Retinal Pigment Epithelial Cell Function Research Articles

Dynamics of microRNA secreted via extracellular vesicles during the maturation of embryonic stem cell-derived retinal pigment epithelium.

Retinal pigment epithelial (RPE) cells are exclusive to the retina, critically multifunctional in maintaining the visual functions and health of photoreceptors and the retina. Despite their vital functions throughout lifetime, RPE cells lack regenerative capacity, rendering them vulnerable which can lead to degenerative retinal diseases. With advancements in stem cell technology enabling the differentiation of functional cells from pluripotent stem cells and leveraging the robust autocrine and paracrine functions of RPE cells, extracellular vesicles (EVs) secreted by RPE cells hold significant therapeutic potential in supplementing RPE cell activity. While previous research has primarily focused on the trophic factors secreted by RPE cells, there is a lack of studies investigating miRNA, which serves as a master regulator of gene expression. Profiling and defining the functional role of miRNA contained within RPE-secreted EVs is critical as it constitutes a necessary step in identifying the optimal phenotype of the EV-secreting cell and understanding the biological cargo of EVs to develop EV-based therapeutics. In this study, we present a comprehensive profile of miRNA in small extracellular vesicles (sEVs) secreted during RPE maturation following differentiation from human embryonic stem cells (hESCs); early-stage hESC-RPE (20-21 days in culture), mid-stage hESC-RPE (30-31 days in culture) and late-stage hESC-RPE (60-61 days in culture). This exploration is essential for ongoing efforts to develop and optimize EV-based intraocular therapeutics utilizing RPE-secreted EVs, which may significantly impact the function of dysfunctional RPE cells in retinal diseases.

Gastrodin ameliorates oxidative stress-induced RPE damage by facilitating autophagy and phagocytosis through PPARα-TFEB/CD36 signal pathway

Age-related macular degeneration (AMD), the leading cause of irreversible blindness in the elderly, is primarily characterized by the degeneration of the retinal pigment epithelium (RPE). However, effective therapeutic options for dry AMD are currently lacking, necessitating further exploration into preventive and pharmaceutical interventions. This study aimed to investigate the protective effects of gastrodin on RPE cells exposed to oxidative stress. We constructed an in vitro oxidative stress model of 4-hydroxynonenal (4-HNE) and performed RNA-seq, and demonstrated the protective effect of gastrodin through mouse experiments. Our findings reveal that gastrodin can inhibit 4-HNE-induced oxidative stress, effectively improving the mitochondrial and lysosomal dysfunction of RPE cells. We further elucidated that gastrodin promotes autophagy and phagocytosis through activating the PPARα-TFEB/CD36 signaling pathway. Interestingly, these outcomes were corroborated in a mouse model, in which gastrodin maintained retinal integrity and reduced RPE disorganization and degeneration under oxidative stress. The accumulation of LC3B and SQSTM1 in mouse RPE-choroid was also reduced. Moreover, activating PPARα and downstream pathways to restore autophagy and phagocytosis, thereby countering RPE injury from oxidative stress. In conclusion, this study demonstrated that gastrodin maintains the normal function of RPE cells by reducing oxidative stress, enhancing their phagocytic function, and restoring the level of autophagic flow. These findings suggest that gastrodin is a novel formulation with potential applications in the development of AMD disease.

The significance of upper glycolytic components in regulating retinal pigment epithelial cellular behavior

