Age-related macular degeneration: epidemiology and optimal treatment

Supramolecular Senolytics via Intracellular Oligomerization of Peptides in Response to Elevated Reactive Oxygen Species Levels in Aging Cells

Senolytics, which eliminate senescent cells from tissues, represent an emerging therapeutic strategy for various age-related diseases. Most senolytics target antiapoptotic proteins, which are overexpressed in senescent cells, limiting specificity and inducing severe side effects. To overcome these limitations, we constructed self-assembling senolytics targeting senescent cells with an intracellular oligomerization system. Intracellular aryl-dithiol-containing peptide oligomerization occurred only inside the mitochondria of senescent cells due to selective localization of the peptides by RGD-mediated cellular uptake into integrin αvβ3-overexpressed senescent cells and elevated levels of reactive oxygen species, which can be used as a chemical fuel for disulfide formation. This oligomerization results in an artificial protein-like nanoassembly with a stable α-helix secondary structure, which can disrupt the mitochondrial membrane via multivalent interactions because the mitochondrial membrane of senescent cells has weaker integrity than that of normal cells. These three specificities (integrin αvβ3, high ROS, and weak mitochondrial membrane integrity) of senescent cells work in combination; therefore, this intramitochondrial oligomerization system can selectively induce apoptosis of senescent cells without side effects on normal cells. Significant reductions in key senescence markers and amelioration of retinal degeneration were observed after elimination of the senescent retinal pigment epithelium by this peptide senolytic in an age-related macular degeneration mouse model and in aged mice, and this effect was accompanied by improved visual function. This system provides a strategy for the treatment of age-related diseases using supramolecular senolytics.

Inhibition of prolyl oligopeptidase: A promising pathway to prevent the progression of age-related macular degeneration

Dry age-related macular degeneration (AMD) is a currently untreatable vision threatening disease. Impaired proteasomal clearance and autophagy in the retinal pigment epithelium (RPE) and subsequent photoreceptor damage are connected with dry AMD, but detailed pathophysiology is still unclear. In this paper, we discover inhibition of cytosolic protease, prolyl oligopeptidase (PREP), as a potential pathway to treat dry AMD. We showed that PREP inhibitor exposure induced autophagy in the RPE cells, shown by increased LC3-II levels and decreased p62 levels. PREP inhibitor treatment increased total levels of autophagic vacuoles in the RPE cells. Global proteomics was used to examine the phenotype of a commonly used cell model displaying AMD characteristics, oxidative stress and altered protein metabolism, in vitro. These RPE cells displayed induced protein aggregation and clear alterations in macromolecule metabolism, confirming the relevance of the cell model. Differences in intracellular target engagement of PREP inhibitors were observed with cellular thermal shift assay (CETSA). These differences were explained by intracellular drug exposure (the unbound cellular partition coefficient, Kp_uu). Importantly, our data is in line with previous observations regarding the discrepancy between PREP's cleaving activity and outcomes in autophagy. This highlights the need to further explore PREP's role in autophagy so that more effective compounds can be designed to battle diseases in which autophagy induction is needed. The present work is the first report investigating the PREP pathway in the RPE and we predict that the PREP inhibitors can be further optimized for treatment of dry AMD.

Targeting senescent retinal pigment epithelial cells facilitates retinal regeneration in mouse models of age-related macular degeneration

Although age-related macular degeneration (AMD) is a multifactorial disorder with angiogenic, immune, and inflammatory components, the most common clinical treatment strategies are antiangiogenic therapies. However, these strategies are only applicable to neovascular AMD, which accounts for less than 20% of all AMD cases, and there are no FDA-approved drugs for the treatment of dry AMD, which accounts for ~ 80% of AMD cases. Here, we report that the elimination of senescent cells is a potential novel therapeutic approach for the treatment of all types of AMD. We identified senescent retinal pigment epithelium (RPE) cells in animal models of AMD and determined their contributions to retinal degeneration. We further confirmed that the clearance of senescent RPE cells with the MDM2-p53 inhibitor Nutlin-3a ameliorated retinal degeneration. These findings provide new insights into the use of senescent cells as a therapeutic target for the treatment of AMD.

Xentry-Gap19 inhibits Connexin43 hemichannel opening especially during hypoxic injury

Hypoxic injury results in cell death, tissue damage and activation of inflammatory pathways. This is mediated by pathological Connexin43 (Cx43) hemichannel (HC) opening resulting in osmotic and ionic imbalances as well as cytokine production perpetuating the inflammatory environment. Gap19 is an intracellularly acting Cx43 mimetic peptide that blocks HC opening and thus promotes cell survival. However, native Gap19, which must enter the cell in order to function, exhibits low cell permeability. In this study, Gap19 was conjugated to the cell-penetrating peptide, Xentry, to investigate if cellular uptake could be improved while maintaining peptide function. Cellular uptake of Xentry-Gap19 (XG19) was much greater than that of native Gap19 even under normal cell culture conditions. Peptide function was maintained post uptake as shown by reduced ethidium homodimer influx and ATP release due to Cx43 HC block. While XG19 blocked pathologic HC opening though, normal gap junction communication required for cell repair and survival mechanisms was not affected as shown in a dye scrape-load assay. Under hypoxic conditions, increased expression of Syndecan-4, a plasma membrane proteoglycan targeted by Xentry, enabled even greater XG19 uptake leading to higher inhibition of ATP release and greater cell survival. This suggests that XG19, which is targeted specifically to hypoxic cells, can efficiently and safely block Cx43 HC and could therefore be a novel treatment for hypoxic and inflammatory diseases.

