Turning a blind eye to anti-VEGF toxicities

Inefficacy of anti-VEGF therapy reflected in VEGF-mediated photoreceptor degeneration

Retinal neovascularization (RNV) is primarily driven by vascular endothelial growth factor (VEGF). However, current anti-VEGF therapies are limited by short half-lives and repeated injections, which reduce patient quality of life and increase medical risks. Additionally, not all patients benefit from anti-VEGF monotherapy, and some problems, such as unsatisfactory vision recovery, persist after long-term treatment. In this study, we constructed a recombinant adeno-associated virus (AAV), AAV2-SPLTH, which encodes an anti-VEGF antibody similar to bevacizumab, and assessed its effects in a doxycycline-induced Tet-opsin-VEGFA mouse model of RNV. AAV2-SPLTH effectively inhibited retinal leakage, RNV progression, and photoreceptor apoptosis in a Tet-opsin-VEGF mouse model. However, proteomic sequencing showed that AAV2-SPLTH failed to rescue the expression of phototransduction-related genes, which corresponded to reduced photoreceptor cell numbers. This study suggests that anti-VEGF monotherapy can significantly inhibit RNV to some extent but may not be enough to save visual function in the long term.

The Effect of Blue-light Filtering Intraocular Lenses on the Development and Progression of Macular Atrophy in Eyes With Neovascular Age-related Macular Degeneration

PURPOSE

To assess the effect of blue-light filtering (BLF) intraocular lenses (IOLs) on the development and progression of macular atrophy (MA) in eyes with neovascular age-related macular degeneration (nAMD).

DESIGN

Retrospective, clinical cohort study.

METHODS

The study included patients with nAMD with anti-vascular endothelial growth factor (VEGF) injections who underwent uneventful cataract surgery between 2007 and 2018 with follow-up until June 2023. Subsequent MA rates were compared between subjects who received a BLF IOL or a non-BLF IOL. All optical coherence tomography scans were manually reviewed in a masked manner regarding patient baseline variables and IOL status by an experienced research technician. By using Heidelberg software, the area of MA was manually evaluated and calculated (mm2) by the program. The overall risk of developing new-onset MA and the effect of IOL type on disease progression were assessed. Death was included as a censoring event.

RESULTS

Included were 373 eyes of 373 patients (mean age, 78.6 ± 6.7 years at surgery; 67.4% were female). BLF IOLs were implanted in 206 eyes, and non-BLF IOLs were implanted in 167 eyes with comparable follow-up times (3164 ± 1420 days vs 3180 ± 1403 days, respectively, P = .908) and other baseline parameters (age, gender, corrected distance visual acuity, macular thickness, cumulative number of anti-VEGF injections). Nine preexisting and 77 new-onset MA cases were detected, with similar distribution between BLF and non-BLF eyes (P = .598 and P = .399, respectively). Both univariate Kaplan-Meier (P = .366) and multivariate Cox regression analyses adjusted for age and gender showed that BLF-IOLs were comparable to non-BLF IOLs regarding hazard for new-onset MA (hazard ratio [HR], 1.236; 95% CI, 0.784-1.949; P = .363). Final MA area at the last visit was 5.14 ± 4.71 mm2 for BLF IOLs and 8.56 ± 9.17 mm2 for non-BLF IOLs (P = .028), with the mean annual MA area increase of 0.78 ± 0.84 mm2 and 1.26 ± 1.32 mm2, respectively (P = .042).

CONCLUSIONS

BLF IOLs did not show added benefit over non-BLF IOLs in terms of MA-free survival but were associated with less progression over time in a cohort of patients with nAMD.

Xanthine derivative KMUP-1 ameliorates retinopathy

Retinal neovascularization (RNV) and cell apoptosis observed in retinopathy are the most common cause of vision loss worldwide. Increasing vascular endothelial growth factor (VEGF), which was driven by hypoxia or inflammation, would result in RNV. This study investigated the anti-inflammatory and anti-apoptotic xanthine-based derivative KMUP-1 on hypoxia-induced conditions in vitro and in vivo. In the oxygen-induced retinopathy animal model, KMUP-1 mitigated vaso-obliteration and neovascularization. In the cell model of hypoxic endothelium cultured at 1% O2, KMUP-1 inhibited endothelial migration and tube formation and had no cytotoxic effect on cell growth. Upregulation of pro-angiogenic factors, HIF-1α and VEGF, and pro-inflammatory cytokines, IL-1β and TNF-α, expression in the retinal-derived endothelial cells, RF/6 A cells, upon hypoxia stimulation, was suppressed by KMUP-1 treatment. RF/6 A cells treated with KMUP-1 showed a reduction of PI3K/Akt, ERK, and RhoA/ROCKs signaling pathways and induction of protective pathways such as eNOS and soluble guanylyl cyclase at 1% O2. Furthermore, KMUP-1 decreased the expression of VEGF, ICAM-1, TNF-α, and IL-1β and increased the BCL-2/BAX ratio in the oxygen-induced retinopathy mouse retina samples. In conclusion, the results of this study suggest that KMUP-1 has potential therapeutic value in retinopathy due to its triple effects on anti-angiogenesis, anti-inflammation, and anti-apoptosis in hypoxic endothelium.

