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Aim The current accepted standard treatment for neovascular age-related macular degeneration (AMD) consists of antivascular endothelial growth factor agents including ranibizumab and bevacizumab. The aim of the study was to examine whether bevacizumab is inferior to ranibizumab with respect to maintaining/improving visual acuity. Methods In this prospective randomised parallel group multicentre trial patients aged more than 50 years with treatment naive nAMD were included at 10 Austrian centres. Patients were randomised to treatment either with 0.5 mg ranibizumab or 1.25 mg bevacizumab. Both groups received three initial monthly injections and thereafter monthly evaluation of visual acuity and the activity of the lesion. Re-treatment was scheduled as needed. Outcome measures were early treatment of diabetic retinopathy visual acuity, retinal thickness, lesion size and safety evaluation. Results A total of 321 patients were recruited of which four had to be excluded due to different reasons. Of the 317 remaining patients 154 were randomised into the bevacizumab group and 163 into the ranibizumab group. At month 12, there was a mean increase of early treatment of diabetic retinopathy visual acuity of 4.9 letters in the bevacizumab and 4.1 letters in the ranibizumab group (p=0.78). Furthermore, there were no significant differences in the decrease of retinal thickness, change of lesion size and number of adverse events between the groups. Conclusions Bevacizumab was equivalent to ranibizumab for visual acuity at all time points over 1 year. There was no significant difference of decrease of retinal thickness or number of adverse events.

Diabetic retinopathy has a high probability of causing visual impairment or blindness throughout the disease progression and is characterized by the growth of new blood vessels in the retina at an advanced, proliferative stage. Microglia are a resident immune population in the central nervous system, known to play a crucial role in regulating retinal angiogenesis in both physiological and pathological conditions, including diabetic retinopathy. Physiologically, they are located close to blood vessels and are essential for forming new blood vessels (neovascularization). In diabetic retinopathy, microglia become widely activated, showing a distinct polarization phenotype that leads to their accumulation around neovascular tufts. These activated microglia induce pathogenic angiogenesis through the secretion of various angiogenic factors and by regulating the status of endothelial cells. Interestingly, some subtypes of microglia simultaneously promote the regression of neovascularization tufts and normal angiogenesis in neovascularization lesions. Modulating the state of microglial activation to ameliorate neovascularization thus appears as a promising potential therapeutic approach for managing diabetic retinopathy.

The roles of nitric oxide (NO) and endothelial NO synthase (eNOS) in the regulation of angiogenesis are well documented. However, the involvement of eNOS in the sprouting of endothelial tip-cells at the vascular front during sprouting angiogenesis remains poorly defined. In this study, we show that downregulation of eNOS markedly inhibits VEGF-stimulated migration of endothelial cells but increases their polarization, as evidenced by the reorientation of the Golgi in migrating monolayers and by the fewer filopodia on tip cells at ends of sprouts in endothelial cell spheroids. The effect of eNOS inhibition on EC polarization was prevented in Par3-depleted cells. Importantly, downregulation of eNOS increased the expression of polarity genes, such as PARD3B, PARD6A, PARD6B, PKCΖ, TJP3, and CRB1 in endothelial cells. In retinas of eNOS knockout mice, vascular development is retarded with decreased vessel density and vascular branching. Furthermore, tip cells at the extremities of the vascular front have a marked reduction in the number of filopodia per cell and are more oriented. In a model of oxygen-induced retinopathy (OIR), eNOS deficient mice are protected during the initial vaso-obliterative phase, have reduced pathological neovascularization, and retinal endothelial tip cells have fewer filopodia. Single-cell RNA sequencing of endothelial cells from OIR retinas revealed enrichment of genes related to cell polarity in the endothelial tip-cell subtype of eNOS deficient mice. These results indicate that inhibition of eNOS alters the polarity program of endothelial cells, which increases cell polarization, regulates sprouting angiogenesis and normalizes pathological neovascularization during retinopathy.

