A brief history of anti-VEGF for the treatment of ocular angiogenesis

AutoTube: a novel software for the automated morphometric analysis of vascular networks in tissues

Due to their involvement in many physiologic and pathologic processes, there is a great interest in identifying new molecular pathways that mediate the formation and function of blood and lymphatic vessels. Vascular research increasingly involves the image-based analysis and quantification of vessel networks in tissue whole-mounts or of tube-like structures formed by cultured endothelial cells in vitro. While both types of experiments deliver important mechanistic insights into (lymph)angiogenic processes, the manual analysis and quantification of such experiments are typically labour-intensive and affected by inter-experimenter variability. To bypass these problems, we developed AutoTube, a new software that quantifies parameters like the area covered by vessels, vessel width, skeleton length and branching or crossing points of vascular networks in tissues and in in vitro assays. AutoTube is freely downloadable, comprises an intuitive graphical user interface and helps to perform otherwise highly time-consuming image analyses in a rapid, automated and reproducible manner. By analysing lymphatic and blood vascular networks in whole-mounts prepared from different tissues or from gene-targeted mice with known vascular abnormalities, we demonstrate the ability of AutoTube to determine vascular parameters in close agreement to the manual analyses and to identify statistically significant differences in vascular morphology in tissues and in vascular networks formed in in vitro assays.

Biodegradable Microsphere-Hydrogel Ocular Drug Delivery System for Controlled and Extended Release of Bioactive Aflibercept In Vitro

PURPOSE

Current standard of care for neovascular eye diseases require repeated intravitreal bolus injections of anti-vascular endothelial growth factors (anti-VEGFs). The purpose of this study was to validate a degradable microsphere-thermoresponsive hydrogel drug delivery system (DDS) capable of releasing bioactive aflibercept in a controlled and extended manner for 6 months.

MATERIALS AND METHODS

The DDS was fabricated by suspending aflibercept-loaded poly(lactic-co-glycolic acid) microspheres within a biodegradable poly(ethylene glycol)-co-(l-lactic acid) diacrylate/N-isopropylacrylamide (PEG-PLLA-DA/NIPAAm) thermoresponsive hydrogel. Encapsulation efficiency of DDSs and in vitro release profiles were characterized by iodine-125 radiolabeled aflibercept. The degradation of hydrogel was determined by dry weight changes. The cytotoxicity from degraded DDS byproducts was investigated by quantifying cell viability using LIVE/DEAD® assay. In addition, dot blot and enzyme-linked immunosorbent assay were used to determine the bioactivity of released drug. Finally, morphology of microspheres and hydrogel were investigated by cryo-scanning electron microscopy before and after thermal transformation.

RESULTS

The microsphere-hydrogel DDS was capable of releasing bioactive aflibercept in a controlled and extended manner for 6 months. The amount and rate of aflibercept release can be controlled by both the cross-linker concentration and microspheres load amount. The initial burst (release within 24 h) was from 37.35 ± 4.92 to 74.56 ± 6.16 µg (2 and 3 mM hydrogel, each loaded with 10 and 20 mg/ml of microspheres, respectively), followed by controlled drug release of 0.07-0.15 µg/day. Higher PEG-PLLA-DA concentration (3 mM) degraded faster than the lower concentration (2 mM). No significant cytotoxicity from degraded DDS byproducts was found for all investigated time points. Bioactivity of released drug was maintained at therapeutic level over entire release period.

CONCLUSIONS

The microsphere-hydrogel DDS is safe and can deliver bioactive aflibercept in a controlled manner. This may provide a significant advantage over current bolus injection therapies in the treatment of ocular neovascularization.

Cytokine Signaling Protein 3 Deficiency in Myeloid Cells Promotes Retinal Degeneration and Angiogenesis through Arginase-1 Up-Regulation in Experimental Autoimmune Uveoretinitis

The suppressor of cytokine signaling protein 3 (SOCS3) critically controls immune cell activation, although its role in macrophage polarization and function remains controversial. Using experimental autoimmune uveoretinitis (EAU) as a model, we show that inflammation-mediated retinal degeneration is exaggerated and retinal angiogenesis is accelerated in mice with SOCS3 deficiency in myeloid cells (LysM^Cre/+SOCS3^fl/fl). At the acute stage of EAU, the population of infiltrating neutrophils was increased and the population of macrophages decreased in LysM^Cre/+SOCS3^fl/fl mice compared with that in wild-type (WT) mice. Real-time RT-PCR showed that the expression of tumor necrosis factor-α, IL-1β, interferon-γ, granulocyte-macrophage colony-stimulating factor, and arginase-1 was significantly higher in the LysM^Cre/+SOCS3^fl/fl EAU retina in contrast to the WT EAU retina. The percentage of arginase-1⁺ infiltrating cells was significantly higher in the LysM^Cre/+SOCS3^fl/fl EAU retina than that in the WT EAU retina. In addition, bone marrow-derived macrophages and neutrophils from the LysM^Cre/+SOCS3^fl/fl mice express significantly higher levels of chemokine (C-C motif) ligand 2 and arginase-1 compared with those from WT mice. Inhibition of arginase using an l-arginine analog amino-2-borono-6-hexanoic suppressed inflammation-induced retinal angiogenesis without affecting the severity of inflammation. Our results suggest that SOCS3 critically controls the phenotype and function of macrophages and neutrophils under inflammatory conditions and loss of SOCS3 promotes the angiogenic phenotype of the cells through up-regulation of arginase-1.

Ranibizumab Plus Panretinal Photocoagulation versus Panretinal Photocoagulation Alone for High-Risk Proliferative Diabetic Retinopathy (PROTEUS Study)

PURPOSE

Comparison of the efficacy of ranibizumab (RBZ) 0.5 mg intravitreal injections plus panretinal photocoagulation (PRP) versus PRP alone in the regression of the neovascularization (NV) area in subjects with high-risk proliferative diabetic retinopathy (HR-PDR) over a 12-month period.

DESIGN

Prospective, randomized, multicenter, open-label, phase II/III study.