Cell adhesion to the extracellular matrix and its natural outcome of cell spreading, along with the maintenance of barrier activity, are essential behaviors of epithelial cells, including retinal pigment epithelium (RPE). Disruptions in these characteristics can result in severe vision-threatening diseases such as diabetic macular edema and age-related macular degeneration. However, the precise mechanisms underlying how RPE cells regulate their barrier integrity and cell spreading are not fully understood. This study aims to elucidate the relative importance of upper glycolytic components in governing these cellular behaviors of RPE cells. Electric Cell-Substrate Impedance Sensing (ECIS) technology was utilized to assess in real-time the effects of targeting various upper glycolytic enzymes on RPE barrier function and cell spreading by measuring cell resistance and capacitance, respectively. Specific inhibitors used included WZB117 for Glut1 inhibition, Lonidamine for Hexokinase inhibition, PFK158 for PFKFB3/PFK axis inhibition, and TDZD-8 for Aldolase inhibition. Additionally, the viability of RPE cells was evaluated using a lactate dehydrogenase (LDH) cytotoxicity assay. The most significant decrease in electrical resistance and increase in capacitance of RPE cells were observed due to dose-dependent inhibition of Glut1 using WZB117, as well as Aldolase inhibition with TDZD-8. LDH level analysis at 24–72 h post-treatment with WZB117 (1 and 10 μM) or TDZD-8 (1 μM) showed no significant difference compared to the control, indicating that the disruption of RPE functionality was not attributed to cell death. Lastly, inhibition of other upper glycolytic components, including PFKFB3/PFK with PFK158 or Hexokinase with Lonidamine, did not significantly affect RPE cell behavior. This study provides insights into the varied roles of upper glycolytic components in regulating the functionality of RPE cells. Specifically, it highlights the critical roles of Glut1 and Aldolase in preserving barrier integrity and promoting RPE cell adhesion and spreading. Such understanding will guide the development of safe interventions to treat RPE cell dysfunction in various retinal disorders.

Diabetes and high-glucose could upregulate the expression of receptor for activated C kinase 1 in retina.

Diabetic retinopathy (DR) is a major ocular complication of diabetes mellitus, leading to visual impairment. Retinal pigment epithelium (RPE) injury is a key component of the outer blood retinal barrier, and its damage is an important indicator of DR. Receptor for activated C kinase 1 (RACK1) activates protein kinase C-ε (PKC-ε) to promote the generation of reactive oxygen species (ROS) in RPE cells, leading to apoptosis. Therefore, we hypothesize that the activation of RACK1 under hypoxic/high-glucose conditions may promote RPE cell apoptosis by modulating PKC-ε/ROS, thereby disrupting the barrier effect of the outer blood retinal barrier and contributing to the progression of DR. To investigate the role and associated underlying mechanisms of RACK1 in the development of early DR. In this study, Sprague-Dawley rats and adult RPE cell line-19 (ARPE-19) cells were used as in vivo and in vitro models, respectively, to explore the role of RACK1 in mediating PKC-ε in early DR. Furthermore, the impact of RACK1 on apoptosis and barrier function of RPE cells was also investigated in the former model. Streptozotocin-induced diabetic rats showed increased apoptosis and up-regulated expression of RACK1 and PKC-ε proteins in RPE cells following a prolonged modeling. Similarly, ARPE-19 cells exposed to high glucose and hypoxia displayed elevated mRNA and protein levels of RACK1 and PKC-ε, accompanied by an increases in ROS production, apoptosis rate, and monolayer permeability. However, silencing RACK1 significantly downregulated the expression of PKC-ε and ROS, reduced cell apoptosis and permeability, and protected barrier function. RACK1 plays a significant role in the development of early DR and might serve as a potential therapeutic target for DR by regulating RPE apoptosis and barrier function.

The Impact of Aging on Ocular Diseases: Unveiling Complex Interactions.

Aging is characterized by a progressive loss of physiological integrity, leading to impaired function and increased vulnerability to death. Aging is an important risk factor for eye diseases. The gradual deterioration of ocular tissue structure and function with age leads to the onset and progression of ocular diseases. During aging, ocular tissues such as the lens, vitreous and retina are affected by age-related changes, such as oxidative stress and protein accumulation in the lens leading to cataract formation, and a decline in retinal pigment epithelial cell function associated with macular degeneration. This article reviews the relationships between aging and ocular diseases, takes age-related macular degeneration, age-related cataracts, glaucoma, diabetic retinal degeneration, and dry eye disease as focal points, analyses the complex interactions between aging and ocular diseases, and describes the therapeutic options and potential targets for age-related ocular diseases.

