GMFB/AKT/TGF-ß3 in Müller cells mediated early retinal degeneration in a streptozotocin-induced rat diabetes model.

Retinal degeneration, characterized by Müller cell gliosis and photoreceptor apoptosis, is considered an early event in diabetic retinopathy (DR). Our previous study proposed that GMFB may mediate diabetic retinal degeneration. This study identified GMFB as a sensitive and functional gliosis marker for DR. Compared to the wild type (WT) group, Gmfb knockout (KO) significantly improved visual function, attenuated gliosis, reduced the apoptosis of neurons, and decreased the mRNA levels of tumor necrosis factor α (Tnf-α) and interleukin-1ß (Il-1ß) in diabetic retinas. Tgf-ß3 was enriched by hub genes using RNA sequencing in primary WT and KO Müller cells. Gmfb KO significantly upregulated the transforming growth factor (TGF)-ß3 protein level via the AKT pathway. The protective effect of TGF-ß3 in the vitreous resulted in significantly improved visual function and decreased the number of apoptotic cells in the diabetic retina. The protection of Gmfb KO in primary Müller cells against high glucose (HG)-induced photoreceptor apoptosis was partially counteracted by TGF-ß3 antibody and administration of TGFBR1/2 inhibitors. Nuclear receptor subfamily 3 group C member 1 (NR3C1) binds to the promoter region of Gmfb and regulates Gmfb mRNA at the transcriptional level. NR3C1 was increased in the retinas of early diabetic rats but decreased in the retinas of late diabetic rats. N'-[(1E)-(3-Methoxyphenyl)Methylene]-3-Methyl-1H-Pyrazole-5-Carbohydrazide (DS-5) was identified as an inhibitor of GMFB, having a protective role in DR. We demonstrated that GMFB/AKT/TGF-ß3 mediated early diabetic retinal degeneration in diabetic rats. This study provides a novel therapeutic strategy for treating retinal degeneration in patients with DR.

Wnt5a/ß-catenin-mediated epithelial-mesenchymal transition: a key driver of subretinal fibrosis in neovascular age-related macular degeneration.

BACKGROUND: Neovascular age-related macular degeneration (nAMD), accounts for up to 90% of AMD-associated vision loss, ultimately resulting in the formation of fibrotic scar in the macular region. The pathogenesis of subretinal fibrosis in nAMD involves the process of epithelial-mesenchymal transition (EMT) occurring in retinal pigment epithelium (RPE). Here, we aim to investigate the underlying mechanisms involved in the Wnt signaling during the EMT of RPE cells and in the pathological process of subretinal fibrosis secondary to nAMD. METHODS: In vivo, the induction of subretinal fibrosis was performed in male C57BL/6J mice through laser photocoagulation. Either FH535 (a ß-catenin inhibitor) or Box5 (a Wnt5a inhibitor) was intravitreally administered on the same day or 14 days following laser induction. The RPE-Bruch's membrane-choriocapillaris complex (RBCC) tissues were collected and subjected to Western blot analysis and immunofluorescence to examine fibrovascular and Wnt-related markers. In vitro, transforming growth factor beta 1 (TGFß1)-treated ARPE-19 cells were co-incubated with or without FH535, Foxy-5 (a Wnt5a-mimicking peptide), Box5, or Wnt5a shRNA, respectively. The changes in EMT- and Wnt-related signaling molecules, as well as cell functions were assessed using qRT-PCR, nuclear-cytoplasmic fractionation assay, Western blot, immunofluorescence, scratch assay or transwell migration assay. The cell viability of ARPE-19 cells was determined using Cell Counting Kit (CCK)-8. RESULTS: The in vivo analysis demonstrated Wnt5a/ROR1, but not Wnt3a, was upregulated in the RBCCs of the laser-induced CNV mice compared to the normal control group. Intravitreal injection of FH535 effectively reduced Wnt5a protein expression. Both FH535 and Box5 effectively attenuated subretinal fibrosis and EMT, as well as the activation of ß-catenin in laser-induced CNV mice, as evidenced by the significant reduction in areas positive for fibronectin, alpha-smooth muscle actin (α-SMA), collagen I, and active ß-catenin labeling. In vitro, Wnt5a/ROR1, active ß-catenin, and some other Wnt signaling molecules were upregulated in the TGFß1-induced EMT cell model using ARPE-19 cells. Co-treatment with FH535, Box5, or Wnt5a shRNA markedly suppressed the activation of Wnt5a, nuclear translocation of active ß-catenin, as well as the EMT in TGFß1-treated ARPE-19 cells. Conversely, treatment with Foxy-5 independently resulted in the activation of abovementioned molecules and subsequent induction of EMT in ARPE-19 cells. CONCLUSIONS: Our study reveals a reciprocal activation between Wnt5a and ß-catenin to mediate EMT as a pivotal driver of subretinal fibrosis in nAMD. This positive feedback loop provides valuable insights into potential therapeutic strategies to treat subretinal fibrosis in nAMD patients.

