Bone morphogenetic protein-6 suppresses TGF-β2-induced epithelial-mesenchymal transition in retinal pigment epithelium

AIM

To evaluate the effect of bone morphogenetic protein-6 (BMP-6) on transforming growth factor (TGF)-β2-induced epithelial-mesenchymal transition (EMT) in retinal pigment epithelium (RPE).

METHODS

Adult retinal pigment epithelial cell line (ARPE-19) were randomly divided into control, TGF-β2 (5 µg/L), and BMP-6 small interfering RNA (siRNA) group. The cell morphology was observed by microscopy, and the cell migration ability were detected by Transwell chamber. The EMT-related indexes and BMP-6 protein levels were detected by Western blotting. Furthermore, a BMP-6 overexpression plasmid was constructed and RPE cells were divided into the control group, TGF-β2+empty plasmid group, BMP-6 overexpression group, and TGF-β2+BMP-6 overexpression group. The EMT-related indexes and extracellular regulated protein kinases (ERK) protein levels were detected.

RESULTS

Compared with the control group, the migration of RPE cells in the TGF-β2 group was significantly enhanced. TGF-β2 increased the protein expression levels of α-smooth muscle actin (α-SMA), fibronectin and vimentin but significantly decreased the protein levels of E-cadherin and BMP-6 (P<0.05) in RPE. Similarly, the migration of RPE cells in the BMP-6 siRNA group was also significantly enhanced. BMP-6 siRNA increased the protein expression levels of α-SMA, fibronectin and vimentin but significantly decreased the protein expression levels of E-cadherin (P<0.05). Overexpression of BMP-6 inhibited the migration of RPE cells induced by TGF-β2 and prevented TGF-β2 from affecting EMT-related biomarkers (P<0.05).

CONCLUSION

BMP-6 prevents the EMT in RPE cells induced by TGF-β2, which may provide a theoretical basis for the prevention and treatment of proliferative vitreoretinopathy.

SIRT1/P53 in retinal pigment epithelial cells in diabetic retinopathy: a gene co-expression analysis and He-Ying-Qing-Re formula treatment

Objective

Diabetic retinopathy (DR) is a severe diabetic complication that leads to severe visual impairment or blindness. He-Ying-Qing-Re formula (HF), a traditional Chinese medicinal concoction, has been identified as an efficient therapy for DR with retinal vascular dysfunction for decades and has been experimentally reported to ameliorate retinal conditions in diabetic mice. This study endeavors to explore the therapeutic potential of HF with key ingredients in DR and its underlying novel mechanisms.

Methods

Co-expression gene modules and hub genes were calculated by weighted gene co-expression network analysis (WGCNA) based on transcriptome sequencing data from high-glucose-treated adult retinal pigment epithelial cell line-19 (ARPE-19). The chromatographic fingerprint of HF was established by ultra-performance liquid chromatography coupled with high-resolution mass spectrometry (UPLC-Q-TOF-MS). The molecular affinity of the herbal compound was measured by molecular docking. Reactive oxygen species (ROS) was measured by a DCFDA/H2DCFDA assay. Apoptosis was detected using the TUNEL Assay Kit, while ELISA, Western blot, and real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) were used for detecting the cytokine, protein, and mRNA expressions, respectively.

Results

Key compounds in HF were identified as luteolin, paeoniflorin, and nobiletin. For WGCNA, ME-salmon ("protein deacetylation") was negatively correlated with ME-purple ("oxidative impairment") in high-glucose-treated ARPE-19. Luteolin has a high affinity for SIRT1 and P53, as indicated by molecular docking. Luteolin has a hypoglycemic effect on type I diabetic mice. Moreover, HF and luteolin suppress oxidative stress production (ROS and MDA), inflammatory factor expression (IL-6, TNF-α, IL1-β, and MCP-1), and apoptosis, as shown in the in vivo and in vitro experiments. Concurrently, treatment with HF and luteolin led to an upregulation of SIRT1 and a corresponding downregulation of P53.

Conclusion

Using HF and its active compound luteolin as therapeutic agents offers a promising approach to diabetic retinopathy treatment. It primarily suppressed protein acetylation and oxidative stress via the SIRT1/P53 pathway in retinal pigment epithelial cells.

Preparation of Lutein Nanoparticles by Glycosylation of Saccharides and Casein for Protecting Retinal Pigment Epithelial Cells

Age-related macular degeneration (AMD), a leading cause of visual impairment in the aging population, lacks effective treatment options due to a limited understanding of its pathogenesis. Lutein, with its strong antioxidant properties and ability to mitigate AMD by absorbing ultraviolet (UV) rays, faces challenges related to its stability and bioavailability in functional foods. In this study, we aimed to develop delivery systems using protein-saccharide conjugates to enhance lutein delivery and protect adult retinal pigment epithelial (ARPE-19) cells against sodium iodate (NaIO3)-induced damage. Various saccharides, including mannose, galactose, lactose, maltose, dextran, and maltodextrin, were conjugated to casein via the Maillard reaction for lutein delivery. The resulting lutein-loaded nanoparticles exhibited small size and spherical characteristics and demonstrated improved thermal stability and antioxidant capacity compared to free lutein. Notably, these nanoparticles were found to be nontoxic, as evidenced by reduced levels of cellular reactive oxygen species production (167.50 ± 3.81, 119.57 ± 3.45, 195.15 ± 1.41, 183.96 ± 3.11, 254.21 ± 3.97, 283.56 ± 7.27%) and inhibition of the mitochondrial membrane potential decrease (58.60 ± 0.29, 65.05 ± 2.91, 38.88 ± 1.81, 42.95 ± 1.39, 23.52 ± 1.04, 25.24 ± 0.08%) caused by NaIO3, providing protection against cellular damage and death. Collectively, our findings suggest that lutein-loaded nanoparticles synthesized via the Maillard reaction hold promise for enhanced solubility, oral bioavailability, and biological efficacy in the treatment of AMD.

Inhibition of Connective Tissue Growth Factor Expression in Adult Retinal Pigment Epithelial-19 Cells by Blocking Yes-Associated Protein/Transcriptional Coactivator with PDZ-Binding Motif Activity

Purpose: To investigate the effect of yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) on connective tissue growth factor (CTGF) expression in adult retinal pigment epithelial (ARPE)-19 cells. We also studied the inhibitory effect of K-975, a new pan-transcriptional enhanced associate domain (TEAD) inhibitor, and luteolin, a plant-derived flavonoid on CTGF expression. Methods: ARPE-19 cells were transfected with either YAP or TAZ overexpression plasmid or treated with transforming growth factor (TGF)-β2. The cells were cultured either with or without K-975 or luteolin. The expression of YAP, TAZ, and CTGF was examined using real-time PCR. Results: ARPE-19 cells overexpressing YAP or TAZ exhibited significantly increased CTGF expression. This increase was attenuated by K-975 or luteolin alone. TGF-β2 treatment significantly raised the expression of not just YAP and TAZ, but also CTGF in ARPE-19 cells. TGF-β2 treatment-enhanced CTGF expression was considerably lowered by the addition of K-975 or luteolin. Conclusions: Overexpression of YAP or TAZ and treatment with TGF-β2 led to an increase in the expression of CTGF in ARPE-19 cells. These increases were attenuated by treatment with K-975 and luteolin. These findings suggest that YAP and TAZ may be related to the expression of CTGF in ARPE-19 cells and that K-975 and luteolin can be explored as potential therapeutic agents for preventing CTGF production in vitreoretinal fibrosis.

Gigantol protects retinal pigment epithelial cells against high glucose-induced apoptosis, oxidative stress and inflammation by inhibiting MTDH-mediated NF-kB signaling pathway

OBJECTIVE

As a frequent complication of diabetes mellitus (DM), diabetic retinopathy (DR) is now one of the major causes of blindness. Recent reports have shown that retinal pigment epithelial cell (RPEC) damage plays an essential part in DR development and progression. This work intended to explore the potential effects of Gigantol on high glucose (HG)-stimulated RPEC damage and identify potential mechanisms.

METHODS

Cell viability, cell damage, and cell apoptosis were evaluated by CCK-8, lactate dehydrogenase (LDH) and flow cytometry assays. The levels of oxidative stress biomarkers and pro-inflammatory cytokines were assessed using corresponding commercial kits and ELISA. Additionally, the levels of MTDH and NF-kB signaling pathway-related proteins were detected by western blotting.

RESULTS

Gigantol dose-dependently enhanced cell viability and decreased apoptosis in HG-challenged ARPE-19 cells. Also, Gigantol notably relieved oxidative stress and inflammatory responses in ARPE-19 cells under HG conditions. Gigantol dose-dependently suppressed MTDH expression. In addition, MTDH restoration partially counteracted the protective effects of Gigantol on ARPE-19 cells subject to HG treatment. Mechanically, Gigantol inactivated the NF-kB signaling pathway, which was partly restored after MTDH overexpression.

CONCLUSION

Our findings suggested that Gigantol protected against HG-induced RPEC damage by inactivating the NF-kB signaling via MTDH inhibition, offering a potent therapeutic drug for DR treatment.

Lee Extract Alleviates Oxidative Stress and Inflammation in H2O2-Treated Retinal Pigment Epithelial Cells and in High-Fat Diet-Fed Mouse Retinas

BACKGROUND

Age-related macular degeneration (AMD) is the most common cause of visual disorders in the aged population and is characterized by the formation of retinal pigment epithelium (RPE) deposits and dysfunction/death of the RPE and photoreceptors. It is supposed that both oxidative stress and inflammation play a critical role in the pathogenesis of AMD. The development of therapeutic strategies against oxidative stress and inflammation in AMD is urgently needed. Rubus suavissimus S. Lee (RS), a medicinal plant growing in the southwest region of China, has been used as an herbal tea and medicine for various diseases.