Clinical‐grade hPSC‐derived RPE grafts for the treatment of age‐related macular degeneration

Aims/Purpose: Age‐related Macular Degeneration (AMD), a prevalent global cause of vision loss in the elderly, necessitates the development of efficacious treatments. Existing therapies do not cure AMD due to its complexity and the irreversible loss of photoreceptors and Retinal Pigment Epithelium (RPE). Cell replacement therapies targeting faulty RPE cells offer potential for slowing AMD progression, but the immunocompatibility of such therapies is challenging. We aim to develop a cell therapy strategy to minimize immune rejection.Methods: Our strategy entailed establishing a Good Manufacturing Practice (GMP)‐compatible induced Pluripotent Stem Cell (iPSC) cell bank representing the most frequent homozygous human leukocyte antigen (HLA) haplotypes in the Andalusian population, facilitating derivation of immunocompatible RPE cells. We utilized and refined existing RPE differentiation protocols for generating clinically compliant RPE cells. Furthermore, we tested three bioscaffolds for RPE growth and maturation and compared the physical properties of the resulting RPE cell‐bioscaffold biopatch for transplantability.Results: We successfully established three GMP‐compatible iPSC lines featuring common homozygous HLA profiles. Through our refined differentiation protocols, these iPSCs were converted into functional, high‐purity and safe RPE cells. Comparative analysis of different bioscaffolds revealed variable capabilities for RPE growth, maturation and transplantability, thereby informing the final bioscaffold selection for RPE biopatch generation.Conclusions: Our study underscores the feasibility of generating clinical‐grade, immunocompatible iPSC‐derived RPE grafts using GMP‐compliant procedures for AMD treatment. This innovative approach addresses a critical unmet medical need and suggests potential for similar strategies in other cell replacement therapies. The selection of an optimal bioscaffold for RPE growth and maturation is critical for effective RPE biopatch development. Further pre‐clinical and clinical studies are required to evaluate the safety and efficacy of these RPE grafts in AMD treatment.

Microglia preserve visual function in the aging retina by supporting retinal pigment epithelial health

BackgroundIncreased age is a risk factor for the development and progression of retinal diseases including age-related macular degeneration (AMD). Understanding the changes that occur in the eye due to aging is important in enhancing our understanding of AMD pathogenesis and the development of novel AMD therapies. Microglia, the resident brain and retinal immune cells are associated with both maintaining homeostasis and protection of neurons and loss of microglia homeostasis could be a significant player in age related neurodegeneration. One important characteristic of retinal aging is the migration of microglia from the inner to outer retina where they reside in the subretinal space (SRS) in contact with the retinal pigment epithelial (RPE) cells. The role of aged subretinal microglia is unknown. Here, we depleted microglia in aged C57/BL6 mice fed for 6 weeks with a chow containing PLX5622, a small molecule inhibitor of colony-stimulating factor-1 receptor (Csf1r) required for microglial survival.ResultsThe subretinal P2RY12 + microglia in aged mice displayed a highly amoeboid and activated morphology and were filled with autofluorescence droplets reminiscent of lipofuscin. TEM indicates that subretinal microglia actively phagocytize shed photoreceptor outer segments, one of the main functions of retinal pigmented epithelial cells. PLX5622 treatment depleted up to 90% of the retinal microglia and was associated with significant loss in visual function. Mice on the microglia depletion diet showed reduced contrast sensitivity and significantly lower electroretinogram for the c-wave, a measurement of RPE functionality, compared to age-matched controls. The loss of c-wave coincided with a loss of RPE cells and increased RPE swelling in the absence of microglia.ConclusionsWe conclude that microglia preserve visual function in aged mice and support RPE cell function, by phagocytosing shed photoreceptor outer segments and lipids, therefore compensating for the known age-related decline of RPE phagocytosis.

Does taurine have a role in the phagocytic function of the retinal pigment epithelium?