Construction of living-cell tissue engineered amniotic membrane for ocular surface disease.

BACKGROUND: Human amniotic membrane (AM) transplantation has been applied to treat ocular surface diseases, including corneal trauma. The focus of much deliberation is to balance the mechanical strength of the amniotic membrane, its resistance to biodegradation, and its therapeutic efficacy. It is commonly observed that the crosslinked human decellularized amniotic membranes lose the functional human amniotic epithelial cells (hAECs), which play a key role in curing the injured tissues. METHODS AND RESULTS: In this study, we crosslinked human decellularized amniotic membranes (dAM) with genipin and re-planted the hAECs onto the genipin crosslinked AM. The properties of the AM were evaluated based on optical clarity, biodegradation, cytotoxicity, and ultrastructure. The crosslinked AM maintained its transparency. The color of crosslinked AM deepened with increasing concentrations of genipin. And the extracts from low concentrations of genipin crosslinked AM had no toxic effect on human corneal epithelial cells (HCECs), while high concentrations of genipin exhibited cytotoxicity. The microscopic observation and H&E staining revealed that 2 mg/mL genipin-crosslinked dAM (2 mg/mL cl-dAM) was more favorable for the attachment, migration, and proliferation of hAECs. Moreover, the results of the CCK-8 assay and the transwell assay further indicated that the living hAECs' tissue-engineered amniotic membranes could facilitate the proliferation and migration of human corneal stromal cells (HCSCs) in vitro. CONCLUSIONS: In conclusion, the cl-dAM with living hAECs demonstrates superior biostability and holds significant promise as a material for ocular surface tissue repair in clinical applications.

Molecular pathogenesis of subretinal fibrosis in neovascular AMD focusing on epithelial-mesenchymal transformation of retinal pigment epithelium.

Age-related macular degeneration (AMD) is a leading cause of vision loss among elderly people in developed countries. Neovascular AMD (nAMD) accounts for more than 90% of AMD-related vision loss. At present, intravitreal injection of anti-vascular endothelial growth factor (anti-VEGF) is widely used as the first-line therapy to decrease the choroidal and retinal neovascularizations, and thus to improve or maintain the visual acuity of the patients with nAMD. However, about 1/3 patients still progress to irreversible visual impairment due to subretinal fibrosis even with adequate anti-VEGF treatment. Extensive literatures support the critical role of epithelial-mesenchymal transformation (EMT) of retinal pigment epithelium (RPE) in the pathogenesis of subretinal fibrosis in nAMD, but the underlying mechanisms still remain largely unknown. This review summarized the molecular pathogenesis of subretinal fibrosis in nAMD, especially focusing on the transforming growth factor-ß (TGF-ß)-induced EMT pathways. It was also discussed how these pathways crosstalk and respond to signals from the microenvironment to mediate EMT and contribute to the progression of nAMD-related subretinal fibrosis. Targeting EMT signaling pathways might provide a promising and effective therapeutic strategy to treat subretinal fibrosis secondary to nAMD.

Aquaporin 11 alleviates retinal Müller intracellular edema through water efflux in diabetic retinopathy.

