstrate that cadherins directly affect epithelial cell phenotype by remodeling the distributions of constitutively expressed proteins and by induced accumulation of specific proteins, which together lead to the generation of structurally and functionally distinct epithelial cell types.
3
Szatmári-Tóth, Mária, Tanja Ilmarinen, Alexandra Mikhailova, Heli Skottman, Anu Kauppinen, Kai Kaarniranta, Endre Kristóf, et al. "Human Embryonic Stem Cell-Derived Retinal Pigment Epithelium-Role in Dead Cell Clearance and Inflammation." International Journal of Molecular Sciences 20, no. 4 (February 20, 2019): 926. http://dx.doi.org/10.3390/ijms20040926.
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Inefficient removal of dying retinal pigment epithelial (RPE) cells by professional phagocytes can result in debris formation and development of age-related macular degeneration (AMD). Chronic oxidative stress and inflammation play an important role in AMD pathogenesis. Only a few well-established in vitro phagocytosis assay models exist. We propose human embryonic stem cell-derived-RPE cells as a new model for studying RPE cell removal by professional phagocytes. The characteristics of human embryonic stem cells-derived RPE (hESC-RPE) are similar to native RPEs based on their gene and protein expression profile, integrity, and barrier properties or regarding drug transport. However, no data exist about RPE death modalities and how efficiently dying hESC-RPEs are taken upby macrophages, and whether this process triggers an inflammatory responses. This study demonstrates hESC-RPEs can be induced to undergo anoikis or autophagy-associated cell death due to extracellular matrix detachment or serum deprivation and hydrogen-peroxide co-treatment, respectively, similar to primary human RPEs. Dying hESC-RPEs are efficiently engulfed by macrophages which results in high amounts of IL-6 and IL-8 cytokine release. These findings suggest that the clearance of anoikic and autophagy-associated dying hESC-RPEs can be used as a new model for investigating AMD pathogenesis or for testing the in vivo potential of these cells in stem cell therapy.
4
Daniele, Elena, Lorenzo Bosio, Noor Ahmed Hussain, Barbara Ferrari, Stefano Ferrari, Vanessa Barbaro, Brian McArdle, et al. "Denuded Descemet’s membrane supports human embryonic stem cell-derived retinal pigment epithelial cell culture." PLOS ONE 18, no. 2 (February 6, 2023): e0281404. http://dx.doi.org/10.1371/journal.pone.0281404.
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Recent clinical studies suggest that retinal pigment epithelial (RPE) cell replacement therapy may preserve vision in retinal degenerative diseases. Scaffold-based methods are being tested in ongoing clinical trials for delivering pluripotent-derived RPE cells to the back of the eye. The aim of this study was to investigate human embryonic stem cell-derived retinal pigment epithelial (hESC-RPE) cells survival and behaviour on a decellularized Descemet’s Membrane (DM), which may be of clinical relevance in retinal transplantation. DMs were isolated from human donor corneas and treated with thermolysin. The DM surface topology and the efficiency of the denudation method were evaluated by atomic force microscope, scanning electron microscopy and histology. hESC-RPE cells were seeded onto the endothelial-side surface of decellularized DM in order to determine the potential of the membrane to support hESC-RPE cell culture, alongside maintaining their viability. Integrity of the hESC-RPE monolayer was assessed by measuring transepithelial resistance. RPE-specific gene expression and growth factors secretion were assessed to confirm maturation and functionality of the cells over the new substrate. Thermolysin treatment did not affect the integrity of the tissue, thus ensuring a reliable method to standardize the preparation of decellularized DM. 24 hours post-seeding, hESC-RPE cell attachment and initial proliferation rate over the denuded DM were higher than hESC-RPE cells cultured on tissue culture inserts. On the new matrix, hESC-RPE cells succeeded in forming an intact monolayer with mature tight junctions. The resulting cell culture showed characteristic RPE cell morphology and proper protein localization. Gene expression analysis and VEGF secretion demonstrate DM provides supportive scaffolding and inductive properties to enhance hESC-RPE cells maturation. Decellularized DM was shown to be capable of sustaining hESC-RPE cells culture, thus confirming to be potentially a suitable candidate for retinal cell therapy.
5
Kindzelskii, Andrei L., Victor M. Elner, Susan G. Elner, Dongli Yang, Bret A. Hughes, and Howard R. Petty. "Toll-Like Receptor 4 (TLR4) of Retinal Pigment Epithelial Cells Participates in Transmembrane Signaling in Response to Photoreceptor Outer Segments." Journal of General Physiology 124, no. 2 (July 26, 2004): 139–49. http://dx.doi.org/10.1085/jgp.200409062.
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Retinal pigment epithelial (RPE) cells mediate the recognition and clearance of effete photoreceptor outer segments (POS), a process central to the maintenance of normal vision. Given the emerging importance of Toll-like receptors (TLRs) in transmembrane signaling in response to invading pathogens as well as endogenous substances, we hypothesized that TLRs are associated with RPE cell management of POS. TLR4 clusters on human RPE cells in response to human, but not bovine, POS. However, TLR4 clustering could be inhibited by saturating concentrations of an inhibitory anti-TLR4 mAb. Furthermore, human POS binding to human RPE cells elicited transmembrane metabolic and calcium signals within RPE cells, which could be blocked by saturating doses of an inhibitory anti-TLR4 mAb. However, the heterologous combination of bovine POS and human RPE did not trigger these signals. The pattern recognition receptor CD36 collected at the POS–RPE cell interface for both homologous and heterologous samples, but human TLR4 only collected at the human POS–human RPE cell interface. Kinetic experiments of human POS binding to human RPE cells revealed that CD36 arrives at the POS–RPE interface followed by TLR4 accumulation within 2 min. Metabolic and calcium signals immediately follow. Similarly, the production of reactive oxygen metabolites (ROMs) was observed for the homologous human system, but not the heterologous bovine POS–human RPE cell system. As (a) the bovine POS/human RPE combination did not elicit TLR4 accumulation, RPE signaling, or ROM release, (b) TLR4 arrives at the POS–RPE cell interface just before signaling, (c) TLR4 blockade with an inhibitory anti-TLR4 mAb inhibited TLR4 clustering, signaling, and ROM release in the human POS–human RPE system, and (d) TLR4 demonstrates similar clustering and signaling responses to POS in confluent RPE monolayers, we suggest that TLR4 of RPE cells participates in transmembrane signaling events that contribute to the management of human POS.
6
Voisin, Audrey, Christelle Monville, Alexandra Plancheron, Emile Béré, Afsaneh Gaillard, and Nicolas Leveziel. "Cathepsin B pH-Dependent Activity Is Involved in Lysosomal Dysregulation in Atrophic Age-Related Macular Degeneration." Oxidative Medicine and Cellular Longevity 2019 (December 6, 2019): 1–15. http://dx.doi.org/10.1155/2019/5637075.
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Age-related macular degeneration (AMD) is characterized by retinal pigment epithelial (RPE) cell dysfunction beginning at early stages of the disease. The lack of an appropriate in vitro model is a major limitation in understanding the mechanisms leading to the occurrence of AMD. This study compared human-induced pluripotent stem cell- (hiPSC-) RPE cells derived from atrophic AMD patients (77 y/o±7) to hiPSC-RPE cells derived from healthy elderly individuals with no drusen or pigmentary alteration (62.5 y/o±17.5). Control and AMD hiPSC-RPE cell lines were characterized by immunofluorescence, flow cytometry, and electronic microscopy. The toxicity level of iron after Fe-NTA treatment was evaluated by an MTT test and by the detection of dichloro-dihydro-fluorescein diacetate. Twelve hiPSC-RPE cell lines (6 AMD and 6 controls) were used for the experiment. Under basal conditions, all hiPSC-RPE cells expressed a phenotypic profile of senescent cells with rounded mitochondria at passage 2. However, the treatment with Fe-NTA induced higher reactive oxygen species production and cell death in hiPSC-RPE AMD cells than in hiPSC-RPE Control cells. Interestingly, functional analysis showed differences in lysosomal activity between the two populations. Indeed, Cathepsin B activity was higher in hiPSC-RPE AMD cells compared to hiPSC-RPE Control cells in basal condition and link to a pH more acidic in this cell population. Moreover, oxidative stress exposure leads to an increase of Cathepsin D immature form levels in both populations, but in a higher proportion in hiPSC-RPE AMD cells. These findings could demonstrate that hiPSC-RPE AMD cells have a typical disease phenotype compared to hiPSC-RPE Control cells.
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Arai, Rei, Ayumi Usui-Ouchi, Yosuke Ito, Keitaro Mashimo, Akira Murakami, and Nobuyuki Ebihara. "Effects of Secreted Mast Cell Mediators on Retinal Pigment Epithelial Cells: Focus on Mast Cell Tryptase." Mediators of Inflammation 2017 (2017): 1–10. http://dx.doi.org/10.1155/2017/3124753.
Full textAbstract:
Numerous mast cells are present in the choroid, but the effects of mast cell mediators on retinal pigment epithelial (RPE) cells are not well understood. We investigated the influence of mast cell mediators on RPE cells in vitro, focusing on tryptase. Expression of receptors was examined by the reverse transcription polymerase chain reaction. We also assessed production of interleukin 8 and vascular endothelial growth factor (VEGF) after RPE cells were stimulated with mast cell mediators by using an antibody array and enzyme-linked immunosorbent assay. Furthermore, we investigated the influence of tryptase on RPE cell migration and integrity by the scratch assay and the transepithelial resistance. RPE cells expressed protease-activated receptor 2 (PAR2), histamine receptor 1, tumor necrosis factor-α (TNF-α) receptor 1, and CCR 1, 3, 4, 8, and 11. Tryptase, PAR2 agonists, histamine, and TNF-α all enhanced interleukin 8 production by RPE cells, while only tryptase enhanced VEGF production. Tryptase also enhanced expression of phosphorylated extracellular signal-regulated kinases 1/2, resulting in increased migration of RPE cells. However, tryptase did not alter epithelial integrity or the expression of zonula occludens-1 and junctional adhesion molecule-A by RPE cells. Mast cell mediators, especially tryptase, may influence RPE cell inflammation.
8
Hellinen, Laura, Heidi Hongisto, Eva Ramsay, Kai Kaarniranta, Kati-Sisko Vellonen, Heli Skottman, and Marika Ruponen. "Drug Flux Across RPE Cell Models: The Hunt for An Appropriate Outer Blood–Retinal Barrier Model for Use in Early Drug Discovery." Pharmaceutics 12, no. 2 (February 19, 2020): 176. http://dx.doi.org/10.3390/pharmaceutics12020176.