METHODS

In this project, we evaluate the therapeutic potential of RS extract for AMD. We prepared RS extracts from dried leaves, which contained the main functional compounds.

RESULTS

RS extract significantly increased cell viability, upregulated the expression of antioxidant genes, lowered the generation of malondialdehyde and reactive oxygen species, and suppressed inflammation in H2O2-treated human RPE cells. In the in vivo study, treatment with RS extract attenuated body weight gain, lowered cholesterol and triglyceride levels in the liver and serum, increased antioxidant capacity, and alleviated inflammation in the retina and RPE/choroid of mice fed a high-fat diet.

CONCLUSIONS

Our findings suggest that RS extract offers therapeutic potential for treating AMD patients.

PRGF Membrane with Tailored Optical Properties Preserves the Cytoprotective Effect of Plasma Rich in Growth Factors: In Vitro Model of Retinal Pigment Epithelial Cells

The present study evaluates the ability of a novel plasma rich in growth factors (PRGF) membrane with improved optical properties to reduce oxidative stress in retinal pigment epithelial cells (ARPE-19 cells) exposed to blue light. PRGF was obtained from three healthy donors and divided into four main groups: (i) PRGF membrane (M-PRGF), (ii) PRGF supernatant (S-PRGF), (iii) platelet-poor plasma (PPP) membrane diluted 50% with S-PRGF (M-PPP 50%), and (iv) M-PPP 50% supernatant (S-PPP 50%). ARPE-19 cells were exposed to blue light and then incubated with the different PRGF-derived formulations or control for 24 and 48 h under blue light exposure. Mitochondrial and cell viability, reactive oxygen species (ROS) production, and heme oxygenase-1 (HO-1) and ZO-1 expression were evaluated. Mitochondrial viability and cell survival were significantly increased after treatment with the different PRGF-derived formulations. ROS synthesis and HO-1 expression were significantly reduced after cell treatment with any of the PRGF-derived formulations. Furthermore, the different PRGF-derived formulations significantly increased ZO-1 expression in ARPE-19 exposed to blue light. The new PRGF membrane with improved optical properties and its supernatant (M-PPP 50% and S-PPP 50%) protected and reversed blue light-induced oxidative stress in ARPE-19 cells at levels like those of a natural PRGF membrane and its supernatant.

Palmitic acid promotes human retinal pigment epithelial cells migration by upregulating miR-222 expression and inhibiting NUMB

High glucose promotes retinal pigment epithelial cell (RPEC) migration. However, the underlying molecular mechanisms explaining how high fatty acid levels affect RPEC migration remain largely unknown. We investigated whether and how palmitic acid (PA) impacts the migration of human RPEC cell line ARPE-19. ARPE-19 cells were treated with varying doses of palmitic acid, and the RPEC migration was evaluated by scratch and transwell migration assays. Cell viability was determined by the CCK-8 method. The levels of epithelial-mesenchymal transition (EMT)-associated proteins, including E-cadherin, vimentin, MMP2, and MMP3, were evaluated by western blot. The microRNAs and mRNAs levels were assessed by quantitative PCR. miRNA targets were predicted with online tools and validated with the luciferase reporter assay. miRNA mimics, inhibitors, and siRNA oligos were used to perform gain-of-function and loss-of-function studies. We found that PA increased viability of ARPE-19 cells, promoted their migration and EMT. PA decreased E-cadherin protein expression, and increased vimentin, MMP2, and MMP3 protein levels. Additionally, PA increased miR-222 expression in ARPE-19 cells, and functionally blocking miR-222 suppressed the PA-induced RPEC migration and EMT. NUMB was identified as a downstream target of miR-222, and NUMB knockdown abolished the effects of PA on promoting the migration and EMT of ARPE-19 cells. Therefore, PA promotes human RPEC migration by upregulating miR-222 expression and downregulating NUMB. This study unravels a novel PA-miR-222-NUMB axis that can be potentially targeted for therapy of high fat acid-related ocular diseases.

Cysteinyl leukotriene receptor 1 is a potent regulator of the endosomal-lysosomal system in the ARPE-19 retinal pigment epithelial cell line

The endosomal-lysosomal system is central for cell homeostasis and comprises the functions and dynamics of particular organelles including endosomes, lysosomes and autophagosomes. In previous studies, we found that the cysteinyl leukotriene receptor 1 (CysLTR1) regulates autophagy in the retinal pigment epithelial cell line ARPE-19 under basal cellular conditions. However, the underlying mechanism by which CysLTR1 regulates autophagy is unknown. Thus, in the present study, the effects of CysLTR1 inhibition on the endosomal-lysosomal system are analyzed in detail to identify the role of CysLTR1 in cell homeostasis and autophagy regulation. CysLTR1 inhibition in ARPE-19 cells by Zafirlukast, a CysLTR1 antagonist, depleted the lysosomal pool. Furthermore, CysLTR1 antagonization reduced endocytic capacity and internalization of epidermal growth factor and decreased levels of the transferrin receptor, CD71. Serum starvation abolished the effect of Zafirlukast on the autophagic flux, which identifies the endocytic regulation of serum components by CysLTR1 as an important autophagy-modulating mechanism. The role of CysLTR1 in inflammation and cell stress has been exceedingly studied, but its involvement in the endosomal-lysosomal pathway is largely unknown. This current study provides new insights into basal activity of CysLTR1 on cellular endocytosis and the subsequent impact on downstream processes like autophagy.

Internalization of Angiotensin-(1-12) in Adult Retinal Pigment Epithelial-19 Cells

Purpose: Angiotensin-(1-12) [Ang-(1-12)] serves as a primary substrate to generate angiotensin II (Ang II) by angiotensin-converting enzyme and/or chymase suggests it may be an unrecognized source of Ang II-mediated microvascular complication in hypertension-mediated retinopathy. We investigated Ang-(1-12) expression and internalization in adult retinal pigment epithelial-19 (ARPE-19) cultured cells. We performed the internalization of Ang-(1-12) in ARPE-19 cells in the presence of a highly specific monoclonal antibody (mAb) developed against the C-terminal end of the Ang-(1-12) sequence. Methods: All experiments were performed in confluent ARPE-19 cells (passage 28-35). We employed high-performance liquid chromatography to purify radiolabeled, ¹²⁵I-Ang-(1-12) and immuno-neutralization with Ang-(1-12) mAb to demonstrate Ang-(1-12)'s internalization in ARPE-19 cells. Internalization was also demonstrated by immunofluorescence (IF) method. Results: These procedures revealed internalization of an intact ¹²⁵I-Ang-(1-12) in ARPE-19 cells. A significant reduction (∼53%, P < 0.0001) in ¹²⁵I-Ang-(1-12) internalization was detected in APRE-19 cells in the presence of the mAb. IF staining experiments further confirms internalization of Ang-(1-12) into the cells from the extracellular culture medium. No endogenous expression was detected in the ARPE-19 cells. An increased intensity of IF staining was detected in cells exposed to 1.0 μM Ang-(1-12) compared with 0.1 μM. Furthermore, we found hydrolysis of Ang-(1-12) into Ang II by ARPE-19 cells' plasma membranes. Conclusions: Intact Ang-(1-12) peptide is internalized from the extracellular spaces in ARPE-19 cells and metabolized into Ang II. The finding that a selective mAb blocks cellular internalization of Ang-(1-12) suggests alternate therapeutic approaches to prevent/reduce the RPE cells Ang II burden.

Recognizing the Differentiation Degree of Human Induced Pluripotent Stem Cell-Derived Retinal Pigment Epithelium Cells Using Machine Learning and Deep Learning-Based Approaches

Induced pluripotent stem cells (iPSCs) can be differentiated into mesenchymal stem cells (iPSC-MSCs), retinal ganglion cells (iPSC-RGCs), and retinal pigmental epithelium cells (iPSC-RPEs) to meet the demand of regeneration medicine. Since the production of iPSCs and iPSC-derived cell lineages generally requires massive and time-consuming laboratory work, artificial intelligence (AI)-assisted approach that can facilitate the cell classification and recognize the cell differentiation degree is of critical demand. In this study, we propose the multi-slice tensor model, a modified convolutional neural network (CNN) designed to classify iPSC-derived cells and evaluate the differentiation efficiency of iPSC-RPEs. We removed the fully connected layers and projected the features using principle component analysis (PCA), and subsequently classified iPSC-RPEs according to various differentiation degree. With the assistance of the support vector machine (SVM), this model further showed capabilities to classify iPSCs, iPSC-MSCs, iPSC-RPEs, and iPSC-RGCs with an accuracy of 97.8%. In addition, the proposed model accurately recognized the differentiation of iPSC-RPEs and showed the potential to identify the candidate cells with ideal features and simultaneously exclude cells with immature/abnormal phenotypes. This rapid screening/classification system may facilitate the translation of iPSC-based technologies into clinical uses, such as cell transplantation therapy.