Retinal Müller glial dysfunction and intracellular edema are important mechanisms leading to diabetic macular edema (DME). Aquaporin 11 (AQP11) is primarily expressed in Müller glia with unclear functions. This study aims to explore the role of AQP11 in the pathogenesis of intracellular edema of Müller glia in diabetic retinopathy (DR). Here, we found that AQP11 expression, primarily located at the endfeet of Müller glia, was down-regulated with diabetes progression, accompanied by intracellular edema, which was alleviated by intravitreal injection of lentivirus-mediated AQP11 overexpression. Similarly, intracellular edema of hypoxia-treated rat Müller cell line (rMC-1) was aggravated by AQP11 inhibition, while attenuated by AQP11 overexpression, accompanied by enhanced function in glutamate metabolism and reduced cell death. The down-regulation of AQP11 was also verified in the Müller glia from the epiretinal membranes (ERMs) of proliferative DR (PDR) patients. Mechanistically, down-regulation of AQP11 in DR was mediated by the HIF-1α-dependent and independent miRNA-AQP11 axis. Overall, we deciphered the AQP11 down-regulation, mediated by miRNA-AQP11 axis, resulted in Müller drainage dysfunction and subsequent intracellular edema in DR, which was partially reversed by AQP11 overexpression. Our findings propose a novel mechanism for the pathogenesis of DME, thus targeting AQP11 regulation provides a new therapeutic strategy for DME.

Comprehensive Bibliometric Analysis of Stem Cell Research in Alzheimer's Disease from 2004 to 2022.

INTRODUCTION: Stem cell-based regenerative medicine has provided an excellent opportunity to investigate therapeutic strategies and innovative treatments for Alzheimer's disease (AD). However, there is an absence of visual overviews to assess the published literature systematically. METHODS: In this review, the bibliometric approach was used to estimate the searched data on stem cell research in AD from 2004 to 2022, and we also utilized CiteSpace and VOSviewer software to evaluate the contributions and co-occurrence relationships of different countries/regions, institutes, journals, and authors as well as to discover research hot spots and encouraging future trends in this field. RESULTS: From 2004 to 2022, a total of 3,428 publications were retrieved. The number of publications and citations on stem cell research in AD has increased dramatically in the last nearly 20 years, especially since 2016. North America and Asia were the top 2 highest output regions. The leading country in terms of publications and access to collaborative networks was the USA. Centrality analysis revealed that the UCL (0.05) was at the core of the network. The Journal of Alzheimer's Disease (n = 102, 2.98%) was the most productive academic journal. The analyses of keyword burst detection indicated that exosomes, risk factors, and drug delivery only had burst recently. Citations and co-citation achievements clarified that cluster #0 induced pluripotent stem cells, #2 mesenchymal stem cells, #3 microglia, and #6 adult hippocampal neurogenesis persisted to recent time. CONCLUSION: This bibliometric analysis provides a comprehensive guide for clinicians and scholars working in this field. These analysis and results hope to provide useful information and references for future understanding of the challenges behind translating underlying stem cell biology into novel clinical therapeutic potential in AD.

Enhancing fractalkine/CX3CR1 signalling pathway can reduce neuroinflammation by attenuating microglia activation in experimental diabetic retinopathy.

The concept of diabetic retinopathy (DR) has been extended from microvascular disease to neurovascular disease in which microglia activation plays a remarkable role. Fractalkine (FKN)/CX3CR1 is reported to regulate microglia activation in central nervous system diseases. To characterize the effect of FKN on microglia activation in DR, we employed streptozotocin-induced diabetic rats, glyoxal-treated R28 cells and hypoxia-treated BV2 cells to mimic diabetic conditions and explored retinal neuronal apoptosis, reactive oxygen species (ROS), as well as the expressions of FKN, Iba-1, TSPO, NF-κB, Nrf2 and inflammation-related cytokines. The results showed that FKN expression declined with diabetes progression and in glyoxal-treated R28 cells. Compared with normal control, retinal microglia activation and inflammatory factors surged in both diabetic rat retinas and hypoxia-treated microglia, which was largely dampened by FKN. The NF-κB and Nrf2 expressions and intracellular ROS were up-regulated in hypoxia-treated microglia compared with that in normoxia control, and FKN significantly inhibited NF-κB activation, activated Nrf2 pathway and decreased intracellular ROS. In conclusion, the results demonstrated that FKN deactivated microglia via inhibiting NF-κB pathway and activating Nrf2 pathway, thus to reduce the production of inflammation-related cytokines and ROS, and protect the retina from diabetes insult.

Elimination of senescent cells inhibits epithelial-mesenchymal transition of retinal pigment epithelial cells.