"One stone and two birds" strategy to treat neovascular age-related macular degeneration by a novel retinoid drug, EYE-101

Choroidal neovascularization (CNV) is a typical pathological feature of neovascular age-related macular degeneration and has become a major cause of vision loss in the elderly. Current therapies require repeated intraocular injections of anti-VEGF drugs by inhibiting endothelial angiogenic effects, which is painful and may cause adverse effects on normal vascular and neuronal functions. Herein, we designed a novel retinoid drug, EYE-101, determined its therapeutic effects on CNV, and clarified the anti-angiogenic mechanism. The results show that administration of EYE-101 did not cause obvious cytotoxicity and ocular tissue toxicity at the concentrations less than 5 μM. Topical administration of EYE-101 could reduce choroidal sprouting, suppress laser-induced CNV formation, and decrease pericyte coverages on ocular vessels. Administration of EYE-101 also suppressed endothelial cell proliferation, migration, and tube formation and reduced pericyte proliferation, migration, recruitment towards endothelial cells. EYE-101 exerted its anti-angiogenic effects by targeting endothelial cells and pericytes via antagonizing Wnt/β-catenin signaling and PDGF signaling. Thus, EYE-101 administration may offer an"one stone and two birds" strategy for the prevention and treatment of ocular neovascular disorders.

Vascular heterogeneity: VEGF receptors make blood vessels special

Karaman et al. (2022. J. Exp. Med.https://doi.org/10.1084/jem.20210565) examined the differential effects of the conditional deletion of genes encoding each VEGF receptor, VEGFR1, VEGFR2 and VEGFR 3, as well as combinations thereof in mice. The results highlight the crosstalk between receptors in different organs and emphasize the importance of VEGF receptor expression and interplay in vascular heterogeneity.

Targeting circular RNA-MET for anti-angiogenesis treatment via inhibiting endothelial tip cell specialization

Endothelial tip cell specialization plays an essential role in angiogenesis, which is tightly regulated by the complicated gene regulatory network. Circular RNA (circRNA) is a type of covalently closed non-coding RNA that regulates gene expression in eukaryotes. Here, we report that the levels of circMET expression are significantly upregulated in the retinas of mice with oxygen-induced retinopathy, choroidal neovascularization, and diabetic retinopathy. circMET silencing significantly reduces pathological angiogenesis and inhibits tip cell specialization in vivo. circMET silencing also decreases endothelial migration and sprouting in vitro. Mechanistically, circMET regulates endothelial sprouting and pathological angiogenesis by acting as a scaffold to enhance the interaction between IGF2BP2 and NRARP/ESM1. Clinically, circMET is significantly upregulated in the clinical samples of the patients of diabetic retinopathy. circMET silencing could reduce diabetic vitreous-induced endothelial sprouting and retinal angiogenesis in vivo. Collectively, these data identify a circRNA-mediated mechanism that coordinates tip cell specialization and pathological angiogenesis. circMET silencing is an exploitable therapeutic approach for the treatment of neovascular diseases.

Relationships Among Retinal Nerve Fiber Layer Thickness, Vascular Endothelial Growth Factor, and Cognitive Impairment in Patients with Schizophrenia

BACKGROUND

Studies have suggested retinal nerve fiber layer (RNFL) involvement in the pathogenesis of schizophrenia. Additionally, research has shown that vascular endothelial growth factor (VEGF) potentially contributes to the pathophysiology of psychiatric disorders. Therefore, this study aimed to investigate VEGF, RNFL, and correlations with cognitive impairments in schizophrenia patients.

METHODS

Patients with schizophrenia (n = 138) were compared to healthy controls (n = 160). RNFLs were measured with optical coherence tomography (OCT). The Stroop color and word test (SCWT) was used to evaluate neurocognition. Blood samples were collected to measure VEGF. SPSS 20.0 was used to perform analysis of covariance, t-tests, partial correlation analysis, and linear regression.

RESULTS

Thinner RNFLs were found in schizophrenia patients (p < 0.001). RNFL showed a significant correlation with SCWT scores (all p < 0.05). Serum level of VEGF was lower in patients with schizophrenia (p = 0.010). Total and inferior RNFL thicknesses of right eyes were positively correlated to VEGF level (RNFL total thickness p = 0.032, inferior thickness p = 0.014).Total RNFL thicknesses were shown to be reduced following a prolonged duration of illness (both p < 0.01).

CONCLUSION

These findings suggest that patients with schizophrenia have degeneration with RNFL thickness following illness duration, which may contribute to neurocognitive impairments observed in schizophrenia. VEGF is speculated to play some important role on RNFL degeneration with schizophrenia patients.

Efficacy of combining intravitreal injections of ranibizumab with micropulse diode laser versus intravitreal injections of ranibizumab alone in diabetic macular edema (ReCaLL): a single center, randomised, controlled, non-inferiority clinical trial

Background

To evaluate if a combination therapy with micropulse diode laser (MPL) shows non-inferiority on visual acuity (BCVA) within 12 months in comparison to standard therapy, i.e. intravitreal injection of ranibizumab alone.

Setting

Institutional. Prospective randomized single-center trial.

Methods

Patients with diabetic macular edema (DME) received three intravitreal injections of 0.5 mg ranibizumab during the upload phase and were then randomised 1:1 to receive either the same dosage of ranibizumab (0.5 mg) injections pro re nata alone (IVOM-Group; n = 9), or with two additional treatments with micropulse diode laser (IVOM+Laser-Group; n = 10). The primary endpoint was change in BCVA after 12 months. Secondary endpoints were change in central macular thickness and overall number of ranibizumab injections.

