αB-Crystallin Regulates Subretinal Fibrosis by Modulation of Epithelial-Mesenchymal Transition

Subretinal fibrosis secondary to neovascular age-related macular degeneration: mechanisms and potential therapeutic targets

Subretinal fibrosis is the end-stage sequelae of neovascular age-related macular degeneration. It causes local damage to photoreceptors, retinal pigment epithelium, and choroidal vessels, which leads to permanent central vision loss of patients with neovascular age-related macular degeneration. The pathogenesis of subretinal fibrosis is complex, and the underlying mechanisms are largely unknown. Therefore, there are no effective treatment options. A thorough understanding of the pathogenesis of subretinal fibrosis and its related mechanisms is important to elucidate its complications and explore potential treatments. The current article reviews several aspects of subretinal fibrosis, including the current understanding on the relationship between neovascular age-related macular degeneration and subretinal fibrosis; multimodal imaging techniques for subretinal fibrosis; animal models for studying subretinal fibrosis; cellular and non-cellular constituents of subretinal fibrosis; pathophysiological mechanisms involved in subretinal fibrosis, such as aging, infiltration of macrophages, different sources of mesenchymal transition to myofibroblast, and activation of complement system and immune cells; and several key molecules and signaling pathways participating in the pathogenesis of subretinal fibrosis, such as vascular endothelial growth factor, connective tissue growth factor, fibroblast growth factor 2, platelet-derived growth factor and platelet-derived growth factor receptor-β, transforming growth factor-β signaling pathway, Wnt signaling pathway, and the axis of heat shock protein 70-Toll-like receptors 2/4-interleukin-10. This review will improve the understanding of the pathogenesis of subretinal fibrosis, allow the discovery of molecular targets, and explore potential treatments for the management of subretinal fibrosis.

Inhibition of hypoxia-inducible factors suppresses subretinal fibrosis

Age-related macular degeneration (AMD) is a common cause of vision loss. The aggressive form of AMD is associated with ocular neovascularization and subretinal fibrosis, representing a responsive outcome against neovascularization mediated by epithelial-mesenchymal transition of retinal pigment epithelium (RPE) cells. A failure of the current treatment (anti-vascular endothelial growth factor therapy) has also been attributed to the progression of subretinal fibrosis. Hypoxia-inducible factors (HIFs) increase gene expressions to promote fibrosis and neovascularization. HIFs act as a central pathway in the pathogenesis of AMD. HIF inhibitors may suppress ocular neovascularization. Nonetheless, further investigation is required to unravel the aspects of subretinal fibrosis. In this study, we used RPE-specific HIFs or von Hippel-Lindau (VHL, a regulator of HIFs) conditional knockout (cKO) mice, along with pharmacological HIF inhibitors, to demonstrate the suppression of subretinal fibrosis. Fibrosis was suppressed by treatments of HIF inhibitors, and similar suppressive effects were detected in RPE-specific Hif1a/Hif2a- and Hif1a-cKO mice. Promotive effects were observed in RPE-specific Vhl-cKO mice, where fibrosis-mediated pathologic processes were evident. Marine products' extracts and their component taurine suppressed fibrosis as HIF inhibitors. Our study shows critical roles of HIFs in the progression of fibrosis, linking them to the potential development of therapeutics for AMD.

Underlying Mechanisms and Treatment of Cellular Senescence-Induced Biological Barrier Interruption and Related Diseases

Given its increasing prevalence, aging is of great concern to researchers worldwide. Cellular senescence is a physiological or pathological cellular state caused by aging and a prominent risk factor for the interruption of the integrity and functionality of human biological barriers. Health barriers play an important role in maintaining microenvironmental homeostasis within the body. The senescence of barrier cells leads to barrier dysfunction and age-related diseases. Cellular senescence has been reported to be a key target for the prevention of age-related barrier diseases, including Alzheimer's disease, Parkinson's disease, age-related macular degeneration, diabetic retinopathy, and preeclampsia. Drugs such as metformin, dasatinib, quercetin, BCL-2 inhibitors, and rapamycin have been shown to intervene in cellular senescence and age-related diseases. In this review, we conclude that cellular senescence is involved in age-related biological barrier impairment. We further outline the cellular pathways and mechanisms underlying barrier impairment caused by cellular senescence and describe age-related barrier diseases associated with senescent cells. Finally, we summarize the currently used anti-senescence pharmacological interventions and discuss their therapeutic potential for preventing age-related barrier diseases.

Inactivation of adenosine receptor 2A suppresses endothelial-to-mesenchymal transition and inhibits subretinal fibrosis in mice

Anti-vascular endothelial growth factor therapy has had a substantial impact on the treatment of choroidal neovascularization (CNV) in patients with neovascular age-related macular degeneration (nAMD), the leading cause of vision loss in older adults. Despite treatment, many patients with nAMD still develop severe and irreversible visual impairment because of the development of subretinal fibrosis. We recently reported the anti-inflammatory and antiangiogenic effects of inhibiting the gene encoding adenosine receptor 2A (Adora2a), which has been implicated in cardiovascular disease. Here, using two mouse models of subretinal fibrosis (mice with laser injury-induced CNV or mice with a deficiency in the very low-density lipoprotein receptor), we found that deletion of Adora2a either globally or specifically in endothelial cells reduced subretinal fibrosis independently of angiogenesis. We showed that Adora2a-dependent endothelial-to-mesenchymal transition contributed to the development of subretinal fibrosis in mice with laser injury-induced CNV. Deficiency of Adora2a in cultured mouse and human choroidal endothelial cells suppressed induction of the endothelial-to-mesenchymal transition. A metabolomics analysis of cultured human choroidal endothelial cells showed that ADORA2A knockdown with an siRNA reversed the increase in succinate because of decreased succinate dehydrogenase B expression under fibrotic conditions. Pharmacological inhibition of ADORA2A with a small-molecule KW6002 in both mouse models recapitulated the reduction in subretinal fibrosis observed in mice with genetic deletion of Adora2a. ADORA2A inhibition may be a therapeutic approach to treat subretinal fibrosis associated with nAMD.

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-β (TGF-β)-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.

Characterization and contribution of RPE senescence to Age-related macular degeneration in Tnfrsf10 knock out mice

Background

Retinal pigment epithelial cells (RPE) play vital role in the pathogenesis of age-related macular degeneration (AMD). Our laboratory has shown that RPE cellular senescence contributed to the pathophysiology of experimental AMD, and SASP members are involved in this process. Recently, we presented confirmatory evidence to earlier GWAS studies that dysregulation of tumor necrosis factor receptor superfamily 10A (TNFRSF10A) dysregulation leads to AMD development and is linked to RPE dysfunction. This study aims to investigate the contribution of RPE senescence to AMD pathophysiology using TNFRSF10A silenced human RPE (hRPE) cells and Tnfrsf10 KO mice.

Methods

Sub-confluent primary hRPE cells and TNFRSF10A silenced hRPE were exposed to stress-induced premature senescence with H2O2 (500 μM, 48h), and senescence-associated markers (βgal, p16, and p21) were analyzed by RT-PCR and WB analysis. The effect of H2O2-induced senescence in non-silenced and silenced hRPE on OXPHOS and glycolysis was determined using Seahorse XF96 analyzer. Male C57BL/6J Tnfrsf10 KO ( Tnfrsf10 -/- ) mice were used to study the regulation of senescence by TNFRSF10A in vivo . Expression of p16 and p21 in control and KO mice of varying ages were determined by RT-PCR, WB, and immunostaining analysis.

Results

The senescence-associated p16 and p21 showed a significant ( p < 0.01) upregulation with H2O2 induction at the gene (1.8- and 3-fold) and protein (3.2- and 4-fold) levels in hRPE cells. The protein expression of p16 and p21 was further significantly increased by co-treatment with siRNA ( p < 0.05 vs. H2O2). Mitochondrial oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) (pmol/min/total DNA) increased with senescence induction by H2O2 for 48h in control RPE, and knockdown of TNFRSF10A caused a further increase in OCR and ECAR. In addition, co-treatment with PKC activator significantly improved all parameters. Similarly, in vivo studies showed upregulation of p16 and p21 by RT-PCR, WB, and immunostaining analysis in RPE/choroid of Tnfrsf10 KO mice. When subjected to examination across distinct age groups, namely young (1-3 months), middle (6-9 months), and old (12-15 months) mice, a discernible age-related elevation in the expression of p16 and p21 was observed.

Conclusions

Our findings suggest that TNRSF10A is a regulator of regulates in RPE senescence. Further work on elucidating pathways of senescence will facilitate the development of new therapeutic targets for AMD.