Age-related macular degeneration (AMD) is one of the most common leading causes of irreversible blindness, and there is no effective treatment for it. It has been reported that aging is the greatest risk factor for AMD, and epithelial-mesenchymal transition (EMT) of retinal pigment epithelium (RPE) cells plays an important role in the pathogenesis of AMD. To clarify the relationship between senescence and EMT in RPE cells, we used the replicative senescence model, H2O2- and/or Nutlin3a-induced senescence model, and low-density and/or TGF-ß-induced EMT model to detect the expression of senescence-, RPE- and EMT-related genes, and assessed the motility of cells by using a scratch wound migration assay. The results showed that replicative senescence of RPE cells was accompanied by increased expression of EMT markers. However, senescent RPE cells themselves did not undergo EMT, as the H2O2and Nutlin3a treated cells showed no increase in EMT characteristics, including unchanged or decreased expression of EMT markers and decreased motility. Furthermore, conditioned medium (CM) from senescent cells induced EMT in presenescent RPE cells, and EMT accelerated the process of senescence. Importantly, dasatinib plus quercetin, which selectively eliminates senescent cells, inhibited low-density-induced EMT in RPE cells. These findings provide a better understanding of the interconnection between senescence and EMT in RPE cells. Removal of senescent cells by certain methods such as senolytics, might be a promising potential approach to prevent or delay the progression of RPE-EMT-related retinal diseases such as AMD.

CHIR99021 balance TGFß1 induced human corneal endothelial-to-mesenchymal transition to favor corneal endothelial cell proliferation.

Corneal endothelial cells (CECs) play a major role in the maintenance of stromal hydration via the barrier and pump function for clear vision. Adult CECs cannot regenerate after injury. CECs cultured in vitro can undergo mitosis but may undergo corneal endothelial-to-mesenchymal transition (EnMT) and lose their endothelial characteristics. In this study, we examined the effects of CHIR99021 on transforming growth factor beta-1(TGFß1)-induced EnMT in human CECs (hCECs) lines. CHIR99021 kept hCECs in the hexagonal shape and could downregulate the EnMT markers alpha-smooth muscle actin (α-SMA) and fibronectin (FN1), meanwhile maintained the hCECs function markers Na+/K+-ATPase and zonula occludens-1 (ZO-1) at levels comparable to those in the normal control. Interestingly, we found that the combination of CHIR99021 and TGFß1 at appropriate concentrations would significantly promote the proliferation and migration of hCECs. These effects may be related to the inhibition of RhoA or Rac1, as well as the activation of Wnt and Erk pathway, with a calcium homeostasis. Our findings indicate that CHIR99021 inhibit EnMT and that the combination of CHIR99021 and TGFß1 may provide new ideas for corneal endothelial regeneration and wound healing.

An in vitro cell model to study microglia activation in diabetic retinopathy.

Microglial activation has been studied extensively in diabetic retinopathy. We have previously detected activation and migration of microglia in 8-week-old diabetic rat retinas. It is widely acknowledged that microglia-mediated inflammation contributes to the progression of diabetic retinopathy. However, existing cell models do not explore the role of activated microglia in vitro. In this study, microglia were subject to various conditions mimicking diabetic retinopathy, including high glucose, glyoxal, and hypoxia. Under high glucose or glyoxal treatment, microglia demonstrated only partially functional changes, while under hypoxia, microglia became fully activated showing enlarged cell bodies, enhanced migration and phagocytosis as well as increased production of pro-inflammatory factors such as cyclooxygenase-2 (COX-2), interleukin-1ß (IL-1ß), and inducible nitric oxide synthase (iNOS). The data indicate that hypoxia-treated microglia is an optimal in vitro model for exploration of microglia activation in diabetic retinopathy.

Hyperrefective foci in diabetic macular edema with subretinal fluid: association with visual outcomes after anti-VEGF treatment.