Results

BCVA increased significantly in both groups (IVOM: + 5.86, p < 0.001; IVOM+Laser: + 9.30; p < 0.001) with corresponding decrease in central macular thickness (IVOM: − 105 μm, p < 0.01; IVOM+Laser: − 125 μm; p < 0.01). Patients with additional laser treatment had better visual improvement (group comparison p = 0.075) and needed fewer ranibizumab injections (cumulative proportion of injections 9.68 versus 7.46 in IVOM-Group and IVOM+Laser-Group, respectively).

Conclusion

Non-inferiority of combination therapy in comparison to standard therapy alone could be demonstrated. Patients with additional laser therapy needed fewer ranibizumab injections.

Trial registration

Registered 10 February 2014 on ClinicalTrials.gov; NCT02059772.

Correlation between the rate of intravitreal injections, use of aflibercept as a second-line treatment and visual impairment for wet AMD in Finland

PURPOSE

To correlate the rate of intravitreal anti-VEGF injections and the use of aflibercept as a second-line treatment with visual impairment throughout Finland.

METHODS

Information related to anti-VEGF treatment, proportions of bevacizumab and aflibercept and new visual impairments due to wet age-related macular degeneration (AMD) was gathered from 5 university hospitals and 14 central hospital districts between 2015 and 2017 covering 232 568 injections and 1172 visual impairments.

RESULTS

Between 2015 and 2017, the number of annual total anti-VEGF injections increased from 60 412 to 93 589 (+24.5% annual change) and of aflibercept injections from 8299 to 20 833 (+58.7% annual change). The 3-year average for total anti-VEGF injections ranged from 9.6 to 21.1 (median 13.3) per 1000 citizens between hospital districts and for aflibercept injections from 0.8 to 4.0 (median 1.9). According to the primary protocol for wet AMD, during 2015-2017, the number of total anti-VEGF injections increased from 10.9 to 15.2 per 1000 citizens with the pro re nata (PRN) protocol and from 11.3 to 18.9 with the treat-and-extend regimen (TER). The 3-year average of aflibercept injections as a second-line treatment, but not the total number of anti-VEGF or bevacizumab injections, inversely correlated with new onset visual impairments (R = -0.505, P = 0.027) in the hospital districts. The number of visual impairments did not differ between the hospital districts according to the PRN and TER protocols (1.23 ± 0.41 and 1.14 ± 0.67, respectively, per 1000 citizens aged ≥64 years, P = 0.713).

CONCLUSION

These results emphasize that the use of aflibercept injections as a second-line treatment may decrease new onset visual impairments.

Combination Antioxidant/NSAID Therapies and Oral/Topical Ocular Delivery Modes for Prevention of Oxygen-Induced Retinopathy in a Rat Model

Given the complexity of oxygen-induced retinopathy (OIR), we tested the hypothesis that combination therapies and modes of administration would synergistically optimize efficacy for prevention of OIR. Newborn rats were exposed to neonatal intermittent hypoxia (IH) from the first day of life (P0) until P14 during which they received: (1) oral glutathione nanoparticles (nGSH) with topical ocular phosphate buffered saline (PBS); (2) nGSH with topical ocular Acuvail (ACV); (3) oral coenzyme Q10 (CoQ10) + ACV; (4) oral omega 3 polyunsaturated fatty acids (n-3 PUFAs) + ACV; (5) CoQ10 + n-3 PUFAs + PBS; or (6) CoQ10 + n-3 PUFAs + ACV. Treated groups raised in room air (RA) served as controls. At P14, pups were placed in RA with no treatment until P21. Retinal vascular pathology, ocular angiogenesis biomarkers, histopathology, and morphometry were determined. All combination treatments in IH resulted in the most beneficial retinal outcomes consistent with suppression of angiogenesis growth factors during reoxygenation/reperfusion and no significant adverse effects on somatic growth. nGSH + PBS also reversed IH-induced retinopathy, but had negative effects on growth. Simultaneously targeting oxidants, inflammation, and poor growth mitigates the damaging effects of neonatal IH on the developing retina. Therapeutic synergy with combination delivery methods enhance individual attributes and simultaneously target multiple pathways involved in complex diseases such as OIR.

Hypoxia-inducible factor-1α: A promising therapeutic target for vasculopathy in diabetic retinopathy

Diabetic retinopathy (DR) is a serious condition that can cause blindness in diabetic patients. It is a neurovascular disease, but the pathogenesis leading to the onset of this disease is still not completely understood. However, hypoxia with subsequent neovascularization is a characteristic phenomenon observed with DR. Cellular response to hypoxia is mediated by the transcriptional regulator hypoxia-inducible factor (HIF). Long-term research has shown that one isotype of HIF, HIF-1α, may play a pivotal role under hypoxic conditions, and an increasing number of studies have shown that HIF-1α and its target genes contribute to retinal neovascularization. Therefore, targeting HIF-1α may lead to more effective DR treatments. This review describes the possible mechanisms of HIF-1α in neovascularization of DR. Furthermore, various inhibitors of HIF-1α that may have viable potential in the treatment of DR are also discussed.

The role of Müller cell glucocorticoid signaling in diabetic retinopathy

Diabetic retinopathy (DR) is a sight-threatening complication associated with the highly prevalent diabetes disorder. Both the microvascular damage and neurodegeneration detected in the retina caused by chronic hyperglycemia have brought special attention to Müller cells, the major macroglia of the retina that are responsible for retinal homeostasis. Given the role of glucocorticoid signaling in anti-inflammatory responses and the almost exclusive expression of glucocorticoid receptors (GRs) in retinal Müller cells, administration of corticosteroid agonists as a potential treatment option has been widely studied. Although these approaches have been moderately efficacious in treating or de-escalating DR pathomechanisms, there are various side effects and gaps of knowledge with regard to introducing exogenous glucocorticoids to the diseased retina. In this paper, we provide a review of the literature concerning the available evidence for the role of Müller cell glucocorticoid signaling in DR and we discuss previously investigated approaches in modulating this system as possible treatment options. Furthermore, we propose a novel alternative to the available choices of treatment by using gene therapy as a tool to regulate the expression of GR in retinal Müller cells. Upregulating GR expression allows for induced glucocorticoid signaling with more enduring effects compared to injection of agonists. Hence, repetitive injections would no longer be required. Lastly, side effects of glucocorticoid therapy such as glucocorticoid resistance of GR following chronic exposure to excess ligands or agonists can be avoided.