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The retinal pigment epithelial (RPE) cell monolayer forms the outer blood–retinal barrier and has a crucial role in ocular pharmacokinetics. Although several RPE cell models are available, there have been no systematic comparisons of their barrier properties with respect to drug permeability. We compared the barrier properties of several RPE secondary cell lines (ARPE19, ARPE19mel, and LEPI) and both primary (hfRPE) and stem-cell derived RPE (hESC-RPE) cells by investigating the permeability of nine drugs (aztreonam, ciprofloxacin, dexamethasone, fluconazole, ganciclovir, ketorolac, methotrexate, voriconazole, and quinidine) across cell monolayers. ARPE19, ARPE19mel, and hfRPE cells displayed a narrow Papp value range, with relatively high permeation rates (5.2–26 × 10−6 cm/s. In contrast, hESC-RPE and LEPI cells efficiently restricted the drug flux, and displayed even lower Papp values than those reported for bovine RPE-choroid, with the range of 0.4–32 cm−6/s (hESC-RPE cells) and 0.4–29 × 10−6 cm/s, (LEPI cells). Therefore, ARPE19, ARPE19mel, and hfRPE cells failed to form a tight barrier, whereas hESC-RPE and LEPI cells restricted the drug flux to a similar extent as bovine RPE-choroid. Therefore, LEPI and hESC-RPE cells are valuable tools in ocular drug discovery.
9
Gupta, Santosh, Lyubomyr Lytvynchuk, Taras Ardan, Hana Studenovska, Georgina Faura, Lars Eide, Ljubo Znaor, et al. "Retinal Pigment Epithelium Cell Development: Extrapolating Basic Biology to Stem Cell Research." Biomedicines 11, no. 2 (January 23, 2023): 310. http://dx.doi.org/10.3390/biomedicines11020310.
Full textAbstract:
The retinal pigment epithelium (RPE) forms an important cellular monolayer, which contributes to the normal physiology of the eye. Damage to the RPE leads to the development of degenerative diseases, such as age-related macular degeneration (AMD). Apart from acting as a physical barrier between the retina and choroidal blood vessels, the RPE is crucial in maintaining photoreceptor (PR) and visual functions. Current clinical intervention to treat early stages of AMD includes stem cell-derived RPE transplantation, which is still in its early stages of evolution. Therefore, it becomes essential to derive RPEs which are functional and exhibit features as observed in native human RPE cells. The conventional strategy is to use the knowledge obtained from developmental studies using various animal models and stem cell-based exploratory studies to understand RPE biogenies and developmental trajectory. This article emphasises such studies and aims to present a comprehensive understanding of the basic biology, including the genetics and molecular pathways of RPE development. It encompasses basic developmental biology and stem cell-based developmental studies to uncover RPE differentiation. Knowledge of the in utero developmental cues provides an inclusive methodology required for deriving RPEs using stem cells.
10
Kamao, Hiroyuki, Atsushi Miki, and Junichi Kiryu. "ROCK Inhibitor-Induced Promotion of Retinal Pigment Epithelial Cell Motility during Wound Healing." Journal of Ophthalmology 2019 (June 19, 2019): 1–10. http://dx.doi.org/10.1155/2019/9428738.
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Purpose. No standard therapy for RPE tear, a complication of neovascular age-related macular degeneration, exists even though RPE tears cause severe vision loss, and promotion of cell proliferation and/or migration could be a candidate RPE tear therapy. The aim of this study is to evaluate the effect of Rho-associated coiled-coil containing kinase (ROCK) inhibitor Y27632 on retinal pigment epithelial (RPE) cell motility during wound healing. Methods. Human RPE cells were cultured in media with and without 10 μM Y27632. A luminescent cell viability assay and vinculin immunocytochemistry were used to test the Y27632 effect on RPE cell adhesion. The mean size of vinculin puncta was quantified from immunofluorescence images. RPE cell motility during wound healing was evaluated using time-lapse imaging and measuring cell migration distances and cell coverage rate in wound fields. Results. The number of adhered RPE and mean size of vinculin puncta were, respectively, 20519 cells and 3.65 μm2 under nontreatment and 23569 cells and 0.66 μm2 under Y27632 treatment. Cell migration distance and cell coverage percentage for untreated and Y27632-treated cells were 98.9 and 59.4% and 203.4 and 92.5%, respectively. Conclusions. Inhibition of ROCK signaling by using 10 μM Y27632 promoted RPE cell motility during wound healing by reducing RPE cell adhesion strength.
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Vinores, S. A., R. McGehee, A. Lee, C. Gadegbeku, and P. A. Campochiaro. "Ultrastructural localization of blood-retinal barrier breakdown in diabetic and galactosemic rats." Journal of Histochemistry & Cytochemistry 38, no. 9 (September 1990): 1341–52. http://dx.doi.org/10.1177/38.9.2117624.
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Breakdown of the blood-retinal barrier (BRB) is an early event in diabetic and galactosemic rats, but the location and nature of the specific defect(s) are controversial. Using an electron microscopic immunocytochemical technique, the retinas of normal, diabetic, and galactosemic rats were immunostained for endogenous albumin. Normal rats showed little evidence of BRB breakdown at either the inner barrier (retinal vasculature) or the outer barrier (retinal pigment epithelium) (RPE). In diabetic and galactosemic rats, as was true in human diabetics, BRB breakdown occurred predominantly at the inner BRB, but in some cases at the outer barrier as well. Treatment with the aldose reductase inhibitor sorbinil largely prevented BRB failure in galactosemic rats. In the inner retina of diabetic and galactosemic rats, albumin was frequently demonstrated on the abluminal side of the retinal capillary endothelium (RCE) in intercellular spaces, basal laminae, pericytes, ganglion cells, astrocytes, and the perinuclear cytoplasm of cells in the inner nuclear layer. Albumin did not appear to cross RCE cell junctions; however, it was occasionally seen in RCE cytoplasm of galactosemic rats. In the outer retina, albumin was frequently detected in the subretinal space, in the intercellular space between photoreceptors, and in the perinuclear cytoplasm of photoreceptor cells, but was only infrequently found in the RPE cells constituting the barrier. Albumin derived from the choroidal vasculature did not appear to cross the tight junctions of the RPE. These findings suggest that specific sites of BRB compromise are infrequent but that once albumin has crossed the RCE or RPE it freely permeates the retinal tissue by filling intercellular spaces and permeating the membranes of cells not implicated in BRB formation. The diffuse cytoplasmic staining of some RCE and RPE cells suggests that the predominant means of BRB breakdown in diabetes and galactosemia involves increased focal permeability of the surface membranes of the RCE and RPE cells rather than defective tight junctions or vesicular transport.
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Yang, Jee Myung, Sunho Chung, KyungA Yun, Bora Kim, Seongjun So, Seoon Kang, Eunju Kang, and Joo Yong Lee. "Long-term effects of human induced pluripotent stem cell-derived retinal cell transplantation in Pde6b knockout rats." Experimental & Molecular Medicine 53, no. 4 (April 2021): 631–42. http://dx.doi.org/10.1038/s12276-021-00588-w.
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AbstractRetinal degenerative disorders, including age-related macular degeneration and retinitis pigmentosa (RP), are characterized by the irreversible loss of photoreceptor cells and retinal pigment epithelial (RPE) cells; however, the long-term effect of implanting both human induced pluripotent stem cell (hiPSC)-derived RPE and photoreceptor for retinal regeneration has not yet been investigated. In this study, we evaluated the long-term effects of hiPSC-derived RPE and photoreceptor cell transplantation in Pde6b knockout rats to study RP; cells were injected into the subretinal space of the right eyes of rats before the appearance of signs of retinal degeneration at 2–3 weeks of age. Ten months after transplantation, we evaluated the cells using fundus photography, optical coherence tomography, and histological evaluation, and no abnormal cell proliferation was observed. A relatively large number of transplanted cells persisted during the first 4 months; subsequently, the number of these cells decreased gradually. Notably, immunohistochemical analysis revealed that the hiPSC-derived retinal cells showed characteristics of both RPE cells and photoreceptors of human origin after transplantation. Functional analysis of vision by scotopic electroretinogram revealed significant preservation of vision after transplantation. Our study suggests that the transplantation of hiPSC-derived retinal cells, including RPE cells and photoreceptors, has a potential therapeutic effect against irreversible retinal degenerative diseases.
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Troutt, L. L., and B. Burnside. "The unusual microtubule polarity in teleost retinal pigment epithelial cells." Journal of Cell Biology 107, no. 4 (October 1, 1988): 1461–64. http://dx.doi.org/10.1083/jcb.107.4.1461.
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In cells of the teleost retinal pigment epithelium (RPE), melanin granules disperse into the RPE cell's long apical projections in response to light onset, and aggregate toward the base of the RPE cell in response to dark onset. The RPE cells possess numerous microtubules, which in the apical projections are aligned longitudinally. Nocodazole studies have shown that pigment granule aggregation is microtubule-dependent (Troutt, L. L., and B. Burnside, 1988b Exp. Eye Res. In press.). To investigate further the mechanism of microtubule participation in RPE pigment granule aggregation, we have used the tubulin hook method to assess the polarity of microtubules in the apical projections of teleost RPE cells. We report here that virtually all microtubules in the RPE apical projections are uniformly oriented with plus ends toward the cell body and minus ends toward the projection tips. This orientation is opposite that found for microtubules of dermal melanophores, neurons, and most other cell types.
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Rzhanova, Lyubov A., Yuliya V. Markitantova, and Maria A. Aleksandrova. "Recent Achievements in the Heterogeneity of Mammalian and Human Retinal Pigment Epithelium: In Search of a Stem Cell." Cells 13, no. 3 (February 4, 2024): 281. http://dx.doi.org/10.3390/cells13030281.
Full textAbstract:
Retinal pigment epithelium (RPE) cells are important fundamentally for the development and function of the retina. In this regard, the study of the morphological and molecular properties of RPE cells, as well as their regenerative capabilities, is of particular importance for biomedicine. However, these studies are complicated by the fact that, despite the external morphological similarity of RPE cells, the RPE is a population of heterogeneous cells, the molecular genetic properties of which have begun to be revealed by sequencing methods only in recent years. This review carries out an analysis of the data from morphological and molecular genetic studies of the heterogeneity of RPE cells in mammals and humans, which reveals the individual differences in the subpopulations of RPE cells and the possible specificity of their functions. Particular attention is paid to discussing the properties of “stemness,” proliferation, and plasticity in the RPE, which may be useful for uncovering the mechanisms of retinal diseases associated with pathologies of the RPE and finding new ways of treating them.
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Sharma, Ruchi, Vladimir Khristov, Aaron Rising, Balendu Shekhar Jha, Roba Dejene, Nathan Hotaling, Yichao Li, et al. "Clinical-grade stem cell–derived retinal pigment epithelium patch rescues retinal degeneration in rodents and pigs." Science Translational Medicine 11, no. 475 (January 16, 2019): eaat5580. http://dx.doi.org/10.1126/scitranslmed.aat5580.