INTRODUCTION: To describe the hyperreflective foci (HRF) on optical coherence tomography angiography (OCTA) in diabetic macular edema (DME) with subretinal fluid (SRF) and explore the association of HRF in the outer retina with photoreceptor integrity and visual outcomes after anti-vascular endothelial growth factor (anti-VEGF) treatment. METHODS: We retrospectively reviewed 46 eyes (36 patients) with DME treated with anti-VEGF drugs. The following parameters, including best-corrected visual acuity (BCVA), central macular thickness (CMT), the height of subretinal fluid (SRF), the number of HRF in the superficial capillary plexus (SCP), deep capillary plexus (DCP), and the outer retina, as well as the integrity of external limiting membrane (ELM) and ellipsoid zone (EZ), were evaluated and compared between the baseline and after 2 monthly injections of anti-VEGF drugs. The relationship between the HRF in the outer retina and the integrity of ELM and EZ, as well as BCVA was analyzed. RESULTS: BCVA was significantly improved in DME after anti-VEGF treatment, however, for the subgroup of DME patients with SRF, visual acuity remained unchanged after anti-VEGF treatment (p < 0.05 vs. p = 0.375). The number of HRF (p < 0.05), CMT (p ＜ 0.001), and SRF height (p ＜ 0.001) were significantly reduced, accompanied with partial restoration of ELM and EZ integrity after anti-VEGF injection. The HRF in the outer retina was correlated with the final ELM (p = 0.036) and EZ (p = 0.004) status. The final BCVA was significantly better in eyes with intact ELM (p = 0.002) and EZ at final visit (p< 0.001). CONCLUSION: The number of HRF in outer retina was negatively associated with the microstructural restoration of ELM and EZ, as well as the visual outcome in DME patients with SRF after anti-VEGF treatment.

Erythropoietin protects the inner blood-retinal barrier by inhibiting microglia phagocytosis via Src/Akt/cofilin signalling in experimental diabetic retinopathy.

AIMS/HYPOTHESIS: Microglial activation in diabetic retinopathy and the protective effect of erythropoietin (EPO) have been extensively studied. However, the regulation of microglia in the retina and its relationship to inner blood-retinal barrier (iBRB) maintenance have not been fully characterised. In this study, we investigated the role of microglia in iBRB breakdown in diabetic retinopathy and the protective effects of EPO in this context. METHODS: Male Sprague Dawley rats were injected intraperitoneally with streptozotocin (STZ) to establish the experimental model of diabetes. At 2 h after STZ injection, the right and left eyes were injected intravitreally with EPO (16 mU/eye, 2 µl) and an equivalent volume of normal saline (NaCl 154 mmol/l), respectively. The rats were killed at 2 or 8 weeks after diabetes onset. Microglia activation was detected by ionised calcium binding adaptor molecule (IBA)-1 immunolabelling. Leakage of the iBRB was evaluated by albumin staining and FITC-dextran permeability assay. BV2 cells and primary rat microglia under hypoxic conditions were used to model microglial activation in diabetic retinopathy. Phagocytosis was examined by confocal microscopy in flat-mounted retina preparations and in microglia and endothelial cell cocultures. Protein levels of IBA-1, CD11b, complement component 1r (C1r), and Src/Akt/cofilin signalling pathway components were assessed by western blotting. RESULTS: In diabetic rat retinas, phagocytosis of endothelial cells by activated microglia was observed at 8 weeks, resulting in an increased number of acellular capillaries (increased by 426.5%) and albumin leakage. Under hypoxic conditions, activated microglia transmigrated to the opposite membrane of the transwell, where they disrupted the endothelial cell monolayer by engulfing endothelial cells. The activation and phagocytic activity of microglia was blocked by intravitreal injection of EPO. In vitro, IBA-1, CD11b and C1r protein levels were increased by 50.9%, 170.0% and 135.5%, respectively, by hypoxia, whereas the phosphorylated proteins of Src/Akt/cofilin signalling pathway components were decreased by 74.2%, 47.8% and 39.7%, respectively, compared with the control; EPO treatment abrogated these changes. CONCLUSIONS/INTERPRETATION: In experimental diabetic retinopathy, activated microglia penetrate the basement membrane of the iBRB and engulf endothelial cells, leading to iBRB breakdown. EPO exerts a protective effect that preserves iBRB integrity via activation of Src/Akt/cofilin signalling in microglia, as demonstrated in vitro. These data support a causal role for activated microglia in iBRB breakdown and highlight the therapeutic potential of EPO for the treatment of diabetic retinopathy. Graphical abstract.

Melatonin maintains inner blood-retinal barrier via inhibition of p38/TXNIP/NF-κB pathway in diabetic retinopathy.