Significance of the p38MAPK-CRP2 axis in myofibroblastic phenotypic transition

We have recently demonstrated that a LIM domain protein, cysteine and glycine-rich protein 2 (CSRP2 [CRP2]), plays a vital role in the functional expression of myofibroblasts and cancer-associated fibroblasts. CRP2 binds directly to myocardin-related transcription factors (MRTF [MRTF-A or MRTF-B]) and serum response factor (SRF) to stabilize the MRTF/SRF/CArG-box complex, leading to the expression of smooth muscle cell (SMC) genes such as α-smooth muscle actin (α-SMA) and collagens. These are the marker genes for myofibroblasts. Here, we show that the adhesion of cultured human skin fibroblasts (HSFs) to collagen reduces the myofibroblastic features. HSF adhesion to collagen suppresses the expression of CRP2 and CSRP2-binding protein (CSRP2BP [CRP2BP]) and reduces the expression of SMC genes. Although CRP2BP is known as an epigenetic factor, we find that CRP2BP also acts as an adaptor protein to enhance the function of CRP2 mentioned above. This CRP2BP function does not depend on its histone acetyltransferase activity. We also addressed the molecular mechanism of the reduced myofibroblastic features of HSFs on collagen. HSF adhesion to collagen inhibits the p38MAPK-mediated pathway, and reducing the p38MAPK activity decreases the expression of CRP2 and SMC genes. Thus, the activation of p38MAPK is critical for the myofibroblastic features. We also show evidence that CRP2 plays a role in the myofibroblastic transition of retinal pigment epithelial cells (RPEs). Like HSFs, such phenotypic modulation of RPEs depends on the p38MAPK pathway.Key words: CRP2, p38MAPK, MRTF, myofibroblasts, retinal pigment epithelial cells.

Sulforaphane alleviates LPS-induced inflammatory injury in ARPE-19 cells by repressing the PWRN2/NF-kB pathway

BACKGROUND

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly population and its pathogenesis has been associated with inflammatory damage to retinal pigment epithelial (RPE) cells. Here, we explored the ability of sulforaphane to protect ARPE-19 cells from lipopolysaccharide (LPS)-induced inflammatory injury and elucidated the underlying molecular mechanism.

METHODS

Cell viability, apoptosis, inflammation, PWRN2 expression, nuclear transcription factor-kappa B (NF-kB) activity, and the interaction between PWRN2 and the IkBa protein were assessed in RPE cells under- or over-expressing PWRN2 that had been treated with LPS and sulforaphane.

RESULTS

Overexpression of PWRN2 in LPS-treated cells promoted NF-kB activation by interacting with IkBa, thus reducing cell viability. In contrast, PWRN2 downregulation repressed LPS-induced NF-kB activation and apoptosis in RPE cells. Similarly, sulforaphane downregulated PWRN2 and inhibited NF-kB activation in a concentration-dependent manner. Conversely, PWRN2 overexpression or NF-kB upregulation weakened the anti-inflammatory effects of sulforaphane.

CONCLUSION

Our results suggest that sulforaphane protects RPE cells from LPS-induced inflammatory injury by suppressing the PWRN2/NF-kB pathway.

Palmitic Acid Induced a Long-Lasting Lipotoxic Insult in Human Retinal Pigment Epithelial Cells, which Is Partially Counteracted by TRAIL

Hyperglycaemia and increased circulating saturated fatty acids are key metabolic features of type 2 diabetes mellitus (T2DM) that contribute to diabetic retinopathy pathogenesis. Contrarily, tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) has been shown to improve or prevent T2DM. This study aimed at investigating the effect of TRAIL in an in vitro model of human retinal pigment epithelium: the ARPE-19 cell line, treated with palmitic acid (PA) in the presence of high glucose concentration. PA caused a drop in cellular metabolic activity and cell viability as well as an increase in apoptosis rates, which were paralleled by an upregulation of reactive oxygen species (ROS) generation as well as mitochondrial fragmentation. Despite ARPE-19 cells expressing TRAIL-R2 at the cell surface, TRAIL failed to counteract the cytotoxic effects of PA. However, when TRAIL was used alongside PA and then removed or used alone following PA challenge, it partially attenuated PA-induced lipotoxicity. This effect of TRAIL appeared to rely upon the modulation of inflammation and ROS production. Thus, TRAIL exerted a trophic effect on ARPE-19 cells, which became evident only when the lipotoxic insult was removed. Nevertheless, whether recombinant TRAIL might have a therapeutic potential for the treatment of diabetic retinopathy requires further investigation.

A Trojan horse biomimetic delivery system using mesenchymal stem cells for HIF-1α siRNA-loaded nanoparticles on retinal pigment epithelial cells under hypoxia environment

AIM

To demonstrate the feasibility of mesenchymal stem cell (MSC)-mediated nano drug delivery, which was characterized by the "Trojan horse"-like transport of hypoxia-inducible factor-1α small interfering RNA (HIF-1α siRNA) between MSCs and retinal pigment epithelial cells (RPE) under hypoxia environment.

METHODS

Plasmid and lentivirus targeting the human HIF-1α gene were designed and constructed. HIF-1α siRNA was encapsulated into poly(lactic-co-glycolic acid) nanoparticles (PLGA-NPs) through the water-in-oil-in-water (w/o/w) multiple emulsion technique. The effect of PLGA-NPs uptake on the expression of HIF-1α mRNA was tested in RPE cells by real-time quantitative polymerase chain reaction (qPCR) and additional transfected conditions were used as control, including lentivirus group, nude plasmid group and blank PLGA group. MSCs were transfected with the NPs and the transfection efficacy was evaluated by flow cytometry. Transwell co-culture system of transfected MSCs and RPE cells was constructed under hypoxia environment. The effects of MSC-loaded HIF-1α siRNA PLGA-NPs on proliferation, apoptosis, and migration of RPE cells were then evaluated. The effect of transfected MSCs on HIF-1α expression of RPE cells was analyzed by using qPCR at the time points 24h, 3d, and 7d.

RESULTS

The average diameter of PLGA-NPs loaded with HIF siRNA was 314.1 nm and the zeta potential was -0.36 mV. The transfection efficiency of PLGA-NPs was 67.3%±5.2% into MSCs by using flow cytometry. Compared with the lentivirus group, the PLGA-NPs loaded with HIF-1α siRNA can effectively reduce the expression of HIF-1α mRNA up to 7d in RPE (0.63±0.05 at 7d, P<0.001). In the Transwell co-culture system of transfected MSCs and RPE, the abilities of proliferation (2.34±0.17, 2.40±0.28, 2.47±0.24 at 48h, F=0.23, P=0.80), apoptosis (14.83%±2.43%, 12.94%±2.19%, 12.39%±3.21%; F=0.70, P=0.53) and migration (124.5±7.78, 119.5±5.32, 130±9.89, F=1.33, P=0.33) of the RPE cells had no differences between MSC-loaded HIF-1α siRNA PLGA-NPs and other groups. The inhibition of PLGA on the HIF-1α mRNA expression in RPE cells could continue until the 7^th day, the level of HIF-1α mRNA was lower than that of other groups (F=171.98, P<0.001).

CONCLUSION

The delivery of PLGA-NPs loaded with HIF-1α siRNA carried by MSCs is found to be beneficial temporally for HIF-1α mRNA inhibition in RPE cells under hypoxia environment. The MSC-based bio-mimetic delivery of HIF-1α siRNA nanoparticles is a potential method for therapy against choroidal neovascularization.

Diosgenin protects retinal pigment epithelial cells from inflammatory damage and oxidative stress induced by high glucose by activating AMPK/Nrf2/HO-1 pathway

INTRODUCTION

Diosgenin is a natural steroidal compound with reported antidiabetic and many other protective properties. This study aimed to explore the protective effect of diosgenin on high-glucose (HG)-induced retinal pigment epithelial cells.

METHODS

HG-induced ARPE-19 cells were considered as a cell model of diabetic retinopathy (DR). The viability and apoptosis of ARPE-19 cells induced by HG treated with either diosgenin or Compound C (CC; dorsomorphin) were detected by Cell Counting Kit-8 assay and flow cytometric analysis. The expression of apoptosis-related proteins, inflammation-related proteins, and AMPK/Nrf2/HO-1 pathway-related proteins was detected by western blotting. The levels of inflammatory cytokines and detection of oxidative stress indexes were performed using the appropriate assay kits. The messenger RNA expression of inflammatory cytokines was detected by real-time quantitative polymerase chain reaction.

RESULTS

There was no obvious effect of diosgenin on the viability of ARPE-19 cells and the viability of ARPE-19 cells was significantly reduced after HG induction. However, diosgenin increased the viability, inhibited the apoptosis, and reduced the inflammatory response and oxidative stress of ARPE-19 cells induced by HG. In addition, diosgenin could activate the AMPK/Nrf2/HO-1 pathway. CC, an AMPK inhibitor, could reverse the above changes caused by diosgenin treatment in ARPE-19 cells induced by HG.

CONCLUSIONS

Diosgenin could protect ARPE-19 cells from inflammatory damage and oxidative stress induced by HG, by activating the AMPK/Nrf2/HO-1 pathway.

Pluripotent Stem Cells in Clinical Cell Transplantation: Focusing on Induced Pluripotent Stem Cell-Derived RPE Cell Therapy in Age-Related Macular Degeneration

Human pluripotent stem cells (PSCs), including both embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), represent valuable cell sources to replace diseased or injured tissues in regenerative medicine. iPSCs exhibit the potential for indefinite self-renewal and differentiation into various cell types and can be reprogrammed from somatic tissue that can be easily obtained, paving the way for cell therapy, regenerative medicine, and personalized medicine. Cell therapies using various iPSC-derived cell types are now evolving rapidly for the treatment of clinical diseases, including Parkinson's disease, hematological diseases, cardiomyopathy, osteoarthritis, and retinal diseases. Since the first interventional clinical trial with autologous iPSC-derived retinal pigment epithelial cells (RPEs) for the treatment of age-related macular degeneration (AMD) was accomplished in Japan, several preclinical trials using iPSC suspensions or monolayers have been launched, or are ongoing or completed. The evolution and generation of human leukocyte antigen (HLA)-universal iPSCs may facilitate the clinical application of iPSC-based therapies. Thus, iPSCs hold great promise in the treatment of multiple retinal diseases. The efficacy and adverse effects of iPSC-based retinal therapies should be carefully assessed in ongoing and further clinical trials.