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Considerable progress has been made in testing stem cell–derived retinal pigment epithelium (RPE) as a potential therapy for age-related macular degeneration (AMD). However, the recent reports of oncogenic mutations in induced pluripotent stem cells (iPSCs) underlie the need for robust manufacturing and functional validation of clinical-grade iPSC-derived RPE before transplantation. Here, we developed oncogenic mutation-free clinical-grade iPSCs from three AMD patients and differentiated them into clinical-grade iPSC-RPE patches on biodegradable scaffolds. Functional validation of clinical-grade iPSC-RPE patches revealed specific features that distinguished transplantable from nontransplantable patches. Compared to RPE cells in suspension, our biodegradable scaffold approach improved integration and functionality of RPE patches in rats and in a porcine laser-induced RPE injury model that mimics AMD-like eye conditions. Our results suggest that the in vitro and in vivo preclinical functional validation of iPSC-RPE patches developed here might ultimately be useful for evaluation and optimization of autologous iPSC-based therapies.
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Mora, Rosalia C., Vera L. Bonilha, Bo-Chul Shin, Jane Hu, Leona Cohen-Gould, Dean Bok, and Enrique Rodriguez-Boulan. "Bipolar assembly of caveolae in retinal pigment epithelium." American Journal of Physiology-Cell Physiology 290, no. 3 (March 2006): C832—C843. http://dx.doi.org/10.1152/ajpcell.00405.2005.
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Caveolae and their associated structural proteins, the caveolins, are specialized plasmalemmal microdomains involved in endocytosis and compartmentalization of cell signaling. We examined the expression and distribution of caveolae and caveolins in retinal pigment epithelium (RPE), which plays key roles in retinal support, visual cycle, and acts as the main barrier between blood and retina. Electron microscopic observation of rat RPE, in situ primary cultures of rat and human RPE and a rat RPE cell line (RPE-J) demonstrated in all cases the presence of caveolae in both apical and basolateral domains of the plasma membrane. Caveolae were rare in RPE in situ but were frequent in primary RPE cultures and in RPE-J cells, which correlated with increased levels in the expression of caveolin-1 and -2. The bipolar distribution of caveolae in RPE is striking, as all other epithelial cells examined to date (liver, kidney, thyroid, and intestinal) assemble caveolae only at the basolateral side. This might be related to the nonpolar distribution of both caveolin-1 and 2 in RPE because caveolin-2 is basolateral and caveolin-1 nonpolar in other epithelial cells. The bipolar localization of plasmalemmal caveolae in RPE cells may reflect specialized roles in signaling and trafficking important for visual function.
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Pandey, Ravi S., Mark P. Krebs, Mohan T. Bolisetty, Jeremy R. Charette, Jürgen K. Naggert, Paul Robson, Patsy M. Nishina, and Gregory W. Carter. "Single-Cell RNA Sequencing Reveals Molecular Features of Heterogeneity in the Murine Retinal Pigment Epithelium." International Journal of Molecular Sciences 23, no. 18 (September 8, 2022): 10419. http://dx.doi.org/10.3390/ijms231810419.
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Transcriptomic analysis of the mammalian retinal pigment epithelium (RPE) aims to identify cellular networks that influence ocular development, maintenance, function, and disease. However, available evidence points to RPE cell heterogeneity within native tissue, which adds complexity to global transcriptomic analysis. Here, to assess cell heterogeneity, we performed single-cell RNA sequencing of RPE cells from two young adult male C57BL/6J mice. Following quality control to ensure robust transcript identification limited to cell singlets, we detected 13,858 transcripts among 2667 and 2846 RPE cells. Dimensional reduction by principal component analysis and uniform manifold approximation and projection revealed six distinct cell populations. All clusters expressed transcripts typical of RPE cells; the smallest (C1, containing 1–2% of total cells) exhibited the hallmarks of stem and/or progenitor (SP) cells. Placing C1–6 along a pseudotime axis suggested a relative decrease in melanogenesis and SP gene expression and a corresponding increase in visual cycle gene expression upon RPE maturation. K-means clustering of all detected transcripts identified additional expression patterns that may advance the understanding of RPE SP cell maintenance and the evolution of cellular metabolic networks during development. This work provides new insights into the transcriptome of the mouse RPE and a baseline for identifying experimentally induced transcriptional changes in future studies of this tissue.
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Du, Jianhai, Aya Yanagida, Kaitlen Knight, Abbi L. Engel, Anh Huan Vo, Connor Jankowski, Martin Sadilek, et al. "Reductive carboxylation is a major metabolic pathway in the retinal pigment epithelium." Proceedings of the National Academy of Sciences 113, no. 51 (December 1, 2016): 14710–15. http://dx.doi.org/10.1073/pnas.1604572113.
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The retinal pigment epithelium (RPE) is a monolayer of pigmented cells that requires an active metabolism to maintain outer retinal homeostasis and compensate for oxidative stress. Using13C metabolic flux analysis in human RPE cells, we found that RPE has an exceptionally high capacity for reductive carboxylation, a metabolic pathway that has recently garnered significant interest because of its role in cancer cell survival. The capacity for reductive carboxylation in RPE exceeds that of all other cells tested, including retina, neural tissue, glial cells, and a cancer cell line. Loss of reductive carboxylation disrupts redox balance and increases RPE sensitivity to oxidative damage, suggesting that deficiencies of reductive carboxylation may contribute to RPE cell death. Supporting reductive carboxylation by supplementation with an NAD+precursor or its substrate α-ketoglutarate or treatment with a poly(ADP ribose) polymerase inhibitor protects reductive carboxylation and RPE viability from excessive oxidative stress. The ability of these treatments to rescue RPE could be the basis for an effective strategy to treat blinding diseases caused by RPE dysfunction.
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Marmorstein, Alan D., Yunbo C. Gan, Vera L. Bonilha, Silvia C. Finnemann, Karl G. Csaky, and Enrique Rodriguez-Boulan. "Apical Polarity of N-CAM and EMMPRIN in Retinal Pigment Epithelium Resulting from Suppression of Basolateral Signal Recognition." Journal of Cell Biology 142, no. 3 (August 10, 1998): 697–710. http://dx.doi.org/10.1083/jcb.142.3.697.
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Retinal pigment epithelial (RPE) cells apically polarize proteins that are basolateral in other epithelia. This reversal may be generated by the association of RPE with photoreceptors and the interphotoreceptor matrix, postnatal expansion of the RPE apical surface, and/or changes in RPE sorting machinery. We compared two proteins exhibiting reversed, apical polarities in RPE cells, neural cell adhesion molecule (N-CAM; 140-kD isoform) and extracellular matrix metalloproteinase inducer (EMMPRIN), with the cognate apical marker, p75-neurotrophin receptor (p75-NTR). N-CAM and p75-NTR were apically localized from birth to adulthood, contrasting with a basolateral to apical switch of EMMPRIN in developing postnatal rat RPE. Morphometric analysis demonstrated that this switch cannot be attributed to expansion of the apical surface of maturing RPE because the basolateral membrane expanded proportionally, maintaining a 3:1 apical/basolateral ratio. Kinetic analysis of polarized surface delivery in MDCK and RPE-J cells showed that EMMPRIN has a basolateral signal in its cytoplasmic tail recognized by both cell lines. In contrast, the basolateral signal of N-CAM is recognized by MDCK cells but not RPE-J cells. Deletion of N-CAM's basolateral signal did not prevent its apical localization in vivo. The data demonstrate that the apical polarity of EMMPRIN and N-CAM in mature RPE results from suppressed decoding of specific basolateral signals resulting in randomized delivery to the cell surface.
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Kamao, Hiroyuki, Atsushi Miki, and Junichi Kiryu. "Evaluation of Retinal Pigment Epithelial Cell Cytotoxicity of Recombinant Tissue Plasminogen Activator Using Human-Induced Pluripotent Stem Cells." Journal of Ophthalmology 2019 (March 19, 2019): 1–10. http://dx.doi.org/10.1155/2019/7189241.
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Purpose. The evaluation of drug-induced cytotoxicity is of great importance for the clinical application of pharmaceutical products, and human-induced pluripotent stem cells (hiPSCs) have received considerable scrutiny as a cell source for in vitro cytotoxicity testing. The aim of this study is to validate the concept of cytotoxicity testing using hiPSC-derived retinal pigment epithelium (hiPSC-RPE) by comparing the responsiveness of human fetal RPE (hfRPE) and human RPE cell line (ARPE19) to recombinant tissue plasminogen activator (rtPA). Methods. HfRPE, two types of hiPSC-RPE, and ARPE19 were cultured in media with or without rtPA. A lactate dehydrogenase release assay was performed to investigate the dose- and time-dependent effects of rtPA on cell death. RPE function was evaluated by measuring the secretion of pigment epithelium-derived factor (PEDF) and vascular endothelial growth factor (VEGF) and RPE-specific gene expression. Results. Rates of cell damage in hfRPE and both hiPS-RPE were increased by rtPA supplementation (2000 and 4000 μg/ml) for 1 hour, whereas ARPE19 cell damage was increased by supplementation with rtPA at concentrations higher than 50 μg/ml. Although 100 μg/ml rtPA for 24 hours did not affect RPE cell function, sustained rtPA exposure induced prolonged cytotoxic effects in hfRPE and two hiPSC-RPE, but not ARPE19. Conclusion. The responsiveness of hiPSC-RPE to rtPA is similar to that of hfRPE in terms of cell death and cell function. Thus, hiPSC-RPE is a valuable cell source for in vitro cytotoxicity testing.
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Kalnins, Vitauts I., Martin Sandig, Greg J. Hergott, and Haruhiko Nagai. "Microfilament organization and wound repair in retinal pigment epithelium." Biochemistry and Cell Biology 73, no. 9-10 (September 1, 1995): 709–22. http://dx.doi.org/10.1139/o95-079.