The pathophysiology of diabetic retinopathy (DR) was complex. Under hyperglycemic conditions, the release of proinflammatory cytokines and the adhesion of leukocytes to retinal capillaries contribute to endothelial damage and the subsequent increase in vascular permeability resulting in macular edema. Melatonin, produced in the retina to regulate redox reactions and dopamine metabolism, plays protective roles against inflammation and oxidative stress. Considering its anti-inflammatory and antioxidative properties, melatonin was speculated to exert beneficial effects in DR. In this study, we characterized the protective effects of melatonin on the inner blood-retinal barrier (iBRB), as well as the possible mechanisms in experimental DR. Results showed that in diabetic rat retinas, the leakage of iBRB and the expression of inflammatory factors (VEGF, TNF-α, IL-1ß, ICAM-1, and MMP9) increased dramatically, while the expression of tight junction proteins (ZO-1, occludin, JAM-A, and claudin-5) decreased significantly. The above changes were largely ameliorated by melatonin. The in vivo data were confirmed in vitro. In addition, the protein expressions of p38 MAPK, NF-κB, and TXNIP were upregulated significantly in diabetes and were downregulated following melatonin treatment. Melatonin could maintain the iBRB integrity by upregulating the expression of tight junction proteins via inhibiting p38/TXNIP/NF-κB pathway, thus decreasing the production of inflammatory factors. This study may shed light on the development of melatonin-based DR therapy.

Silencing Nogo-B improves the integrity of blood-retinal barrier in diabetic retinopathy via regulating Src, PI3K/Akt and ERK pathways.

OBJECTIVE: To examine the mechanisms of Nogo-B (RTN4B) in the protection of blood-retinal barrier in experimental diabetic retinopathy. METHODS: The level of Nogo-B in vitreous and plasma samples was detected with ELISA. Diabetes was induced in Sprague-Dawley rats with intraperitoneal injection of streptozotocin. The rats were injected intravitreally with adeno-associated virus (AAV) for knockdown the expression of Nogo-B in retina or/and as AAV negative control. The permeability of blood-retinal barrier was detected with Rhodamine-B-dextran leakage assay. The expressions of Nogo-B, junctional proteins, inflammatory factors and signaling pathways were examined with Western blot and quantitative real-time PCR. RESULTS: Nogo-B expression was significantly upregulated in clinical samples and experimental diabetic rat models. Under normal condition, Nogo-B knockdown resulted in the increased permeability of retinal blood vessels. In diabetic rat retinas, the vascular leakage was increased significantly, which was partially decreased by Nogo-B knockdown through increasing p/t-Src (Tyr529) and p/t-Akt (Ser473), and decreasing p/t-ERK1/2. CONCLUSION: Nogo-B was increased in diabetic retinopathy and silencing Nogo-B is a promising therapy for diabetic retinopathy.

Identification of novel key molecular signatures in the pathogenesis of experimental diabetic retinopathy.

Deep mining of the molecular mechanisms underlying diabetic retinopathy (DR) is critical for the development of novel therapeutic targets. This study aimed to identify key molecular signatures involved in experimental DR on the basis of integrated bioinformatics analysis. Four datasets consisting of 37 retinal samples were downloaded from the National Center of Biotechnology Information Gene Expression Omnibus. After batch-effect adjustment, bioinformatics tools such as Networkanalyst, Enrichr, STRING, and Metascape were used to evaluate the differentially expressed genes (DEGs), perform enrichment analysis, and construct protein-protein interaction networks. The hub genes were identified using Cytoscape software. The DEGs of interest from the meta-analysis were confirmed by quantitative reverse transcription-polymerase chain reaction in diabetic rats and a high-glucose-treated retinal cell model, respectively. A total of 743 DEGs related to lens differentiation, insulin resistance, and high-density lipoprotein (HDL) cholesterol metabolism were obtained using the meta-analysis. Alterations of dynamic gene expression in the chloride ion channel, retinol metabolism, and fatty acid metabolism were involved in the course of DR in rats. Importantly, H3K27m3 modifications regulated the expression of most DEGs at the early stage of DR. Using an integrated bioinformatics approach, novel molecular signatures were obtained for different stages of DR progression, and the findings may represent distinct therapeutic strategies for DR patients.

Inhibition of PARP activity improves therapeutic effect of ARPE-19 transplantation in RCS rats through decreasing photoreceptor death.