NMDA Receptor Antagonists Degrade Lipofuscin via Autophagy in Human Retinal Pigment Epithelial Cells

Background and Objectives: Age-related macular degeneration is a slow-progressing disease in which lipofuscin accumulates in the retina, causing inflammation and apoptosis of retinal pigment epithelial (RPE) cells. This study aimed to identify N-methyl-D-aspartate (NMDA) signaling as a novel mechanism for scavenging N-retinylidene-N-retinylethanolamine (A2E), a component of ocular lipofuscin, in human RPE cells. Materials and Methods: A2E degradation assays were performed in ARPE-19 cells using fluorescently labeled A2E. The autophagic activity in ARPE-19 cells was measured upon blue light (BL) exposure, after A2E treatment. Autophagy flux was determined by measuring LC3-II formation using immunoblotting and confocal microscopy. To determine whether autophagy via the NMDA receptor is involved in A2E clearance, ATG5-deficient cells were used. Results: Ro 25-6981, an NR2B-selective NMDA receptor antagonist, effectively cleared A2E. Ro 25-6981 reduced A2E accumulation in the lysosomes of ARPE-19 cells at sub-cytotoxic concentrations, while increasing the formation of LC3-II and decreasing p62 protein levels in a concentration-dependent manner. The autophagic flux monitored by RFP-GFP-LC3 and bafilomycin A1 assays was significantly increased by Ro 25-6981. A2E clearance by Ro 25-6981 was abolished in ATG5-depleted ARPE-19 cells, suggesting that A2E degradation by Ro 25-6981 was mediated by autophagy. Furthermore, treatment with other NMDA receptor antagonists, CP-101,606 and AZD6765, showed similar effects on autophagy activation and A2E degradation in ARPE-19 cells. In contrast, glutamate, an NMDA receptor agonist, exhibited a contrasting effect, suggesting that both the activation of autophagy and the degradation of A2E by Ro 25-6981 in ARPE-19 cells occur through inhibition of the NMDA receptor pathway. Conclusions: This study demonstrates that NMDA receptor antagonists degrade lipofuscin via autophagy in human RPE cells and suggests that NMDA receptor antagonists could be promising new therapeutics for retinal degenerative diseases.

Effects of the Calix[4]arene Derivative Compound OTX008 on High Glucose-Stimulated ARPE-19 Cells: Focus on Galectin-1/TGF-β/EMT Pathway

Diabetic retinopathy (DR) is a neurovascular disease characterized by the reduction of retina integrity and functionality, as a consequence of retinal pigment epithelial cell fibrosis. Although galectin-1 (a glycan-binding protein) has been associated with dysregulated retinal angiogenesis, no evidence has been reported about galectin-1 roles in DR-induced fibrosis. ARPE-19 cells were cultured in normal (5 mM) or high glucose (35 mM) for 3 days, then exposed to the selective galectin-1 inhibitor OTX008 (2.5–5–10 μM) for 6 days. The determination of cell viability and ROS content along with the analysis of specific proteins (by immunocytochemistry, Western blotting, and ELISA) or mRNAs (by real time-PCR) were performed. OTX008 5 μM and 10 μM improved cell viability and markedly reduced galectin-1 protein expression in cells exposed to high glucose. This was paralleled by a down-regulation of the TGF-β/, NF-kB p65 levels, and ROS content. Moreover, epithelial–mesenchymal transition markers were reduced by OTX008 5 μM and 10 μM. The inhibition of galectin-1 by OTX008 in DR may preserve retinal pigment epithelial cell integrity and functionality by reducing their pro-fibrotic phenotype and epithelial–mesenchymal transition phenomenon induced by diabetes.

PPARδ Inhibits Hyperglycemia-Triggered Senescence of Retinal Pigment Epithelial Cells by Upregulating SIRT1

Emerging evidence shows that peroxisome proliferator-activated receptor delta (PPARδ) plays a pivotal role in cellular aging. However, its function in retinal disease processes such as hyperglycemia-associated diabetic retinopathy is unclear. Here, we demonstrate that PPARδ inhibits premature senescence of retinal pigment epithelial (RPE) cells induced by high glucose (HG) through SIRT1 upregulation. A specific ligand GW501516-activation of PPARδ suppressed premature senescence and production of reactive oxygen species induced by HG in ARPE-19 cells, a spontaneously arising human RPE cell line. These effects were accompanied by the regulation of the premature senescence-associated genes p53, p21, and SMP-30. Furthermore, GW501516-activated PPARδ almost completely abolished the effects of HG treatment on the formation of phosphorylated H2A histone family member X (γ-H2A.X) foci, a molecular marker of aging. These inhibitory effects of GW501516 were significantly reversed in ARPE-19 cells stably expressing small hairpin RNA targeting PPARδ. Notably, GW501516 significantly increased the mRNA and protein levels of SIRT1, indicating that GW501516-activated PPARδ exerted its beneficial effects through SIRT1. In addition, GW501516 restored HG-suppressed SIRT1 expression, corroborating the role of SIRT1 in the anti-senescence function of PPARδ. The effects of PPARδ on HG-induced premature senescence and the expression of the senescence-associated genes p53, p21, and SMP-30 were mimicked by the SIRT1 activator resveratrol, but blocked by the SIRT1 inhibitor sirtinol. Collectively, these results indicate that GW501516-activated PPARδ inhibits HG-triggered premature senescence of RPE cells by modulating SIRT1 signaling.

Oxidative-Induced Angiogenesis Is Modulated by Small Extracellular Vesicle miR-302a-3p Cargo in Retinal Pigment Epithelium Cells

Extracellular vesicles are released from cells under diverse conditions. Widely studied in cancer, they are associated with different diseases playing major roles. Recent reports indicate that oxidative damage promotes the release of small extracellular vesicle (sEVs) from the retinal pigment epithelium (RPE), with an angiogenic outcome and changes in micro-RNA (miRNA) levels. The aim of this study was to determine the role of the miRNA miR-302a-3p, included within RPE-released sEVs, as an angiogenic regulator in cultures of endothelial cells (HUVEC). ARPE-19 cell cultures, treated with H₂O₂ to cause an oxidative insult, were transfected with a miR-302a-3p mimic. Later, sEVs from the medium were isolated and added into HUVEC or ARPE-19 cultures. sEVs from ARPE-19 cells under oxidative damage presented a decrease of miR-302a-3p levels and exhibited proangiogenic properties. In contrast, sEVs from miR-302a-3p-mimic transfected cells resulted in control angiogenic levels. The results herein indicate that miR-302a-3p contained in sEVs can modify VEGFA mRNA expression levels as part of its antiangiogenic features.

Methyltransferase-like (METTL)14-mediated N6-methyladenosine modification modulates retinal pigment epithelial (RPE) activity by regulating the methylation of microtubule-associated protein (MAP)2

The expression of METTL14 is significantly reduced in patients with retinitis pigmentosa (RP). To clarify the significance of the N6-methyladenosine (m⁶A) RNA modification in RP, we examined phagocytosis, apoptosis, and cell cycle distribution in a human RPE cell line, ARPE-19, following lentivirus-mediated knockdown of METTL14. Differentially expressed genes and changes in m⁶A level were evaluated by RNA sequencing (RNA-seq) and methylated RNA immunoprecipitation sequencing (MeRIP-seq), respectively. The results showed that phagocytosis and proliferation were decreased whereas apoptosis was increased in RPE cells by METTL14 silencing. We found that METTL14 directly regulated m⁶A level and the expression of MAP2, as determined by RNA-seq, MeRIP-seq, MeRIP quantitative PCR, and the RNA pull-down assay. Additionally, MAP2 could bind to neuronal differentiation (NEUROD)1, a pathogenic gene in RPE-associated diseases. A family member of the YTH domain, (YTHDF)2 was recognized as an m⁶A reader of MAP2 mRNA. MAP2 overexpression had the same effects as METTL14 knockdown in RPE cells. Thus, METTL14 regulates the expression of MAP2 via the modification of m⁶A, resulting in the dysregulation of NEUROD1 and pathologic changes in RPE cells. These findings suggest that therapeutic strategies targeting the m⁶A modification of MAP2 or the METTL14/YTHDF2/MAP2/NEUROD1 signaling axis may be effective in the treatment of RPE-associated ocular diseases.

Caffeine Protects Against Retinal Inflammation

Caffeine, one of the most consumed central nervous system (CNS) stimulants, is an antagonist of A₁ and A_2A adenosine receptors. In this study, we investigated the potential protective effects of this methylxanthine in the retinal tissue. We tested caffeine by using in vitro and in vivo paradigms of retinal inflammation. Human retinal pigment epithelial cells (ARPE-19) were exposed to lipopolysaccharide (LPS) with or without caffeine. This latter was able to reduce the inflammatory response in ARPE-19 cells exposed to LPS, attenuating the release of IL-1β, IL-6, and TNF-α and the nuclear translocation of p-NFκB. Additionally, caffeine treatment restored the integrity of the ARPE-19 monolayer assessed by transepithelial electrical resistance (TEER) and the sodium fluorescein permeability test. Finally, the ischemia reperfusion (I/R) injury model was used in C57BL/6J mice to induce retinal inflammation and investigate the effects of caffeine treatment. Mouse eyes were treated topically with caffeine, and a pattern electroretinogram (PERG) was used to assess the retinal ganglion cell (RGC) function; furthermore, we evaluated the levels of IL-6 and BDNF in the retina. Retinal BDNF dropped significantly (p < 0.05) in the I/R group compared to the control group (normal mice); on the contrary, caffeine treatment maintained physiological levels of BDNF in the retina of I/R eyes. Caffeine was also able to reduce IL-6 mRNA levels in the retina of I/R eyes. In conclusion, these findings suggest that caffeine is a good candidate to counteract inflammation in retinal diseases.