METTL3-mediated m6A modification of HMGA2 mRNA promotes subretinal fibrosis and epithelial-mesenchymal transition

Subretinal fibrosis is a major cause of the poor visual prognosis for patients with neovascular age-related macular degeneration (nAMD). Myofibroblasts originated from retinal pigment epithelial (RPE) cells through epithelial-mesenchymal transition (EMT) contribute to the fibrosis formation. N6-Methyladenosine (m6A) modification has been implicated in the EMT process and multiple fibrotic diseases. The role of m6A modification in EMT-related subretinal fibrosis has not yet been elucidated. In this study, we found that during subretinal fibrosis in the mouse model of laser-induced choroidal neovascularization, METTL3 was upregulated in RPE cells. Through m6A epitranscriptomic microarray and further verification, high-mobility group AT-hook 2 (HMGA2) was identified as the key downstream target of METTL3, subsequently activating potent EMT-inducing transcription factor SNAIL. Finally, by subretinal injections of adeno-associated virus vectors, we confirmed that METTL3 deficiency in RPE cells could efficiently attenuate subretinal fibrosis in vivo. In conclusion, our present research identified an epigenetic mechanism of METTL3-m6A-HMGA2 in subretinal fibrosis and EMT of RPE cells, providing a novel therapeutic target for subretinal fibrosis secondary to nAMD.

Persistence of vascular empty sleeves in choroidal neovascularization after VEGF therapy in both animal models and humans

PURPOSE

Choroidal neovascularization (CNV) often recurs during anti-vascular endothelial growth factor (VEGF) therapy; however, little is known about the mechanism of vascular regrowth. Vascular regrowth along the empty sleeves of basement membranes was proposed as a mechanism for recurrence after the reversal of VEGF inhibition in tumors. This study investigated whether the proposed mechanism is involved in CNV during VEGF therapy.

METHODS

We made two observations using a mice model, as well as patients with CNV. Laser-induced CNV mice were used to examine the vascular empty sleeves of the basement membrane and CNV with the immunohistochemistry of type IV collagen and CD31, respectively. A retrospective cohort study included 17 eyes from 17 patients with CNV treated with anti-VEGF treatment. Vascular regrowth during anti-VEGF treatment was assessed using optical coherence tomography angiography (OCTA).

RESULTS

In the CNV mouse model, the CD31+ vascular endothelium area was decreased during anti-VEGF treatment compared with the IgG control (33516.7 ± 10864.7 vs. 10745.9 ± 5755.9 μm2, P < 0.05), whereas a significant difference was not observed in the area of type IV collagen+ vascular empty sleeve after the treatment compared with the control (29135.0 ± 7432.9 vs. 24592.0 ± 5935.3 μm2, P = 0.7). The proportions of CD31+ to type IV collagen+ areas were significantly decreased after the treatment (38.7 ± 7.4% vs. 17.1 ± 5.4%, P < 0.05). In the OCTA observations, the follow-up period in the retrospective cohort study was 58.2 ± 23.4 months. CNV regrowth was observed in 682 neovessels of the 17 eyes. In group 1, CNV regression and regrowth are in the same form (129 neovessels, 18.9%). In group 2, CNV regression and regrowth are in a different form (170 neovessels, 24.9%). In group 3, CNV regrowth is with a different form without the regression (383 neovessels, 56.2%).

CONCLUSIONS

Parts of CNV regrowth may occur along the vascular empty sleeve, which remain after anti-VEGF treatment.

Phosphorylation of αB-Crystallin Involves Interleukin-1β-Mediated Intracellular Retention in Retinal Müller Cells: A New Mechanism Underlying Fibrovascular Membrane Formation

Purpose

Chronic inflammation plays a pivotal role in the pathology of proliferative diabetic retinopathy (PDR), in which biological alterations of retinal glial cells are one of the key elements. The phosphorylation of αB-crystallin/CRYAB modulates its molecular dynamics and chaperone activity, and attenuates αB-crystallin secretion via exosomes. In this study, we investigated the effect of phosphorylated αB-crystallin in retinal Müller cells on diabetic mimicking conditions, including interleukin (IL)-1β stimuli.

Methods

Human retinal Müller cells (MIO-M1) were used to examine gene and protein expressions with real-time quantitative PCR, enzyme linked immunosorbent assay (ELISA), and immunoblot analyses. Cell apoptosis was assessed by Caspase-3/7 assay and TdT-mediated dUTP nick-end labeling staining. Retinal tissues isolated from the Spontaneously Diabetic Torii (SDT) fatty rat, a type 2 diabetic animal model with obesity, and fibrovascular membranes from patients with PDR were examined by double-staining immunofluorescence.

Results

CRYAB mRNA was downregulated in MIO-M1 cells with the addition of 10 ng/mL IL-1β; however, intracellular αB-crystallin protein levels were maintained. The αB-crystallin serine 59 (Ser59) residue was phosphorylated with IL-1β application in MIO-M1 cells. Cell apoptosis in MIO-M1 cells was induced by CRYAB knockdown. Immunoreactivity for Ser59-phosphorylated αB-crystallin and glial fibrillary acidic protein was colocalized in glial cells of SDT fatty rats and fibrovascular membranes.

Conclusions

The Ser59 phosphorylation of αB-crystallin was modulated by IL-1β in Müller cells under diabetic mimicking inflammatory conditions, suggesting that αB-crystallin contributes to the pathogenesis of PDR through an anti-apoptotic effect.

A systems biology approach uncovers novel disease mechanisms in age-related macular degeneration

Age-related macular degeneration (AMD) is a leading cause of blindness, affecting 200 million people worldwide. To identify genes that could be targeted for treatment, we created a molecular atlas at different stages of AMD. Our resource is comprised of RNA sequencing (RNA-seq) and DNA methylation microarrays from bulk macular retinal pigment epithelium (RPE)/choroid of clinically phenotyped normal and AMD donor eyes (n = 85), single-nucleus RNA-seq (164,399 cells), and single-nucleus assay for transposase-accessible chromatin (ATAC)-seq (125,822 cells) from the retina, RPE, and choroid of 6 AMD and 7 control donors. We identified 23 genome-wide significant loci differentially methylated in AMD, over 1,000 differentially expressed genes across different disease stages, and an AMD Müller state distinct from normal or gliosis. Chromatin accessibility peaks in genome-wide association study (GWAS) loci revealed putative causal genes for AMD, including HTRA1 and C6orf223. Our systems biology approach uncovered molecular mechanisms underlying AMD, including regulators of WNT signaling, FRZB and TLE2, as mechanistic players in disease.

Animal model of subretinal fibrosis without active choroidal neovascularization

Subretinal fibrosis can occur during neovascular age-related macular degeneration (nAMD) and consequently provokes progressing deterioration of AMD patient's vision. Intravitreal anti-vascular endothelial growth factor (VEGF) injections decrease choroidal neovascularization (CNV), however, subretinal fibrosis remains principally unaffected. So far, no successful treatment nor established animal model for subretinal fibrosis exists. In order to investigate the impact of anti-fibrotic compounds on solely fibrosis, we refined a time-dependent animal model of subretinal fibrosis without active choroidal neovascularization (CNV). To induce CNV-related fibrosis, wild-type (WT) mice underwent laser photocoagulation of the retina with rupture of Bruch's membrane. The lesions volume was assessed with optical coherence tomography (OCT). CNV (Isolectin B4) and fibrosis (type 1 collagen) were separately quantified with confocal microscopy of choroidal whole-mounts at every time point post laser induction (day 7-49). In addition, OCT, autofluorescence and fluorescence angiography were carried out at designated timepoints (day 7, 14, 21, 28, 35, 42, 49) to monitor CNV and fibrosis transformation over time. From 21 to 49 days post laser lesion leakage in the fluorescence angiography decreased. Correspondingly, Isolectin B4 decreased in lesions of choroidal flat mounts and type 1 collagen increased. Fibrosis markers, namely vimentin, fibronectin, alpha-smooth muscle actin (α-SMA) and type 1 collagen were detected at different timepoints of tissue repair in choroids and retinas post laser. These results prove that the late phase of the CNV-related fibrosis model enables screening of anti-fibrotic compounds to accelerate the therapeutic advancement for the prevention, reduction, or inhibition of subretinal fibrosis.