PARTICIPANTS

Eighty-seven participants (aged ≥18 years) with type 1/2 diabetes and HR-PDR (mean age, 55.2 years; 37% were female).

METHODS

Participants were randomized (1:1) to receive RBZ+PRP (n = 41) or PRP monotherapy (n = 46). The RBZ+PRP group received 3 monthly RBZ injections along with standard PRP. The PRP monotherapy group received standard PRP between day 1 and month 2; thereafter, re-treatments in both groups were at the investigators' discretion.

MAIN OUTCOME MEASURES

The primary outcome was regression of NV total, on the disc (NVD) plus elsewhere (NVE), defined as any decrease in the area of NV from the baseline to month 12. Secondary outcomes included best-corrected visual acuity (BCVA) changes from baseline to month 12, time to complete NV regression, recurrence of NV, macular retinal thickness changes from baseline to month 12, need for treatment for diabetic macular edema, need for vitrectomy because of occurrence of vitreous hemorrhage, tractional retinal detachment or other complications of DR, and adverse events (AEs) related to treatments.

RESULTS

Seventy-seven participants (88.5%) completed the study. Overall baseline demographics were similar for both groups, except for age. At month 12, 92.7% of participants in the RBZ+PRP group presented NV total reduction versus 70.5% of the PRP monotherapy participants (P = 0.009). The number of participants with NVD and NVE reductions was higher with RBZ+PRP (93.3% and 91.4%, respectively) versus PRP (68.8% and 73.7%, respectively), significant only for NVE (P = 0.048). Complete NV total regression was observed in 43.9% in the RBZ+PRP group versus 25.0% in the PRP monotherapy group (P = 0.066). At month 12, the mean BCVA was 75.2 letters (20/32) in the RBZ+PRP group versus 69.2 letters (20/40) in the PRP monotherapy group (P = 0.104). In the RBZ+PRP group, the mean number of PRP treatments over month 12 was 3.5±1.3, whereas in the PRP monotherapy group, it was 4.6±1.5 (P = 0.001). No deaths or unexpected AEs were reported.

CONCLUSIONS

Treatment with RBZ+PRP was more effective than PRP monotherapy for NV regression in HR-PDR participants over 12 months.

Relationship between Pericytes and Endothelial Cells in Retinal Neovascularization: A Histological and Immunofluorescent Study of Retinal Angiogenesis

Purpose

To evaluate the relationship between pericytes and endothelial cells in retinal neovascularization through histological and immunofluorescent studies.

Methods

C57BL/6J mice were exposed to hyperoxia from postnatal day (P) 7 to P12 and were returned to room air at P12 to induce a model of oxygen-induced retinopathy (OIR). The cross sections of enucleated eyes were processed with hematoxylin and eosin. Immunofluorescent staining of pericytes, endothelial cells, and N-cadherin was performed. Microfluidic devices were fabricated out of polydimethylsiloxane using soft lithography and replica molding. Human retinal microvascular endothelial cells, human brain microvascular endothelial cells, human umbilical vein endothelial cells and human placenta pericyte were mixed and co-cultured.

Results

Unlike the three-layered vascular plexus found in retinal angiogenesis of a normal mouse, angiogenesis in the OIR model is identified by the neovascular tuft extending into the vitreous. Neovascular tufts and the three-layered vascular plexus were both covered with pericytes in the OIR model. In this pathologic vascularization, N-cadherin, known to be crucial intercellular adhesion molecule, was also present. Further evaluation using the microfluidic in vitro model, successfully developed a microvascular network of endothelial cells covered with pericytes, mimicking normal retinal angiogenesis within 6 days.

Conclusions

Pericytes covering endothelial cells were observed not only in vasculature of normal retina but also pathologic neovascularization of OIR mouse at P17. Factors involved in the endothelial cell-pericyte interaction can be evaluated as an attractive novel treatment target. These future studies can be performed using microfluidic systems, which can shorten the study time and provide three-dimensional structural evaluation.

Introduction of a nurse-led intravitreal injection service in ophthalmology

Anti-VEGF (anti-vascular endothelial growth factor) agents are useful for a variety of previously untreatable eye conditions; indications for their use are increasing. As this treatment evolved from cutting-edge to mainstream NHS practice, it resulted in a significant increase in appointments for intravitreal (IVT) injections, clinical assessment and follow-up, and hence an increasing challenge to ensure its timely availability to all who needed it. In addressing that challenge, NHS Lothian successfully initiated an advanced nurse practitioner IVT service in addition to its medical IVT service, which has increased its capacity to provide the requisite high-quality care to this patient group.

Resveratrol reverses the adverse effects of bevacizumab on cultured ARPE-19 cells

Age-related macular degeneration (AMD) and proliferative diabetic retinopathy (PDR) are one of the major causes of blindness caused by neo-vascular changes in the retina. Intravitreal anti-VEGF injections are widely used in the treatment of wet-AMD and PDR. A significant percentage of treated patients have complications of repeated injections. Resveratrol (RES) is a polyphenol phytoalexin with anti-oxidative, anti-inflammatory and anti-proliferative properties. Hence, we hypothesized that if RES is used in combination with bevacizumab (BEV, anti-VEGF), it could reverse the adverse effects that precipitate fibrotic changes, drusen formation, tractional retinal detachment and so on. Human retinal pigment epithelial cells were treated with various combinations of BEV and RES. There was partial reduction in secreted VEGF levels compared to untreated controls. Epithelial-mesenchymal transition was lower in BEV + RES treated cultures compared to BEV treated cultures. The proliferation status was similar in BEV + RES as well as BEV treated cultures both groups. Phagocytosis was enhanced in the presence of BEV + RES compared to BEV. Furthermore, we observed that notch signaling was involved in reversing the adverse effects of BEV. This study paves way for a combinatorial strategy to treat as well as prevent adverse effects of therapy in patients with wet AMD and PDR.