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Several systems of microfilaments (MF) associated with adherens-type junctions between adjacent retinal pigment epithelial (RPE) cells and between these cells and the substratum play an important role in maintaining the integrity and organization of the RPE. They include prominent, contractile circumferential MF bundles that are associated with the zonula adherens (ZA) junctions. In chick RPE, these junctions are assembled from smaller subunits thus giving greater structural flexibility to the junctional region. Because the separation of the junctions requires trypsin and low calcium, both calcium-dependent and -independent mechanisms are involved in keeping adjacent RPE cells attached to one another. Another system of MF bundles that crosses the cell at the level of ZA junctions can be induced to form by stretching the epithelium. The MF bundles forming this system are oriented in the direction in which the RPE is stretched, thereby preventing the overextension of the cell in any one direction. The system may be useful as an indicator of the direction in which tension is experienced by RPE during development of the eye, in animal models of disease and during repair of experimentally induced wounds. Numerous single-cell wounds resulting from death of RPE cells by apoptosis at various stages of repair are normally present in developing chick and adult mammalian RPE. These wounds are repaired by the spreading of adjacent RPE cells and by the contraction of MF bundles oriented parallel to the wound edge, which develop during this time. As a result of the spreading in the absence of cell proliferation, the RPE cells increase in diameter with age. Experimentally induced wounds made by removing 5–10 RPE cells are repaired by a similar mechanism within 24 h. In repair of larger wounds, over 125 μm in width, the MF bundles oriented parallel to the wound edge characteristic of spreading cells are later replaced by stress fibers (SFs) that run perpendicularly to the wound edge and interact with the substratum at focal contacts (FCs) as RPE cells start to migrate. Cell proliferation is induced in cells along the wound edge only when the wounds are wide enough to require cell migration. In the presence of antibodies to beta-1-integrins, a component of FCs, cell spreading is not prevented but both cell migration and cell proliferation are inhibited. Thus, only the organization of the cytoskeleton characteristic of migrating RPE cells that have SFs that interact with the substratum at FCs, is associated with the induction of cell proliferation.Key words: retinal pigment epithelium, microfilaments, wound repair.
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Yang, Chao, Lijun Ge, Xiyong Yu, Philip Lazarovici, and Wenhua Zheng. "Artemisinin Confers Cytoprotection toward Hydrogen Peroxide-Induced Cell Apoptosis in Retinal Pigment Epithelial Cells in Correlation with the Increased Acetylation of Histone H4 at Lysine 8." Molecules 29, no. 8 (April 15, 2024): 1789. http://dx.doi.org/10.3390/molecules29081789.
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Increased oxidative stress is one of the critical pathologies inducing age-related macular degeneration (AMD), characterized by retinal pigment epithelial (RPE) cell damage and death. The unbalanced acetylation and deacetylation of histones have been implicated in AMD pathogenesis or hydrogen peroxide (H2O2)-induced cell damage. Therefore, strategies aimed at controlling the balance between acetylation and deacetylation may effectively protect RPE cells from oxidative damage. Artemisinin is an antimalarial lactone drug derived from Artemisia annua, with antioxidant activity known to modulate histone acetylation in the brain, but its effect on the retina is unknown. In this study, we aimed to investigate whether Artemisinin exerts a cytoprotective effect on oxidative stress-induced apoptosis in RPE cells by regulating histone acetylation. We hypothesized that Artemisinin confers cytoprotection toward H2O2-induced apoptosis in RPE cells through this mechanism. In the present study, we found that Artemisinin at a sub-clinic dosage of 20 μM inhibited the H2O2-induced cell viability decrease and B-cell lymphoma 2 (Bcl-2) protein level decrease and attenuated the H2O2-induced decrease in the histone H4 lysine (Lys) 8 acetylation [Acetyl-H4 (Lys 8)] level in the retinal RPE cell line D407. As expected, histone deacetylase inhibitor Trichostatin A at the concentration of 250 nM increased the Acetyl-H4 (Lys 8) level in D407 cells and attenuated the H2O2-induced cell viability decrease and apoptosis. Similar findings were obtained using adult RPE (ARPE)19 cells, another human RPE cell line, and primary human RPE cell cultures. In conclusion, these results confirmed our hypothesis and indicated that Artemisinin attenuated H2O2-induced apoptosis in apparent correlation with the increase in the Acetyl-H4 (Lys 8) level, which is associated with gene transcription and cell survival. By modulating histone acetylation, Artemisinin may restore the balance between acetylation and deacetylation and enhance the resistance and survival of RPE cells under oxidative stress. Our study provides novel mechanistic insights into the effect of Artemisinin on histone acetylation and apoptosis in RPE cells and supports the potential application of Artemisinin in the prevention and/or treatment of AMD.
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Percopo, C. M., J. J. Hooks, T. Shinohara, R. Caspi, and B. Detrick. "Cytokine-mediated activation of a neuronal retinal resident cell provokes antigen presentation." Journal of Immunology 145, no. 12 (December 15, 1990): 4101–7. http://dx.doi.org/10.4049/jimmunol.145.12.4101.
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Abstract The retinal pigment epithelial (RPE) cell has long been considered an important regulatory cell, maintaining physiological and structural balance within the retina. We have previously shown that the RPE cell may also be important in autoimmunity and transplantation. These cells can be induced by cytokines to express MHC class II Ag in ocular inflammatory and autoimmune conditions. In this report we show that isolated rat RPE cells can be induced to express class II Ag following incubation with rat rIFN-gamma. The ability of RPE cells to present Ag was determined by both T cell proliferation assays and IL-2 production. Only the Ia-positive RPE cells can present retinal Ag (S-Ag and interphotoreceptor-binding protein) to specifically sensitized rat Th cells. Moreover, the ability of chloroquine to inhibit this activity suggests that the RPE cell is also capable of processing Ag prior to Ag presentation. These studies indicate that cytokine-mediated activation of RPE cells may be a basic component of ocular immunity and an important aspect of RPE cell transplantation.
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Mäenpää, Hanna, Tarja Toimela, Pirjo Saransaari, Lotta Salminen, and Hanna Tähti. "Mechanism of Tamoxifen's Retinal Toxicity, Studied in Pig Pigment Epithelial Cell Cultures." Alternatives to Laboratory Animals 25, no. 3 (May 1997): 297–302. http://dx.doi.org/10.1177/026119299702500310.
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The anticancer drug tamoxifen is widely used in breast cancer therapy. Tamoxifen has been reported to cause ocular toxicity and impairment of vision in epidemiological studies. To study the possible role of an excitotoxic mechanism in the ocular toxicity of tamoxifen, we investigated the effect of tamoxifen on retinal pigment epithelium (RPE) glutamate uptake in vitro. RPE, a layer of cells between photoreceptors and choroidal capillaries, contributes to the regulation of the concentration of the major excitatory amino acid, glutamate, in the sub-retinal space. Dysfunction in RPE glutamate uptake can lead to accumulation of extracellular glutamate and can cause various excitotoxic effects in the retina. The study was conducted by using cultured pig RPE cells. Six different tamoxifen citrate concentrations, ranging from lμM to 100μM, and [3H]-L-glutamate were added to the culture medium. To specify the glutamate uptake, 1mM dinitrophenol was added and a Na+-free culture was used. Due to the anti-oestrogenic character of tamoxifen, the possible effect of β-oestradiol on the glutamate uptake of RPE was also examined. The results show that glutamate uptake by RPE cells was reduced in the presence of tamoxifen, and that the reduction was dose-dependent. These results suggest that tamoxifen exposure could lead to the extracellular accumulation of glutamate. Disturbances in glutamate uptake can cause eye toxicity via an excitotoxic mechanism. The glutamate uptake of RPE cells was reduced under Na+-free conditions and was also reduced in the presence of dinitrophenol.
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Zou, Hui, Chenli Shan, Linlin Ma, Jia Liu, Ning Yang, and Jinsong Zhao. "Polarity and epithelial-mesenchymal transition of retinal pigment epithelial cells in proliferative vitreoretinopathy." PeerJ 8 (October 20, 2020): e10136. http://dx.doi.org/10.7717/peerj.10136.
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Under physiological conditions, retinal pigment epithelium (RPE) is a cellular monolayer composed of mitotically quiescent cells. Tight junctions and adherens junctions maintain the polarity of RPE cells, and are required for cellular functions. In proliferative vitreoretinopathy (PVR), upon retinal tear, RPE cells lose cell-cell contact, undergo epithelial-mesenchymal transition (EMT), and ultimately transform into myofibroblasts, leading to the formation of fibrocellular membranes on both surfaces of the detached retina and on the posterior hyaloids, which causes tractional retinal detachment. In PVR, RPE cells are crucial contributors, and multiple signaling pathways, including the SMAD-dependent pathway, Rho pathway, MAPK pathways, Jagged/Notch pathway, and the Wnt/β-catenin pathway are activated. These pathways mediate the EMT of RPE cells, which play a key role in the pathogenesis of PVR. This review summarizes the current body of knowledge on the polarized phenotype of RPE, the role of cell-cell contact, and the molecular mechanisms underlying the RPE EMT in PVR, emphasizing key insights into potential approaches to prevent PVR.
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Esteve-Rudd, Julian, Roni A. Hazim, Tanja Diemer, Antonio E. Paniagua, Stefanie Volland, Ankita Umapathy, and David S. Williams. "Defective phagosome motility and degradation in cell nonautonomous RPE pathogenesis of a dominant macular degeneration." Proceedings of the National Academy of Sciences 115, no. 21 (May 7, 2018): 5468–73. http://dx.doi.org/10.1073/pnas.1709211115.
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Stargardt macular dystrophy 3 (STGD3) is caused by dominant mutations in the ELOVL4 gene. Like other macular degenerations, pathogenesis within the retinal pigment epithelium (RPE) appears to contribute to the loss of photoreceptors from the central retina. However, the RPE does not express ELOVL4, suggesting photoreceptor cell loss in STGD3 occurs through two cell nonautonomous events: mutant photoreceptors first affect RPE cell pathogenesis, and then, second, RPE dysfunction leads to photoreceptor cell death. Here, we have investigated how the RPE pathology occurs, using a STGD3 mouse model in which mutant human ELOVL4 is expressed in the photoreceptors. We found that the mutant protein was aberrantly localized to the photoreceptor outer segment (POS), and that resulting POS phagosomes were degraded more slowly in the RPE. In cell culture, the mutant POSs are ingested by primary RPE cells normally, but the phagosomes are processed inefficiently, even by wild-type RPE. The mutant phagosomes excessively sequester RAB7A and dynein, and have impaired motility. We propose that the abnormal presence of ELOVL4 protein in POSs results in phagosomes that are defective in recruiting appropriate motor protein linkers, thus contributing to slower degradation because their altered motility results in slower basal migration and fewer productive encounters with endolysosomes. In the transgenic mouse retinas, the RPE accumulated abnormal-looking phagosomes and oxidative stress adducts; these pathological changes were followed by pathology in the neural retina. Our results indicate inefficient phagosome degradation as a key component of the first cell nonautonomous event underlying retinal degeneration due to mutant ELOVL4.
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Rajendran Nair, Deepthi S., Danhong Zhu, Ruchi Sharma, Juan Carlos Martinez Camarillo, Kapil Bharti, David R. Hinton, Mark S. Humayun, and Biju B. Thomas. "Long-Term Transplant Effects of iPSC-RPE Monolayer in Immunodeficient RCS Rats." Cells 10, no. 11 (October 29, 2021): 2951. http://dx.doi.org/10.3390/cells10112951.