Mechanisms of Epithelial-Mesenchymal Transition and Prevention of Dispase-Induced PVR by Delivery of an Antioxidant αB Crystallin Peptide

Proliferative Vitreoretinopathy (PVR) is a refractory retinal disease whose primary pathogenesis involves the epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells. At present, there is no effective treatment other than surgery for PVR. The purpose of this study was to investigate the effect of αB crystallin peptide (αBC-P) on EMT in PVR. We have previously shown that this peptide is antiapoptotic and regulates RPE redox status. Subconfluent primary human RPE (hRPE) cells were stimulated by TGFβ2 (10 ng/mL) with or without αBC-P (50 or 75 μg/mL) for 48 h and expression of EMT/mesenchymal to epithelial transition (MET) markers was determined. Mitochondrial ROS (mtROS) generation in hRPE cells treated with TGFβ2 was analyzed. The effect of TGFβ2 and αBC-P on oxidative phosphorylation (OXPHOS) and glycolysis in hRPE was studied. RPE cell migration was also assessed. A PVR-like phenotype was induced by intravitreal dispase injection in C57BL/6J mice. PVR progression and potential therapeutic efficiency of αBC-Elastin-like polypeptides (ELP) was studied using fundus photography, OCT imaging, ERG, and histologic analysis of the retina. αSMA, E-cadherin, Vimentin, Fibronectin and, RPE65, and CTGF were analyzed on Day 28. Additionally, the amount of VEGF-A in retinal cell lysates was measured. The EMT-associated αSMA, Vimentin, SNAIL and SLUG showed a significant upregulation with TGFβ2, and their expression was significantly suppressed by cotreatment with αBC-P. The MET-associated markers, E-cadherin and Sirt1, were significantly downregulated by TGFβ2 and were restored by αBC-P. Incubation of hRPE with TGFβ2 for 24 h showed a marked increase in mitochondrial ROS which was noticeably inhibited by αBC-ELP. We also showed that after TGFβ2 treatment, SMAD4 translocated to mitochondria which was blocked by αBC-ELP. Mitochondrial oxygen consumption rate increased with TGFβ2 treatment for 48 h, and αBC-P co-treatment caused a further increase in OCR. Glycolytic functions of RPE were significantly suppressed with αBC-P (75 μg/mL). In addition, αBC-P significantly inhibited the migration from TGFβ2 treatment in hRPE cells. The formation of proliferative membranes was suppressed in the αBC-ELP-treated group, as evidenced by fundus, OCT, and H&E staining in dispase-induced PVR in mice. Furthermore, ERG showed an improvement in c-wave amplitude. In addition, immunostaining showed significant suppression of αSMA and RPE65 expression. It was also observed that αBC-ELP significantly reduced the expression level of vimentin, fibronectin, and CTGF. Our findings suggest that the antioxidant αBC-P may have therapeutic potential in preventing PVR by reversing the phenotype of EMT/MET and improving the mitochondrial function in RPE cells.

Suppression of choroidal neovascularization and epithelial-mesenchymal transition in retinal pigmented epithelium by adeno-associated virus-mediated overexpression of CCN5 in mice

Choroidal neovascularization (CNV) is a defining characteristic feature of neovascular age-related macular degeneration (nAMD) that frequently results in irreversible vision loss. The current strategies for the treatment of nAMD are mainly based on neutralizing vascular endothelial growth factor (VEGF). However, anti-VEGF therapies are often associated with subretinal fibrosis that eventually leads to damages in macula. In this study, we tested whether an anti-fibrotic and anti-angiogenic protein CCN5 can potentially be an effective and safe therapeutic modality in a mouse model of CNV. Laser photocoagulation was utilized to induce CNV, which was followed by intravitreal injection of recombinant adeno-associated virus serotype 2 encoding CCN5 (rAAV2-CCN5). Our data demonstrated that rAAV2-CCN5, but not a control viral vector, rAAV2-VLP, prominently attenuated both CNV lesions and angiogenesis. Aflibercept, which was utilized as a positive control, exhibited similar effects on CNV lesions and angiogenesis in our experimental settings. Upon laser photocoagulation, retinal pigmented epithelium (RPE) cells underwent significant morphological changes including cellular enlargement and loss of hexagonality. rAAV2-CCN5 significantly normalized these morphological defects. Laser photocoagulation also led to fibrotic deformation in RPE cells through inducing epithelial-mesenchymal transition (EMT), which was completely blocked by rAAV2-CCN5. In a striking contrast, aflibercept as well as rAAV2-VLP failed to exhibit any effects on EMT. Collectively, this study suggest that CCN5 might provide a potential novel strategy for the treatment of nAMD with a capability to inhibit CNV and fibrosis simaultaneously.

YAP is critical to inflammation, endothelial-mesenchymal transition and subretinal fibrosis in experimental choroidal neovascularization

Subretinal fibrosis causes local damage to the retina and irreversible vision loss, as the final stage of neovascular age-related macular degeneration (nAMD). More recently, the endothelial-to-mesenchymal transition (EndoMT) has been considered one of the most significant sources of myofibroblasts in subretinal fibrosis, though the underpinning molecular mechanisms remain unclear. In this study, a series of experiments were performed to test the hypothesis that Yes-associated protein (YAP) may be involved in EndoMT and subretinal fibrosis. We demonstrated that transforming growth factor (TGF)-β2 stimulation induces YAP dephosphorylation (activated) and nuclear transcription in human umbilical vein endothelial cells (HUVECs) by increasing reactive oxygen species (ROS) levels. Moreover, TGF-β2-mediated EndoMT and proinflammatory cytokine production in HUVECs were reduced by ROS clearance or YAP knockdown. Furthermore, the severity of subretinal fibrosis was markedly relieved by intravitreal administration of a small interfering RNA targeting YAP in the mouse laser-induced choroidal neovascularization (CNV) model. Our findings provide novel insights into a previously unknown effect of YAP on the EndoMT process and reveal YAP as a potential target for suppressing CNV-related subretinal fibrosis and protect vision.

Small Heat Shock Proteins in Retinal Diseases

This review summarizes the latest findings on small heat shock proteins (sHsps) in three major retinal diseases: glaucoma, diabetic retinopathy, and age-related macular degeneration. A general description of the structure and major cellular functions of sHsps is provided in the introductory remarks. Their role in specific retinal diseases, highlighting their regulation, role in pathogenesis, and possible use as therapeutics, is discussed.

MiR-122-5p promotes peritoneal fibrosis in a rat model of peritoneal dialysis by targeting Smad5 to activate Wnt/β-catenin pathway

Peritoneal fibrosis (PF) is the main reason leading to declining efficiency and ultrafiltration failure of peritoneum, which restricts the application of peritoneal dialysis (PD). We aimed to investigate the effects and mechanisms of miR-122-5p on the PF. Sprague-Dawley (SD) rats were infused with glucose-based standard PD fluid to establish PF model. HE staining was performed to evaluate the extent of PF. Real-time fluorescence quantitative polymerase chain reaction (RT-qPCR) and fluorescence in situ hybridization (FISH) were performed to measure the expression level of miR-122-5p. Western blot was used to test the expression of transforming growth factor (TGF)-β1, platelet-derived growth factor (PDGF)-A, Fibronectin 1 (FN1), extracellular matrix protein 1 (ECM1), Smad5, α-smooth muscle actin (SMA), collagen type 1(COL-1), Vimentin, E-Cadherin, Wnt1, β-catenin, p-β-catenin, c-Myc, c-Jun, and Cyclin D1. Immunohistochemistry (IHC) staining was used to detect type I collagen alpha 1 (Col1α1), α-SMA, and E-Cadherin expression. We found PF was glucose concentration-dependently enhanced in peritoneum of PD rat. The PD rats showed increased miR-122-5p and decreased Smad5 expression. MiR-122-5p silencing improved PF and epithelial–mesenchymal transition (EMT) process in PD rats. MiR-122-5p silencing attenuated the activity of the Wnt/β-catenin signaling pathway. Importantly, dual-luciferase reporter assay showed Smad5 was a target gene of miR-122-5p. Smad5 overexpression significantly reversed the increases of PF and EMT progression induced by miR-122-5p overexpression. Moreover, miR-122-5p mimic activated Wnt/β-catenin activity, which was blocked by Smad5 overexpression. Overall, present results demonstrated that miR-122-5p overexpression showed a deterioration effect on PD-related PF by targeting Smad5 to activate Wnt/β-catenin pathway.