Real-time photoacoustic sensing for photo-mediated ultrasound therapy

Photo-mediated ultrasound therapy (PUT) is a novel, noninvasive antimicrovascular approach that can treat neovascularization with high precision. We developed a photoacoustic (PA) sensing (PAS) system for PUT and achieved real-time PAS-guided PUT. Experiments performed on a chicken yolk sac membrane model demonstrated that PAS could monitor the treatment effect in a microvessel during PUT. Vessel shrinkage induced a decrease in the PA signal amplitude, while vessel rupture induced an abrupt increase in the PA signal amplitude. The integrated PUT and PAS system can significantly improve the safety and effectiveness of PUT, and may assist with clinical translation of this novel antimicrovascular technique.

[(Immuno‑)Pathology of drug side effects in the kidney]

Nephrotoxicity or renal side effects of drugs are frequent and may vary in their clinical presentation. Various types of acute and chronic kidney disease are known to develop as a consequence or side effect of a long list of drugs with nephrotoxicity most commonly being associated with injury in the tubulointerstitial compartment. In addition, drug-induced glomerular and vascular disease have also been reported, either as the result of direct cellular injury or immune-mediated injury to glomerular or endothelial cells. From a clinical point of view it is important to recognize such drug-induced nephropathies early in order to prevent or adequately treat them to favour kidney recovery and to avoid long-lasting negative consequences for kidney function.This article will focus on the typical morphology and pathogenesis of some frequent drug-induced renal diseases.

Diabetic retinopathy: Focus on NADPH oxidase and its potential as therapeutic target

Diabetic retinopathy is a common complication of diabetes that affects the retina due to a sustained high blood sugar level. Recent studies have demonstrated that high glucose-driven oxidative stress plays an important role in the microvascular complications of retina in diabetes. Oxidative stress occurs due to the excess of reactive oxygen species, which causes oxidative damage to retina, leading to the leak of tiny blood vessels, or acts as signaling molecules to trigger neovascularization, resulting in new fragile vessels. NADPH oxidase (NOX) is a key enzymatic source of reactive oxygen species in the retina, and it is involved in the early as well as the advanced stage of diabetic retinopathy. To date, at least 7 NOX isoforms, including NOX1 to NOX5, dual oxidase1 and dual oxidase 2, have been identified. It has been shown that NOX isoforms exert different roles in the pathogenesis of diabetic retinopathy. Intervention of NOX by its inhibitors or modulators shows beneficial effect on improving the retinal functions in the models of diabetic retinopathy in vivo or in vitro. Thereby, NOX might be a potential target for the therapy of diabetic retinopathy. The present review focuses on the role of NOX, particularly the NOX isoforms, in promoting the development of diabetic retinopathy. In addition, NOX isoforms as potential targets for therapy of diabetic retinopathy are also discussed.

Fabrication of antibody-loaded microgels using microfluidics and thiol-ene photoclick chemistry

Reducing burst effects, providing controlled release, and safeguarding biologics against degradation are a few of several highly attractive applications for microgels in the field of controlled release. However, the incorporation of proteins into microgels without impairing stability is highly challenging. In this proof of concept study, the combination of microfluidics and thiol-ene photoclick chemistry was evaluated for the fabrication of antibody-loaded microgels with narrow size distribution. Norbornene-modified eight-armed poly(ethylene glycol) with an average molecular mass of 10,000 Da, 20,000 Da, or 40,000 Da were prepared as macromonomers for microgel formation. For functionalization, either hydrolytically cleavable ester or stable amide bonds were used. A microfluidic system was employed to generate precursor solution droplets containing macromonomers, the cross-linker dithiothreitol and the initiator Eosin-Y. Irradiation with visible light was used to trigger thiol-ene reactions which covalently cross-linked the droplets. For all bond-types, molecular masses, and concentrations gelation was very rapid (<20 s) and a plateau for the complex shear modulus was reached after only 5 min. The generated microgels had a rod-like shape and did not show considerable cellular toxicity. Stress conditions during the fabrication process were simulated and it could be shown that fabrication did not impair the activity of the model proteins lysozyme and bevacizumab. It was confirmed that the average hydrogel network mesh size was similar or smaller than the hydrodynamic diameter of bevacizumab which is a crucial factor for restricting diffusion and delaying release. Finally, microgels were loaded with bevacizumab and a sustained release over a period of 30 ± 4 and 47 ± 7 days could be achieved in vitro.

[Current approach and the role of laser photocoagulation in the treatment of retinal vein occlusions]

Despite the emergence of new approaches in the treatment of retinal vein thrombosis and post-thrombotic complications, namely, intravitreal pharmacotherapy and surgical treatment, laser photocoagulation continues to play a significant role in the management of patients with this pathology. Although the method of laser photocoagulation has been used for quite a long time, different views exist on its indications and execution in specific clinical situations. At that, not all opinions regarding the use of laser photocoagulation in thrombosis are based on convincing clinical studies. The aim of this work was to summarize current literature data on the use of laser photocoagulation in the integrated treatment of retinal vein occlusions and, also, to show which aspects of the treatment of thromboses can be considered well-established and reasonable and which remain a subject of debate.