Photoreceptor (PR) dysfunction or death is the key pathological change in retinal degeneration (RD). The death of PRs might be due to a primary change in PRs themselves or secondary to the dysfunction of the retinal pigment epithelium (RPE). Poly(ADP-ribose) polymerase (PARP) was reported to be involved in primary PR death, but whether it plays a role in PR death secondary to RPE dysfunction has not been determined. To clarify this question and develop a new therapeutic approach, we studied the changes in PAR/PARP in the RCS rat, a RD model, and tested the effect of PARP intervention when given alone or in combination with RPE cell transplantation. The results showed that poly(ADP-ribosyl)ation of proteins was increased in PRs undergoing secondary death in RCS rats, and this result was confirmed by the observation of similar changes in sodium iodate (SI)-induced secondary RD in SD rats. The increase in PAR/PARP was highly associated with increased apoptotic PRs and decreased visual function, as represented by lowered b-wave amplitudes on electroretinogram (ERG). Then, as we expected, when the RCS rats were treated with subretinal injection of the PARP inhibitor PJ34, the RD process was delayed. Furthermore, when PJ34 was given simultaneously with subretinal ARPE-19 cell transplantation, the therapeutic effects were significantly improved and lasted longer than those of ARPE-19 or PJ34 treatment alone. These results provide a potential new approach for treating RD.

MicroRNA-24 protects retina from degeneration in rats by down-regulating chitinase-3-like protein 1.

MicroRNAs (miRNAs) have been shown to play critical roles in the pathogenesis and progression of degenerative retinal diseases like age-related macular degeneration (AMD). In this study, we first demonstrated that miR-24 plays an important role in maintaining retinal structure and visual function of rats by targeting chitinase-3-like protein 1 (CHI3L1). In the retinal pigment epithelial (RPE) cells of Royal College of Surgeons (RCS) rats, an animal model of genetic retinal degeneration (RD), miR-24 was found lower and CHI3L1 level was higher in comparison with those in Sprague-Dawley (SD) rats. Other changes in the eyes of RCS rats include activated AKT/mTOR and ERK pathways and abnormal autophagy in the RPE cells. Such roles of miR-24 and CHI3L1 were further confirmed in RCS rats by subretinal injection of agomiR-24, which decreased CHI3L1 level and preserved retinal structure and function. Upstream, NF-κB was identified as the regulator of miR-24 in the RPE cells of these rats. On the other hand, in SD rats, intraocular treatment of antagomiR-24 induced pathological changes similar to those in RCS rats. The results revealed the protective roles for miR-24 to RPE cells and a mechanism for RD in RCS rats was proposed: extracellular stress stimuli first activate the NF-κB signaling pathway, which lowers miR-24 expression so that CHI3L1 increased. CHI3L1 sequentially results in aberrant autophagy and RPE dysfunction by activating AKT/mTOR and ERK pathways. Taken together, although the possibility, that the therapeutic effects in RCS rats are caused by other transcriptional changes regulated by miR-24, cannot be excluded, these findings indicate that miR-24 protects rat retina by targeting CHI3L1. Thus, miR-24 and CHI3L1 might be the targets for developing more effective therapy for degenerative retinal diseases like AMD.

Identification of two novel RHO mutations in Chinese retinitis pigmentosa patients.

Retinitis pigmentosa (RP) is a group of genetically heterogeneous retinal diseases with more than 80 identified causative genes to date. Mutations in the RHO (rhodopsin, OMIM, 180380) are the most common cause of autosomal dominant RP (adRP) worldwide. RHO is also one of the few RP genes that can cause autosomal recessive RP (arRP). To explore the frequency of RP mutations in Chinese populations, panel-based NGS (next-generation sequencing) screening and Sanger sequencing validation were performed for RP patients from 72 unrelated Chinese families. Here we reported the identified mutations only in the RHO gene. Our results showed that 4 mutations in RHO were detected in 5 (6.94%) of the 72 RP families, including two known missense mutations, c.158C > G (p.P53R) and c.551A > C (p.Q184P), and two novel mutations, c.34delC (p.P12NA) and c.82C > T (p.Q28X). The c.34delC (p.P12NA) mutation was detected in heterozygous state in one patient with intermediate RP phenotype. The c.82C > T (p.Q28X) mutation was found in a homozygous state in one proband with advanced RP phenotype at the age of 32. Clinical examination of the heterozygous carriers of c.82C > T (p.Q28X) in that family showed that the father at the age of 60s experienced no symptoms of RP and normal fundus examinations but displayed reduced electroretinography (ERG) and abnormal visual field. The sister and brother at the age of 30s showed no typical aspects of RP phenotypes. Our results not only expand the mutation spectrum of the RHO gene, but also suggest that the 2 null mutations might play minor dominant effects, leading to less severe and slower retinal degeneration in heterozygous state and more severe phenotype in homozygous state.