Downregulation of AlphaB-crystallin in Retinal Pigment Epithelial Cells Exposed to Diabetes-related Stimuli In Vivo and In Vitro

BACKGROUND/AIM

AlphaB-crystallin plays a pivotal role in many diseases. However, the involvement of alphaB-crystallin in retinal pigment epithelial (RPE) cells with diabetes stimuli remains unknown. The aim of this study is to examine the alterations of RPE cells and alphaB-crystallin expression in diabetic models in vivo and in vitro.

MATERIALS AND METHODS

Diabetic conditions in mice were induced by streptozotocin (STZ). The thickness of the RPE/choroid complex was measured by optical coherence tomography (OCT). Periodic acid-Schiff (PAS) staining was used to investigate the choriocapillaris in histological sections of murine eyeballs and oxidative stress was evaluated using immunofluorescence with anti-4-hydroxynonenal (HNE) antibody. AlphaB-crystallin expression was examined in the RPE/choroid complex using ELISA. Real-Time PCR was performed to evaluate the alphaB-crystallin expression in cultured human RPE cells with high glucose or following advanced glycation end-products (AGE) stimulation.

RESULTS

In diabetic mice, OCT-based RPE/choroidal layers were thickened 2 months after STZ stimulation, where PAS-positive dilated choriocapillaris was noted. Immunoreactivity of 4-HNE was strongly observed in the RPE layer, from which a significant number of RPE cells was lost. Meanwhile, alphaB-crystallin expression in 2-month STZ mice was significantly lower compared to controls. In accordance with these results, in vitro data showed that the alphaB-crystallin expression was also significantly lower in RPE cells with high glucose or following AGE stimulation compared to untreated cells.

CONCLUSION

In both types of diabetic models the expression of alphaB-crystallin was found to be downregulated in RPE cells and was associated with increased levels of oxidative stress.

Lutein nanodisks protect human retinal pigment epithelial cells from UV light-induced damage

The hydrophobic carotenoid, lutein, was conferred with aqueous solubility upon formulation into reconstituted discoidal high density lipoprotein particles, termed lutein nanodisks (ND). When formulated with phosphatidylcholine (PC), apolipoprotein (apo) A-I and lutein (formulation ratio = 5 mg PC/2 mg apoA-I/1 mg lutein), lutein solubilization efficiency in phosphate buffered saline (PBS) was ~90%. The UV/Vis absorbance maxima for lutein ND in PBS were red shifted by 6-13 nm versus the corresponding lutein absorbance maxima in ethanol. FPLC gel filtration chromatography gave rise to a single major absorbance peak in the size range of ND. Incubation of cultured ARPE-19 cells with lutein ND resulted in lutein uptake, as determined by HPLC analysis of cell extracts. Compared to control incubations, ARPE-19 cells incubated with lutein ND were protected from UV light-induced loss of cell viability. Consistent with this, reactive oxygen species generation, induced by exposure to UV irradiation, was lower in lutein-enriched cells than in control cells. Thus, uptake of ND-associated lutein protects ARPE-19 cells from UV light-induced damage. Taken together, the data indicate ND provide an aqueous lutein delivery vehicle for biotechnological or therapeutic applications.

Effects of E-Cigarette Refill Liquid Flavorings with and without Nicotine on Human Retinal Pigment Epithelial Cells: A Preliminary Study

Smoking is an etiologic factor for age-related macular degeneration (AMD). Although cigarette smoke has been extensively researched for retinal pigment epithelial (RPE) cell degeneration, the potential for adverse effects on the retinal epithelium following exposure to flavored e-cigarette refill liquid has never been explored. In this preliminary study, we have examined the effects of 20 e-liquids (10 different flavored nicotine-free and 10 nicotine-rich e-liquids) used in e-cigarettes on the metabolic activity, membrane integrity, and mitochondrial membrane potential of RPE cells. Our results showed that of the flavors studied over the concentration range: 0.5, 1, and 2% v/v for a duration of 48 h, cinnamon was the most toxic and menthol was the second most toxic, while other flavors showed lesser or no cytotoxicity. The presence of nicotine augmented cytotoxicity for cinnamon, menthol, strawberry, vanilla, and banana while for other flavors there was no synergism. Together, our results demonstrate that exposure of RPE to flavored e-cigarette refill liquids caused significant cytotoxicity and may be a risk factor for the development of retinal pathogenesis, although further in-depth studies are necessary.

Yes-associated protein is essential for proliferative vitreoretinopathy development via the epithelial-mesenchymal transition in retinal pigment epithelial fibrosis

This study was aim to investigate whether the progression of proliferative vitreoretinopathy (PVR) depended on the activation of Yes‐associated protein (YAP) and the subsequent epithelial‐mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cell. The effect of YAP activation on retinal fibrosis in a PVR mouse model and in human ARPE‐19 cells in vitro was studied. After treated with transforming growth factor‐β2(TGF‐β2), the expressions of fibrogenic molecules, YAP activation and the TGF‐β2‐Smad signalling pathway in ARPE‐19 cells were detected by Western blot and immunocytochemical analyses. The effect of YAP on change in fibrosis and EMT was tested by knockdown experiment using verteporfin (YAP inhibitor). YAP was upregulated in the PVR mouse model and during TGF‐β2–induced RPE cell EMT. In an in vivo study, verteporfin attenuated PVR progression in a mouse model. Additionally, YAP knockdown retained phenotype of RPE cells and ameliorated TGF‐β2–induced migration, gel contraction and EMT in vitro. YAP knockdown inhibited the TGF‐β2–induced upregulation of connective tissue growth factor (CTGF), smooth muscle actin (SMA‐α) and fibronectin. YAP was essential for the TGF‐β2–induced nuclear translocation and phosphorylation of Smad2/3. Our work provides direct evidence that YAP is an essential regulator of EMT and profibrotic responses in PVR and indicates that YAP inhibition could be a potential target in PVR therapeutic intervention.

Triamcinolone acetonide modulates TGF‑β2‑induced angiogenic and tissue‑remodeling effects in cultured human retinal pigment epithelial cells

Transforming growth factor-β2 (TGF-β2) has been implicated in the pathogenesis of proliferative vitreoretinopathy (PVR) and proliferative diabetic retinopathy (PDR), due to its ability to stimulate the overproduction of pro-angiogenic factors, such as vascular endothelial growth factor (VEGF), and remodeling of the extracellular matrix (ECM). Although intravitreal triamcinolone acetonide (TA) is clinically useful in the treatment of PVR and PDR, its molecular mechanism has yet to be fully elucidated. The present study investigated whether TA treatment altered TGF-β2-driven biological effects on the behavior of cultured human retinal pigment epithelial (RPE) cells, in order to determine which signaling pathway may be essential for the pharmacological action of TA. The R-50 human RPE cell line was treated with TA in the presence of TGF-β2, followed by analyses of cell viability and contraction using cell viability and collagen gel contraction assays. VEGF mRNA expression and protein production were measured using reverse transcription-quantitative PCR and ELISA, respectively. The phosphorylation status of signaling mediators and the protein expression of type I collagen (COL1A1), α-smooth muscle actin (α-SMA), and ECM-remodeling enzymes, including MMP-2 and MMP-9, were analyzed using western blotting. The gelatinolytic activity of MMPs was detected using gelatin zymography. TA treatment exhibited no prominent cytotoxicity but markedly antagonized TGF-β2-induced cytostatic effects on RPE cell viability and TGF-β2-enhanced contractility in collagen gels. In the context of TGF-β2-related signaling, TA significantly attenuated TGF-β2-elicited Smad2, extracellular-regulated kinase (ERK)1/2 and p38 mitogen-activated protein kinase (MAPK) phosphorylation. Moreover, TA markedly mitigated TGF-β2-induced VEGF upregulation through ablation of p38 signaling activity. TA also partially attenuated TGF-β2-elicted expression of COL1A1, α-SMA, MMP-2, and MMP-9, but only suppressed TGF-β2-induced MMP-9 gelatinolytic activity. Mechanistically, the MEK/ERK signaling pathway may have a critical role in the TGF-β2-induced upregulation of COL1A1, α-SMA and MMP-9. In conclusion, TA may be considered a useful therapeutic agent for treating TGF-β2-associated intraocular angiogenesis and tissue remodeling, the underlying mechanism of which may involve the ERK and p38 MAPK signaling pathways.

Comprehensive Evidence of Carrier-Mediated Distribution of Amantadine to the Retina across the Blood-Retinal Barrier in Rats

Amantadine, a drug used for the blockage of NMDA receptors, is well-known to exhibit neuroprotective effects. Accordingly, assessment of amantadine transport at retinal barriers could result in the application of amantadine for retinal diseases such as glaucoma. The objective of this study was to elucidate the retinal distribution of amantadine across the inner and outer blood–retinal barrier (BRB). In vivo blood-to-retina [³H]amantadine transport was investigated by using the rat retinal uptake index method, which was significantly reduced by unlabeled amantadine. This result indicated the involvement of carrier-mediated processes in the retinal distribution of amantadine. In addition, in vitro model cells of the inner and outer BRB (TR-iBRB2 and RPE-J cells) exhibited saturable kinetics (K_m in TR-iBRB2 cells, 79.4 µM; K_m in RPE-J cells, 90.5 and 9830 µM). The inhibition of [³H]amantadine uptake by cationic drugs/compounds indicated a minor contribution of transport systems that accept cationic drugs (e.g., verapamil), as well as solute carrier (SLC) organic cation transporters. Collectively, these outcomes suggest that carrier-mediated transport systems, which differ from reported transporters and mechanisms, play a crucial role in the retinal distribution of amantadine across the inner/outer BRB.