3D endothelial cell spheroid/human vitreous humor assay for the characterization of anti-angiogenic inhibitors for the treatment of proliferative diabetic retinopathy

Proliferative diabetic retinopathy (PDR) represents a main cause of acquired blindness. Despite the recognition of the key role exerted by vascular endothelial growth factor (VEGF) in the pathogenesis of PDR, limitations to anti-VEGF therapies do exist. Thus, rapid and cost-effective angiogenesis assays are crucial for the screening of anti-angiogenic drug candidates for PDR therapy. In this context, evaluation of the angiogenic potential of PDR vitreous fluid may represent a valuable tool for preclinical assessment of angiostatic molecules. Here, vitreous fluid obtained from PDR patients after pars plana vitrectomy was used as a pro-angiogenic stimulus in a 3D endothelial cell spheroid/human vitreous assay. The results show that PDR vitreous is able to stimulate the sprouting of fibrin-embedded HUVEC spheroids in a time- and dose-dependent manner. A remarkable variability was observed among 40 individual vitreous fluid samples in terms of sprouting-inducing activity that was related, at least in part, to defined clinical features of the PDR patient. This activity was hampered by various extracellular and intracellular signaling pathway inhibitors, including the VEGF antagonist ranibizumab. When tested on 20 individual vitreous fluid samples, the inhibitory activity of ranibizumab ranged between 0 and 100% of the activity measured in the absence of the drug, reflecting a variable contribution of angiogenic mediators distinct from VEGF. In conclusion, the 3D endothelial cell spheroid/human vitreous assay represents a rapid and cost-effective experimental procedure suitable for the evaluation of the anti-angiogenic activity of novel extracellular and intracellular drug candidates, with possible implications for the therapy of PDR.

Age-related macular degeneration and mortality: the Melbourne Collaborative Cohort Study

AimsTo assess associations between features of age-related macular degeneration (AMD) and mortality.MethodsA total of 21 129 participants from the Melbourne Collaborative Cohort Study aged 47-85 years (60% female) were assessed for AMD (2003-2007). Mortality data to December 31, 2012 were obtained through linkage with the National Death Index. Associations were assessed using Cox regression, adjusting for age, sex, smoking, region of birth, education, physical activity, diet and alcohol.ResultsLate AMD was identified in 122 (0.6%) participants, including those with choroidal neovascularisation (n=55, 0.3%), geographic atrophy (n=87, 0.4%) and reticular pseudodrusen (n=87, 0.4%). After a median follow-up period of 8.1 years, 1669 (8%) participants had died, including those from cardiovascular diseases (386), tobacco-related cancers (179), and neurodegenerative disease (157). There was evidence of an increased rate of all-cause mortality for those with choroidal neovascularisation (Hazard Ratio (HR) 1.71 95% CI 1.06-2.76) and geographic atrophy (HR 1.46 95% CI 0.99-2.16). Choroidal neovascularisation was also associated with an increased rate of cardiovascular mortality (HR 3.16 95% CI 1.62-6.15) and geographic atrophy was associated with an increased rate of death from tobacco-related cancer (HR 2.86 95% CI 1.15-7.09). Weak evidence was also present for an association between choroidal neovascularisation and death from neurodegenerative disease (HR 2.49 95% CI 0.79-7.85). Neither reticular pseudodrusen nor the earlier stages of AMD were associated with mortality.ConclusionsLate AMD is associated with an increased rate of all-cause mortality. Choroidal neovascularisation and geographic atrophy were associated with death from cardiovascular disease and tobacco-related cancer, respectively.

EDIL3 knockdown inhibits retinal angiogenesis through the induction of cell cycle arrest in vitro

Pathological retinal angiogenesis is one of the most common causes of blindness, with limited treatment options being currently available. Epidermal growth factor (EGF)-like repeat and discoidin I-like domain-containing protein 3 (EDIL3) has been reported to serve an important role in embryonic vasculogenesis and tumor angiogenesis; however, its implication in retinal angiogenesis has yet to be elucidated. The present study aimed to investigate the putative roles of EDIL3 in retinal endothelial cells. RNA interference was used to disrupt the expression of EDIL3 in human retinal endothelial cells (HRECs) in vitro, and the resulting effects were examined. Cell proliferation was assessed using cell counting kit-8 reagent, Cell migration was investigated using a transwell chamber and a tube formation assay was used to study angiogenic capability in vitro. Flow cytometry was used to detect the cell cycle distribution and western blotting was used to study protein expression. The present results demonstrated that silencing EDIL3 expression significantly impaired the proliferative, migratory and tube forming capabilities of HRECs. Furthermore, EDIL3 knockdown was revealed to induce cell cycle arrest at the G₁ phase. Western blot analysis suggested that the possible mechanisms underlying the antiproliferative effects of EDIL3 silencing may involve the inhibition of EGF receptor-mediated pathways, and the suppression of cyclin D1 and cyclin E1 expression in HRECs. In conclusion, the findings of the present study suggested that EDIL3 may be implicated in retinal angiogenesis, and may have potential as a novel therapeutic target for the treatment of pathological angiogenesis.

Identification of RUNX1 as a Mediator of Aberrant Retinal Angiogenesis

Proliferative diabetic retinopathy (PDR) is a common cause of blindness in the developed world's working adult population and affects those with type 1 and type 2 diabetes. We identified Runt-related transcription factor 1 (RUNX1) as a gene upregulated in CD31⁺ vascular endothelial cells obtained from human PDR fibrovascular membranes (FVMs) via transcriptomic analysis. In vitro studies using human retinal microvascular endothelial cells (HRMECs) showed increased RUNX1 RNA and protein expression in response to high glucose, whereas RUNX1 inhibition reduced HRMEC migration, proliferation, and tube formation. Immunohistochemical staining for RUNX1 showed reactivity in vessels of patient-derived FVMs and angiogenic tufts in the retina of mice with oxygen-induced retinopathy, suggesting that RUNX1 upregulation is a hallmark of aberrant retinal angiogenesis. Inhibition of RUNX1 activity with the Ro5-3335 small molecule resulted in a significant reduction of neovascular tufts in oxygen-induced retinopathy, supporting the feasibility of targeting RUNX1 in aberrant retinal angiogenesis.