Mechanisms of RPE senescence and potential role of αB crystallin peptide as a senolytic agent in experimental AMD

Oxidative stress in the retinal pigment epithelium (RPE) can cause mitochondrial dysfunction and is likely a causative factor in the pathogenesis of age-related macular degeneration (AMD). Under oxidative stress conditions, some of the RPE cells become senescent and a contributory role for RPE senescence in AMD pathology has been proposed. The purpose of this study is to 1) characterize senescence in human RPE; 2) investigate the effect of an αB Crystallin chaperone peptide (mini Cry) in controlling senescence, in particular by regulating mitochondrial function and senescence-associated secretory phenotype (SASP) production and 3) develop mouse models for studying the role of RPE senescence in dry and nAMD. Senescence was induced in human RPE cells in two ways. First, subconfluent cells were treated with 0.2 μg/ml doxorubicin (DOX); second, subconfluent cells were treated with 500 μM H₂O₂. Senescence biomarkers (senescence-associated beta-galactosidase (SA-βgal), p21, p16) and mitochondrial proteins (Fis1, DRP1, MFN2, PGC1-α, mtTFA) were analyzed in control and experimental groups. The effect of mini Cry on mitochondrial bioenergetics, glycolysis and SASP was determined. In vivo, retinal degeneration was induced by intravenous injection of NaIO3 (20 mg/kg) and subretinal fibrosis by laser-induced choroidal neovascularization. Increased SA-βgal staining and p16 and p21 expression was observed after DOX- or H₂O₂-induced senescence and mini Cry significantly decreased senescence-positive cells. The expression of mitochondrial biogenesis proteins PGC-1 and mTFA increased with senescence, and mini Cry reduced expression significantly. Senescent RPE cells were metabolically active, as evidenced by significantly enhanced oxidative phosphorylation and anaerobic glycolysis, mini Cry markedly reduced rates of respiration and glycolysis. Senescent RPE cells maintain a proinflammatory phenotype characterized by significantly increased production of cytokines (IFN-ˠ, TNF-α, IL1-α IL1-β, IL-6, IL-8, IL-10), and VEGF-A; mini Cry significantly inhibited their secretion. We identified and localized senescent RPE cells for the first time in NaIO3-induced retinal degeneration and laser-induced subretinal fibrosis mouse models. We conclude that mini Cry significantly impairs stress-induced senescence by modulating mitochondrial biogenesis and fission proteins in RPE cells. Characterization of senescence could provide further understanding of the metabolic changes that accompany the senescent phenotype in ocular disease. Future studies in vivo may better define the role of senescence in AMD and the therapeutic potential of mini Cry as a senotherapeutic.

Transcriptomic analysis of choroidal neovascularization reveals dysregulation of immune and fibrosis pathways that are attenuated by a novel anti-fibrotic treatment

Neovascular AMD (nAMD) leads to vision loss and is a leading cause of visual impairment in the industrialised world. Current treatments that target blood vessel growth have not been able to treat subretinal fibrosis and nAMD patients continue to lose vision. The molecular mechanisms involved in the development of fibrotic lesions in nAMD are not well understood. The aim of this study was to further understand subretinal fibrosis in the laser photocoagulation model of choroidal neovascularization (CNV) by studying the whole transcriptome of the RPE/choroid following CNV and the application of an anti-fibrotic following CNV. Seven days after laser induced CNV, RPE and choroid tissue was separated and underwent RNAseq. Differential expression analysis and pathway analysis revealed an over representation of immune signalling and fibrotic associated pathways in CNV compared to control RPE/choroid tissue. Comparisons between the mouse CNV model to human CNV revealed an overlap in upregulated expression for immune genes (Ccl2, Ccl8 and Cxcl9) and extracellular matrix remodeling genes (Comp, Lrcc15, Fndc1 and Thbs2). Comparisons between the CNV model and other fibrosis models showed an overlap of over 60% of genes upregulated in either lung or kidney mouse models of fibrosis. Treatment of CNV using a novel cinnamoyl anthranilate anti-fibrotic (OCX063) in the laser induced CNV model was selected as this class of drugs have previously been shown to target fibrosis. CNV lesion leakage and fibrosis was found to be reduced using OCX063 and gene expression of genes within the TGF-beta signalling pathway. Our findings show the presence of fibrosis gene expression pathways present in the laser induced CNV mouse model and that anti-fibrotic treatments offer the potential to reduce subretinal fibrosis in AMD.

Clusterin, other extracellular chaperones, and eye disease

Proteostasis refers to all the processes that maintain the correct expression level, location, folding and turnover of proteins, essential to organismal survival. Both inside cells and in body fluids, molecular chaperones play key roles in maintaining proteostasis. In this article, we focus on clusterin, the first-recognized extracellular mammalian chaperone, and its role in diseases of the eye. Clusterin binds to and inhibits the aggregation of proteins that are misfolded due to mutations or stresses, clears these aggregating proteins from extracellular spaces, and facilitates their degradation. Clusterin exhibits three main homeostatic activities: proteostasis, cytoprotection, and anti-inflammation. The so-called "protein misfolding diseases" are caused by aggregation of misfolded proteins that accumulate pathologically as deposits in tissues; we discuss several such diseases that occur in the eye. Clusterin is typically found in these deposits, which is interpreted to mean that its capacity as a molecular chaperone to maintain proteostasis is overwhelmed in the disease state. Nevertheless, the role of clusterin in diseases involving such deposits needs to be better defined before therapeutic approaches can be entertained. A more straightforward case can be made for therapeutic use of clusterin based on its proteostatic role as a proteinase inhibitor, as well as its cytoprotective and anti-inflammatory properties. It is likely that clusterin works together in this way with other extracellular chaperones to protect the eye from disease, and we discuss several examples. We end this article by predicting future steps that may lead to development of clusterin as a biological drug.

Physiological and pathological functions of βB2-crystallins in multiple organs: a systematic review

Crystallins, the major constituent proteins of mammalian lenses, are significant not only for the maintenance of eye lens stability, transparency, and refraction, but also fulfill various physiopathological functions in extraocular tissues. βB2-crystallin, for example, is a multifunctional protein expressed in the human retina, brain, testis, ovary, and multiple tumors. Mutations in the βB2 crystallin gene or denaturation of βB2-crystallin protein are associated with cataracts, ocular pathologies, and psychiatric disorders. A prominent role for βB2-crystallins in axonal growth and regeneration, as well as in dendritic outgrowth, has been demonstrated after optic nerve injury. Studies in βB2-crystallin-null mice revealed morphological and functional abnormalities in testis and ovaries, indicating βB2-crystallin contributes to male and female fertility in mice. Interestingly, although pathogenic significance remains obscure, several studies identified a clear correlation between βB2 crystallin expression and the prognosis of patients with breast cancer, colorectal cancer, prostate cancer, renal cell carcinoma, and glioblastoma in the African American population. This review summarizes the physiological and pathological functions of βB2-crystallin in the eye and other organs and tissues and discusses findings related to the expression and potential role of βB2-crystallin in tumors.

Limb-bud and heart (LBH) inhibits cellular migration, invasion and epithelial-mesenchymal transition in nasopharyngeal carcinoma via downregulating αB-crystallin expression

Limb-bud and heart (LBH) gene has received increasing attention in recent cancer studies. Here we investigated the role of the LBH gene in regulating the metastasis capacity and epithelial-mesenchymal transition (EMT) of nasopharyngeal carcinoma (NPC) cells, and its potential mechanism. The expressions of LBH and αB-crystallin (CRYAB) were modulated by lentiviral infection, or plasmid/siRNA transfection, and the phosphorylation of p38 was suppressed by an inhibitor, to explore their functions in modulating NPC cell phenotypes, as well as the relationships of these factors with each other. Cellular proliferation, migration and invasion were examined by RTCA system, Transwell assays and Matrigel Transwell assays respectively. The EMT progression was indicated by RT-qPCR and Western blotting measuring the expressions of EMT biomarkers. NPC xenografts were constrcucted, and formed tumors were sectioned for morphology and immunohistofluorescence. The interaction between LBH and CRYAB was examined by colocalization and Fluorescence resonance energy transfer (FRET) analysis. We reached the conclusion that LBH inhibits the proliferation, migration, invasion and EMT of NPC cells, and its effects were partially achieved by suppressing p38 phosphorylation, which subsequently downregulates the mRNA expression and phosphorylation of CRYAB, while CRYAB directly interacts with LBH in NPC cells. This LBH-related pathway we revealed provides a novel therapeutic target for nasopharyngeal carcinoma research.

Physiological response of the retinal pigmented epithelium to 3-ns pulse laser application, in vitro and in vivo

BACKGROUND

To treat healthy retinal pigmented epithelium (RPE) with the 3-ns retinal rejuvenation therapy (2RT) laser and to investigate the subsequent wound-healing response of these cells.