AbstractPurpose: To study the role of taurine in the morphology and phagocytic function of the retinal pigment epithelium (RPE) in normal and dystrophic rats.Methods: Albino Sprague–Dawley (SD) rats and pigmented dystrophic Royal College of Surgeons (RCS‐p+) rats that suffer a severe form of inherited photoreceptor degeneration due to RPE phagocytosis impairment, were used for this study. SD rats received β‐alanine in drinking water (3%) for 2 months from P21 to induce taurine depletion and RCS‐p + rats received taurine supplementation in drinking water (0.2 M) for 24 days from P21. Groups of untreated RCS and SD rats were used as control. SD rats were processed 2 months after the start of treatment, while RCS rats were processed at P45. Twenty‐four hours before processing, the animals received an intravitreal injection of 1.5 μl of 3% fluorogold (FG) diluted in saline 24 to label the RPE cells. Animals were processed and the RPE was dissected flat‐mounted and observed using a confocal microscope (Leica SP8).Results: In control SD animals, Fluorogold (FG) accumulates homogeneously in the cytoplasm of the RPE cells. Taurine‐depleted SD animals showed less FG accumulation in the cytoplasm in all cells and, and some cells had FG accumulation only in part of the cytoplasm or no FG accumulation at all. Untreated RCS‐p + animals showed an inverted accumulation of FG because it appeared mainly in the membrane of the RPE but not in the cytoplasm. Finally, taurine‐treated RCS‐p + animals showed FG accumulation in the cytoplasm of the RPE cells, although the accumulation of FG was smaller than that found in SD rats.Conclusions: Taurine influences the phagocytic capacity of the RPE cells. Taurine depletion impairs the phagocytic capacity of the RPE cells in healthy retinas, and taurine supplementation improves the phagocytic function of RPE cells in dystrophic RCS‐p + rats.

Transient Retention of Photoreceptor Outer Segments in Matrigel-Embedded Retinal Organoids

Retinal organoids (ROs) are three-dimensional retinal tissues, which are differentiated in vitro from induced pluripotent stem cells (iPSC), ultimately forming all main retinal cell types under defined culture conditions. ROs show several highly specialized retinal features, including the outgrowth of photoreceptor outer segments (OSs). In vivo, the photoreceptor OSs are enveloped and maintained by protrusions of retinal pigment epithelium (RPE) cells, the so-called apical microvilli, while ROs fail to recapitulate this critical interaction in culture development. Here, we define specific co-culture conditions aiming to compensate for the missing physical proximity of RPE and OSs in RO development. Accordingly, functional RPE cells and ROs were differentiated simultaneously from the same iPSC clone, the former resulting in byproduct RPE or bRPE cells. While some co-culture approaches indicated a temporary functional interaction between bRPE and RO photoreceptors, they did not improve the photoreceptor histoarchitecture. In contrast, embedding ROs in a basement membrane extract without bRPE cells showed a robust improvement in the rate of photoreceptor OS retention. RO embedding is a quick and easy method that greatly enhances the preservation of photoreceptor OSs, an important structure for modelling retinal diseases with the involvement of photoreceptors.

Targeting Phospholipase D Pharmacologically Prevents Phagocytic Function Loss of Retinal Pigment Epithelium Cells Exposed to High Glucose Levels.

We previously described the participation of canonical phospholipase D isoforms (PLD1 and PLD2) in the inflammatory response of retinal pigment epithelium (RPE) cells exposed to high glucose concentrations (HG). Here, we studied the role of the PLD pathway in RPE phagocytic function. For this purpose, ARPE-19 cells were exposed to HG (33 mM) or to normal glucose concentration (NG, 5.5 mM) and phagocytosis was measured using pHrodo™ green bioparticles® or photoreceptor outer segments (POS). HG exposure for 48 and 72 h reduced phagocytic function of ARPE-19 cells, and this loss of function was prevented when cells were treated with 5 μM of PLD1 (VU0359595 or PLD1i) or PLD2 (VU0285655-1 or PLD2i) selective inhibitors. Furthermore, PLD1i and PLD2i did not affect RPE phagocytosis under physiological conditions and prevented oxidative stress induced by HG. In addition, we demonstrated PLD1 and PLD2 expression in ABC cells, a novel human RPE cell line. Under physiological conditions, PLD1i and PLD2i did not affect ABC cell viability, and partial silencing of both PLDs did not affect ABC cell POS phagocytosis. In conclusion, PLD1i and PLD2i prevent the loss of phagocytic function of RPE cells exposed to HG without affecting RPE function or viability under non-inflammatory conditions.