Pathogenic role and therapeutic potential of pleiotrophin in mouse models of ocular vascular disease

Angiogenic factors play an important role in the pathogenesis of diabetic retinopathy (DR), neovascular age-related macular degeneration (nAMD) and retinopathy of prematurity (ROP). Pleiotrophin, a well-known angiogenic factor, was recently reported to be upregulated in the vitreous fluid of patients with proliferative DR (PDR). However, its pathogenic role and therapeutic potential in ocular vascular diseases have not been defined in vivo. Here using corneal pocket assays, we demonstrated that pleiotrophin induced angiogenesis in vivo. To investigate the pathological role of pleiotrophin we used neutralizing antibody to block its function in multiple in vivo models of ocular vascular diseases. In a mouse model of DR, intravitreal injection of pleiotrophin-neutralizing antibody alleviated diabetic retinal vascular leakage. In a mouse model of oxygen-induced retinopathy (OIR), which is a surrogate model of ROP and PDR, we demonstrated that intravitreal injection of anti-pleiotrophin antibody prevented OIR-induced pathological retinal neovascularization and aberrant vessel tufts. Finally, pleiotrophin-neutralizing antibody ameliorated laser-induced choroidal neovascularization, a mouse model of nAMD, suggesting that pleiotrophin is involved in choroidal vascular disease. These findings suggest that pleiotrophin plays an important role in the pathogenesis of DR with retinal vascular leakage, ROP with retinal neovascularization and nAMD with choroidal neovascularization. The results also support pleiotrophin as a promising target for anti-angiogenic therapy.

The roles of academia, rare diseases, and repurposing in the development of the most transformative drugs

Transformative drugs, defined as pharmaceuticals that are both innovative and have groundbreaking effects on patient care, are the "holy grail" of drug research and development. The sources of drug innovation are often debated, with pharmaceutical manufacturers arguing that high drug prices support innovative output from their sector. We studied the developmental histories of twenty-six drugs or drug classes approved by the Food and Drug Administration between 1984 and 2009 that were judged by expert physicians to be transformative (in two cases, the first drug in a transformative class was approved before 1984). Most of the twenty-six were first approved early in the study period; only four were approved in 2000 or later. Many were based on discoveries made by academic researchers who were supported by federal government funding. Others were jointly developed in both publicly funded and commercial institutions; the fewest number of drugs had originated solely within pharmaceutical industry research programs. Nine of the twenty-six (35 percent) were repurposed from products developed for other indications, and ten (38 percent) were developed for rare diseases before much broader applicability was found. The insights from these case studies provide an experience-based foundation for policies to encourage the development of future transformative drugs.

How does age-related macular degeneration affect real-world visual ability and quality of life? A systematic review

OBJECTIVES

To review systematically the evidence of age-related macular degeneration (AMD) affecting real-world visual ability and quality of life (QoL). To explore trends in specific topics within this body of the literature.

DESIGN

Systematic review.

METHODS

A systematic literature search was carried out using MEDLINE, EMBASE, CINAHL, PsycINFO, PsychARTICLES and Health and Psychosocial Instruments for articles published up to January 2015 for studies including people diagnosed with AMD, assessing real-world visual ability or QoL as an outcome. Two researchers screened studies for eligibility. Details of eligible studies including study design, characteristics of study population and outcomes measured were recorded in a data extraction table. All included studies underwent quality appraisal using the Mixed Methods Appraisal Tool 2011 Version (MMAT).

RESULTS

From 5284 studies, 123 were eligible for inclusion. A range of approaches were identified, including performance-based methods, quantitative and qualitative patient-reported outcome measures (PROMs). AMD negatively affects tasks including mobility, face recognition, perception of scenes, computer use, meal preparation, shopping, cleaning, watching TV, reading, driving and, in some cases, self-care. There is evidence for higher rates of depression among people with AMD than among community dwelling elderly. A number of adaptation strategies have been associated with AMD of varying duration. Much of the research fails to report the type of AMD studied (59% of included studies) or the duration of disease in participants (74%). Of those that do report type studied, the breakdown is as follows: wet AMD 20%, dry AMD 4% and both types 17%.

CONCLUSIONS

There are many publications highlighting the negative effects of AMD in various domains of life. Future research should focus on delivering some of this research knowledge into patient management and clinical trials and differentiating between the types of AMD.

Rethinking Nuclear Receptors as Potential Therapeutic Targets for Retinal Diseases

Collectively, retinal diseases, including age-related macular degeneration, retinitis pigmentosa, and diabetic retinopathy, result in severe vision impairment worldwide. The absence and/or limited availability of successful drug therapies for these blinding disorders necessitates further understanding their pathobiology and identifying new targetable signaling pathways. Nuclear receptors are transcription regulators of many key aspects of human physiology, as well as pathophysiology, with reported roles in development, aging, and disease. Some of the pathways regulated by nuclear receptors include, but are not limited to, angiogenesis, inflammation, and lipid metabolic dysregulation, mechanisms also important in the initiation and development of several retinal diseases. Herein, we present an overview of the biology of three diseases affecting the posterior eye, summarize a growing body of evidence that suggests direct or indirect involvement of nuclear receptors in disease progression, and discuss the therapeutic potential of targeting nuclear receptors for treatment.

Manipulating Angiogenesis by Targeting Endothelial Metabolism: Hitting the Engine Rather than the Drivers-A New Perspective?

Excessive angiogenesis (i.e., the formation of new blood vessels) contributes to different pathologies, among them cancer and ocular disorders. Conversely, dysfunction of endothelial cells (ECs) contributes to cardiovascular complications, as is the case in diabetes. Inhibition of pathologic angiogenesis in blinding eye disease and cancer by targeting growth factors such as vascular endothelial growth factor has become an accepted therapeutic strategy. However, recent studies also unveiled the emerging importance of EC metabolism in controlling angiogenesis. In this overview, we will discuss recent insights in the metabolic regulation of angiogenesis, focusing on the best-characterized metabolic pathways, and highlight deregulation of EC metabolism in cancer and diabetes. We will give an outlook on how targeting EC metabolism can be used for blocking pathologic angiogenesis and for normalizing EC dysfunction.