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Retinal pigment epithelium (RPE) replacement therapy is evolving as a feasible approach to treat age-related macular degeneration (AMD). In many preclinical studies, RPE cells are transplanted as a cell suspension into immunosuppressed animal eyes and transplant effects have been monitored only short-term. We investigated the long-term effects of human Induced pluripotent stem-cell-derived RPE (iPSC-RPE) transplants in an immunodeficient Royal College of Surgeons (RCS) rat model, in which RPE dysfunction led to photoreceptor degeneration. iPSC-RPE cultured as a polarized monolayer on a nanoengineered ultrathin parylene C scaffold was transplanted into the subretinal space of 28-day-old immunodeficient RCS rat pups and evaluated after 1, 4, and 11 months. Assessment at early time points showed good iPSC-RPE survival. The transplants remained as a monolayer, expressed RPE-specific markers, performed phagocytic function, and contributed to vision preservation. At 11-months post-implantation, RPE survival was observed in only 50% of the eyes that were concomitant with vision preservation. Loss of RPE monolayer characteristics at the 11-month time point was associated with peri-membrane fibrosis, immune reaction through the activation of macrophages (CD 68 expression), and the transition of cell fate (expression of mesenchymal markers). The overall study outcome supports the therapeutic potential of RPE grafts despite the loss of some transplant benefits during long-term observations.
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Si, Zhibo, Yajuan Zheng, and Jing Zhao. "The Role of Retinal Pigment Epithelial Cells in Age-Related Macular Degeneration: Phagocytosis and Autophagy." Biomolecules 13, no. 6 (May 29, 2023): 901. http://dx.doi.org/10.3390/biom13060901.
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Age-related macular degeneration (AMD) causes vision loss in the elderly population. Dry AMD leads to the formation of Drusen, while wet AMD is characterized by cell proliferation and choroidal angiogenesis. The retinal pigment epithelium (RPE) plays a key role in AMD pathogenesis. In particular, helioreceptor renewal depends on outer segment phagocytosis of RPE cells, while RPE autophagy can protect cells from oxidative stress damage. However, when the oxidative stress burden is too high and homeostasis is disturbed, the phagocytosis and autophagy functions of RPE become damaged, leading to AMD development and progression. Hence, characterizing the roles of RPE cell phagocytosis and autophagy in the pathogenesis of AMD can inform the development of potential therapeutic targets to prevent irreversible RPE and photoreceptor cell death, thus protecting against AMD.
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Shang, Peng, Nadezda A. Stepicheva, Haitao Liu, Olivia Chowdhury, Jonathan Franks, Ming Sun, Stacey Hose, et al. "A Novel Method of Mouse RPE Explant Culture and Effective Introduction of Transgenes Using Adenoviral Transduction for In Vitro Studies in AMD." International Journal of Molecular Sciences 22, no. 21 (November 5, 2021): 11979. http://dx.doi.org/10.3390/ijms222111979.
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Degeneration of retinal pigment epithelium (RPE) is one of the most critical phenotypic changes of age-related macular degeneration (AMD), the leading cause of vision loss in the elderly. While cultured polarized RPE cells with original properties are valuable in in vitro models to study RPE biology and the consequences of genetic and/or pharmacological manipulations, the procedure to establish mouse primary PRE cell culture or pluripotent stem cell-derived RPE cells is time-consuming and yields a limited number of cells. Thus, establishing a mouse in situ RPE culture system is highly desirable. Here we describe a novel and efficient method for RPE explant culture that allows for obtaining biologically relevant RPE cells in situ. These RPE explants (herein referred to as RPE flatmounts) are viable in culture for at least 7 days, can be efficiently transduced with adenoviral constructs, and/or treated with a variety of drugs/chemicals followed by downstream analysis of the signaling pathways/biological processes of interest, such as assessment of the autophagy flux, inflammatory response, and receptor tyrosine kinases stimulation. This method of RPE explant culture is highly beneficial for pharmacological and mechanistic studies in the field of RPE biology and AMD research.
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Fanelli, Giorgia, Marco Romano, Giovanna Lombardi, and Steven H. Sacks. "Soluble Collectin 11 (CL-11) Acts as an Immunosuppressive Molecule Potentially Used by Stem Cell-Derived Retinal Epithelial Cells to Modulate T Cell Response." Cells 12, no. 13 (July 7, 2023): 1805. http://dx.doi.org/10.3390/cells12131805.
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Retinal pigment epithelium (RPE) cell allotransplantation is seen as a possible solution to retinal diseases. However, the RPE-complement system triggered by the binding of collectin-11 (CL-11) is a potential barrier for RPE transplantation as the complement-mediated inflammatory response may promote T cell recognition. To address this, we investigated the role of CL-11 on T cell immuno-response. We confirmed that RPE cells up-regulated MHC class I and expressed MHC class II molecules in an inflammatory setting. Co-cultures of RPE cells with T cells led to the inhibition of T cell proliferation. We found that CL-11 was partially responsible for this effect as T cell binding of CL-11 inhibited T cell proliferation in association with the downregulation of CD28. We also found that the suppressive action of CL-11 was abrogated in the presence of the RGD peptide given to block the T cell binding of CL-11 by its collagen-like domain. Because RPE cells can bind and secrete CL-11 under stress conditions, we postulate that soluble CL-11 contributes to the immunosuppressive properties of RPE cells. The investigation of this dual biological activity of CL-11, namely as a trigger of the complement cascade and a modulator of T cell responses, may provide additional clues about the mechanisms that orchestrate the immunogenic properties of RPE cells.
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Zhu, Xin-Yue, Ting Zhang, Su-Jun Liu, Xin-Yue Bai, Xian-Yu Huang, Mei Jiang, and Xiao-Dong Sun. "Improvement of human embryonic stem cell-derived retinal pigment epithelium cell adhesion, maturation, and function through coating with truncated recombinant human vitronectin." International Journal of Ophthalmology 14, no. 8 (August 18, 2021): 1160–67. http://dx.doi.org/10.18240/ijo.2021.08.04.
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AIM: To explore an xeno-free and defined coating substrate suitable for the culture of H9 human embryonic stem cell-derived retinal pigment epithelial (hES-RPE) cells in vitro, and compare the behaviors and functions of hES-RPE cells on two culture substrates, laminin521 (LN-521) and truncated recombinant human vitronectin (VTN-N). METHODS: hES-RPE cells were used in the experiment. The abilities of LN-521 and VTN-N at different concentrations to adhere to hES-RPE cells were compared with a high-content imaging system. Quantitative real-time polymerase chain reaction was used to evaluate RPE-specific gene expression levels midway (day 10) and at the end (day 20) of the time course. Cell polarity was observed by immunofluorescent staining for apical and basal markers of the RPE. The phagocytic ability of hES-RPE cells was identified by flow cytometry and immunofluorescence. RESULTS: The cell adhesion assay showed that the ability of LN-521 to adhere to hES-RPE cells was dose-dependent. With increasing coating concentration, an increasing number of cells attached to the surface of LN-521-coated wells. In contrast, VTN-N presented a strong adhesive ability even at a low concentration. The optimal concentration of LN-521 and VTN-N required to coat and adhesion to hES-RPE cells were 2 and 0.25 µg/cm2, respectively. Furthermore, both LN-521 and VTN-N could facilitate adoption of the desired cobblestone cellular morphology with tight junction and showed polarity by the hES-RPE cells. However, hES-RPE cells cultivated in VTN-N had a greater phagocytic ability, and it took less time for these hES-RPE cells to mature. CONCLUSION: VTN-N is a more suitable coating substrate for cultivating hES-RPE cells.
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Park, Sun Young, Woo Chang Song, Beomjin Kim, Jin-Woo Oh, and Geuntae Park. "Nano-Graphene Oxide-Promoted Epithelial–Mesenchymal Transition of Human Retinal Pigment Epithelial Cells through Regulation of Phospholipase D Signaling." Nanomaterials 11, no. 10 (September 28, 2021): 2546. http://dx.doi.org/10.3390/nano11102546.
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Nano-graphene oxide (Nano-GO) is an extensively studied multifunctional carbon nanomaterial with attractive applications in biomedicine and biotechnology. However, few studies have been conducted to assess the epithelial-to-mesenchymal transition (EMT) in the retinal pigment epithelium (RPE). We aimed to determine whether Nano-GO induces EMT by regulating phospholipase D (PLD) signaling in human RPE (ARPE-19) cells. The physicochemical characterization of Nano-GO was performed using a Zetasizer, X-ray diffraction, Fourier-transform infrared spectroscopy, and transmission electron microscopy. RPE cell viability assays were performed, and the migratory effects of RPE cells were evaluated. RPE cell collagen gel contraction was also determined. Intracellular reactive oxygen species (ROS) levels were determined by fluorescence microscopy and flow cytometry. Immunofluorescence staining and western blot analysis were used to detect EMT-related protein expression. Phospholipase D (PLD) enzymatic activities were also measured. Nano-GO significantly enhanced the scratch-healing ability of RPE cells, indicating that the RPE cell migration ability was increased. Following Nano-GO treatment, the RPE cell penetration of the chamber was significantly promoted, suggesting that the migratory ability was strengthened. We also observed collagen gel contraction and the generation of intracellular ROS in RPE cells. The results showed that Nano-GO induced collagen gel contraction and intracellular ROS production in RPE cells. Moreover, immunofluorescence staining and western blot analysis revealed that Nano-GO significantly regulated key molecules of EMT, including epithelial-cadherin, neural-cadherin, α-smooth muscle actin, vimentin, and matrix metalloproteinases (MMP-2 and MMP-9). Interestingly, Nano-GO-induced RPE cell migration and intracellular ROS production were abrogated in PLD-knockdown RPE cells, indicating that PLD activation played a crucial role in the Nano-GO-induced RPE EMT process. We demonstrate for the first time that Nano-GO promotes RPE cell migration through PLD-mediated ROS production. We provide preliminary evidence to support the hypothesis that Nano-GO has adverse health effects related to RPE damage.
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O’Neill, Helen C., Ioannis J. Limnios, and Nigel L. Barnett. "Advancing a Stem Cell Therapy for Age-Related Macular Degeneration." Current Stem Cell Research & Therapy 15, no. 2 (March 26, 2020): 89–97. http://dx.doi.org/10.2174/1574888x15666191218094020.