Oxidative stress-induced lncRNA CYLD-AS1 promotes RPE inflammation via Nrf2/miR-134-5p/NF-κB signaling pathway.

Oxidative stress-induced damage to and dysfunction of retinal pigment epithelium (RPE) cells are important pathogenetic factors of age-related macular degeneration (AMD); however, the underlying molecular mechanism is not fully understood. Long noncoding RNAs (lncRNAs) have important roles in various biological processes. In this study, using an oxidative damage model in RPE cells, we identified a novel oxidation-related lncRNA named CYLD-AS1. We further revealed that the expression of CYLD-AS1 was increased in RPEs during oxidative stress. Depletion of CYLD-AS1 promoted cell proliferation and mitochondrial function and protected RPE cells against hydrogen peroxide (H2 O2 )-induced damage. Mechanistically, CYLD-AS1 also regulated the expression of NRF2, which is related to oxidative stress, and NF-κB signaling pathway members, which are related to inflammation. Remarkably, these two signaling pathways were mediated by the CYLD-AS1 interactor miR-134-5p. Moreover, exosomes secreted by CYLD-AS1 knockdown RPE cells had a lower proinflammatory effect than those secreted by control cells. In summary, our study revealed that CYLD-AS1 affects the oxidative stress-related and inflammatory functions of RPE cells by sponging miR-134-5p to mediate NRF2/NF-κB signaling pathway activity, suggesting that targeting CYLD-AS1 could be a promising strategy for the treatment of AMD and related diseases.

NURR1 expression regulates retinal pigment epithelial–mesenchymal transition and age-related macular degeneration phenotypes

Phenotypic variations in the retinal pigment epithelial (RPE) layer are often a predecessor and driver of ocular degenerative diseases, such as age-related macular degeneration (AMD), the leading cause of vision loss in the elderly. We previously identified the orphan nuclear receptor-related 1 (NURR1), from a nuclear receptor atlas of human RPE cells, as a candidate transcription factor potentially involved in AMD development and progression. In the present study we characterized the expression of NURR1 as a function of age in RPE cells harvested from human donor eyes and in donor tissue from AMD patients. Mechanistically, we found an age-dependent shift in NURR1 dimerization from NURR1-RXRα heterodimers toward NURR1-NURR1 homodimers in primary human RPE cells. Additionally, overexpression and activation of NURR1 attenuated TNF-α-induced epithelial-to-mesenchymal transition (EMT) and migration, and modulated EMT-associated gene and protein expression in human RPE cells independent of age. In vivo, oral administration of IP7e, a potent NURR1 activator, ameliorated EMT in an experimental model of wet AMD and improved retinal function in a mouse model that presents with dry AMD features, impacting AMD phenotype, structure, and function of RPE cells, inhibiting accumulation of immune cells, and diminishing lipid accumulation. These results provide insight into the mechanisms of action of NURR1 in the aging eye, and demonstrate that the relative expression levels and activity of NURR1 is critical for both physiological and pathological functions of human RPE cells through RXRα-dependent regulation, and that targeting NURR1 may have therapeutic potential for AMD by modulating EMT, inflammation, and lipid homeostasis.