Erythropoietin protects outer blood-retinal barrier in experimental diabetic retinopathy by up-regulating ZO-1 and occludin.

PURPOSE: To explore the mechanisms of erythropoietin (EPO) in maintaining outer blood-retinal barrier (BRB) in diabetic rats. METHODS: Sprague-Dawley rats were rendered diabetic with intraperitoneal injection of streptozotocin, and then followed by intravitreal injection of EPO. Two and four weeks later, the permeability of outer BRB was examined with FITC-dextran leakage assay, following a method to demarcate the inner and outer retina based on retinal blood supply. The glyoxal-treated ARPE-19 cells, incubated with EPO, soluble EPO receptor (sEPOR), Gö6976, or digoxin, were studied for cell viability and barrier function. The expressions of ZO-1, occludin, VEGFR2, HIF-1α, MAPKs, and AKT were examined with Western blot and immunofluorescence. RESULTS: The major Leakage of FITC-dextran was detected in the outer nuclear layer in both 2- and 4-week diabetic rats. The leakage was largely ameliorated in EPO-treated diabetic rats. The protein expressions of ZO-1 and occludin in the RPE-Bruch's membrane choriocapillaris complex were significantly decreased, whereas HIF-1α and JNK pathways were activated, in 4-week diabetic rats. These changes were prevented by EPO treatment. The in vitro study with ARPE-19 cells confirmed these changes, and the protective effect of EPO was abolished by sEPOR. Gö6976 and digoxin rescued the tight junction and barrier function in glyoxal-treated ARPE-19 cells. CONCLUSIONS: In early diabetic rats, the outer BRB might be more severely damaged and its breakdown is the major factor for retinal oedema. EPO maintains the outer BRB integrity through down-regulation of HIF-1α and JNK signallings, and thus up-regulating ZO-1 and occludin expressions in RPE cells.

Protective Effects of Fucoidan on Epithelial-Mesenchymal Transition of Retinal Pigment Epithelial Cells and Progression of Proliferative Vitreoretinopathy.

BACKGROUND/AIMS: Proliferative vitreoretinopathy (PVR) is a severe blinding complication of rhegmatogenous retinal detachment. Epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells is thought to play a pivotal role in the pathogenesis of PVR. Fucoidan, a marine extract, reportedly has many benefits effects in a variety of tissues and organs such as anti-inflammation, anti-oxidative stress, and anti-carcinogenesis. In this study, we investigated the potential role of fucoidan on EMT in RPE cells and its effect on the development of PVR. METHODS: MTS, Transwell, and collagen gel contraction assays were employed to measure the viability, migration, and contraction of RPE cells, respectively. mRNA and protein expression were evaluated via real-time quantitative PCR and western blot analysis, respectively. In vivo, a pigmented rabbit model of PVR was established to examine the anti-PVR effect of fucoidan. RESULTS: Fucoidan reversed the transforming growth factor (TGF)-ß1-induced EMT of RPE cells, including the increased expression of α-smooth muscle actin (α-SMA) and fibronectin and down-regulation of E-cadherin in human primary RPE cells. Moreover, the upregulation of phosphorylated Smad2/3 induced by TGF-ß1 was suppressed by fucoidan. Fucoidan also inhibited the migration and contraction of RPE cells induced by TGF-ß1. In vivo, fucoidan inhibited the progression of experimental PVR in rabbit eyes. Histological findings showed that fucoidan suppressed the formation of α-SMA-positive epiretinal membranes. CONCLUSION: Our findings regarding the protective effects of fucoidan on the EMT of RPE cells and experimental PVR suggest the potential clinical application of fucoidan as an anti-PVR agent.