The regulatory role of hepatoma-derived growth factor as an angiogenic factor in the eye

PURPOSE

Hepatoma-derived growth factor (HDGF) is a mitogen that promotes endothelial proliferation and neuronal survival. Using a unique technology of ligandomics, we recently identified HDGF as a retinal endothelial binding protein. The purpose of this study is to examine the role of HDGF in regulating ocular vasculature and the expression of HDGF in the retina.

METHODS

HDGF expression in the retinal was analyzed with western blot and immunohistochemistry. Angiogenic activity was investigated in human retinal microvascular endothelial cells (HRMVECs) with in vitro endothelial proliferation, migration, and permeability assays. In vivo angiogenic activity was quantified with a corneal pocket assay. The Evans blue assay and western blot using anti-mouse albumin were performed to detect the capacity of HDGF to induce retinal vascular leakage.

RESULTS

Immunohistochemistry revealed that HDGF is expressed in the retina with a distinct pattern. HDGF was detected in retinal ganglion cells and the inner nuclear layer but not in the inner plexiform layer, suggesting that HDGF is expressed in the nucleus, but not in the cytoplasm, of retinal neurons. In contrast to family member HDGF-related protein 3 (HRP-3) that has no expression in photoreceptors, HDGF is also present in the outer nuclear layer and the inner and outer segments of photoreceptors. This suggests that HDGF is expressed in the nucleus as well as the cytoplasm of photoreceptors. In vitro functional assays showed that HDGF induced the proliferation, migration, and permeability of HRMVECs. Corneal pocket assay indicated that HDGF directly stimulated angiogenesis in vivo. Intravitreal injection of HDGF significantly induced retinal vascular leakage.

CONCLUSIONS

These results suggest that HDGF is an angiogenic factor that regulates retinal vasculature in physiologic and pathological conditions. Identification of HDGF by ligandomics and its independent characterization in this study also support the validity of this new technology for systematic identification of cellular ligands, including angiogenic factors.

Phosphatidylserine (PS) Is Exposed in Choroidal Neovascular Endothelium: PS-Targeting Antibodies Inhibit Choroidal Angiogenesis In Vivo and Ex Vivo

PURPOSE

Choroidal neovascularization (CNV) accounts for 90% of cases of severe vision loss in patients with advanced age-related macular degeneration. Identifying new therapeutic targets for CNV may lead to novel combination therapies to improve outcomes and reduce treatment burden. Our goal was to test whether phosphatidylserine (PS) becomes exposed in the outer membrane of choroidal neovascular endothelium, and whether this could provide a new therapeutic target for CNV.

METHODS

Choroidal neovascularization was induced in C57BL/6J mice using laser photocoagulation. Choroidal neovascularization lesions costained for exposed PS and for intercellular adhesion molecule 2 (or isolectin B4) were imaged in flat mounts and in cross sections. The laser CNV model and a choroidal sprouting assay were used to test the effect of PS-targeting antibodies on choroidal angiogenesis. Choroidal neovascularization lesion size was determined by intercellular adhesion molecule 2 (ICAM-2) staining of flat mounts.

RESULTS

We found that PS was exposed in CNV lesions and colocalized with vascular endothelial staining. Treatment with PS-targeting antibodies led to a 40% to 80% reduction in CNV lesion area when compared to treatment with a control antibody. The effect was the same as that seen using an equal dose of an anti-VEGF antibody. Results were confirmed using the choroid sprouting assay, an ex vivo model of choroidal angiogenesis.

CONCLUSIONS

We demonstrated that PS is exposed in choroidal neovascular endothelium. Furthermore, targeting this exposed PS with antibodies may be of therapeutic value in CNV.

Differential effects of bevacizumab, ranibizumab and aflibercept on cell viability, phagocytosis and mitochondrial bioenergetics of retinal pigment epithelial cell

PURPOSE

To evaluate the short- and long-term effects of most clinically used anti-vascular endothelial growth factor agents, including bevacizumab, ranibizumab or aflibercept, on cell viability, phagocytosis, mitochondrial bioenergetics and the oxidant acrolein-induced oxidative stress of human adult retinal pigment epithelial (ARPE)-19 cells.

METHODS

In cultured ARPE-19 cells, cell viability was measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, phagocytotic activity and intracellular reactive oxygen species (ROS) level were determined by flow cytometry, mitochondrial bioenergetics was assessed using a Seahorse XF24 Extracellular Flux Analyzer, and protein expression was measured by Western blotting.

RESULTS

Long-term exposure to all three agents had no effect on cell viability; but rescued the ARPE-19 cells from acrolein-induced decrease in cell viability. Bevacizumab, but not ranibizumab or aflibercept, suppressed the phagocytotic activity of ARPE-19 cells and exerted significantly less protection against acrolein-induced inhibition of phagocytosis. Both ranibizumab and aflibercept increased basal respiratory rate and maximal mitochondrial respiratory capacity after 1-hr exposure; but returned to baseline following 24- or 72-hr exposure. In contrast, both responses were reduced on short-term exposure, but augmented after long-term exposure to bevacizumab. Long-term pretreatment with all three agents reversed acrolein-induced impairment of mitochondrial bioenergetics, overproduction of ROS and phosphorylation of the mitogen-activated protein kinases in ARPE-19 cells.

CONCLUSION

Bevacizumab might affect mitochondrial bioenergetics differently from that by ranibizumab and aflibercept. Ranibizumab and aflibercept at their therapeutic dose protect against acrolein-induced oxidative cytotoxicity in human ARPE-19 cells via an increase in mitochondrial bioenergetics. An early protective action on mitochondrial bioenergetic capacity might be used to predict possible long-term antioxidative effects of the agents in the eye.