Suppression of EZH2 inhibits TGF-β1-induced EMT in human retinal pigment epithelial cells

Epithelial–mesenchymal transition (EMT) of retinal pigment epithelium (RPE) cells is critically involved in the occurrence of subretinal fibrosis. This study aimed to investigate the role of enhancer of zeste homolog 2 (EZH2) in EMT of human primary RPE cells and the underlying mechanisms of the anti-fibrotic effect of EZH2 suppression. Primary cultures of human RPE cells were treated with TGF-β1 for EMT induction. EZH2 was silenced by siRNA to assess the expression levels of epithelial and fibrotic markers using qRT-PCR, Western blot, and immunofluorescence staining assay. Furthermore, the cellular migration, proliferation and barrier function of RPE cells were evaluated. RNA-sequencing analyses were performed to investigate the underlying mechanisms of EZH2 inhibition. Herein, EZH2 silencing up-regulated epithelial marker ZO-1 and downregulated fibrotic ones including α-SMA, fibronectin, and collagen 1, alleviating EMT induced by TGF-β1 in RPE cells. Moreover, silencing EZH2 inhibited cellular migration and proliferation, but didn't affect cell apoptosis. Additionally, EZH2 suppression contributed to improved barrier functions after TGF-β1 stimulation. The results from RNA sequencing suggested that the anti-fibrotic effect of EZH2 inhibition was associated with the MAPK signaling pathway, cytokine-cytokine receptor interaction, and the TGF-beta signaling pathway. Our findings provide evidence that the suppression of EZH2 might reverse EMT and maintain the functions of RPE cells. EZH2 could be a potential therapeutic avenue for subretinal fibrosis.

Simulated microgravity promotes oxidative stress-induced apoptosis in ARPE-19 cells associated with Nrf2 signaling pathway

Spaceflight associated neuro-ocular syndrome (SANS) has become a high-risk complication for astronauts in the microgravity environment. Growing evidences suggest that altered hemodynamics of the cerebrospinal fluid system under microgravity may affect optic nerve-related structures and lead to ocular diseases. Retinal pigment epithelial (RPE) cells play a pivotal role in maintaining the blood-retinal barrier, participating in the metabolism of visual circulation. Previous study has observed that the structure, shape, adhesion, migration and angiogenesis of RPE cells were significantly changed under microgravity. However, the interrelated molecular mechanisms underlying the cytological functions of RPE cells under microgravity have yet to be elucidated. Here, we exposed ARPE-19 cells in Random Positioning Machine (RPM) system. The preliminary analysis of cytological functions found that the viability of ARPE-19 cells was decreased and the cell cycle was arrested in S phase. Further results revealed that elevated ROS in microgravity caused oxidative stress, resulting in the activation of the Nrf2-HO-1 pathway. Meanwhile, cells subjected to oxidative damage result in apoptosis by regulating the expression of apoptosis-related genes. Taken together, these findings have significant implications for the understanding the molecular mechanism of SANS.

Microglia Prevent the Loss of Visual Function in the Aging Retina by Maintaining the Health of Retinal Pigment Epithelial Cells

Even in healthy individuals, aging leads to the progressive deterioration of visual function that coincides with increasing cellular dysfunction in retinal neurons and retinal pigment epithelial (RPE) cells. Interestingly, aging also coincides with the migration of microglia from the inner to the outer retina where they reside in the subretinal space between photoreceptor outer segments and the apical surface of RPE. Healthy young microglia act as the immune sentinels of the retina, and thus are protective and maintain retinal homeostasis. However, age alters cellular functions and the role of aging subretinal microglia is not known. Here we investigated whether aged microglia residing in the subretinal space are either preventing or promoting loss of visual function.Microglia were depleted in 33‐month‐old C57/BL6 mice fed for 6 weeks with a chow containing PLX5622, a small molecule inhibitor of colony‐stimulating factor‐1 receptor (Csf1r) which is expressed by microglia and is required for their proliferation, differentiation, and survival. As a negative control, age‐matched mice received a control diet. Following microglia depletion, the optomotor reflex (OMR) was used to assess visual acuity and contrast sensitivity and electroretinogram (ERG) assessed retinal function. Morphological analysis was determined by immunohistochemical staining and TEM.To distinguish microglia from infiltrating macrophages, retinas from old mice were stained with P2RY12, a microglia‐specific marker. The vast majority of cells residing between the photoreceptor outer segments and RPE layer in old mice were P2RY12+ microglia. These cells displayed a highly amoeboid and activated morphology and were filled with autofluorescence droplets similar to lipofuscin. PLX5622 treatment depleted up to 90% of the microglia. Microglia preserved visual function, and in the absence of microglia, there was a significant loss of contrast sensitivity and ERG c‐wave, as compared with untreated controls. Loss of microglia coincided with a loss of RPE cells and increased RPE swelling indicating that microglia support RPE in aged animals. TEM indicates that subretinal microglia actively phagocytize shed photoreceptor outer segments, thereby compensating for the known age‐related decline of RPE phagocytosis.We conclude that microglia in aging mice migrate to the subretinal space of the outer retina to support and maintain RPE cell functions that preserves vision.