A phase I clinical trial of human embryonic stem cell-derived retinal pigment epithelial cells for early-stage Stargardt macular degeneration: 5-years' follow-up

Objectives

To evaluate the long‐term biosafety and efficacy of transplantation of human embryonic stem cells‐derived retinal pigment epithelial (hESC‐RPE) cells in early‐stage of Stargardt macular degeneration (STGD1).

Materials and methods

Seven patients participated in this prospective clinical study, where they underwent a single subretinal transplantation of 1 × 10⁵ hESC‐RPE cells in one eye, whereas the fellow eye served as control. These patients were reassessed for a 60‐month follow‐up through systemic and ophthalmic examinations.

Results

None of the patients experienced adverse reactions systemically or locally, except for two who had transiently high intraocular pressure post‐operation. Functional assessments demonstrated that all of the seven operated eyes had transiently increased or stable visual function 1‐4 months after transplantation. At the last follow‐up visit, two of the seven eyes showed visual function loss than the baseline; however, one of them showed a stable visual acuity when compared with the change of fellow eye. Obvious small high reflective foci in the RPE layer were displayed after the transplantation, and maintained until the last visit. Interestingly, three categories of patients who were classified based on autofluorescence, exhibited distinctive patterns of morphological and functional change.

Conclusions

Subretinal transplantation of hESC‐RPE in early‐stage STGD1 is safe and tolerated in the long term. Further investigation is needed for choosing proper subjects according to the multi‐model image and function assessments.

Stem Cell Therapy for Retinal Degeneration: The Evidence to Date

There is a rise in the number of people who have vision loss due to retinal diseases, and conventional therapies for treating retinal degeneration fail to repair and regenerate the damaged retina. Several studies in animal models and human trials have explored the use of stem cells to repair the retinal tissue to improve visual acuity. In addition to the treatment of age-related macular degeneration (AMD) and diabetic retinopathy (DR), stem cell therapies were used to treat genetic diseases such as retinitis pigmentosa (RP) and Stargardt’s disease, characterized by gradual loss of photoreceptor cells in the retina. Transplantation of retinal pigment epithelial (RPE) cells derived from embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) have shown promising results in improving retinal function in various preclinical models of retinal degeneration and clinical studies without any severe side effects. Mesenchymal stem cells (MSCs) were utilized to treat optic neuropathy, RP, DR, and glaucoma with positive clinical outcomes. This review summarizes the preclinical and clinical evidence of stem cell therapy and current limitations in utilizing stem cells for retinal degeneration.

MicroRNA-29b participates in the epithelial-mesenchymal transition of retinal pigment epithelial cells through p-p65

Epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells is considered to be the main mechanism of proliferative vitreoretinopathy (PVR). Our previous study demonstrated that microRNA-29b (miR-29b) and its target protein kinase B (Akt2) played vital roles in this process. miR-29b, a mesenchymal marker α-smooth muscle actin (α-SMA) and the epithelial marker E-cadherin were assessed in epiretinal membranes of patients with PVR. The potential mechanism of miR-29b and EMT was also investigated. The expression levels of miR-29b, E-cadherin, and α-SMA in PVR epiretinal membranes were measured using quantitative PCR. The expression levels of Akt2, phosphorylated (p)-Akt2, p65, p-p65, and Snail in ARPE-19 cells were assessed using western blotting. The expression levels of miR-29b were positively correlated with E-cadherin mRNA expression, while an inverse correlation was observed between miR-29b and α-SMA mRNA expression in epiretinal membranes of patients with PVR. When miR-29b was transfected into ARPE-19 cells, the expression levels of Akt2, p-Akt2, p-p65 and Snail were downregulated. shRNA-Akt2 inhibited p-p65 and Snail expression, while the NF-κB inhibitor BAY11-7082 reduced Snail expression. The Akt2/p-p65/Snail pathway may be the underlying mechanism of miR-29b in EMT of RPE cells. The results of the present study may provide a new strategy for prevention and therapy of PVR.

Role of LINC01592 in TGF-β1-induced epithelial-mesenchymal transition of retinal pigment epithelial cells

Regulation of long-chain non-coding RNA01592 (LINC01592) in the process of transforming retinal pigment epithelial (RPE) cells into mesenchymal cells following induction by transforming growth factor beat 1 (TGF-β1) was investigated by interfering with LINC01592 expression in human RPE (hRPE) cells. LINC01592 expression in hRPE cells was significantly increased following treatment with 10 ng/mL TGF-β1 for 48 h. Expression of E-cadherin and Snail were decreased in hRPE cells following induction with TGF-β1 compared with the control group (P < 0.05). Following induction by TGF-β1, expression of E-cadherin, alpha-smooth muscle actin (α-SMA), and Snail were significantly lower in the LINC01592-knockdown group compared with the negative control group (P < 0.05). LINC01592 overexpression significantly enhanced the viability, proliferation, and migration of hRPE cells induced by TGF-β1 (P < 0.05). Following induction by TGF-β1, E-cadherin expression was significantly decreased and α-SMA and Snail expression were significantly increased in the LINC01592-overexpression group compared with the negative control group (P < 0.05). RPE cells induced by TGF-β1 exhibited epithelial-mesenchymal transition (EMT). Inhibiting LINC01592 expression could significantly reduce TGF-β1-induced EMT of hRPE cells. The regulatory effect of LINC01592 on EMT in hRPE cells induced by TGF-β1 provides a novel treatment for proliferative vitreoretinopathy.

Attenuation of High Glucose-Induced Damage in RPE Cells through p38 MAPK Signaling Pathway Inhibition

This study aimed to investigate the high glucose damage on human retinal pigment epithelial (RPE) cells, the role of p38 MAPK signaling pathway and how dimethyl fumarate can regulate that. We carried out in vitro studies on ARPE-19 cells exposed to physiological and high glucose (HG) conditions, to evaluate the effects of DMF on cell viability, apoptosis, and expression of inflammatory and angiogenic biomarkers such as COX-2, iNOS, IL-1β, and VEGF. Our data have demonstrated that DMF treatment attenuated HG-induced apoptosis, as confirmed by reduction of BAX/Bcl-2 ratio. Furthermore, in RPE cells exposed to HG we observed a significant increase of iNOS, COX-2, and IL-1β expression, that was reverted by DMF treatment. Moreover, DMF reduced the VEGF levels elicited by HG, inhibiting p38 MAPK signaling pathway. The present study demonstrated that DMF provides a remarkable protection against high glucose-induced damage in RPE cells through p38 MAPK inhibition and the subsequent down-regulation of VEGF levels, suggesting that DMF is a small molecule that represents a good candidate for diabetic retinopathy treatment and warrants further in vivo and clinical evaluation.

Anti-inflammatory activities of Gardenia jasminoides extracts in retinal pigment epithelial cells and zebrafish embryos

Age-related macular degeneration (AMD) is the most common cause of visual impairment in developed countries. Inflammation serves a critical role in the pathogenesis of AMD. Gardenia jasminoides is found in several regions of China and is traditionally used as an organic yellow dye but has also been widely used as a therapeutic agent in numerous diseases, including inflammation, depression, hepatic and vascular disorders, which may reflect the variability of functional compounds that are present in Gardenia jasminoides extracts (GJE). To investigate the therapeutic potential of GJE for AMD, ARPE-19 cells were treated with lipopolysaccharide (LPS) or LPS plus GJE. GJE significantly decreased LPS-induced expression of proinflammatory cytokines, including IL-1β, IL-6 and TNF-α. In the in vivo study, GJE inhibited CuSO4-induced migration of primitive macrophages to the lateral line in zebrafish embryos. GJE also attenuated expression of cytokines (IL-1β, IL-6 and TNF-α), NFKB activating protein (nkap) and TLR4 in ARPE-19 cells. The results of the present study demonstrated the anti-inflammatory potential of GJE in vitro and in vivo, and suggested GJE as a therapeutic candidate for AMD.

Optogenetic control of neural differentiation in Opto-mGluR6 engineered retinal pigment epithelial cell line and mesenchymal stem cells

In retinal degenerative disorders, when neural retinal cells are damaged, cell transplantation is one of the most promising therapeutic approaches. Optogenetic technology plays an essential role in the neural differentiation of stem cells via membrane depolarization. This study explored the efficacy of blue light stimulation in neuroretinal differentiation of Opto-mGluR6-engineered mouse retinal pigment epithelium (mRPE) and bone marrow mesenchymal stem cells (BMSCs). mRPE and BMSCs were selected for optogenetic study due to their capability to differentiate into retinal-specific neurons. BMSCs were isolated and phenotypically characterized by the expression of mesenchymal stem cell-specific markers, CD44 (99%) and CD105 (98.8%). mRPE culture identity was confirmed by expression of RPE-specific marker, RPE65, and epithelial cell marker, ZO-1. mRPE cells and BMSCs were transduced with AAV-MCS-IRES-EGFP-Opto-mGluR6 viral vector and stimulated for 5 days with blue light (470 nm). RNA and protein expression of Opto-mGluR6 were verified. Optogenetic stimulation-induced elevated intracellular Ca²⁺ levels in mRPE- and BMS-treated cells. Significant increase in cell growth rate and G1/S phase transition were detected in mRPE- and BMSCs-treated cultures. Pou4f1, Dlx2, Eomes, Barlh2, Neurod2, Neurod6, Rorb, Rxrg, Nr2f2, Ascl1, Hes5, and Sox8 were overexpressed in treated BMSCs and Barlh2, Rorb, and Sox8 were overexpressed in treated mRPE cells. Expression of Rho, Thy1, OPN1MW, Recoverin, and CRABP, as retinal-specific neuron markers, in mRPE and BMS cell cultures were demonstrated. Differentiation of ganglion, amacrine, photoreceptor cells, and bipolar and Muller precursors were determined in BMSCs-treated culture and were compared with mRPE. mRPE cells represented more abundant terminal Muller glial differentiation compared with BMSCs. Our results also demonstrated that optical stimulation increased the intracellular Ca²⁺ level and proliferation and differentiation of Opto-mGluR6-engineered BMSCs. It seems that optogenetic stimulation of mRPE- and BMSCs-engineered cells would be a potential therapeutic approach for retinal degenerative disorders.