Intravitreally Injected Anti-VEGF Antibody Reduces Brown Fat in Neonatal Mice

Anti-vascular endothelial growth factor (VEGF) agents are the mainstay treatment for various angiogenesis-related retinal diseases. Currently, bevacizumab, a recombinant humanized anti-VEGF antibody, is trailed in retinopathy of prematurity, a vasoproliferative retinal disorder in premature infants. However, the risks of systemic complications after intravitreal injection of anti-VEGF antibody in infants are not well understood. In this study, we show that intravitreally injected anti-VEGF antibody is transported into the systemic circulation into the periphery where it reduces brown fat in neonatal C57BL/6 mice. A considerable amount of anti-VEGF antibody was detected in serum after intravitreal injection. Furthermore, in interscapular brown adipose tissue, we found lipid droplet accumulation, decreased VEGF levels, loss of vascular network, and decreased expression of mitochondria-related genes, Ppargc1a and Ucp1, all of which are characteristics of "whitening" of brown fat. With increasing age and body weight, brown fat restored its morphology and vascularity. Our results show that there is a transient, but significant impact of intravitreally administered anti-VEGF antibody on brown adipose tissue in neonatal mice. We suggest that more attention should be focused on the metabolic and developmental significance of brown adipose tissue in bevacizumab treated retinopathy of prematurity infants.

Nanoengineering of therapeutics for retinal vascular disease

Retinal vascular diseases, including diabetic retinopathy, neovascular age related macular degeneration, and retinal vein occlusion, are leading causes of blindness in the Western world. These diseases share several common disease mechanisms, including vascular endothelial growth factor (VEGF) signaling, hypoxia, and inflammation, which provide opportunities for common therapeutic strategies. Treatment of these diseases using laser therapy, anti-VEGF injections, and/or steroids has significantly improved clinical outcomes. However, these strategies do not address the underlying root causes of pathology, and may have deleterious side effects. Furthermore, many patients continue to progress toward legal blindness despite receiving regular therapy. Nanomedicine, the engineering of therapeutics at the 1-100 nm scale, is a promising approach for improving clinical management of retinal vascular diseases. Nanomedicine-based technologies have the potential to revolutionize the treatment of ophthalmology, through enabling sustained release of drugs over several months, reducing side effects due to specific targeting of dysfunctional cells, and interfacing with currently "undruggable" targets. We will discuss emerging nanomedicine-based applications for the treatment of complications associated with retinal vascular diseases, including angiogenesis and inflammation.

Nanoparticle-mediated expression of a Wnt pathway inhibitor ameliorates ocular neovascularization

OBJECTIVE

The deficiency of very low-density lipoprotein receptor resulted in Wnt signaling activation and neovascularization in the retina. The present study sought to determine whether the very low-density lipoprotein receptor extracellular domain (VLN) is responsible for the inhibition of Wnt signaling in ocular tissues.

APPROACH AND RESULTS

A plasmid expressing the soluble VLN was encapsulated with poly(lactide-co-glycolide acid) to form VLN nanoparticles (VLN-NP). Nanoparticles containing a plasmid expressing the low-density lipoprotein receptor extracellular domain nanoparticle were used as negative control. MTT, modified Boyden chamber, and Matrigel (™) assays were used to evaluate the inhibitory effect of VLN-NP on Wnt3a-stimulated endothelial cell proliferation, migration, and tube formation. Vldlr(-/-) mice, oxygen-induced retinopathy, and alkali burn-induced corneal neovascularization models were used to evaluate the effect of VLN-NP on ocular neovascularization. Wnt reporter mice (BAT-gal), Western blotting, and luciferase assay were used to evaluate Wnt pathway activity. Our results showed that VLN-NP specifically inhibited Wnt3a-induced endothelial cell proliferation, migration, and tube formation. Intravitreal injection of VLN-NP inhibited abnormal neovascularization in Vldlr(-/-), oxygen-induced retinopathy, and alkali burn-induced corneal neovascularization models, compared with low-density lipoprotein receptor extracellular domain nanoparticle. VLN-NP significantly inhibited the phosphorylation of low-density lipoprotein receptor-related protein 6, the accumulation of β-catenin, and the expression of vascular endothelial growth factor in vivo and in vitro.

CONCLUSIONS

Taken together, these results suggest that the soluble VLN is a negative regulator of the Wnt pathway and has antiangiogenic activities. Nanoparticle-mediated expression of VLN may thus represent a novel therapeutic approach to treat pathological ocular angiogenesis and potentially other vascular diseases affected by Wnt signaling.

Evaluation of intracameral injection of ranibizumab and bevacizumab on the corneal endothelium by scanning electron microscopy

PURPOSE

To evaluate the effects of intracameral injection of ranibizumab and bevacizumab on the corneal endothelium by scanning electron microscopy (SEM).

METHODS

Twenty-eight female rabbits were randomly divided into four equal groups. Rabbits in groups 1 and 2 underwent intracameral injection of 1 mg/0.1 mL and 0.5 mg/0.05 mL ranibizumab, respectively; group 3 was injected with 1.25 mg/0.05 mL bevacizumab. All three groups were injected with a balanced salt solution (BSS) into the anterior chamber of the left (fellow) eye. None of the rabbits in group 4 underwent an injection. Corneal thickness and intraocular pressure were measured before the injections, on the first day, and in the first month after injection. The rabbits were sacrificed and corneal tissues were excised in the first month after injection. Specular microscopy was used for the corneal endothelial cell count. Endothelial cell density was assessed and comparisons drawn between the groups and the control. Micrographs were recorded for SEM examination. The structure of the corneal endothelial cells, the junctional area of the cell membrane, the distribution of microvillus, and the cell morphology of the eyes that underwent intracameral injection of vascular endothelial growth factor (VEGF), BSS, and the control group were compared.

RESULTS

Corneal thickness and intraocular pressure were not significantly different between the groups that underwent anti-VEGF or BSS injection and the control group on the first day and in the first month of injection. The corneal endothelial cell count was significantly diminished in all three groups; predominantly in group 1 and 2 (P<0.05). The SEM examination revealed normal corneal endothelial histology in group 3 and the control group. Eyes in group 1 exhibited indistinctness of corneal endothelial cell borders, microvillus loss in the luminal surface, excessive blebbing, and disintegration of intercellular junctions. In group 2, the cell structure of the corneal endothelium and intercellular junctions were normal. However, a relative reduction was observed in the microvillus density of endothelial cells. Although eyes in group 3 were morphologically similar to fellow eyes and the control group, disarrangement in endothelial cell borders was evident.