Retinal neovascularization, as occurs in age-related macular degeneration, may result from an increase in VEGFA levels due to dysregulated lipid and glucose metabolism within photoreceptors. Tissues with high metabolic rates often use lipids, as well as glucose, for energy, conferring a survival advantage during feast and famine 1 . Current dogma suggests that high-energy–consuming photoreceptors depend on glucose 2 , 3 . Here we show that the retina also uses fatty acid β-oxidation for energy. Moreover, we identify a lipid sensor, free fatty acid receptor 1 (Ffar1), that curbs glucose uptake when fatty acids are available. Very-low-density lipoprotein receptor (Vldlr), which is present in photoreceptors 4 and is expressed in other tissues with a high metabolic rate, facilitates the uptake of triglyceride-derived fatty acid 5 , 6 . In the retinas of Vldlr −/− mice with low fatty acid uptake 6 but high circulating lipid levels, we found that Ffar1 suppresses expression of the glucose transporter Glut1. Impaired glucose entry into photoreceptors results in a dual (lipid and glucose) fuel shortage and a reduction in the levels of the Krebs cycle intermediate α-ketoglutarate (α-KG). Low α-KG levels promotes stabilization of hypoxia-induced factor 1a (Hif1a) and secretion of vascular endothelial growth factor A (Vegfa) by starved Vldlr −/− photoreceptors, leading to neovascularization. The aberrant vessels in the Vldlr −/− retinas, which invade normally avascular photoreceptors, are reminiscent of the vascular defects in retinal angiomatous proliferation, a subset of neovascular age-related macular degeneration (AMD) 7 , which is associated with high vitreous VEGFA levels in humans. Dysregulated lipid and glucose photoreceptor energy metabolism may therefore be a driving force in macular telangiectasia, neovascular AMD and other retinal diseases.

Ischemic retinopathies (IRs) are leading causes of visual impairment. They are characterized by an initial phase of microvascular degeneration and a second phase of aberrant pre-retinal neovascularization (NV). microRNAs (miRNAs) regulate gene expression, and a number play a role in normal and pathological NV. But, post-transcriptional modulation of miRNAs in the eye during the development of IRs has not been systematically evaluated. Using Next Generation Sequencing (NGS) we profiled miRNA expression in the retina and choroid during vasodegenerative and NV phases of oxygen-induced retinopathy (OIR). Approximately 20% of total miRNAs exhibited altered expression (up- or down-regulation); 6% of miRNA were found highly expressed in retina and choroid of rats subjected to OIR. During OIR-induced vessel degeneration phase, miR-199a-3p, -199a-5p, -1b, -126a-3p displayed a robust decreased expression (> 85%) in the retina. While in the choroid, miR-152-3p, -142-3p, -148a-3p, -532-3p were upregulated (>200%) and miR-96-5p, -124-3p, -9a-3p, -190b-5p, -181a-1-3p, -9a-5p, -183-5p were downregulated (>70%) compared to controls. During peak pathological NV, miR-30a-5p, -30e-5p and 190b-5p were markedly reduced (>70%), and miR-30e-3p, miR-335, -30b-5p strongly augmented (by up to 300%) in the retina. Whereas in choroid, miR-let-7f-5p, miR-126a-5p and miR-101a-3p were downregulated by (>81%), and miR-125a-5p, let-7e-5p and let-7g-5p were upregulated by (>570%) during NV. Changes in miRNA observed using NGS were validated using qRT-PCR for the 24 most modulated miRNAs. In silico approach to predict miRNA target genes (using algorithms of miRSystem database) identified potential new target genes with pro-inflammatory, apoptotic and angiogenic properties. The present study is the first comprehensive description of retinal/choroidal miRNAs profiling in OIR (using NGS technology). Our results provide a valuable framework for the characterization and possible therapeutic potential of specific miRNAs involved in ocular IR-triggered inflammation, angiogenesis and degeneration.

Adenosine/adenosine receptor-mediated signaling has been implicated in the development of various ischemic diseases, including ischemic retinopathies. Here, we show that the adenosine A2a receptor (ADORA2A) promotes hypoxia-inducible transcription factor-1 (HIF-1)-dependent endothelial cell glycolysis, which is crucial for pathological angiogenesis in proliferative retinopathies. Adora2a expression is markedly increased in the retina of mice with oxygen-induced retinopathy (OIR). Endothelial cell-specific, but not macrophage-specific Adora2a deletion decreases key glycolytic enzymes and reduces pathological neovascularization in the OIR mice. In human primary retinal microvascular endothelial cells, hypoxia induces the expression of ADORA2A by activating HIF-2α. ADORA2A knockdown decreases hypoxia-induced glycolytic enzyme expression, glycolytic flux, and endothelial cell proliferation, sprouting and tubule formation. Mechanistically, ADORA2A activation promotes the transcriptional induction of glycolytic enzymes via ERK- and Akt-dependent translational activation of HIF-1α protein. Taken together, these findings advance translation of ADORA2A as a therapeutic target in the treatment of proliferative retinopathies and other diseases dependent on pathological angiogenesis. Pathological angiogenesis in the retina is a major cause of blindness. Here the authors show that adenosine receptor A2A drives pathological angiogenesis in the oxygen-induced retinopathy mouse model by promoting glycolysis in endothelial cells via the ERK/Akt/HIF-1α pathway, thereby suggesting new therapeutic targets for disease treatment.