SS-31 protect retinal pigment epithelial cells from H2 O2 -induced cell injury by reducing apoptosis

Evidence has shown that effects from oxidative stress induced damage of retinal or human retinal pigment epithelial (RPE) cells. Antioxidant supplementation is a plausible strategy to avoid oxidative stress and maintain the function of retina. d‐Arg‐2,6‐dimethyltyrosine‐Lys‐Phe‐NH2 (SS‐31) has been used in the treatment of many diseases. In this study, we found that SS‐31 attenuated hydrogen peroxide (H₂O₂)‐induced loss of cell viability, reduced oxidative damage and cell apoptosis in RPE cells. HO‐1, Trx‐1 and Nrf‐2 expression levels significantly increased on pre‐treatment with SS‐31 compared with the H₂O₂ group. SS‐31 inhibited apoptosis through the downregulation of Bax and the upregulation of Bcl‐2. Our results suggest that SS‐31 had a protective effect against H₂O₂ treatment in ARPE‐19 cells by enhancing the antioxidative enzymes expression and decreasing apoptosis, which could be considered a promising therapeutic intervention for retinal degeneration.

Targeting of miR-33 ameliorates phenotypes linked to age-related macular degeneration

Abnormal cholesterol/lipid homeostasis is linked to neurodegenerative conditions such as age-related macular degeneration (AMD), which is a leading cause of blindness in the elderly. The most prevalent form, termed "dry" AMD, is characterized by pathological cholesterol accumulation beneath the retinal pigment epithelial (RPE) cell layer and inflammation-linked degeneration in the retina. We show here that the cholesterol-regulating microRNA miR-33 was elevated in the RPE of aging mice. Expression of the miR-33 target ATP-binding cassette transporter (ABCA1), a cholesterol efflux pump genetically linked to AMD, declined reciprocally in the RPE with age. In accord, miR-33 modulated ABCA1 expression and cholesterol efflux in human RPE cells. Subcutaneous delivery of miR-33 antisense oligonucleotides (ASO) to aging mice and non-human primates fed a Western-type high fat/cholesterol diet resulted in increased ABCA1 expression, decreased cholesterol accumulation, and reduced immune cell infiltration in the RPE cell layer, accompanied by decreased pathological changes to RPE morphology. These findings suggest that miR-33 targeting may decrease cholesterol deposition and ameliorate AMD initiation and progression.

Melanocortin 5 Receptor Expression and Recovery of Ocular Immune Privilege after Uveitis

Purpose: The therapeutic use of the RPE-neuropeptide α-MSH suppresses experimental autoimmune uveitis (EAU). This suppression is partially through the α-MSH melanocortin 5 receptor (MC5r). Therefore, we examined the possible role of MC5r-expression in the recovery of RPE suppression of phagolysosome-activation in macrophages following α-MSH-treatment of EAUMethods: The conditioned media of cultured in situ RPE-eyecup from α-MSH-treated EAU wild-type and MC5r(-/-) mice were used to treat macrophages to assay for phagolysosome activation.Results: MC5r(-/-) mice treated with α-MSH recovered from EAU, but with greater retinal damage, and the RPE suppressed phagolysosome activation in wild type but not in MC5r(-/-) macrophages. In addition, α-MSH did not suppress phagolysosome activation in MC5r(-/-) macrophages, and resting-MC5r(-/-) macrophages had augmented phagocytic activity.Conclusion: α-MSH treatment of EAU mediates a MC5r-dependent recovery of RPE suppression of phagolysosome activation in macrophages possibly altering antigen processing and presentation. Also, MC5r-expression helps protect the retina from inflammatory damage. In addition, MC5r-expression is important in the homeostatic maintenance of phagosome-maturation within macrophages.

Vaccinia Virus Protein B18R: Influence on mRNA Immunogenicity and Translation upon Non-Viral Delivery in Different Ocular Cell Types

In the last few years, interest has grown in the use of nucleic acids as an ocular therapy for retinal genetic diseases. Recently, our research group has demonstrated that mRNA delivery could result in effective protein expression in ocular cells following subretinal injection. Yet, although mRNA therapy comes with many advantages, its immunogenicity resulting in hampered mRNA translation delays development to the clinic. Therefore, several research groups investigate possible strategies to reduce this innate immunity. In this study, we focus on B18R, an immune inhibitor to suppress the mRNA-induced innate immune responses in two ocular cell types. We made use of retinal pigment epithelial (RPE) cells and Müller cells both as immortalized cell lines and primary bovine cells. When cells were co-incubated with both B18R and mRNA-MessengerMAX lipoplexes we observed an increase in transfection efficiency accompanied by a decrease in interferon-β production, except for the Müller cells. Moreover, uptake efficiency and cell viability were not hampered. Taken together, we showed that the effect of B18R is cell type-dependent but remains a possible strategy to improve mRNA translation in RPE cells.

Self-Assembling Tacrolimus Nanomicelles for Retinal Drug Delivery

Neovascular age-related macular degeneration (AMD) is characterized by an increase in reactive oxygen species (ROS) and pro-inflammatory cytokines in the retinal pigment epithelium cells. The primary purpose of this study was the development of a clear, tacrolimus nanomicellar formulation (TAC-NMF) for AMD. The optimized formulation had a mean diameter of 15.41 nm, a zeta potential of 0.5 mV, and an entrapment efficiency of 97.13%. In-vitro cytotoxicity studies revealed the dose-dependent cytotoxicity of TAC-NMF on various ocular cell lines, such as human retinal pigment epithelium (D407), monkey retinal choroidal endothelial (RF/6A) cells, and human corneal epithelium (CCL 20.2) cells. Cellular uptake and in-vitro distribution studies using flow cytometry and confocal microscopy, respectively, indicated an elevated uptake of TAC-NMF in a time-dependent manner. Biocompatibility assay using macrophage RAW 264.7 cell line resulted in low production of inflammatory cytokines such as IL-6, IL-1β and TNF-α after treatment with TAC-NMF. There was a decrease in ROS in D407 cells pre-treated with sodium iodate (ROS inducing agent) after treating with TAC-NMF and tacrolimus drug. Similarly, there was a reduction in the pro-inflammatory cytokines and VEGF-A in D407 cells pretreated with sodium iodate. This indicates that TAC-NMF could lower pro-inflammatory cytokines and ROS commonly seen in AMD.

Cyclic RGD Peptide Targeting Coated Nano Drug Co-Delivery System for Therapeutic Use in Age-Related Macular Degeneration Disease

Vascular endothelial growth factor (VEGF) expression increased significantly in the pathogenesis of age-related macular degeneration, which induced the formation of pathological blood vessels. Dexamethasone is an exogenous anti-angiogenic drug while bevacizumab is an endogenous anti-angiogenic drug. They both have been widely used in ophthalmology. However, independent administration is not enough to completely block the development of choroidal neovascularization (CNV), and the number of eyes vitreous injections is limited. Reasonable combination of drugs may produce significantly better therapeutic effect than single drug treatment. The cyclic RGD (cRGD) peptide has a particularly high affinity with retinal pigment epithelial cells, where VEGF secretes from. In this study, we prepared nanoparticles of bevacizumab and dexamethasone with cRGD peptide as the target (aBev/cRGD-DPPNs). The particle size of the aBev/cRGD-DPPNs was 213.8 ± 1.5 nm, SEM results showed that the nano-carriers were well dispersed and spherical. The cell uptake study demonstrated the selectivity of the aBev/cRGD-DPPN to ARPE-19 with α_Vβ₃ over expressed. The aBev/cRGD-DPPNs had a better apoptosis induction effect and an obvious inhibitory effect on migration, invasion, and capillary-like structures formation of human umbilical vein epithelial cells. The fluorescein fundus angiography study, immunohistochemistry and histopathological evaluation showed the aBev/cRGD-DPPNs greatly reduced the development of CNV on a rabbit model.

ROS production and mitochondrial dysfunction driven by PU.1-regulated NOX4-p22phox activation in Aβ-induced retinal pigment epithelial cell injury

Rationale: Amyloid β (Aβ) deposition, an essential pathological process in age-related macular degeneration (AMD), causes retinal pigment epithelium (RPE) degeneration driven mostly by oxidative stress. However, despite intense investigations, the extent to which overoxidation contributes to Aβ-mediated RPE damage and its potential mechanism has not been fully elucidated.

Methods: We performed tandem mass-tagged (TMT) mass spectrometry (MS) and bioinformatic analysis of the RPE-choroid complex in an Aβ_1-40-induced mouse model of retinal degeneration to obtain a comprehensive proteomic profile. Key regulators in this model were confirmed by reactive oxygen species (ROS) detection, mitochondrial ROS assay, oxygen consumption rate (OCR) measurement, gene knockout experiment, chromatin immunoprecipitation (ChIP), and luciferase assay.