Cyanidin-3-glucoside improves the barrier function of retinal pigment epithelium cells by attenuating endoplasmic reticulum stress-induced apoptosis

Excessive exposure to blue light from smartphones, computers, and other video equipment causes retinal degeneration. Cyanidin-3-glucoside (C3G) exerts protective effects on retinal cells. However, the mechanism by which C3G enhances the barrier function of retinal pigment epithelial (RPE) cells remains unclear. This study investigated the effects of C3G on blue light-irradiated A2E-containing RPE cells and explored whether or not the endoplasmic reticulum (ER) stress and downstream nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathways are involved in the mechanism. Results showed that C3G (10 and 25 μM) observably increased the viability and inhibited the apoptosis of RPE cells. Furthermore, C3G enhanced the barrier function of RPE cells and upregulated the expression of tight junction proteins. Blue light irradiation triggered ER stress, but C3G significantly suppressed the PERK/eIF2α/ATF4/CHOP pathway and maintained normal ER morphology in RPE cells. C3G also activated the Nrf2 pathway to promote RPE survival, which was independent of ER stress modulating Nrf2 activity. This study suggests that C3G promotes the barrier function of RPE cells by regulating ER stress-induced apoptosis, thereby offering a new approach to preventing retinal diseases. Thus, C3G is a potential functional food ingredient to improve visual health.

Proteins Associated with Phagocytosis Alteration in Retinal Pigment Epithelial Cells Derived from Age-Related Macular Degeneration Patients.

Age-related macular degeneration (AMD) is partially characterized by retinal pigment epithelial (RPE) cell dysfunction. This study focused on phagocytosis activity and its involvement in AMD. Phagocytic activity was analyzed by flow cytometry using porcine photoreceptor outer segment (POS) and fluorescent beads in basal and under oxidative stress condition induced by Fe-NTA in fifteen hiPSC-RPE cell lines (six controls, six atrophic AMD and three exudative AMD). Oxidative stress exposure inhibited phagocytosis in the same manner for control, atrophic AMD (AMDa) and exudative AMD (AMDe) cell lines. However, altered phagocytosis in basal condition in hiPSC-RPE AMDa/e was observed compared to control cell lines. Gene expression after 3 or 24 h of POS incubation was analyzed by RNA-Seq based transcriptomic profiling. Differential gene expression was observed by RNA seq after 3 and 24 h POS exposure. We have focused on the genes involved in mTOR/PI3K-AKT/MEK-ERK pathway. We investigated differences in gene expression by analyzing the expression levels and activity of the corresponding proteins by Western blot. We showed the involvement of three proteins essential for phagocytosis activity: fak, tuberin and rictor. These findings demonstrate that hiPSC-RPE AMDa/e cells have a typical disease phenotype characterized by alteration of the main function of RPE cells, phagocytosis activity.

Ilex paraguariensis Extracts Prevent Oxidative Damage in a Mouse Model of Age-Related Macular Degeneration.