Ocular Adverse Effects of Intravitreal Bevacizumab Are Potentiated by Intermittent Hypoxia in a Rat Model of Oxygen-Induced Retinopathy

Intravitreal bevacizumab (Avastin) use in preterm infants with retinopathy of prematurity is associated with severe neurological disabilities, suggesting vascular leakage. We examined the hypothesis that intermittent hypoxia (IH) potentiates intravitreal Avastin leakage. Neonatal rats at birth were exposed to IH from birth (P0)–P14. At P14, the time of eye opening in rats, a single dose of Avastin (0.125 mg) was injected intravitreally into the left eye. Animals were placed in room air (RA) until P23 or P45 for recovery (IHR). Hyperoxia-exposed and RA littermates served as oxygen controls, and equivalent volume saline served as the placebo controls. At P23 and P45 ocular angiogenesis, retinal pathology and ocular and systemic biomarkers of angiogenesis were examined. Retinal flatmounts showed poor peripheral vascularization in Avastin-treated and fellow eyes at P23, with numerous punctate hemorrhages and dilated, tortuous vessels with anastomoses at P45 in the rats exposed to IH. These adverse effects were associated with robust increases in systemic VEGF and in both treated and untreated fellow eyes. Histological analysis showed severe damage in the inner plexiform and inner nuclear layers. Exposure of IH/IHR-induced injured retinal microvasculature to anti-VEGF substances can result in vascular leakage and adverse effects in the developing neonate.

Gene therapy for diabetic retinopathy: Are we ready to make the leap from bench to bedside?

Diabetic retinopathy (DR), a chronic and progressive complication of diabetes mellitus, is a sight-threatening disease characterized in the early stages by neuronal and vascular dysfunction in the retina, and later by neovascularization that further damages vision. A major contributor to the pathology is excess production of vascular endothelial growth factor (VEGF), a growth factor that induces formation of new blood vessels and increases permeability of existing vessels. Despite the recent availability of effective treatments for the disease, including laser photocoagulation and therapeutic VEGF antibodies, DR remains a significant cause of vision loss worldwide. Existing anti-VEGF agents, though generally effective, are limited by their short therapeutic half-lives, necessitating frequent intravitreal injections and the risk of attendant adverse events. Management of DR with gene therapies has been proposed for several years, and pre-clinical studies have yielded enticing findings. Gene therapy holds several advantages over conventional treatments for DR, such as a longer duration of therapeutic effect, simpler administration, the ability to intervene at an earlier stage of the disease, and potentially fewer side-effects. In this review, we summarize the current understanding of the pathophysiology of DR and provide an overview of research into DR gene therapies. We also examine current barriers to the clinical application of gene therapy for DR and evaluate future prospects for this approach.

High-precision, non-invasive anti-microvascular approach via concurrent ultrasound and laser irradiation

Antivascular therapy represents a proven strategy to treat angiogenesis. By applying synchronized ultrasound bursts and nanosecond laser irradiation, we developed a novel, selective, non-invasive, localized antivascular method, termed photo-mediated ultrasound therapy (PUT). PUT takes advantage of the high native optical contrast among biological tissues and can treat microvessels without causing collateral damage to the surrounding tissue. In a chicken yolk sac membrane model, under the same ultrasound parameters (1 MHz at 0.45 MPa and 10 Hz with 10% duty cycle), PUT with 4 mJ/cm² and 6 mJ/cm² laser fluence induced 51% (p = 0.001) and 37% (p = 0.018) vessel diameter reductions respectively. With 8 mJ/cm² laser fluence, PUT would yield vessel disruption (90%, p < 0.01). Selectivity of PUT was demonstrated by utilizing laser wavelengths at 578 nm or 650 nm, where PUT selectively shrank veins or occluded arteries. In a rabbit ear model, PUT induced a 68.5% reduction in blood perfusion after 7 days (p < 0.001) without damaging the surrounding cells. In vitro experiments in human blood suggested that cavitation may play a role in PUT. In conclusion, PUT holds significant promise as a novel non-invasive antivascular method with the capability to precisely target blood vessels.

Differential expression of microRNAs in retinal vasculopathy caused by selective Müller cell disruption

Vascular changes and photoreceptor degeneration are features of age-related macular degeneration, diabetic retinopathy and macular telangiectasis. We have profiled the differential expression of microRNAs and analysed their target genes in transgenic mice in which induced Müller cell disruption results in photoreceptor degeneration, vascular leak and deep retinal neovascularisation. We identified 9 miRNAs which were differentially expressed during the development of retinal neovascularization and chose miR-200b and its target genes for further study. Using qRT-PCR and western blot analysis, we found that downregulation of miR-200b was negatively correlated with its target genes, including zinc finger E-box binding homeobox (ZEB) 1 and 2 and vascular endothelial growth factor receptor 1. Double immunofluorescence labelling revealed that the newly formed vessels in the outer retina were positive for ZEB2. Furthermore, intravitreal injections of a miR-200b-mimic and anti-miR-200b confirmed the negative correlation of miR-200b and its target gene expression. We also found that the miR-200b-mimic inhibited vascular leak in the established mild vascular lesions, whereas anti-miR-200b promoted it. Taken together, these data suggest that miR-200b may play a role in the development of intraretinal neovascularisation.