Results: A total of 4243 proteins were identified, 1069 of which were significantly affected by Aβ_1-40 and found to be enriched in oxidation-related pathways by bioinformatic analysis. Moreover, NADPH oxidases were identified as hub proteins in Aβ_1-40-mediated oxidative stress, as evidenced by mitochondrial dysfunction and reactive oxygen species overproduction. By motif and binding site analyses, we found that the transcription factor PU.1/Spi1 acted as a master regulator of the activation of NADPH oxidases, especially the NOX4-p22^phox complex. Also, PU.1 silencing impeded RPE oxidative stress and mitochondrial dysfunction and rescued the retinal structure and function.

Conclusion: Our study suggests that PU.1 is a novel therapeutic target for AMD, and the regulation of PU.1 expression represents a potentially novel approach against excessive oxidative stress in Aβ-driven RPE injury.

Retinal Pigment Epithelial Cells Derived from Induced Pluripotent Stem (iPS) Cells Suppress or Activate T Cells via Costimulatory Signals

Human retinal pigment epithelial (RPE) cells derived from induced pluripotent stem (iPS) cells have immunosuppressive properties. However, RPE cells are also known as immunogenic cells, and they have major histocompatibility complex expression and produce inflammatory proteins, and thus experience immune rejection after transplantation. In this study, to confirm the immunological properties of IPS-RPE cells, we examined whether human RPE cells derived from iPS cells could suppress or stimulate inflammatory T cells from uveitis patients via costimulatory signals. We established T cells from patients with active uveitis as target cells and used iPS-RPE cells as effector cells. As a result, cultured iPS-RPE cells inhibited cell proliferation and the production of IFN-γ by activated uveitis CD4⁺ T cells, especially Th1-type T cells. In contrast, iPS-RPE cells stimulated T cells of uveitis patients. The iPS-RPE cells constitutively expressed B7-H1/CD274 and B7-DC/CD273, and suppressed the activation of T cells via the PD-1 receptor. iPS-RPE expressed these negative costimulatory molecules, especially when RPE cells were pretreated with recombinant IFN-γ. In addition, iPS-RPE cells also expressed B7-H3/CD276 costimulatory molecules and activated uveitis T cells through the B7-H3-TLT-2 receptor. Thus, cultured iPS-derived retinal cells can suppress or activate inflammatory T cells in vitro through costimulatory interactions.

TRIM31 inhibits NLRP3 inflammasome and pyroptosis of retinal pigment epithelial cells through ubiquitination of NLRP3

NOD-like receptor protein 3 (NLRP3) is associated with age-related macular degeneration (AMD). Retinal pigment epithelial (RPE) cells serve as the immune defense of macula, and their dysfunction causes clinically relevant changes in AMD. In the present study, oxidized low-density lipoprotein (ox-LDL) activated the NLRP3 inflammasome in human RPE cell line ARPE-19. Our data showed that the expression of NLRP3, interleukin-1β (IL-1β), and caspase-1 and the release of IL-1β in ARPE-19 cells were substantially increased by ox-LDL, whereas the addition of NLRP3 inhibitor INF39 dose-dependently reversed the effect of ox-LDL. Overexpression of tripartite motif-containing protein 31 (TRIM31) also suppressed the effect of ox-LDL in ARPE-19 cells. TRIM31 knockdown had similar effects with ox-LDL but INF39 could block the effect of TRIM31 knockdown. Moreover, TRIM31 could interact with NLRP3 in ARPE-19 cells. Overexpression of TRIM31 increased NLRP3 ubiquitination. In conclusion, the results propose that TRIM31 could enhance NLRP3 ubiquitination, therefore inhibiting NLRP3 inflammasome and pyroptosis in human RPE cells.

Blocking VEGF signaling augments interleukin-8 secretion via MEK/ERK/1/2 axis in human retinal pigment epithelial cells

AIM

To identify proangiogenic factors engaged in neovascular age-related macular degeneration (AMD) except vascular endothelial growth factor (VEGF) from human retinal pigment epithelial (hRPE) cells and investigate the underlying mechanisms.

METHODS

VEGF receptor 2 (VEGFR2) in ARPE-19 cells was depleted by siRNA transfection or overexpressed through adenovirus infection. The mRNA and the protein levels of interleukin-8 (IL-8) in ARPE-19 cells were measured by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay respectively. The protein levels of AKT, p-AKT, MEK, p-MEK, ERK1/2, p-ERK1/2, JNK, p-JNK, p38 and p-p38 were detected by Western blotting. A selective chemical inhibitor, LY3214996, was employed to inhibit phosphorylation of ERK1/2. Cell viability was determined by MTT assay.

RESULTS

Knockdown of VEGFR2 in ARPE-19 cells robustly augmented IL-8 production at both the mRNA and the protein levels. Silencing VEGFR2 substantially enhanced phosphorylation of MEK and ERK1/2 while exerted no effects on phosphorylation of AKT, JNK and p38. Inhibiting ERK1/2 phosphorylation by LY3214996 reversed changes in VEGFR2 knockdown-induced IL-8 upregulation at the mRNA and the protein levels with no effects on cell viability. VEGFR2 overexpression significantly reduced IL-8 generation at the mRNA and the protein levels.

CONCLUSION

Blockade of VEGF signaling augments IL-8 secretion via MEK/ERK1/2 axis and overactivation of VEGF pathway decreases IL-8 production in hRPE cells. Upregulated IL-8 expression after VEGF signaling inhibition in hRPE cells may be responsible for being incompletely responsive to anti-VEGF remedy in neovascular AMD, and IL-8 may serve as an alternative therapeutic target for neovascular AMD.

Proteomic analysis of underlying apoptosis mechanisms of human retinal pigment epithelial ARPE-19 cells in response to mechanical stretch

Our previous study demonstrated mechanical stretch (MS) could induce the apoptosis of retinal pigment epithelial (RPE) cells, but the related mechanisms remained unclear. This study was to characterize the protein expression profile in RPE cell line ARPE-19 exposed to MS, cytochalasin D (CD; an inhibitor of actin polymerization) or CD + MS at 2-time points (6, 24 hr; n = 3, at each time point) by using proteomics technique. Our data highlighted that compared with control, ECE1 was continuously downregulated in ARPE-19 cells treated by MS or CD + MS from 6 to 24 hr. Function and protein-protein interaction network analyses showed ATAD2 was downregulated in all three treatment groups compared with control, but successive upregulation of RPS13 and RPL7 and downregulation of AHSG were specifically induced by MS. ATAD2 was enriched in cell cycle; AHSG was associated with membrane organization; RPS13 and RPL7 participated in ribosome biogenesis. Furthermore, transcription factor CREB1 that was upregulated in MS group at 24 hr after treatment, may negatively regulate ATAD2. The expressions of all crucial proteins in ARPE-19 cells were confirmed by western blot analysis. Overexpression of ATAD2 and AHSG were also shown to reverse the apoptosis of ARPE-19 cells induced by MS or CD + MS, with significantly decreased apoptotic rates and caspase-3 activities. Accordingly, our findings suggest downregulation of ATAD2 and AHSG may be potential contributors to the apoptosis of RPE cells induced by MS. Overexpression of them may represent underlying preventive and therapeutic strategies for MS-induced retinal disorders.

A Strategy for Personalized Treatment of iPS-Retinal Immune Rejections Assessed in Cynomolgus Monkey Models

Recently, we successfully transplanted an autograft, or major histocompatibility complex (MHC)-matched allografts, from induced-pluripotent-stem-cell-derived retinal pigment epithelial (iPSC-RPE) cells in patients with age-related macular degeneration. However, there was an issue regarding immune rejection after transplantation. In this study, we established a preoperational in vitro "drug-lymphocytes-grafts immune reaction (Drug-LGIR)" test to determine the medication for immune rejection using host immunocompetent cells (lymphocytes) and transplant cells (target iPSC-RPE cells) together with different medications. The adequacy of the test was assessed by in vivo transplantation in monkey models together with medication based on in vitro data. In the results of Drug-LGIR tests, some drugs exhibited significant suppression of RPE cell-related allogeneic reactions, while other drugs did not, and the efficacy of each drug differed among the recipient monkeys. Based on the results of Drug-LGIR, we applied cyclosporine A or local steroid (triamcinolone) therapy to two monkeys, and successfully suppressed RPE-related immune rejections with RPE grafts, which survived without any signs of rejection under drug administration. We propose that our new preoperational in vitro Drug-LGIR test, which specifies the most efficacious medication for each recipient, is useful for controlling immune attacks with personalized treatment for each patient after retinal transplantation.

Beta-adrenergic agonist protects retinal pigment epithelium against hydroxycholoroquine toxicity via cAMP-PKA signal pathway

AIM

To test our hypothesis that activation of protein kinase A (PKA) signal pathway by β-adrenergic agonist plays an important role in the protecting of cultured retinal pigment epithelial (RPE) cells against the hydroxychloroquine (HCQ) toxicity.

METHODS

Cultured human RPE cells were treated with 1) HCQ, 2) HCQ with salbutamol (a β2-adrenergic receptor agonist), and 3) HCQ with salbutamol and a PKA inhibitor, and compared these to 4) untreated cells (controls). After treated for 24h, cell vacuolation, cells viability, PKA and PKA kinase activity levels were determined by the measurement of the size of vacuoles using Image J software, the cell counting with a dye-exclusion testing, Western blot and PKA kinase detection, respectively.

RESULTS

Cell vacuolation and cell death of cultured RPE cells were significantly increased by the treatment of HCQ. Salbutamol significantly elevated PKA and PKA activity levels and this was associated with the inhibition of the vacuolation and cell death. The PKA inhibitor significantly decreased the PKA levels and eliminated the protective effects of salbutamol on HCQ-treated RPE cells.

CONCLUSION

The PKA pathway plays an important role in the protective effects of β2-adrenergic agonist on the RPE cells against HCQ toxicity. These findings reveal a novel potential strategy against HCQ retinopathy by treatment with PKA activating medications.