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The retinal pigment epithelium (RPE) is a multifunctional monolayer located at the back of the eye required for the survival and function of the light-sensing photoreceptors. In Age-related Macular Degeneration (AMD), the loss of RPE cells leads to photoreceptor death and permanent blindness. RPE cell transplantation aims to halt or reverse vision loss by preventing the death of photoreceptor cells and is considered one of the most viable applications of stem cell therapy in the field of regenerative medicine. Proof-of-concept of RPE cell transplantation for treating retinal degenerative disease, such as AMD, has long been established in animal models and humans using primary RPE cells, while recent research has focused on the transplantation of RPE cells derived from human pluripotent stem cells (hPSC). Early results from clinical trials indicate that transplantation of hPSC-derived RPE cells is safe and can improve vision in AMD patients. Current hPSC-RPE cell production protocols used in clinical trials are nevertheless inefficient. Treatment of large numbers of AMD patients using stem cellderived products may be dependent on the ability to generate functional cells from multiple hPSC lines using robust and clinically-compliant methods. Transplantation outcomes may be improved by delivering RPE cells on a thin porous membrane for better integration into the retina, and by manipulation of the outcome through control of immune rejection and inflammatory responses.
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Ng, Eunice Sze Yin, Nermin Kady, Jane Hu, Arpita Dave, Zhichun Jiang, Jacqueline Pei, Michael B. Gorin, Anna Matynia, and Roxana A. Radu. "Membrane Attack Complex Mediates Retinal Pigment Epithelium Cell Death in Stargardt Macular Degeneration." Cells 11, no. 21 (November 2, 2022): 3462. http://dx.doi.org/10.3390/cells11213462.
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Recessive Stargardt disease (STGD1) is an inherited retinopathy caused by mutations in the ABCA4 gene. The ABCA4 protein is a phospholipid-retinoid flippase in the outer segments of photoreceptors and the internal membranes of retinal pigment epithelial (RPE) cells. Here, we show that RPE cells derived via induced pluripotent stem-cell from a molecularly and clinically diagnosed STGD1 patient exhibited reduced ABCA4 protein and diminished activity compared to a normal subject. Consequently, STGD1 RPE cells accumulated intracellular autofluorescence-lipofuscin and displayed increased complement C3 activity. The level of C3 inversely correlated with the level of CD46, an early negative regulator of the complement cascade. Persistent complement dysregulation led to deposition of the membrane attack complex on the surface of RPE cells, decrease in transepithelial resistance, and subsequent cell death. These findings are strong evidence of complement-mediated RPE cell damage in STGD1, in the absence of photoreceptors, caused by reduced CD46 regulatory protein.
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Zhang, Yibing, Min Li, and Xue Han. "Icariin affects cell cycle progression and proliferation of human retinal pigment epithelial cells via enhancing expression of H19." PeerJ 8 (March 20, 2020): e8830. http://dx.doi.org/10.7717/peerj.8830.
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Background Aberrant proliferation of retinal pigment epithelial (RPE) cells under pathologic condition results in the occurrence of proliferative vitreoretinopathy (PVR). Icariin (ICA)-a flavonol glucoside-has been shown to inhibit proliferation of many cell types, but the effect on RPE cells is unknown. This study aimed to clarify the inhibitory effects of ICA on RPE cells against platelet-derived growth factor (PDGF)-BB-induced cell proliferation, and discuss the regulatory function of H19 in RPE cells. Methods MTS assay was conducted to determine the effects of ICA on cell proliferation. Flow cytometry analysis was performed to detect cell cycle progression. Quantitative real-time PCR and western blot assay were used to measure the expression patterns of genes in RPE cells. Results ICA significantly suppressed PDGF-BB-stimulated RPE cell proliferation in a concentration-dependent manner. Moreover, since administration of ICA induced cell cycle G0/G1 phase arrest, the anti-proliferative activity of ICA may be due to G0/G1 phase arrest in RPE cells. At molecular levels, cell cycle regulators cyclin D1, CDK4, CDK6, p21 and p53 were modulated in response to treatment with ICA. Most importantly, H19 was positively regulated by ICA and H19 depletion could reverse the inhibitory effects of ICA on cell cycle progression and proliferation in PDGF-BB-stimulated RPE cells. Further mechanical explorations showed that H19 knockdown resulted in alternative expressions levels of cyclin D1, CDK4, CDK6, p21 and p53 under ICA treatment. Conclusions Our findings revealed that ICA was an effective inhibitor of PDGF-BB-induced RPE cell proliferation through affecting the expression levels of cell cycle-associated factors, and highlighted the potential application of ICA in PVR therapy. H19 was described as a target regulatory gene of ICA whose disruption may contribute to excessive proliferation of RPE cells, suggesting that modulation of H19 expression may be a novel therapeutic approach to treat PVR.
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Nabi, I. R., A. P. Mathews, L. Cohen-Gould, D. Gundersen, and E. Rodriguez-Boulan. "Immortalization of polarized rat retinal pigment epithelium." Journal of Cell Science 104, no. 1 (January 1, 1993): 37–49. http://dx.doi.org/10.1242/jcs.104.1.37.
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Rat retinal pigment epithelial (RPE) cells were immortalized by infection with a temperature-sensitive tsA SV40 virus and following cloning and selection for epithelial properties the polarized RPE-J cell line was obtained. At the permissive temperature of 33 degrees C, RPE-J cells behave as an immortalized cell line. When RPE-J cells are grown on nitrocellulose filters coated with a thin layer of Matrigel in the presence of 10(−8) M retinoic acid for 6 days at 33 degrees C and then switched for 33–36 hours to the non-permissive temperature of 40 degrees C, they acquire a differentiated polarized RPE phenotype. Under these growth conditions, RPE-J cells exhibit circumferential staining for the tight-junction protein ZO-1 and acquire a transepithelial resistance of 350 ohms cm2. Morphologically, RPE-J cells exhibit a characteristic RPE morphology with extensive apical microvilli as well as numerous dense bodies including premelanosomes and varied multilamellar structures. Ruthenium red labeling revealed the frequent basal localization of the tight junction. The cells were identified to be of rat RPE origin by their expression of the rat RPE marker RET-PE2 and their ability to phagocytose latex beads. While RPE-J cells are capable of sorting influenza and vesicular stomatitis virus to the apical and basal surfaces, respectively, the Na,K-ATPase is not polarized and the neural cell adhesion molecule, N-CAM, is localized exclusively to the lateral surface. In vivo the apical surface of RPE interacts with the adjacent neural retina and the Na,K-ATPase and N-CAM are both apical; the altered polarity of these two proteins in RPE-J cells may be a consequence of the absence of apical interaction with the neural retina in culture. Previous studies of RPE have been restricted to the use of primary cultures and the RPE-J cell line should prove an excellent model system for the study of the mechanisms determining the characteristic polarity and functions of the retinal pigment epithelium.
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Takayama, Kei, Hiroki Kaneko, Keiko Kataoka, Reona Kimoto, Shiang-Jyi Hwang, Fuxiang Ye, Yosuke Nagasaka, et al. "Nuclear Factor (Erythroid-Derived)-Related Factor 2-Associated Retinal Pigment Epithelial Cell Protection under Blue Light-Induced Oxidative Stress." Oxidative Medicine and Cellular Longevity 2016 (2016): 1–9. http://dx.doi.org/10.1155/2016/8694641.
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Purpose. It is a matter of increasing concern that exposure to light-emitting diodes (LED), particularly blue light (BL), damages retinal cells. This study aimed to investigate the retinal pigment epithelium (RPE) damage caused by BL and to elucidate the role of nuclear factor (erythroid-derived)-related factor 2 (Nrf2) in the pathogenesis of BL-induced RPE damage.Methods. ARPE-19, a human RPE cell line, and mouse primary RPE cells from wild-type andNrf2knockout (Nrf2−/−) mice were cultured under blue LED exposure (intermediate wavelength, 450 nm). Cell death rate and reactive oxygen species (ROS) generation were measured. TUNEL staining was performed to detect apoptosis. Real-time polymerase chain reaction was performed onNRF2mRNA, and western blotting was performed to detect Nrf2 proteins in the nucleus or cytoplasm of RPE cells.Results. BL exposure increased cell death rate and ROS generation in ARPE-19 cells in a time-dependent manner; cell death was caused by apoptosis. Moreover, BL exposure inducedNRF2mRNA upregulation and Nrf2 nuclear translocation in RPE. Cell death rate was significantly higher in RPE cells fromNrf2−/−mice than from wild-type mice.Conclusions. The Nrf2 pathway plays an important role in protecting RPE cells against BL-induced oxidative stress.
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Hellinen, Pirskanen, Tengvall-Unadike, Urtti, and Reinisalo. "Retinal Pigment Epithelial Cell Line with Fast Differentiation and Improved Barrier Properties." Pharmaceutics 11, no. 8 (August 13, 2019): 412. http://dx.doi.org/10.3390/pharmaceutics11080412.
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Retinal pigment epithelium (RPE) acts as an outer blood–retinal barrier that limits the access of circulating xenobiotics to the eye. In addition, the RPE limits posterior elimination of intravitreally injected drugs to circulation. Thus, permeation in the RPE has a significant effect on ocular pharmacokinetics. The RPE is also a potentially important drug target in age-related macular degeneration. Therefore, the cell models of the RPE are important tools in ocular drug development, but poor availability and problems in reproducibility limit the use of primary RPE cell cultures. Furthermore, the best and widely used human cell line ARPE19 requires specialized culture conditions and a long time for cellular differentiation. In this paper, we describe a cell population arisen from the ARPE19 culture, with fast differentiation and improved barrier properties. This cell line, LEPI, forms clear microvilli and rapidly displays RPE-like cobblestone morphology after subculture in simple culture conditions. The LEPI cells show RPE-specific functions and expression of RPE65, ezrin, and BEST1 proteins. On filter, the LEPI cells develop tighter barrier than the ex vivo bovine RPE-choroid: permeability coefficients of beta-blockers (atenolol, nadolol, timolol, pindolol, metoprolol, betaxolol) ranged from 0.4 × 10−6 cm/sec to 2.3 × 10−6 cm/sec depending on the drug lipophilicity. This rapidly differentiating cell line will be an asset in ocular studies since it is easily maintained, it grows and differentiates quickly and does not require specialized culture conditions for differentiation. Thus, this cell line is suitable for both small scale assays and high throughput screening in drug discovery and development.
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Chen, Shiu-Jau, Tzer-Bin Lin, Hsien-Yu Peng, Hsiang-Jui Liu, An-Sheng Lee, Cheng-Hsien Lin, and Kuang-Wen Tseng. "Cytoprotective Potential of Fucoxanthin in Oxidative Stress-Induced Age-Related Macular Degeneration and Retinal Pigment Epithelial Cell Senescence In Vivo and In Vitro." Marine Drugs 19, no. 2 (February 18, 2021): 114. http://dx.doi.org/10.3390/md19020114.