Retinal angiogenesis drives both normal vascular development and sight-threatening retinal vascular diseases. While mitochondria are known to fuel this process, the roles of many specific mitochondrial proteins are poorly understood. Here we show that the mitochondrial protein RAB5 interacting factor (RAB5IF) as a critical pro-angiogenic regulator of physiological retinal vascular development in neonatal mice (sex-balanced) and pathological retinal angiogenesis in two models: oxygen-induced retinopathy mice (sex-balanced) and laser-induced choroidal neovascularization mice (sex-balanced). Proteomic sequencing identified SUMO2 as a critical downstream protein of RAB5IF. RAB5IF silencing impeded mitochondrial respiration and ribosome biogenesis, specifically suppressing SUMO2 mRNA translation initiation and consequently lowering SUMO2 protein levels in retinal microvascular endothelial cells. We also identify that SUMO2-mediated SUMOylation of Gαi1/3 is required for their roles in mediating VEGF signaling. Mutations at the SUMOylation sites of Gαi1/3 hindered VEGF-induced signaling and pro-angiogenic activity. Together, these findings delineate a RAB5IF-SUMO2-Gαi1/3 signaling axis essential for retinal angiogenesis, presenting new therapeutic targets for neovascular eye diseases. Endothelial RAB5IF is a critical proangiogenic regulator of both normal and pathological retinal angiogenesis. Here the authors show that RAB5IF-SUMO2-Gαi1/3 signaling axis drives this process, presenting new therapeutic targets for neovascular eye diseases.

Aims/hypothesis Diabetic retinopathy is characterised by neuroinflammation that drives neuronal and vascular degenerative pathology, which in many individuals can lead to retinal ischaemia and neovascularisation. Infiltrating macrophages and activated retina-resident microglia have been implicated in the progression of diabetic retinopathy, although the distinct roles of these immune cells remain ill-defined. Our aim was to clarify the distinct roles of macrophages/microglia in the pathogenesis of proliferative ischaemic retinopathies. Methods Murine oxygen-induced retinopathy is commonly used as a model of ischaemia-induced proliferative diabetic retinopathy (PDR). We evaluated the phenotype macrophages/microglia by immunostaining, quantitative real-time RT-PCR (qRT-PCR), flow cytometry and scRNA-seq analysis. In clinical imaging studies of diabetic retinopathy, we used optical coherence tomography (OCT) and OCT angiography. Results Immunostaining, qRT-PCR and flow cytometry showed expression levels of M1-like macrophages/microglia markers (CD80, CD68 and nitric oxide synthase 2) and M2-like macrophages/microglia markers (CD206, CD163 and macrophage scavenger receptor 1) were upregulated in areas of retinal ischaemia and around neo-vessels, respectively. scRNA-seq analysis of the ischaemic retina revealed distinct ischaemia-related clusters of macrophages/microglia that express M1 markers as well as C-C chemokine receptor 2. Inhibition of Rho-kinase (ROCK) suppressed CCL2 expression and reduced CCR2-positive M1-like macrophages/microglia in areas of ischaemia. Furthermore, the area of retinal ischaemia was reduced by suppressing blood macrophage infiltration not only by ROCK inhibitor and monocyte chemoattractant protein-1 antibody but also by GdCl 3 . Clinical imaging studies of diabetic retinopathy using OCT indicated potential involvement of macrophages/microglia represented by hyperreflective foci in areas of reduced perfusion. Conclusions/interpretation These results collectively indicated that heterotypic macrophages/microglia differentially contribute to retinal ischaemia and neovascularisation in retinal vascular diseases including diabetic retinopathy. This adds important new information that could provide a basis for a more targeted, cell-specific therapeutic approach to prevent progression to sight-threatening PDR. Graphical Abstract