CONCLUSION

The SEM examination pointed out deterioration in endothelial cell morphology after intracameral injection of 1 and 0.5 mg ranizumab. However, the effects of intracameral bevacizumab injection on corneal endothelial cells were similar to those found in fellow eyes and the control group. Further large-scale studies that examine the cellular changes by transmission electron microscopy are required to support the results of the present study that evaluates the structural changes in endothelial cells by SEM.

Imatinib inhibits VEGF-independent angiogenesis by targeting neuropilin 1-dependent ABL1 activation in endothelial cells

Neuropilin 1 regulates angiogenesis in a VEGF-independent manner via association with ABL1, suggesting that Imatinib represents a novel opportunity for anti-angiogenic therapy.

To enable new blood vessel growth, endothelial cells (ECs) express neuropilin 1 (NRP1), and NRP1 associates with the receptor tyrosine kinase VEGFR2 after binding the vascular endothelial growth factor A (VEGF) to enhance arteriogenesis. We report that NRP1 contributes to angiogenesis through a novel mechanism. In human and mouse ECs, the integrin ligand fibronectin (FN) stimulated actin remodeling and phosphorylation of the focal adhesion component paxillin (PXN) in a VEGF/VEGFR2-independent but NRP1-dependent manner. NRP1 formed a complex with ABL1 that was responsible for FN-dependent PXN activation and actin remodeling. This complex promoted EC motility in vitro and during angiogenesis on FN substrates in vivo. Accordingly, both physiological and pathological angiogenesis in the retina were inhibited by treatment with Imatinib, a small molecule inhibitor of ABL1 which is widely used to prevent the proliferation of tumor cells that express BCR-ABL fusion proteins. The finding that NRP1 regulates angiogenesis in a VEGF- and VEGFR2-independent fashion via ABL1 suggests that ABL1 inhibition provides a novel opportunity for anti-angiogenic therapy to complement VEGF or VEGFR2 blockade in eye disease or solid tumor growth.

Neuronal cell death in the inner retina and the influence of vascular endothelial growth factor inhibition in a diabetic rat model

To inhibit vascular changes in diabetic retinopathy, inhibiting vascular endothelial growth factor (VEGF) has become a mainstay of the treatment of diabetic retinopathy. However, its effects on neuronal cells remain to be elucidated. We aimed to evaluate the effect of VEGF inhibition on neuronal cells in a streptozotocin-induced diabetic rat retina. VEGF inhibition was performed by intravitreal VEGF-A antibody injection. After anti-VEGF treatment, apoptosis in retinal ganglion cells (RGCs) increased, and novel apoptosis in amacrine and bipolar cells of the inner nuclear layer was observed by TUNEL staining. Phosphorylated Akt expression was significantly higher in RGCs but was decreased in neuronal cells of the inner nuclear layer after anti-VEGF treatment by Western blot analysis and immunohistochemical staining. These results demonstrate that VEGF inhibition significantly increased RGC apoptosis and neuronal cell apoptosis in the inner nuclear layer of a diabetic retina, which seems to consist primarily of amacrine and bipolar cells. The phosphorylated Akt pathway, which plays a neuroprotective role via VEGF, was significantly affected by VEGF inhibition in the inner nuclear layer, suggesting that neurotrophic factor deprivation is the main mechanism for neuronal cell death after inhibiting VEGF. The results of this study show that inhibiting VEGF may have detrimental effects on the apoptosis of neuronal cells in the inner layers of the diabetic retina.

Intravitreal vascular endothelial growth factor

PURPOSE

To evaluate whether a specific pre-analytical stabilization regimen is needed for naïve vitreous taps to detect true values of intrinsic VEGF levels.

METHODS

Fourteen consecutive patients with different vitreomacular pathologies without blood-retina-barrier breakdown were scheduled for standard 23-gauge three-port pars plana vitrectomy, and naïve vitreous taps were sampled at the beginning of each procedure. The extracted vitreous specimen was split; one half was immediately stored in a -20 °C freezer (unstabilized samples) and the other half was instantly stabilized with albumin (2.5 % final conc.), followed by arginine stabilization (1.25 M final conc.) and consecutively stored in a -20 °C freezer (stabilized samples).

RESULTS

Intravitreal VEGF was detected in all 14 analyzed samples (100 %). VEGF levels were shown to be 46.5 pg/ml  ±  62.3 pg/ml (MV ± SD; range: 5.99-232.3 pg/ml) in unstabilized, and 120.4 pg/ml ± 94.4 pg/ml (range: 42.9 pg/ml-289.6 pg/ml) in stabilized vitreous samples. Intravitreal VEGF levels in stabilized vitreous samples were on average 2.6-fold, and thus significantly higher than in unstabilized taps of same eyes (p = 0.001, Wilcoxon test). VEGF levels in stabilized vitreous samples can be up to 8.5 times higher than in corresponding unstabilized vitreous taps of same eyes (bootstrap analysis). Intravitreal VEGF levels in unstabilized samples correlate with those in stabilized vitreous taps (r = 0.594; p = 0.025; Pearson).

CONCLUSIONS

An adequate pre-analytic stabilization regimen is needed to evaluate the most accurate intravitreal VEGF levels. This in turn will result in a better understanding of the physiological as well as pathological role of VEGF within the eye. Furthermore, knowing the true value of intravitreal VEGF levels will help to calculate the dosage of intravitrealy applied anti-VEGF drugs.

The role of vascular endothelial growth factor and vascular stability in diseases of the ear

OBJECTIVES/HYPOTHESIS

Vascular endothelial growth factor (VEGF) is a critical mediator of vascular permeability and angiogenesis and likely plays an important role in cochlear function and hearing. This review highlights the role of VEGF in hearing loss associated with vestibular schwannomas, otitis media with effusion, and sensorineural hearing loss.