METHODS

Primary rat RPE cells were treated with the 2RT laser at a range of energy settings. Treated cells were fixed up to 7 days post-irradiation and assessed for expression of proteins associated with wound-healing. For in vivo treatments, eyes of Dark Agouti rats were exposed to laser and tissues collected up to 7 days post-irradiation. Isolated wholemount RPE preparations were examined for structural and protein expression changes.

RESULTS

Cultured RPE cells were ablated by 2RT laser in an energy-dependent manner. In all cases, the RPE cell layer repopulated completely within 7 days. Replenishment of RPE cells was associated with expression of the heat shock protein, Hsp27, the intermediate filament proteins, vimentin and nestin, and the cell cycle-associated protein, cyclin D1. Cellular tight junctions were lost in lased regions but re-expressed when cell replenishment was complete. In vivo, 2RT treatment gave rise to both an energy-dependent localised denudation of the RPE and the subsequent repopulation of lesion sites. Cell replenishment was associated with the increased expression of cyclin D1, vimentin and the heat shock proteins Hsp27 and αB-crystallin.

CONCLUSIONS

The 2RT laser was able to target the RPE both in vitro and in vivo, causing debridement of the cells and the consequent stimulation of a wound-healing response leading to layer reformation.

Nicotinamide suppresses bevacizumab-induced epithelial-mesenchymal transition of ARPE-19 cells by attenuating oxidative stress

AIM

To investigate the effects of nicotinamide (NAM) on bevacizumab (BEV)-induced epithelial-mesenchymal transition (EMT) of human retinal pigment epithelial cells (ARPE-19) and the underling mechanisms.

METHODS

ARPE-19 cells were treated with BEV for 24, 48, and 72h, and the variation degrees of EMT-related markers (fibronectin, α-SMA, vimentin, and ZO-1) were assessed by Western blotting to select the optimal treatment time point which exhibited the most obvious changes of EMT-related markers for the subsequent experiments. Furthermore, NAM was added to the medium, the mRNA and protein levels of the EMT-related markers were then measured. The accumulation of reactive oxygen species (ROS) and H₂O₂ and the total antioxidant capacity (TAC) of the cells were also measured to evaluate the level of oxidative stress.

RESULTS

After being treated with BEV for 72h, the protein expression levels of EMT-related markers in ARPE-19 cells showed significant changes. Meanwhile the levels of ROS and H₂O₂ were obviously increased, and the TAC of ARPE-19 cells was decreased. Totally 72h was chosen to be the optimal treatment time point in subsequent experiments. Furthermore, NAM inhibited BEV-induced EMT by downregulating fibronectin, α-SMA, and vimentin and upregulating ZO-1, decreased the accumulation of ROS and H₂O₂, and enhanced TAC in BEV-treated ARPE-19 cells.

CONCLUSION

This study demonstrates that NAM suppressed BEV-induced EMT in ARPE-19 cells by attenuating oxidative stress. Hence, NAM may be a potential therapeutic agent for alleviating neovascular fibrosis of the ocular fundus after anti-vascular endothelial growth factor therapy.

LRG1 promotes epithelial-mesenchymal transition of retinal pigment epithelium cells by activating NOX4

AIM

To investigate the effect of leucine-rich-alpha-2-glycoprotein 1 (LRG1) on epithelial-mesenchymal transition (EMT) in retinal pigment epithelium (RPE) cells, and to explore the role of NADPH oxidase 4 (NOX4).

METHODS

RPE cells (ARPE-19 cell line) were treated with transforming growth factor-β1 (TGF-β1) to induce EMT. Changes of the mRNA and protein expression levels of LRG1 were tested in the TGF-β1 treated cells. The recombinant human LRG1 protein (rLRG1) and siRNA of LRG1 were used to establish accumulation of exogenous LRG1 model and the down-regulation of LRG1 model in ARPE-19 cells respectively, and to detect EMT-related markers including fibronectin, α-smooth muscle actin (α-SMA) and zonula occludens-1 (ZO-1). The mRNA and protein expression level of NOX4 were measured according to the above treatments. VAS2870 was used as a NOX4 inhibitor in rLRG1-treated cells. EMT-related markers were detected to verify the effect of NOX4 in the process of EMT.

RESULTS

TGF-β1 promoted the expression of LRG1 at both the mRNA and protein levels during the process of EMT which showed the up-regulation of fibronectin and α-SMA, as well as the down-regulation of ZO-1. Furthermore, the rLRG1 promoted EMT of ARPE-19 cells, which manifested high levels of fibronectin and α-SMA and low level of ZO-1, whereas knockdown of LRG1 prevented EMT by decreasing the expressions of fibronectin and α-SMA and increasing the expression of ZO-1 in ARPE-19 cells. Besides, the rLRG1 activated and LRG1 siRNA suppressed NOX4 expression. EMT was inhibited when VAS2870 was used in the rLRG1-treated cells.

CONCLUSION

These results for the first time demonstrate that LRG1 promotes EMT of RPE cells by activating NOX4, which may provide a novel direction to explore the mechanisms of subretinal fibrosis.

Limb-bud and Heart (LBH) mediates proliferation, fibroblast-to-myofibroblast transition and EMT-like processes in cardiac fibroblasts

Cardiac fibrosis is an important pathological change after myocardial infarction (MI). Its progression is essential for post-MI infarct healing, during which transforming growth factor beta1 (TGF-β1) plays a critical role. Limb-bud and Heart (LBH), a newly discovered target gene of TGF-β1, was shown to promote normal cardiogenesis. αB-crystallin (CRYAB), an LBH-interacting protein, was demonstrated to be involved in TGF-β1-induced fibrosis. The roles and molecular mechanisms of LBH and CRYAB during cardiac fibrosis remain largely unexplored. In this study, we investigated the alterations of LBH and CRYAB expression in mouse cardiac tissue after MI. LBH and CRYAB were upregulated in activated cardiac fibroblasts (CFs), while in vitro TGF-β1 stimulation induced the upregulation of LBH, CRYAB, and fibrogenic genes in primary CFs of neonatal rats. The results of the ectopic expression of LBH proved that LBH accelerated CF proliferation under hypoxia, mediated the expression of CRYAB and fibrogenic genes, and promoted epithelial-mesenchymal transition (EMT)-like processes in rat CFs, while subsequent CRYAB silencing reversed the effects induced by elevated LBH expression. We also verified the protein-protein interaction (PPI) between LBH and CRYAB in fibroblasts. In summary, our work demonstrated that LBH promotes the proliferation of CFs, mediates TGF-β1-induced fibroblast-to-myofibroblast transition and EMT-like processes through CRYAB upregulation, jointly functioning in post-MI infarct healing. These findings suggest that LBH could be a promising potential target for the study of cardiac repair and cardiac fibrosis.

Proteomic analysis of anti-angiogenic effects by conbercept in the mice with oxygen induced retinopathy

AIM

To analyze the retinal proteomes with and without conbercept treatments in mice with oxygen-induced retinopathy (OIR) and identify proteins involved in the molecular mechanisms mediated by conbercept.

METHODS

OIR was induced in fifty-six C57BL/6J mouse pups and randomly divided into four groups. Group 1: Normal17 (n=7), mice without OIR and treated with normal air. Group 2: OIR12/EXP1 (n=14), mice received 75% oxygen from postnatal day (P) 7 to 12. Group 3: OIR17/Control (n=14), mice received 75% oxygen from P7 to P12 and then normal air to P17. Group 4: Lang17/EXP2 (n=21), mice received 75% oxygen from P7 to P12 with intravitreal injection of 1 µL conbercept at the concentration of 10 mg/mL at P12, and then normal air from P12 to P17. Liquid Chromatography-Mass Spectrometry (LC-MS)/MS data were reviewed to find proteins that were up-regulated after the conbercept treatment. Gene ontology (GO) analysis was performed of conbercept-mediated changes in proteins involved in single-organism processes, biological regulation, cellular processes, immune responses, metabolic processes, locomotion and multiple-organism processes.

RESULTS

Conbercept induced a reversal of hypoxia-inducible factor 1 signaling pathway as revealed by the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and also induced down-regulation of proteins involved in blood coagulation and fibrin clot formation as demonstrated by the Database for Annotation, Visualization and Integrated Discovery (DAVID) and the stimulation of interferon genes studies. These appear to be risk factors of retinal fibrosis. Additional conbercept-specific fibrosis risk factors were also identified and may serve as therapeutic targets for fibrosis.

CONCLUSION

Our studies reveal that many novel proteins are differentially regulated by conbercept. The new insights may warrant a valuable resource for conbercept treatment.