The genetics of age-related macular degeneration (AMD)--Novel targets for designing treatment options?

Age-related macular degeneration (AMD) is a progressive disease of the central retina and the main cause of legal blindness in industrialized countries. Risk to develop the disease is conferred by both individual as well as genetic factors with the latter being increasingly deciphered over the last decade. Therapeutically, striking advances have been made for the treatment of the neovascular form of late stage AMD while for the late stage atrophic form of the disease, which accounts for almost half of the visually impaired, there is currently no effective therapy on the market. This review highlights our current knowledge on the genetic architecture of early and late stage AMD and explores its potential for the discovery of novel, target-guided treatment options. We reflect on current clinical and experimental therapies for all forms of AMD and specifically note a persisting lack of efficacy for treatment in atrophic AMD. We further explore the current insight in AMD-associated genes and pathways and critically question whether this knowledge is suited to design novel treatment options. Specifically, we point out that known genetic factors associated with AMD govern the risk to develop disease and thus may not play a role in its severity or progression. Treatments based on such knowledge appear appropriate rather for prevention than treatment of manifest disease. As a consequence, future research in AMD needs to be greatly focused on approaches relevant to the patients and their medical needs.

A lipidomic screen of hyperglycemia-treated HRECs links 12/15-Lipoxygenase to microvascular dysfunction during diabetic retinopathy via NADPH oxidase

Retinal hyperpermeability and subsequent macular edema is a cardinal feature of early diabetic retinopathy (DR). Here, we investigated the role of bioactive lipid metabolites, in particular 12/15-lipoxygenase (LOX)-derived metabolites, in this process. LC/MS lipidomic screen of human retinal endothelial cells (HRECs) demonstrated that 15-HETE was the only significantly increased metabolite (2.4 ± 0.4-fold, P = 0.0004) by high glucose (30 mM) treatment. In the presence of arachidonic acid, additional eicosanoids generated by 12/15-LOX, including 12- and 11-HETEs, were significantly increased. Fluorescein angiography and retinal albumin leakage showed a significant decrease in retinal hyperpermeability in streptozotocin-induced diabetic mice lacking 12/15-LOX compared with diabetic WT mice. Our previous studies demonstrated the potential role of NADPH oxidase in mediating the permeability effect of 12- and 15-HETEs, therefore we tested the impact of intraocular injection of 12-HETE in mice lacking the catalytic subunit of NADPH oxidase (NOX2). The permeability effect of 12-HETE was significantly reduced in NOX2(-/-) mice compared with the WT mice. In vitro experiments also showed that 15-HETE induced HREC migration and tube formation in a NOX-dependent manner. Taken together our data suggest that 12/15-LOX is implicated in DR via a NOX-dependent mechanism.

Ubiquitin carboxyl-terminal esterase L1 promotes proliferation of human choroidal and retinal endothelial cells

PURPOSE

We aimed: (1) to establish endothelial expression of ubiquitin carboxyl-terminal esterase L1 (UCHL1) in human choroid and retina and; (2) to investigate a role for UCHL1 in basic processes involved in intraocular neovascularization.

DESIGN

Controlled translational experimental study.

METHODS

Ethanol-fixed human choroid and retina (n = 3 eyes) were indirectly immunostained with rabbit anti-human UCHL1 antibody. Endothelial proliferation and migration assays were performed using cultured human choroidal and retinal endothelial cells (n = 6 isolates/assay). Cells were transfected with UCHL1-targeted or non-targeted small interfering (si)RNA and a commercially available transfection system, and used 48 hours later in experiments. Cell proliferation was evaluated using an assay in which cellular DNA was fluorescently tagged for quantification by microplate reader. Cell migration was examined in an assay that involved counting the number of endothelial cells moving across a perforated membrane. Transcript silencing was verified by Western blot for all assays.

RESULTS

Immunohistochemistry confirmed expression of UCHL1 by endothelium in human choroid and retina in vivo. UCHL1-specific knockdown resulted in significantly less proliferation (p < 0.0001) for 3 human choroidal endothelial isolates and 3 human retinal endothelial isolates, and significantly less migration (p ≤ 0.016) for 2 of 3 human choroidal endothelial isolates and 1 of 3 human retinal endothelial isolates.

CONCLUSIONS

Our results suggest that UCHL1 may be involved in choroidal and retinal endothelial proliferation in most persons, and endothelial migration in some persons. UCHL1 may be a suitable target for a new treatment of intraocular neovascularisation.

Anti-angiogenic effects of a mutant endostatin: a new prospect for treating retinal and choroidal neovascularization

Purpose

Pathological fundus angiogenesis is a major cause of vision loss in retina diseases. Endostatin, a C-terminal fragment of collagen XVIII, is an endogenous anti-angiogenic protein. The present study aimed to investigate the in vitro and in vivo anti-angiogenic properties of two proteins: an N-terminal H1D/H3D mutant endostatin (M-ES) and a polyethylene glycol propionaldehyde (PEG) covalent M-ES (PEG-M-ES).

Methods

M-ES and PEG-M-ES properties were characterized in vitro using a zinc ion binding assay and a stability test. Activity assays, including migration, proliferation, and tube formation assays, were performed with human retinal microvascular endothelial cells (HRMECs) and human umbilical vein endothelial cells (HUVECs). Mouse oxygen-induced retinopathy (OIR) and choroidal neovascularization (CNV) models were used to evaluate in vivo anti-angiogenic effects. In addition, a rabbit model was used to study the retinal pharmacokinetic profile following an intravitreal injection.