Age-related macular degeneration (AMD), a chronic disease of the retina, leads to severe visual loss. AMD affects the retinal pigment epithelium (RPE) and the visual cells (photoreceptors). RPE failure, the first step of this disease, is associated with oxidative stress. Since antioxidants can slow down AMD progression, the intake of foods and drinks rich in antioxidant compounds may reduce retinal damage. Ilex paraguariensis (yerba mate, YM) extracts reduce oxidative damage of RPE cells in vitro as shown in previous study. Here, the effects of YM drinking on RPE and photoreceptor survival after oxidative damage with sodium iodate (NaIO3; SI) in a murine AMD model are described. Funduscopy and histology show that YM treatment prevents RPE and photoreceptor damage. YM also increases the expression of NRF2, the master antioxidant gene, and its effectors HO-1 and SOD2. In mice receiving YM and SI, the antioxidant response is larger than in mice receiving YM or SI alone. The YM drink also increases expression of RPE65, a gene that is involved in the functionality and survival of photoreceptors and RPE cells. The results suggest YM can play an important role in the prevention of retinal damage associated with oxidative stress, such as AMD.

Human Amniotic Epithelial Stem Cell-Derived Retinal Pigment Epithelium Cells Repair Retinal Degeneration.

Age-related macular degeneration (AMD), featured with dysfunction and loss of retinal pigment epithelium (RPE), is lacking efficient therapeutic approaches. According to our previous studies, human amniotic epithelial stem cells (hAESCs) may serve as a potential seed cell source of RPE cells for therapy because they have no ethical concerns, no tumorigenicity, and little immunogenicity. Herein, trichostatin A and nicotinamide can direct hAESCs differentiation into RPE like cells. The differentiated cells display the morphology, marker expression and cellular function of the native RPE cells, and noticeably express little MHC class II antigens and high level of HLA-G. Moreover, visual function and retinal structure of Royal College of Surgeon (RCS) rats, a classical animal model of retinal degeneration, were rescued after subretinal transplantation with the hAESCs-derived RPE like cells. Our study possibly makes some contribution to the resource of functional RPE cells for cell therapy. Subretinal transplantation of hAESCs-RPE could be an optional therapeutic strategy for retinal degeneration diseases.

FHL-1 interacts with human RPE cells through the \u03b15\u03b21 integrin and confers protection against oxidative stress

Retinal pigment epithelial (RPE) cells that underlie the neurosensory retina are essential for the maintenance of photoreceptor cells and hence vision. Interactions between the RPE and their basement membrane, i.e. the inner layer of Bruch’s membrane, are essential for RPE cell health and function, but the signals induced by Bruch’s membrane engagement, and their contributions to RPE cell fate determination remain poorly defined. Here, we studied the functional role of the soluble complement regulator and component of Bruch’s membrane, Factor H-like protein 1 (FHL-1). Human primary RPE cells adhered to FHL-1 in a manner that was eliminated by either mutagenesis of the integrin-binding RGD motif in FHL-1 or by using competing antibodies directed against the α5 and β1 integrin subunits. These short-term experiments reveal an immediate protein-integrin interaction that were obtained from primary RPE cells and replicated using the hTERT-RPE1 cell line. Separate, longer term experiments utilising RNAseq analysis of hTERT-RPE1 cells bound to FHL-1, showed an increased expression of the heat-shock protein genes HSPA6, CRYAB, HSPA1A and HSPA1B when compared to cells bound to fibronectin (FN) or laminin (LA). Pathway analysis implicated changes in EIF2 signalling, the unfolded protein response, and mineralocorticoid receptor signalling as putative pathways. Subsequent cell survival assays using H2O2 to induce oxidative stress-induced cell death suggest hTERT-RPE1 cells had significantly greater protection when bound to FHL-1 or LA compared to plastic or FN. These data show a non-canonical role of FHL-1 in protecting RPE cells against oxidative stress and identifies a novel interaction that has implications for ocular diseases such as age-related macular degeneration.