Macrophage to myofibroblast transition contributes to subretinal fibrosis secondary to neovascular age-related macular degeneration

BACKGROUND

Macular fibrosis causes irreparable vision loss in neovascular age-related macular degeneration (nAMD) even with anti-vascular endothelial growth factor (VEGF) therapy. Inflammation is known to play an important role in macular fibrosis although the underlying mechanism remains poorly defined. The aim of this study was to understand how infiltrating macrophages and complement proteins may contribute to macular fibrosis.

METHODS

Subretinal fibrosis was induced in C57BL/6J mice using the two-stage laser protocol developed by our group. The eyes were collected at 10, 20, 30 and 40 days after the second laser and processed for immunohistochemistry for infiltrating macrophages (F4/80 and Iba-1), complement components (C3a and C3aR) and fibrovascular lesions (collagen-1, Isolectin B4 and α-SMA). Human retinal sections with macular fibrosis were also used in the study. Bone marrow-derived macrophages (BMDMs) from C57BL/6J mice were treated with recombinant C3a, C5a or TGF-β for 48 and 96 h. qPCR, Western blot and immunohistochemistry were used to examine the expression of myofibroblast markers. The involvement of C3a-C3aR pathway in macrophage to myofibroblast transition (MMT) and subretinal fibrosis was further investigated using a C3aR antagonist (C3aRA) and a C3a blocking antibody in vitro and in vivo.

RESULTS

Approximately 20~30% of F4/80+ (or Iba-1+) infiltrating macrophages co-expressed α-SMA in subretinal fibrotic lesions both in human nAMD eyes and in the mouse model. TGF-β and C3a, but not C5a treatment, significantly upregulated expression of α-SMA, fibronectin and collagen-1 in BMDMs. C3a-induced upregulation of α-SMA, fibronectin and collagen-1 in BMDMs was prevented by C3aRA treatment. In the two-stage laser model of induced subretinal fibrosis, treatment with C3a blocking antibody but not C3aRA significantly reduced vascular leakage and Isolectin B4+ lesions. The treatment did not significantly alter collagen-1+ fibrotic lesions.

CONCLUSIONS

MMT plays a role in macular fibrosis secondary to nAMD. MMT can be induced by TGF-β and C3a but not C5a. Further research is required to fully understand the role of MMT in macular fibrosis. Macrophage to myofibroblast transition (MMT) contributes to subretinal fibrosis. Subretinal fibrosis lesions contain various cell types, including macrophages and myofibroblasts, and are fibrovascular. Myofibroblasts are key cells driving pathogenic fibrosis, and they do so by producing excessive amount of extracellular matrix proteins. We have found that infiltrating macrophages can transdifferentiate into myofibroblasts, a phenomenon termed macrophage to myofibroblast transition (MMT) in macular fibrosis. In addition to TGF-β1, C3a generated during complement activation in CNV can also induce MMT contributing to macular fibrosis. RPE = retinal pigment epithelium. BM = Bruch's membrane. MMT = macrophage to myofibroblast transition. TGFB = transforming growth factor β. a-SMA = alpha smooth muscle actin. C3a = complement C3a.

Transcriptional analysis of cleft palate in TGFβ3 mutant mice

Cleft palate (CP) is one of the most common craniofacial birth defects, impacting about 1 in 800 births in the USA. Tgf-β3 plays a critical role in regulating murine palate development, and Tgf-β3 null mutants develop cleft palate with 100% penetrance. In this study, we compared global palatal transcriptomes of wild type (WT) and Tgf-β3 −/− homozygous (HM) mouse embryos at the crucial palatogenesis stages of E14.5, and E16.5, using RNA-seq data. We found 1,809 and 2,127 differentially expressed genes at E16.5 vs. E14.5 in the WT and HM groups, respectively (adjusted p < 0.05; |fold change|> 2.0). We focused on the genes that were uniquely up/downregulated in WT or HM at E16.5 vs. E14.5 to identify genes associated with CP. Systems biology analysis relating to cell behaviors and function of WT and HM specific genes identified functional non-Smad pathways and preference of apoptosis to epithelial-mesenchymal transition. We identified 24 HM specific and 11 WT specific genes that are CP-related and/or involved in Tgf-β3 signaling. We validated the expression of 29 of the 35 genes using qRT-PCR and the trend of mRNA expression is similar to that of RNA-seq data . Our results enrich our understanding of genes associated with CP that are directly or indirectly regulated via TGF-β.

Role of Epithelial-Mesenchymal Transition in Retinal Pigment Epithelium Dysfunction

Retinal pigment epithelial (RPE) cells maintain the health and functional integrity of both photoreceptors and the choroidal vasculature. Loss of RPE differentiation has long been known to play a critical role in numerous retinal diseases, including inherited rod-cone degenerations, inherited macular degeneration, age-related macular degeneration, and proliferative vitreoretinopathy. Recent studies in post-mortem eyes have found upregulation of critical epithelial-mesenchymal transition (EMT) drivers such as TGF-β, Wnt, and Hippo. As RPE cells become less differentiated, they begin to exhibit the defining characteristics of mesenchymal cells, namely, the capacity to migrate and proliferate. A number of preclinical studies, including animal and cell culture experiments, also have shown that RPE cells undergo EMT. Taken together, these data suggest that RPE cells retain the reprogramming capacity to move along a continuum between polarized epithelial cells and mesenchymal cells. We propose that movement along this continuum toward a mesenchymal phenotype be defined as RPE Dysfunction. Potential mechanisms include impaired tight junctions, accumulation of misfolded proteins and dysregulation of several key pathways and molecules, such as TGF-β pathway, Wnt pathway, nicotinamide, microRNA 204/211 and extracellular vesicles. This review synthesizes the evidence implicating EMT of RPE cells in post-mortem eyes, animal studies, primary RPE, iPSC-RPE and ARPE-19 cell lines.

3-Methyladenine Alleviates Experimental Subretinal Fibrosis by Inhibiting Macrophages and M2 Polarization Through the PI3K/Akt Pathway

Purpose: To explore the effects of 3-methyladenine (3-MA), a selective inhibitor of phosphatidylinositol-3-kinase (PI3K), on experimental subretinal fibrosis (SRF) in mice. Methods: The SRF mouse model was established by 532 nm laser photocoagulation at each fundus of mice on day 0. 3-MA was administered every 2 days from day 0 to 35. Immunofluorescence of choroidal flat mounts was performed to evaluate the size of SRF area, local macrophages, and polarization, respectively. Besides, Western blot analysis was carried out to assess the expression levels of macrophage polarization-related genes, Arg-1, Ym-1, and transforming growth factor-β₂ (TGF-β₂). Co-culture and migration experiments were used to demonstrate the inhibitory effect of 3-MA on fibroblasts. The gene knockout and Western blot analysis were used to explore the signal pathways related to macrophage polarization. Results: Compared with the control group, the 3-MA-treated group showed significantly less size of SRF area. 3-MA treatment reduced both circulating and local macrophages, and counteracted M2 polarization. Moreover, 3-MA inhibited fibroblast recruitment. Mechanistically, we proved that 3-MA inhibits macrophage M2 polarization by suppressing PI3K/Akt signal pathway rather than the PI3K-autophagy-related signal pathway. Conclusions: 3-MA exerts antifibrotic effects on experimental SRF by targeting circulating and local macrophages and M2 polarization, through PI3K/Akt signal pathway. These results support the potential use of 3-MA as a new therapeutic modality for SRF associated with neovascular age-related macular degeneration.

Exploration of Oxygen-Induced Retinopathy Model to Discover New Therapeutic Drug Targets in Retinopathies

Oxygen-induced retinopathy (OIR) is a pure hypoxia-driven angiogenesis model and the most widely used model for ischemic retinopathies, such as retinopathy of prematurity (ROP), proliferative diabetic retinopathy (PDR), and retinal vein occlusion (RVO). OIR model has been used to test new potential anti-angiogenic factors for human diseases. We have recently performed the most comprehensive characterization of OIR by a relatively novel mass spectrometry (MS) technique, sequential window acquisition of all theoretical fragment ion mass spectra (SWATH-MS) proteomics and used genetically modified mice strains to identify novel molecular drug targets in angiogenic retinal diseases. We have confirmed the relevance of the identified molecular targets to human diseases by determining their expression pattern in neovascular membranes obtained from PDR and RVO patients. Based on our results, crystallins were the most prominent proteins induced by early hypoxic environment during the OIR, while actomyosin complex and Filamin A-R-Ras axis, that regulates vascular permeability of the angiogenic blood vessels, stood out at the peak of angiogenesis. Our results have revealed potential new therapeutic targets to address hypoxia-induced pathological angiogenesis and the associated vascular permeability in number of retinal diseases.