Results

The results indicated that the H1D/H3D mutations of endostatin reduced the zinc binding capacity of M-ES and facilitated PEG covalent binding. PEG-M-ES was more stable and persisted longer in the retina compared with M-ES. The in vitro studies demonstrated that M-ES and PEG-M-ES inhibited HRMEC and HUVEC proliferation, migration, and tube formation more efficiently than ES. In vivo, a single intravitreal injection of M-ES and PEG-M-ES significantly decreased neovascularization in both the OIR and CNV animal models.

Conclusion

The present study demonstrated for the first time that PEG-M-ES exhibits a long-term inhibitory effect on neovascularization in vitro and in vivo. These data suggest that PEG-M-ES may represent an innovative therapeutic strategy to prevent fundus neovascularization.

Intraocular pressure rise is predictive of vision improvement after intravitreal triamcinolone acetonide for diabetic macular oedema: a retrospective analysis of data from a randomised controlled trial

Background

Intravitreal triamcinolone acetonide (IVTA) is an effective treatment for recalcitrant diabetic macular oedema (DMO). It has been shown to improve vision with benefits persisting up to five years. The most common initial side effect of IVTA treatment is rise in intraocular pressure, occurring in approximately 50% of patients within the first 6 months of treatment. We evaluated whether there is a correlation between the development of intraocular pressure rise and improvement in vision.

Methods

Analysis of individual data from 33 eyes of 33 participants treated with IVTA for DMO from a prospective, randomised, double-masked, placebo controlled trial. The degree of intraocular pressure (IOP) rise was correlated with improvement in best-corrected visual acuity (BCVA) at 1 and 6 months.

Results

The proportion of eyes gaining 5 or more logMAR letters was higher in eyes with greater IOP rise (p = 0.044). Better absolute improvement in BCVA at 6 months (p = 0.045) was also found in eyes with greater IOP rise. Regression analyses revealed a correlation between IOP rise of 10 or more mmHg and absolute BCVA improvement at 6 months (odds ratio 1.22, 95% confidence interval 1.01-1.48, p = 0.039), but not at 1 month.

Conclusions

IOP rise and vision improvement appear to be correlated following IVTA for DMO, suggesting that the mechanisms that cause both may be linked.

Trial Registration

Clinical trials.gov NCT00167518, September 5, 2005.

Angiopoietin-1 guides directional angiogenesis through integrin αvβ5 signaling for recovery of ischemic retinopathy

Retinopathy of prematurity (ROP) and proliferative diabetic retinopathy (PDR) are ischemic retinal diseases caused by insufficient vascular network formation and vascular regression in addition to aberrant angiogenesis. We examined the role of angiopoietin-1 (Ang1) in retinal vascular network formation during postnatal development using Ang1 gain- and loss-of-function mouse models, and tested the effects of intraocular administration of Ang1 in an oxygen-induced retinopathy (OIR) mouse model that mimics cardinal features of ROP and PDR. We observed that Ang1 plays a substantial role in the formation of the retinal vascular network during postnatal development and that Ang1 supplementation can rescue vascular retinopathies by simultaneously promoting healthy vascular network formation and inhibiting subsequent abnormal angiogenesis, vascular leakage, and neuronal dysfunction in the retinas of the OIR model. We attribute these Ang1-induced effects to a dual signaling pathway-Tie2 signaling in the vascular region and integrin αvβ5 signaling in the astrocytes. The activation of integrin αvβ5 signaling promoted fibronectin accumulation and radial distribution along the sprouting endothelial cells, which consequently stimulated guided angiogenesis in the retina. These findings shed light on the role of Ang1 in the recovery of ischemic retinopathies such as ROP, PDR, and retinal vascular occlusive disease.

The relationship between BCMO1 gene variants and macular pigment optical density in persons with and without age-related macular degeneration

Background

Recent evidence indicates that gene variants related to carotenoid metabolism play a role in the uptake of macular pigments lutein (L) and zeaxanthin (Z). Moreover, these pigments are proposed to reduce the risk for advanced age-related macular degeneration (AMD). This study provides the initial examination of the relationship between the gene variants related to carotenoid metabolism, macular pigment optical density (MPOD) and their combined expression in healthy humans and patients with AMD.

Participants and Methods

Forty-four participants were enrolled from a general population and a private practice including 20 healthy participants and 24 patients with advanced (neovascular) AMD. Participants were genotyped for the three single nucleotide polymorphisms (SNPs) upstream from BCMO1, rs11645428, rs6420424 and rs6564851 that have been shown to either up or down regulate beta-carotene conversion efficiency in the plasma. MPOD was determined by heterochromatic flicker photometry.

Results

Healthy participants with the rs11645428 GG genotype, rs6420424 AA genotype and rs6564851 GG genotype all had on average significantly lower MPOD compared to those with the other genotypes (p<0.01 for all three comparisons). When combining BCMO1 genotypes reported to have “high” (rs11645428 AA/rs6420424 GG/rs6564851 TT) and “low” (rs11645428 GG/rs6420424 AA/rs6564851 GG) beta-carotene conversion efficiency, we demonstrate clear differences in MPOD values (p<0.01). In patients with AMD there were no significant differences in MPOD for any of the three BCMO1 gene variants.

Conclusion

In healthy participants MPOD levels can be related to high and low beta-carotene conversion BCMO1 genotypes. Such relationships were not found in patients with advanced neovascular AMD, indicative of additional processes influencing carotenoid uptake, possibly related to other AMD susceptibility genes. Our findings indicate that specific BCMO1 SNPs should be determined when assessing the effects of carotenoid supplementation on macular pigment and that their expression may be influenced by retinal disease.