STUDY DESIGN

PubMed literature review.

METHODS

A review of the literature was conducted to determine the role of VEGF in diseases affecting hearing.

RESULTS

Therapeutic efficacy has been demonstrated for the anti-VEGF agent bevacizumab in vestibular schwannomas, with tumor size reduction and hearing improvement in patients with neurofibromatosis type 2. The loss of functional Merlin, the protein product of the nf2 gene, results in a decrease in expression of the anti-angiogenic protein SEMA3F through a Rac-1-dependent mechanism, allowing VEGF to promote angiogenesis. Bevacizumab may therefore restore the angiogenic balance through inhibiting the relative increase in VEGF. Many of the clinical findings of otitis media with effusion can be reproduced by delivery of recombinant VEGF through transtympanic injection or submucosal osmotic pump. VEGF receptor inhibitors have been demonstrated to improve hearing in an animal model of otitis media with effusion. VEGF affects both the inner ear damage and repair processes in sensorineural hearing loss.

CONCLUSIONS

VEGF has an important role in vestibular schwannomas, otitis media with effusion, and sensorineural hearing loss.

Loss of caveolin-1 causes blood-retinal barrier breakdown, venous enlargement, and mural cell alteration

Blood-retinal barrier (BRB) breakdown and related vascular changes are implicated in several ocular diseases. The molecules and mechanisms regulating BRB integrity and pathophysiology are not fully elucidated. Caveolin-1 (Cav-1) ablation results in loss of caveolae and microvascular pathologies, but the role of Cav-1 in the retina is largely unknown. We examined BRB integrity and vasculature in Cav-1 knockout mice and found a significant increase in BRB permeability, compared with wild-type controls, with branch veins being frequent sites of breakdown. Vascular hyperpermeability occurred without apparent alteration in junctional proteins. Such hyperpermeability was not rescued by inhibiting eNOS activity. Veins of Cav-1 knockout retinas exhibited additional pathological features, including i) eNOS-independent enlargement, ii) altered expression of mural cell markers (eg, down-regulation of NG2 and up-regulation of αSMA), and iii) dramatic alterations in mural cell phenotype near the optic nerve head. We observed a significant NO-dependent increase in retinal artery diameter in Cav-1 knockout mice, suggesting that Cav-1 plays a role in autoregulation of resistance vessels in the retina. These findings implicate Cav-1 in maintaining BRB integrity in retinal vasculature and suggest a previously undefined role in the retinal venous system and associated mural cells. Our results are relevant to clinically significant retinal disorders with vascular pathologies, including diabetic retinopathy, uveoretinitis, and primary open-angle glaucoma.

Identification of a stable molecular signature in mammary tumor endothelial cells that persists in vitro

Long-term, in vitro propagation of tumor-specific endothelial cells (TEC) allows for functional studies and genome-wide expression profiling of clonally derived, well-characterized subpopulations. Using a genetically engineered mouse model of mammary adenocarcinoma, we have optimized an isolation procedure and defined growth conditions for long-term propagation of mammary TEC. The isolated TEC maintain their endothelial specification and phenotype in culture. Furthermore, gene expression profiling of multiple TEC subpopulations revealed striking, persistent overexpression of several candidate genes including Irx2 and Zfp503 (transcription factors), Alcam and Cd133 (cell surface markers), Ccl4 and neurotensin (Nts) (angiocrine factors), and Gpr182 and Cnr2 (G protein-coupled receptors). Taken together, we have developed an effective method for isolating and culture-expanding mammary TEC, and uncovered several new TEC-selective genes whose overexpression persists even after long-term in vitro culture. These results suggest that the tumor microenvironment may induce changes in vascular endothelium in vivo that are stably transmittable in vitro.

Topical chemotherapy for ocular surface squamous neoplasia

PURPOSE OF REVIEW

Ocular surface squamous neoplasia (OSSN) is an umbrella term for a spectrum of epithelial dysplasias of the cornea, conjunctiva, and limbus. Treatment for OSSN has historically been surgery, but nonsurgical interventions have been increasingly adopted. Advantages of medical treatments include the ability to treat the entire ocular surface and prevention of surgical complications.

RECENT FINDINGS

The primary medical treatments for OSSN include mitomycin C, 5-fluorouracil, and interferon α2b. Mitomycin C has been shown in studies to be highly effective but has short-term and long-term side-effects that may be intolerable. 5-Fluorouracil and interferon α2b have been found to be similar in efficacy to mitomycin, with interferon being extremely well tolerated in the majority of patients. Most recently, other chemotherapeutic agents have been tried for OSSN including antivascular endothelial growth factor agents and vitamin A. The data regarding these latter treatment strategies are still limited.

SUMMARY

An understanding of the recent literature, with respect to the efficacy, advantages, and disadvantages of the various therapies for OSSN will allow us to tailor treatment to each patient.

Advances in our understanding of diabetic retinopathy

Diabetic retinopathy remains the most common complication of diabetes mellitus and is a leading cause of visual loss in industrialized nations. The clinicopathology of the diabetic retina has been extensively studied, although the precise pathogenesis and cellular and molecular defects that lead to retinal vascular, neural and glial cell dysfunction remain somewhat elusive. This lack of understanding has seriously limited the therapeutic options available for the ophthalmologist and there is a need to identify the definitive pathways that initiate retinal cell damage and drive progression to overt retinopathy. The present review begins by outlining the natural history of diabetic retinopathy, the clinical features and risk factors. Reviewing the histopathological data from clinical specimens and animal models, the recent paradigm that neuroretinal dysfunction may play an important role in the early development of the disease is discussed. The review then focuses on the molecular pathogenesis of diabetic retinopathy with perspective provided on new advances that have furthered our understanding of the key mechanisms underlying early changes in the diabetic retina. Studies have also emerged in the past year suggesting that defective repair of injured retinal vessels by endothelial progenitor cells may contribute to the pathogenesis of diabetic retinopathy. We assess these findings and discuss how they could eventually lead to new therapeutic options for diabetic retinopathy.