Potential Role of Myeloid-Derived Suppressor Cells (MDSCs) in Age-Related Macular Degeneration (AMD)

Myeloid cells, such as granulocytes/neutrophils and macrophages, have responsibilities that include pathogen destruction, waste material degradation, or antigen presentation upon inflammation. During persistent stress, myeloid cells can remain partially differentiated and adopt immunosuppressive functions. Myeloid-derived suppressor cells (MDSCs) are primarily beneficial upon restoring homeostasis after inflammation. Because of their ability to suppress adaptive immunity, MDSCs can also ameliorate autoimmune diseases and semi-allogenic responses, e.g., in pregnancy or transplantation. However, immunosuppression is not always desirable. In certain conditions, such as cancer or chronically inflamed tissue, MDSCs prevent restorative immune responses and thereby aggravate disease progression. Age-related macular degeneration (AMD) is the most common disease in Western countries that severely threatens the central vision of aged people. The pathogenesis of this multifactorial disease is not fully elucidated, but inflammation is known to participate in both dry and wet AMD. In this paper, we provide an overview about the potential role of MDSCs in the pathogenesis of AMD.

The Interplay Between E-Cadherin, Connexin 43, and Zona Occludens 1 in Retinal Pigment Epithelial Cells

Purpose

Cell-cell contact in retinal pigment epithelium (RPE) involves adherent junctions, gap junctions, and tight junctions, which are primarily composed by E-cadherin, zona occludens 1 (ZO-1), and connexin 43, respectively. Here, we aimed to explore the relationship and interplay between these junction-associated proteins.

Methods

E-cadherin, connexin 43, and ZO-1 expression in human primary RPE in the early phase after TGF-β1 stimulation was detected. The knockdown of E-cadherin, ZO-1, and connexin 43 was performed to characterize the regulatory network involving these three proteins. Dye transfer and FITC-dextran permeability assays were conducted to observe the epithelial functional alterations. Transmission electron microscopy (TEM) was used to observe the ultrastructure of the cell-cell junctions in mouse RPE. The immunofluorescence staining and coimmunoprecipitation were performed to observe the colocalization and the physical association of E-cadherin, ZO-1, and connexin 43.

Results

Among these three components, E-cadherin appeared to be the first protein that was downregulated after TGF-β1 treatment. The ultrastructures of adherent junctions, gap junctions, and tight junctions could be observed in mouse RPE by TEM. E-cadherin, ZO-1, and connexin 43 were colocalized and physically bound to each other. The knockdown of one of these three proteins led to downregulation of the other two proteins and compromised epithelial function.

Conclusions

E-cadherin, ZO-1, and connexin 43 were physically associated with each other and were mutually regulated. To enhance the understanding of cell-cell contacts, a holistic view is needed. Our results provide new insights in RPE disorders such as proliferative vitreoretinopathy.

The Regulation of NFE2L2 (NRF2) Signalling and Epithelial-to-Mesenchymal Transition in Age-Related Macular Degeneration Pathology

Age-related macular degeneration (AMD) is a mounting cause of loss of sight in the elderly in the developed countries, a trend enhanced by the continual ageing of the population. AMD is a multifactorial and only partly understood, malady. Unfortunately, there is no effective treatment for most AMD patients. It is known that oxidative stress (OS) damages the retinal pigment epithelium (RPE) and contributes to the progression of AMD. We review here the potential importance of two OS-related cellular systems in relation to AMD. First, the nuclear factor erythroid 2-related factor 2 (NFE2L2; NRF2)-mediated OS response signalling pathway is important in the prevention of oxidative damage and a failure of this system could be critical in the development of AMD. Second, epithelial-to-mesenchymal transition (EMT) represents a change in the cellular phenotype, which ultimately leads to the fibrosis encountered in RPE, a characteristic of AMD. Many of the pathways triggering EMT are promoted by OS. The possible interconnections between these two signalling routes are discussed here. From a broader perspective, the control of NFE2L2 and EMT as ways of preventing OS-derived cellular damage could be potentially valuable in the therapy of AMD.

Rare variants and loci for age-related macular degeneration in the Ohio and Indiana Amish

Age-related macular degeneration (AMD) is a leading cause of blindness in the world. While dozens of independent genomic variants are associated with AMD, about one-third of AMD heritability is still unexplained. To identify novel variants and loci for AMD, we analyzed Illumina HumanExome chip data from 87 Amish individuals with early or late AMD, 79 unaffected Amish individuals, and 15 related Amish individuals with unknown AMD affection status. We retained 37,428 polymorphic autosomal variants across 175 samples for association and linkage analyses. After correcting for multiple testing (n = 37,428), we identified four variants significantly associated with AMD: rs200437673 (LCN9, p = 1.50 × 10⁻¹¹), rs151214675 (RTEL1, p = 3.18 × 10⁻⁸), rs140250387 (DLGAP1, p = 4.49 × 10⁻⁷), and rs115333865 (CGRRF1, p = 1.05 × 10⁻⁶). These variants have not been previously associated with AMD and are not in linkage disequilibrium with the 52 known AMD-associated variants reported by the International AMD Genomics Consortium based on physical distance. Genome-wide significant linkage peaks were observed on chromosomes 8q21.11–q21.13 (maximum recessive HLOD = 4.03) and 18q21.2–21.32 (maximum dominant HLOD = 3.87; maximum recessive HLOD = 4.27). These loci do not overlap with loci previously linked to AMD. Through gene ontology enrichment analysis with ClueGO in Cytoscape, we determined that several genes in the 1-HLOD support interval of the chromosome 8 locus are involved in fatty acid binding and triglyceride catabolic processes, and the 1-HLOD support interval of the linkage region on chromosome 18 is enriched in genes that participate in serine-type endopeptidase inhibitor activity and the positive regulation of epithelial to mesenchymal transition. These results nominate novel variants and loci for AMD that require further investigation.

SWATH-MS Proteomic Analysis of Oxygen-Induced Retinopathy Reveals Novel Potential Therapeutic Targets

Purpose

Oxygen-induced retinopathy (OIR) is the most widely used model for ischemic retinopathies such as retinopathy of prematurity (ROP), proliferative diabetic retinopathy (PDR), and retinal vein occlusion (RVO). The purpose of this study was to perform the most comprehensive characterization of OIR by a recently developed technique, sequential window acquisition of all theoretical mass spectra (SWATH-MS) proteomics.

Methods

Control and OIR retina samples collected from various time points were subjected to SWATH-MS and detailed data analysis. Immunohistochemistry from mouse retinas as well as neovascular membranes from human PDR and RVO patients were used for the detection of the localization of the proteins showing altered expression in the retina and to address their relevance to human ischemic retinopathies.

Results

We report the most extensive proteomic profiling of OIR to date by quantifying almost 3000 unique proteins and their expression differences between control and OIR retinas. Crystallins were the most prominent proteins induced by hypoxia in the retina, while angiogenesis related proteins such as Filamin A and nonmuscle myosin IIA stand out at the peak of angiogenesis. Majority of the changes in protein expression return to normal at P42, but there is evidence to suggest that proteins involved in neurotransmission remain at reduced level.

Conclusions

The results reveal new potential therapeutic targets to address hypoxia-induced pathological angiogenesis taking place in number of retinal diseases. The extensive proteomic profiling combined with pathway analysis also identifies novel molecular networks that could contribute to the pathogenesis of retinal diseases.

A monoclonal antibody targeted to the functional peptide of αB-crystallin inhibits the chaperone and anti-apoptotic activities

αB-Crystallin is a member of the small heat shock protein family. It is a molecular chaperone and an anti-apoptotic protein. Previous studies have shown that the peptide (⁷³DRFSVNLDVKHFSPEELKVKV⁹³, hereafter referred to as peptain-1) from the core domain of αB-crystallin exhibits both chaperone and anti-apoptotic properties similar to the parent protein. We developed a mouse monoclonal antibody against peptain-1 with the aim of blocking the functions of αB-crystallin. The antibody reacted with peptain-1, it did not react with the chaperone peptide of αA-crystallin. The antibody strongly reacted with human recombinant αB-crystallin but weakly with Hsp20; it did not react with αA-crystallin or Hsp27. The antibody specifically reacted with αB-crystallin in human and mouse lens proteins but not with αA-crystallin. The antibody reacted with αB-crystallin in human lens epithelial cells, human retinal endothelial cells, and with peptain-1 in peptain-1-transduced cells. Unlike the commercial antibodies against αB-crystallin, the antibody against peptain-1 inhibited the chaperone and anti-apoptotic activities of peptain-1. The antibody might find use in inhibiting αB-crystallin's chaperone and anti-apoptotic activities in diseases where αB-crystallin is a causative or contributing factor.