Diabetic Retinopathy-Update on Prevention Techniques, Present Therapies, and New Leads

Diabetic retinopathy is the major ocular complication associated with diabetes, and represents the leading cause of legal blindness in the working-age population of developed countries. Although classically diagnosed based on abnormalities of the retinal microvasculature, diabetic retinopathy is now widely recognized as a neurovascular disease. While all patients with diabetes are at increased risk for eye disease including diabetic retinopathy, proactive measures, and timely intervention can prevent or delay subsequent vision loss. Systemic management of diabetes by combined control of glycemia, blood pressure, and serum lipid levels remains the most important method of preventing diabetic retinopathy onset and progression. Once detected, surgical and medical interventions including photocoagulation, vitrectomy, and intravitral drug injection can help preserve vision. However, the need for improved detection methods and therapies that will allow earlier diagnosis and treatment remains apparent. This review summarizes current techniques for the prevention and intervention for diabetic retinopathy, and examines ongoing developments in the search for new endpoints and therapies as they apply to preventing vision loss associated with diabetes.

Ritonavir inhibits HIF-1α-mediated VEGF expression in retinal pigment epithelial cells in vitro

PURPOSE

Retinal hypoxia-mediated activation of the hypoxia-inducible factor (HIF pathway) leading to angiogenesis is a major signaling mechanism underlying a number of sight-threatening diseases. Inhibiting this signaling mechanism with an already approved therapeutic molecule may have promising anti-angiogenic role with fewer side effects. Hence, the primary objective of this study was to examine the expression of HIF-1α and VEGF in human retinal pigment epithelial cells treated with ritonavir under hypoxic and normoxic conditions.

METHODS

ARPE-19 and D407 cells were cultured in normoxic or hypoxic conditions, alone or in the presence of ritonavir. Quantitative real-time polymerase chain reaction, immunoblot analysis, sandwich ELISA, endothelial cell proliferation, and cytotoxicity were performed.

RESULTS

A 12-h hypoxic exposure resulted in elevated mRNA expression levels of both HIF-1α and VEGF in ARPE-19 and D407 cells. Hence, this time point was selected for subsequent experiments. Presence of ritonavir in the culture medium strongly inhibited VEGF expression in a concentration-dependent manner under hypoxic conditions. Immunoblot analysis demonstrated a substantially reduced protein expression of HIF-1α in the presence of ritonavir. Further, hypoxic exposure-induced VEGF secretion was also inhibited by ritonavir, as demonstrated using ELISA. Finally, ritonavir significantly diminished the proliferation of choroid-retinal endothelial (RF/6A) cells demonstrating potential anti-angiogenic activity. Cytotoxicity studies showed that ritonavir is non-toxic to RPE cells.

CONCLUSIONS

This study demonstrates for the first time that ritonavir can inhibit HIF-1α and VEGF in ARPE-19 and D407 cells. Such inhibition may form a platform for application of ritonavir in the treatment of various ocular diseases.

Hypoxia-inducible factor-1 (HIF-1): a potential target for intervention in ocular neovascular diseases

Constant oxygen supply is essential for proper tissue development, homeostasis and function of all eukaryotic organisms. Cellular response to reduced oxygen levels is mediated by the transcriptional regulator hypoxia-inducible factor-1 (HIF-1). It is a heterodimeric complex protein consisting of an oxygen dependent subunit (HIF-1α) and a constitutively expressed nuclear subunit (HIF-1β). In normoxic conditions, de novo synthesized cytoplasmic HIF-1α is degraded by 26S proteasome. Under hypoxic conditions, HIF-1α is stabilized, binds with HIF-1β and activates transcription of various target genes. These genes play a key role in regulating angiogenesis, cell survival, proliferation, chemotherapy, radiation resistance, invasion, metastasis, genetic instability, immortalization, immune evasion, metabolism and stem cell maintenance. This review highlights the importance of hypoxia signaling in development and progression of various vision threatening pathologies such as diabetic retinopathy, retinopathy of prematurity, age-related macular degeneration and glaucoma. Further, various inhibitors of HIF-1 pathway that may have a viable potential in the treatment of oxygen-dependent ocular diseases are also discussed.

Targeted intraceptor nanoparticle therapy reduces angiogenesis and fibrosis in primate and murine macular degeneration

Monthly intraocular injections are widely used to deliver protein-based drugs that cannot cross the blood-retina barrier for the treatment of leading blinding diseases such as age-related macular degeneration (AMD). This invasive treatment carries significant risks, including bleeding, pain, infection, and retinal detachment. Further, current therapies are associated with a rate of retinal fibrosis and geographic atrophy significantly higher than that which occurs in the described natural history of AMD. A novel therapeutic strategy which improves outcomes in a less invasive manner, reduces risk, and provides long-term inhibition of angiogenesis and fibrosis is a felt medical need. Here we show that a single intravenous injection of targeted, biodegradable nanoparticles delivering a recombinant Flt23k intraceptor plasmid homes to neovascular lesions in the retina and regresses CNV in primate and murine AMD models. Moreover, this treatment suppressed subretinal fibrosis, which is currently not addressed by clinical therapies. Murine vision, as tested by OptoMotry, significantly improved with nearly 40% restoration of visual loss induced by CNV. We found no evidence of ocular or systemic toxicity from nanoparticle treatment. These findings offer a nanoparticle-based platform for targeted, vitreous-sparing, extended-release, nonviral gene therapy.