Retinal neovascularization (RNV) membranes can lead to a tractional retinal detachment, the primary reason for severe vision loss in end-stage disease proliferative diabetic retinopathy (PDR). The aim of this study was to characterize the molecular, cellular and immunological features of RNV in order to unravel potential novel drug treatments for PDR. A total of 43 patients undergoing vitrectomy for PDR, macular pucker or macular hole (control patients) were included in this study. The surgically removed RNV and epiretinal membranes were analyzed by RNA sequencing, single-cell based Imaging Mass Cytometry and conventional immunohistochemistry. Immune cells of the vitreous body, also known as hyalocytes, were isolated from patients with PDR by flow cytometry, cultivated and characterized by immunohistochemistry. A bioinformatical drug repurposing approach was applied in order to identify novel potential drug options for end-stage diabetic retinopathy disease. The in-depth transcriptional and single-cell protein analysis of diabetic RNV tissue samples revealed an accumulation of endothelial cells, macrophages and myofibroblasts as well as an abundance of secreted ECM proteins such as SPARC, FN1 and several types of collagen in RNV tissue. The immunohistochemical staining of cultivated vitreal hyalocytes from patients with PDR showed that hyalocytes express α-SMA (alpha-smooth muscle actin), a classic myofibroblast marker. According to our drug repurposing analysis, imatinib emerged as a potential immunomodulatory drug option for future treatment of PDR. This study delivers the first in-depth transcriptional and single-cell proteomic characterization of RNV tissue samples. Our data suggest an important role of hyalocyte-to-myofibroblast transdifferentiation in the pathogenesis of diabetic vitreoretinal disease and their modulation as a novel possible clinical approach.

Choroidal neovascularization (CNV) is a key manifestation of intraocular neovascularization, and it is considered one of the main causes of blindness in ophthalmology. Additionally, multiple anti-vascular endothelial growth factor (VEGF) drugs have been used as first-line treatment for CNV. However, several issues posed challenges to the anti-VEGF drugs, which were mainly composed of short duration of action, requirement for repeated injections, and complications. Thrombospondin-1 (TSP-1) is an endogenous protein that was found to regulate multiple biological processes within the body, and it has been proven to exhibit an inhibitory effect on neovascularization. Besides, the function of TSP-1 during the inhibition of neovascularization was currently considered to mainly focus on its type Ⅰ repeats (TSRs), which was attributed to the large molecular weight, complex structure, and possible unknown functions of TSP-1. Therefore, TSRs can be applied as targets and research directions for the further development and exploration of potential therapeutic drugs. Based on the type I repeats (TSRs) of thrombospondin-1 (TSP-1), amino acid sequences of different lengths were designed and synthesized in this study, named as VR-9 VR-10、VR-11、VR-12、VR-13. The objective was to explore the effects of the above five peptides on angiogenesis in Chori-retinal neovascularization, alongside the screening of the best peptides and the deep exploration into the underlying mechanism, aimed to provide a basis for the development and application of peptide drugs in the treatment of CNV. Wound healing, CCK-8, and 5-ethynyl-2'-deoxyuridine (EdU) assays were employed to evaluate the proliferation and migration ability of cells. CRISPR-Cas9 technology was utilized to establish CD36 knockdown cell lines, alongside the conduction of qPCR to verify the efficiency of gene knockdown. The expression levels of VEGF and CD31 in RF/6A cells and rats were assessed by Western blot. Additionally, Hematoxylin and eosin (HE) staining was performed to examine the structural integrity of the rat retina, while Fluorescein Isothiocyanate-Dextran Cardiac Perfusion (FITC) labeling was used to observe the occurrence and development of choroidal neovascularization (CNV). According to the wound-healing and CCK-8 assays, VR-13 was the most effective in inhibiting the proliferation and migration of endothelial cells. Furthermore, VR-13 peptide effectively inhibited the pathological development of CNV without the detection of retinal toxicity in the rat CNV model. Overall, it was found that VR-13 exhibit significant effects on the inducing of apoptosis and the inhibition of the progression of angiogenesis by regulating the expression of VEGF and CD31 via CD36 signaling pathway.