Myofibroblasts in macular fibrosis secondary to neovascular age-related macular degeneration - the potential sources and molecular cues for their recruitment and activation

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly in developed countries. Neovascular AMD (nAMD) accounts for 90% of AMD-related vision loss. Although intravitreal injection of VEGF inhibitors can improve vision in nAMD, approximately 1/3 of patients do not benefit from the therapy due to macular fibrosis. The molecular mechanism underlying the transition of the neovascular lesion to a fibrovascular phenotype remains unknown. Here we discussed the clinical features and risk factors of macular fibrosis secondary to nAMD. Myofibroblasts are key cells in fibrosis development. However, fibroblasts do not exist in the macula. Potential sources of myofibroblast precursors, the molecular cues in the macular microenvironment that recruit them and the pathways that control their differentiation and activation in macular fibrosis were also discussed. Furthermore, we highlighted the challenges in macular fibrosis research and the urgent need for better animal models for mechanistic and therapeutic studies.

A Role for βA3/A1-Crystallin in Type 2 EMT of RPE Cells Occurring in Dry Age-Related Macular Degeneration

Purpose

The RPE cells have a major role in the development of dry age-related macular degeneration (AMD). We present novel evidence that βA3/A1-crystallin, encoded by the Cryba1 gene, a protein known to be important for lysosomal clearance in the RPE, also has a role in epithelial-to-mesenchymal transition (EMT) of RPE cells.

Methods

RPE from dry AMD globes, genetically engineered mice lacking Cryba1 globally or specifically in the RPE, spontaneous mutant rats (Nuc1) with a loss-of-function mutation in Cryba1, and the melanoma OCM3 cell line were used. Spatial localization of proteins was demonstrated with immunofluorescence, gene expression levels were determined by quantitative PCR (qPCR), and protein levels by Western blotting. Cell movement was evaluated using wound healing and cell migration assays. Co-immunoprecipitation was used to identify binding partners of βA3/A1-crystallin.

Results

βA3/A1-crystallin is upregulated in polarized RPE cells compared to undifferentiated cells. Loss of βA3/A1-crystallin in murine and human RPE cells resulted in upregulation of Snail and vimentin, downregulation of E-cadherin, and increased cell migration. βA3/A1-crystallin binds to cortactin, and loss of βA3/A1-crystallin resulted in increased P-cortactin^Y421. The RPE from AMD samples had increased Snail and vimentin, and decreased E-cadherin, compared to age-matched controls.

Conclusions

We introduced a novel concept of dry AMD initiation induced by lysosomal clearance defects in the RPE and subsequent attempts by RPE cells to avoid the resulting stress by undergoing EMT. We demonstrate that βA3/A1-crystallin is a potential therapeutic target for AMD through rejuvenation of lysosomal dysfunction and potentially, reversal of EMT.

Human Vascular Endothelial Growth Factor A165 Expression Induces the Mouse Model of Neovascular Age-Related Macular Degeneration

Vascular endothelial growth factor (VEGF) expression induces age-related macular degeneration (AMD), which is a common vision-threatening disease due to choroidal neovascularization and a fibrovascular membrane. We describe a mouse model of neovascular AMD with the local expression of human VEGF-A₁₆₅ in the eye. We use a transgenic mouse in which human VEGF-A₁₆₅ has been silenced with the loxP-STOP fragment. The choroidal neovascularization and human VEGF-A₁₆₅ expression in the mouse are induced by subretinal adenoviral Cre gene delivery. Cre gene transfer is compared with adenoviral LacZ gene transfer control. We characterize the AMD phenotype and changes in the vasculature by using fluorescein angiography, optical coherence tomography, and immunohistochemistry. At early time points, mice exhibit increases in retinal thickness (348 ± 114 µm vs. 231 ± 32 µm) and choroidal neovascularization area (12000 ± 15174 µm² vs. 2169 ± 3495 µm²) compared with the control. At later time points, choroidal neovascularization develops into subretinal fibrovascular membrane. Human VEGF-A₁₆₅ expression lasts several weeks. In conclusion, the retinas display vascular abnormalities consistent with choroidal neovascularization. Together with immunohistochemical findings, these changes resemble clinical AMD-like ocular pathologies. We conclude that this mouse model of Cre-induced choroidal neovascularization is useful for mimicking the pathogenesis of AMD, studying the effects of human VEGF-A₁₆₅ in the retina, and evaluating anti-VEGF treatments for choroidal neovascularization.

Mechanism of fibrosis inhibition in laser induced choroidal neovascularization by doxycycline

To explore the mechanisms underlying doxycycline suppression of fibrosis in laser-induced choroidal neovascularization (LCNV), C57BL/6J male mice (aged from 6 to 8 weeks) received intraperitoneal injections of PBS/doxycycline solution from one day before laser injury until they were sacrificed. Leakage was assessed by FA, and CNV (stained by IB4) or fibrosis (stained by collagen type I) size was measured. The percentage of Pan-keratin⁺α-SMA⁺ cells was counted in the eyes' cryostat sections by immunohistochemistry. qPCR was used to measure the mRNA of markers of pan-macrophages, M1 and M2-type macrophages (M1 and M2), markers of EMT, and markers in the downstream of STAT6 signaling. Western blotting was used to analyze the expression of Arg-1, α-SMA, E-cadherin, pSTAT6 and STAT6. Our data showed that doxycycline inhibited leakage from CNV, areas of CNV on day 7 and day 14, and suppressed fibrosis, and the ratio of fibrotic/angiogenic areas during day 7 to day 35. We also showed attenuation of EMT in the doxycycline group. The percentage of Pan-keratin⁺α-SMA⁺ cells was lower in the doxycycline group than in the control group. The mRNA and protein levels of mesenchymal markers were downregulated in the doxycycline group, while the epithelial marker was upregulated. In addition, our data showed that the protein expression of Arg-1, the mRNA expression of M1 and M2-markers, were both inhibited by doxycycline, while the level of pan-macrophages (f4/80) showed no significant difference in two groups. Finally, our results showed that doxycycline was able to modulate the STAT6 signaling in transcript and protein levels. Accordingly, we suggested that the mechanism of doxycycline-mediated inhibition of fibrosis in CNV occurs through the STAT6 pathway.

Matrix-bound AGEs enhance TGFβ2-mediated mesenchymal transition of lens epithelial cells via the noncanonical pathway: implications for secondary cataract formation

Advanced glycation end products (AGEs) are post-translational modifications formed from the reaction of reactive carbonyl compounds with amino groups in proteins. Our laboratory has previously shown that AGEs in extracellular matrix (ECM) proteins promote TGFβ2 (transforming growth factor-beta 2)-mediated epithelial-to-mesenchymal transition (EMT) of lens epithelial cells (LECs), which could play a role in fibrosis associated with posterior capsule opacification. We have also shown that αB-crystallin plays an important role in TGFβ2-mediated EMT of LECs. Here, we investigated the signaling mechanisms by which ECM-AGEs enhance TGFβ2-mediated EMT in LECs. We found that in LECs cultured on AGE-modified basement protein extract (AGE-BME), TGFβ2 treatment up-regulated the mesenchymal markers α-SMA (α-smooth muscle actin) and αB-crystallin and down-regulated the epithelial marker E-cadherin more than LECs cultured on unmodified BME and treated with TGFβ2. Using a Multiplex Assay, we found that AGE-BME significantly up-regulated the noncanonical pathway by promoting phosphorylation of ERK (extracellular signal-regulated kinases), AKT, and p38 MAPK (mitogen-activated protein kinases) during TGFβ2-mediated EMT. This EMT response was strongly suppressed by inhibition of AKT and p38 MAPK phosphorylation. The AKT inhibitor LY294002 also suppressed TGFβ2-induced up-regulation of nuclear Snail and reduced phosphorylation of GSK3β. Inhibition of Snail expression suppressed TGFβ2-mediated α-SMA expression. αB-Crystallin was up-regulated in an AKT-dependent manner during AGE-BME/TGFβ2-mediated EMT in LECs. The absence of αB-crystallin in LECs suppressed TGFβ2-induced GSK3β phosphorylation, resulting in lower Snail levels. Taken together, these results show that ECM-AGEs enhance the TGFβ2-mediated EMT response through activation of the AKT/Snail pathway, in which αB-crystallin plays an important role as a linker between the TGFβ2 and AGE-mediated signaling pathways.