Full textAbstract:
Oxidative stress is identified as a major inducer of retinal pigment epithelium (RPE) cell dysregulation and is associated with age-related macular degeneration (AMD). The protection of RPE disorders plays an essential role in the pathological progress of retinal degeneration diseases. The pharmacological functions of fucoxanthin, a characteristic carotenoid, including anti-inflammatory and antioxidant properties, may ameliorate an outstanding bioactivity against premature senescence and cellular dysfunction. This study demonstrates that fucoxanthin protects RPE cells from oxidative stress-induced premature senescence and decreased photoreceptor cell loss in a sodium iodate-induced AMD animal model. Similarly, oxidative stress induced by hydrogen peroxide, nuclear phosphorylated histone (γH2AX) deposition and premature senescence-associated β-galactosidase staining were inhibited by fucoxanthin pretreatment in a human RPE cell line, ARPE-19 cells. Results reveal that fucoxanthin treatment significantly inhibited reactive oxygen species (ROS) generation, reduced malondialdehyde (MDA) concentrations and increased the mitochondrial metabolic rate in oxidative stress-induced RPE cell damage. Moreover, atrophy of apical microvilli was inhibited in cells treated with fucoxanthin after oxidative stress. During aging, the RPE undergoes well-characterized pathological changes, including amyloid beta (Aβ) deposition, beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1) expression and tight junction disruption, which were also reduced in fucoxanthin-treated groups by immunofluorescence. Altogether, pretreatment with fucoxanthin may protect against premature senescence and cellular dysfunction in retinal cells by oxidative stress in experimental AMD animal and human RPE cell models.
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Maruotti, Julien, Srinivas R. Sripathi, Kapil Bharti, John Fuller, Karl J. Wahlin, Vinod Ranganathan, Valentin M. Sluch, et al. "Small-molecule–directed, efficient generation of retinal pigment epithelium from human pluripotent stem cells." Proceedings of the National Academy of Sciences 112, no. 35 (August 12, 2015): 10950–55. http://dx.doi.org/10.1073/pnas.1422818112.
Full textAbstract:
Age-related macular degeneration (AMD) is associated with dysfunction and death of retinal pigment epithelial (RPE) cells. Cell-based approaches using RPE-like cells derived from human pluripotent stem cells (hPSCs) are being developed for AMD treatment. However, most efficient RPE differentiation protocols rely on complex, stepwise treatments and addition of growth factors, whereas small-molecule–only approaches developed to date display reduced yields. To identify new compounds that promote RPE differentiation, we developed and performed a high-throughput quantitative PCR screen complemented by a novel orthogonal human induced pluripotent stem cell (hiPSC)-based RPE reporter assay. Chetomin, an inhibitor of hypoxia-inducible factors, was found to strongly increase RPE differentiation; combination with nicotinamide resulted in conversion of over one-half of the differentiating cells into RPE. Single passage of the whole culture yielded a highly pure hPSC-RPE cell population that displayed many of the morphological, molecular, and functional characteristics of native RPE.
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Wei, Ying, Uwimana Alexandre, and Xiang Ma. "Hydrogels to Support Transplantation of Human Embryonic Stem Cell-Derived Retinal Pigment Epithelial Cells." Brain Sciences 12, no. 12 (November 25, 2022): 1620. http://dx.doi.org/10.3390/brainsci12121620.
Full textAbstract:
Purpose: Retinal pigment epithelial (RPE) cells are highly specialized neural cells with several functions essential for vision. Progressive deterioration of RPE cells in elderly individuals can result in visual impairment and, ultimately, blinding disease. While human embryonic stem cell-derived RPE cell (hESC-RPE) growth conditions are generally harsher than those of cell lines, the subretinal transplantation of hESC-RPE is being clinically explored as a strategy to recover the damaged retina and improve vision. The cell-adhesion ability of the support is required for RPE transplantation, where pre-polarized cells can maintain specific functions on the scaffold. This work examined four typical biodegradable hydrogels as supports for hESC-RPE growth. Methods: Four biodegradable hydrogels were examined: gelatin methacryloyl (GelMA), hyaluronic acid methacryloyl (HAMA), alginate, and fibrin hydrogels. ARPE-19 and hESC-RPE cells were seeded onto the hydrogels separately, and the ability of these supports to facilitate adherence, proliferation, and homogeneous distribution of differentiated hESC-RPE cells was investigated. Furthermore, the hydrogel’s subretinal bio-compatibility was assessed in vivo. Results: We showed that ARPE-19 and hESC-RPE cells adhered and proliferated only on the fibrin support. The monolayer formed when cells reached confluency, demonstrating the polygonal semblance, and revealing actin filaments that moved along the cytoplasm. The expression of tight junction proteins at cell interfaces on the 14th day of seeding demonstrated the barrier function of epithelial cells on polymeric surfaces and the interaction between cells. Moreover, the expression of proteins crucial for retinal functions and matrix production was positively affected by fibrin, with an increment of PEDF. Our in vivo investigation with fibrin hydrogels revealed high short-term subretinal biocompatibility. Conclusions: The research of stem cell-based cell therapy for retinal degenerative diseases is more complicated than that of cell lines. Our results showed that fibrin is a suitable scaffold for hESC-RPE transplantation, which could be a new grafting material for tissue engineering RPE cells.
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Ishida, Masaaki, Sunao Sugita, Kenichi Makabe, Shota Fujii, Yoko Futatsugi, Hiroyuki Kamao, Suguru Yamasaki, et al. "A ROCK Inhibitor Promotes Graft Survival during Transplantation of iPS-Cell-Derived Retinal Cells." International Journal of Molecular Sciences 22, no. 6 (March 22, 2021): 3237. http://dx.doi.org/10.3390/ijms22063237.
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Currently, retinal pigment epithelium (RPE) transplantation includes sheet and single-cell transplantation, the latter of which includes cell death and may be highly immunogenic, and there are some issues to be improved in single-cell transplantation. Y-27632 is an inhibitor of Rho-associated protein kinase (ROCK), the downstream kinase of Rho. We herein investigated the effect of Y-27632 in vitro on retinal pigment epithelium derived from induced pluripotent stem cells (iPS-RPE cells), and also its effects in vivo on the transplantation of iPS-RPE cell suspensions. As a result, the addition of Y-27632 in vitro showed suppression of apoptosis, promotion of cell adhesion, and higher proliferation and pigmentation of iPS-RPE cells. Y-27632 also increased the viability of the transplant without showing obvious retinal toxicity in human iPS-RPE transplantation into monkey subretinal space in vivo. Therefore, it is possible that ROCK inhibitors can improve the engraftment of iPS-RPE cell suspensions after transplantation.
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Kiamehr, Mostafa, Alexa Klettner, Elisabeth Richert, Ali Koskela, Arto Koistinen, Heli Skottman, Kai Kaarniranta, Katriina Aalto-Setälä, and Kati Juuti-Uusitalo. "Compromised Barrier Function in Human Induced Pluripotent Stem-Cell-Derived Retinal Pigment Epithelial Cells from Type 2 Diabetic Patients." International Journal of Molecular Sciences 20, no. 15 (August 1, 2019): 3773. http://dx.doi.org/10.3390/ijms20153773.
Full textAbstract:
In diabetic patients, high blood glucose induces alterations in retinal function and can lead to visual impairment due to diabetic retinopathy. In immortalized retinal pigment epithelial (RPE) cultures, high glucose concentrations are shown to lead to impairment in epithelial barrier properties. For the first time, the induced pluripotent stem-cell-derived retinal pigment epithelium (hiPSC-RPE) cell lines derived from type 2 diabetics and healthy control patients were utilized to assess the effects of glucose concentration on the cellular functionality. We show that both type 2 diabetic and healthy control hiPSC-RPE lines differentiate and mature well, both in high and normal glucose concentrations, express RPE specific genes, secrete pigment epithelium derived factor, and form a polarized cell layer. Here, type 2 diabetic hiPSC-RPE cells had a decreased barrier function compared to controls. Added insulin increased the epithelial cell layer tightness in normal glucose concentrations, and the effect was more evident in type 2 diabetics than in healthy control hiPSC-RPE cells. In addition, the preliminary functionality assessments showed that type 2 diabetic hiPSC-RPE cells had attenuated autophagy detected via ubiquitin-binding protein p62/Sequestosome-1 (p62/SQSTM1) accumulation, and lowered pro- matrix metalloproteinase 2 (proMMP2) as well as increased pro-MMP9 secretion. These results suggest that the cellular ability to tolerate stress is possibly decreased in type 2 diabetic RPE cells.
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Lou, Hui, Chunpin Lian, Fanjun Shi, Liqun Chen, Sicheng Qian, Hui Wang, Xiaoyun Zhao, Xiaoyan Ji, Jingfa Zhang, and Guoxu Xu. "The Petri Dish-N2B27 Culture Condition Maintains RPE Phenotype by Inhibiting Cell Proliferation and mTOR Activation." Journal of Ophthalmology 2020 (August 14, 2020): 1–12. http://dx.doi.org/10.1155/2020/4892978.
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Objective. To develop a method for the rapid isolation of rat RPE cells with high yield and maintain its epithelial state in modified culture system. Methods. The eyeballs were incubated with dispase. The retina was isolated with RPE attached and cut into several pieces. Following a brief incubation in growth medium, large RPE sheets can be harvested rapidly. RPE cells were divided into four groups and cultured for several weeks, that is, (1) in cell culture dishes with 10% FBS containing medium (CC dish-FBS), (2) in petri dishes with 10% FBS containing medium (Petri dish-FBS), (3) in cell culture dishes with N2 and B27 containing medium (CC dish-N2B27), and (4) in petri dishes with N2 and B27 containing medium (Petri dish-N2B27). Morphological and biological characteristics were investigated using light microscopy, Q-PCR, and western blot. Results. The retina would curl inwardly during the growth medium incubation period, releasing RPE sheets in the medium. Compared with low density group (5,000 cells/cm2), RPE cells plated at high density (15,000 cells/cm2) can maintain RPE morphology for a more extended period. Meanwhile, plating RPE cells at low density significantly reduced the expression of RPE cell type-specific genes (RPE65, CRALBP, and bestrophin) and increased the expression of EMT-related genes (N-cadherin, fibronectin, and α-SMA), in comparison with the samples from the high density group. The petri dish culture condition reduced cell adhesion and thus inhibited RPE cell proliferation. As compared with other culture conditions, RPE cells in the petri dish-N2B27 condition could maintain RPE phenotype with increased expression of RPE-specific genes and decreased expression of EMT-related genes. The AKT/mTOR pathway was also decreased in petri dish-N2B27 condition. Conclusion. The current study provided an alternative method for easy isolation of RPE cells with high yield and maintenance of its epithelial morphology in the petri dish-N2B27 condition.
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Rohrer, Bärbel, Manas R. Biswal, Elisabeth Obert, Yujing Dang, Yanhui Su, Xiaofeng Zuo, Ben Fogelgren, Altaf A. Kondkar, Glenn P. Lobo, and Joshua H. Lipschutz. "Conditional Loss of the Exocyst Component Exoc5 in Retinal Pigment Epithelium (RPE) Results in RPE Dysfunction, Photoreceptor Cell Degeneration, and Decreased Visual Function." International Journal of Molecular Sciences 22, no. 10 (May 11, 2021): 5083. http://dx.doi.org/10.3390/ijms22105083.
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To characterize the mechanisms by which the highly conserved exocyst trafficking complex regulates eye physiology in zebrafish and mice, we focused on Exoc5 (also known as sec10), a central exocyst component. We analyzed both exoc5 zebrafish mutants and retinal pigmented epithelium (RPE)-specific Exoc5 knockout mice. Exoc5 is present in both the non-pigmented epithelium of the ciliary body and in the RPE. In this study, we set out to establish an animal model to study the mechanisms underlying the ocular phenotype and to establish if loss of visual function is induced by postnatal RPE Exoc5-deficiency. Exoc5−/− zebrafish had smaller eyes, with decreased number of melanocytes in the RPE and shorter photoreceptor outer segments. At 3.5 days post-fertilization, loss of rod and cone opsins were observed in zebrafish exoc5 mutants. Mice with postnatal RPE-specific loss of Exoc5 showed retinal thinning associated with compromised visual function and loss of visual photoreceptor pigments. Abnormal levels of RPE65 together with a reduced c-wave amplitude indicate a dysfunctional RPE. The retinal phenotype in Exoc5−/− mice was present at 20 weeks, but was more pronounced at 27 weeks, indicating progressive disease phenotype. We previously showed that the exocyst is necessary for photoreceptor ciliogenesis and retinal development. Here, we report that exoc5 mutant zebrafish and mice with RPE-specific genetic ablation of Exoc5 develop abnormal RPE pigmentation, resulting in retinal cell dystrophy and loss of visual pigments associated with compromised vision. Together, these data suggest that exocyst-mediated signaling in the RPE is required for RPE structure and function, indirectly leading to photoreceptor degeneration.
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Gundersen, D., J. Orlowski, and E. Rodriguez-Boulan. "Apical polarity of Na,K-ATPase in retinal pigment epithelium is linked to a reversal of the ankyrin-fodrin submembrane cytoskeleton." Journal of Cell Biology 112, no. 5 (March 1, 1991): 863–72. http://dx.doi.org/10.1083/jcb.112.5.863.
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In striking contrast to most other transporting epithelia (e.g., urinary or digestive systems), where Na,K-ATPase is expressed basolaterally, the retinal pigment epithelium (RPE) cells display Na,K-ATPase pumps on the apical membrane. We report here studies aimed to identify the mechanisms underlying this polarity "reversal" of the RPE Na,K-ATPase. By immunofluorescence on thin frozen sections, both alpha and beta subunits were localized on the apical surface of both freshly isolated rat RPE monolayers and RPE monolayers grown in culture. The polarity of the RPE cell is not completely reversed, however, since aminopeptidase, an apically located protein in kidney epithelia, was also found on the apical surface of RPE cells. We used subunit- and isoform-specific cDNA probes to determine that RPE Na,K-ATPase has the same isoform (alpha 1) as the one found in kidney. Ankyrin and fodrin, proteins of the basolateral membrane cytoskeleton of kidney epithelial cells known to be associated with the Na,K-ATPase (Nelson, W. J., and R. W. Hammerton. 1989. J. Cell Biol. 110:349-357) also displayed a reversed apical localization in RPE and were intimately associated to Na,K-ATPase, as revealed by cross-linking experiments. These results indicate that an entire membrane-cytoskeleton complex is assembled with opposite polarity in RPE cells. We discuss our observations in the context of current knowledge on protein sorting mechanisms in epithelial cells.
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Gnana-Prakasam, Jaya P., Muthusamy Thangaraju, Kebin Liu, Yonju Ha, Pamela M. Martin, Sylvia B. Smith, and Vadivel Ganapathy. "Absence of iron-regulatory protein Hfe results in hyperproliferation of retinal pigment epithelium: role of cystine/glutamate exchanger." Biochemical Journal 424, no. 2 (November 11, 2009): 243–52. http://dx.doi.org/10.1042/bj20090424.
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Haemochromatosis is an iron-overload disorder with age-dependent oxidative stress and dysfunction in a variety of tissues. Mutations in HFE (histocompatability leucocyte antigen class I-like protein involved in iron homoeostasis) are responsible for most cases of haemochromatosis. We demonstrated recently that HFE is expressed exclusively in the basal membrane of RPE (retinal pigment epithelium). In the present study, we used Hfe−/− mice to examine ferritin levels (an indirect readout for iron levels) and morphological changes in retina. We found increased ferritin accumulation in retina in 18-month-old, but not in 2-month-old, mice with considerable morphological damage compared with age-matched controls. The retinal phenotype included hypertrophy and hyperplasia of RPE. RPE cells isolated from Hfe−/− mice exhibited a hyperproliferative phenotype. We also compared the gene expression profile between wild-type and Hfe−/− RPE cells by microarray analysis. These studies showed that many cell cycle-related genes were differentially regulated in Hfe−/− RPE cells. One of the genes up-regulated in Hfe−/− RPE cells was Slc7a11 (where Slc is solute carrier) which codes for the ‘transporter proper’ xCT in the heterodimeric cystine/glutamate exchanger (xCT/4F2hc). This transporter plays a critical role in cellular glutathione status and cell-cycle progression. We confirmed the microarrray data by monitoring xCT mRNA levels by RT (reverse transcription)–PCR and also by measuring transport function. We also found increased levels of glutathione and the transcription factor/cell-cycle promoter AP1 (activator protein 1) in Hfe−/− RPE cells. Wild-type mouse RPE cells and human RPE cell lines, when loaded with iron by exposure to ferric ammonium citrate, showed increased expression and activity of xCT, reproducing the biochemical phenotype observed with Hfe−/− RPE cells.
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Duarri, Anna, Eduardo Rodríguez-Bocanegra, Gema Martínez-Navarrete, Marc Biarnés, Miriam García, Lucía Lee Ferraro, Bernd Kuebler, et al. "Transplantation of Human Induced Pluripotent Stem Cell-Derived Retinal Pigment Epithelium in a Swine Model of Geographic Atrophy." International Journal of Molecular Sciences 22, no. 19 (September 28, 2021): 10497. http://dx.doi.org/10.3390/ijms221910497.
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Background: The aim of this study was to test the feasibility and safety of subretinal transplantation of human induced pluripotent stem cell (hiPSC)-derived retinal pigment epithelium (RPE) cells into the healthy margins and within areas of degenerative retina in a swine model of geographic atrophy (GA). Methods: Well-delimited selective outer retinal damage was induced by subretinal injection of NaIO3 into one eye in minipigs (n = 10). Thirty days later, a suspension of hiPSC-derived RPE cells expressing green fluorescent protein was injected into the subretinal space, into the healthy margins, and within areas of degenerative retina. In vivo follow-up was performed by multimodal imaging. Post-mortem retinas were analyzed by immunohistochemistry and histology. Results: In vitro differentiated hiPSC-RPE cells showed a typical epithelial morphology, expressed RPE-related genes, and had phagocytic ability. Engrafted hiPSC-RPE cells were detected in 60% of the eyes, forming mature epithelium in healthy retina extending towards the border of the atrophy. Histological analysis revealed RPE interaction with host photoreceptors in the healthy retina. Engrafted cells in the atrophic zone were found in a patchy distribution but failed to form an epithelial-like layer. Conclusions: These results might support the use of hiPSC-RPE cells to treat atrophic GA by providing a housekeeping function to aid the overwhelmed remnant RPE, which might improve its survival and therefore slow down the progression of GA.
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Schustak, Joshua, Hongwei Han, Kyle Bond, Qian Huang, Magali Saint-Geniez, and Yi Bao. "Phenotypic high-throughput screening identifies aryl hydrocarbon receptor agonism as common inhibitor of toxin-induced retinal pigment epithelium cell death." PLOS ONE 19, no. 4 (April 18, 2024): e0301239. http://dx.doi.org/10.1371/journal.pone.0301239.
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The retinal pigment epithelium (RPE) is essential to maintain retinal function, and RPE cell death represents a key pathogenic stage in the progression of several blinding ocular diseases, including age-related macular degeneration (AMD). To identify pathways and compounds able to prevent RPE cell death, we developed a phenotypic screening pipeline utilizing a compound library and high-throughput screening compatible assays on the human RPE cell line, ARPE-19, in response to different disease relevant cytotoxic stimuli. We show that the metabolic by-product of the visual cycle all-trans-retinal (atRAL) induces RPE apoptosis, while the lipid peroxidation by-product 4-hydroxynonenal (4-HNE) promotes necrotic cell death. Using these distinct stimuli for screening, we identified agonists of the aryl hydrocarbon receptor (AhR) as a consensus target able to prevent both atRAL mediated apoptosis and 4-HNE-induced necrotic cell death. This works serves as a framework for future studies dedicated to screening for inhibitors of cell death, as well as support for the discussion of AhR agonism in RPE pathology.
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Jiang, Mei, Julian Esteve-Rudd, Vanda S. Lopes, Tanja Diemer, Concepción Lillo, Agrani Rump, and David S. Williams. "Microtubule motors transport phagosomes in the RPE, and lack of KLC1 leads to AMD-like pathogenesis." Journal of Cell Biology 210, no. 4 (August 10, 2015): 595–611. http://dx.doi.org/10.1083/jcb.201410112.
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The degradation of phagosomes, derived from the ingestion of photoreceptor outer segment (POS) disk membranes, is a major role of the retinal pigment epithelium (RPE). Here, POS phagosomes were observed to associate with myosin-7a, and then kinesin-1, as they moved from the apical region of the RPE. Live-cell imaging showed that the phagosomes moved bidirectionally along microtubules in RPE cells, with kinesin-1 light chain 1 (KLC1) remaining associated in both directions and during pauses. Lack of KLC1 did not inhibit phagosome speed, but run length was decreased, and phagosome localization and degradation were impaired. In old mice, lack of KLC1 resulted in RPE pathogenesis that was strikingly comparable to aspects of age-related macular degeneration (AMD), with an excessive accumulation of RPE and sub-RPE deposits, as well as oxidative and inflammatory stress responses. These results elucidate mechanisms of POS phagosome transport in relation to degradation, and demonstrate that defective microtubule motor transport in the RPE leads to phenotypes associated with AMD.