The role of future treatments in the management of neovascular age-related macular degeneration in Europe

Anti-vascular endothelial growth factor (VEGF) agents have transformed the management of patients with neovascular age-related macular degeneration (nAMD) over the past two decades. However, as more long-term real-world data become available, it is clear that treatment outcomes are inferior to those reported in large, controlled clinical trials. This is largely driven by undertreatment, that is, not maintaining a consistent injection frequency to achieve sustained VEGF suppression, whether due to patient non-compliance, an important injection burden, or non/incomplete anatomical response. Newer therapeutic advances under evaluation hold promise in achieving more, for less. We review the latest drugs currently in or having successfully finished phase III clinical trials, and determine their potential place in the management of patients with nAMD in Europe.

Biotechnology and Biomaterial-Based Therapeutic Strategies for Age-Related Macular Degeneration. Part I: Biomaterials-Based Drug Delivery Devices

Age-related Macular Degeneration (AMD) is an up-to-date untreatable chronic neurodegenerative eye disease of multifactorial origin, and the main causes of blindness in over 65 years old people. It is characterized by a slow progression and the presence of a multitude of factors, highlighting those related to diet, genetic heritage and environmental conditions, present throughout each of the stages of the illness. Current therapeutic approaches, mainly consisting of intraocular drug delivery, are only used for symptoms relief and/or to decelerate the progression of the disease. Furthermore, they are overly simplistic and ignore the complexity of the disease and the enormous differences in the symptomatology between patients. Due to the wide impact of the AMD and the up-to-date absence of clinical solutions, the development of biomaterials-based approaches for a personalized and controlled delivery of therapeutic drugs and biomolecules represents the main challenge for the defeat of this neurodegenerative disease. Here we present a critical review of the available and under development AMD therapeutic approaches, from a biomaterials and biotechnological point of view. We highlight benefits and limitations and we forecast forthcoming alternatives based on novel biomaterials and biotechnology methods. In the first part we expose the physiological and clinical aspects of the disease, focusing on the multiple factors that give origin to the disorder and highlighting the contribution of these factors to the triggering of each step of the disease. Then we analyze available and under development biomaterials-based drug-delivery devices (DDD), taking into account the anatomical and functional characteristics of the healthy and ill retinal tissue.

First steps for the development of silk fibroin-based 3D biohybrid retina for age-related macular degeneration (AMD)

Age-related macular degeneration is an incurable chronic neurodegenerative disease, causing progressive loss of the central vision and even blindness. Up-to-date therapeutic approaches can only slow down he progression of the disease.

OBJECTIVE

Feasibility study for a multilayered, silk fibroin-based, 3D biohybrid retina.

APPROACH

Fabrication of silk fibroin-based biofilms; culture of different types of cells: retinal pigment epithelium, retinal neurons, Müller and mesenchymal stem cells ; creation of a layered structure glued with silk fibroin hydrogel.

MAIN RESULTS

In vitro evidence for the feasibility of layered 3D biohybrid retinas; primary culture neurons grow and develop neurites on silk fibroin biofilms, either alone or in presence of other cells cultivated on the same biomaterial; cell organization and cellular phenotypes are maintained in vitro for the seven days of the experiment.

SIGNIFICANCE

3D biohybrid retina can be built using silk silkworm fibroin films and hydrogels to be used in cell replacement therapy for AMD and similar retinal neurodegenerative diseases.

Highly Differentiated Human Fetal RPE Cultures Are Resistant to the Accumulation and Toxicity of Lipofuscin-Like Material

Purpose

The accumulation of undigestible autofluorescent material (UAM), termed lipofuscin in vivo, is a hallmark of aged RPE. Lipofuscin derives, in part, from the incomplete degradation of phagocytized photoreceptor outer segments (OS). Whether this accumulated waste is toxic is unclear. We therefore investigated the effects of UAM in highly differentiated human fetal RPE (hfRPE) cultures.

Methods

Unmodified and photo-oxidized OS were fed daily to confluent cultures of ARPE-19 RPE or hfRPE. The emission spectrum, composition, and morphology of resulting UAM were measured and compared to in vivo lipofuscin. Effects of UAM on multiple RPE phenotypes were assessed.

Results

Compared to ARPE-19, hfRPE were markedly less susceptible to UAM buildup. Accumulated UAM in hfRPE initially resembled the morphology of lipofuscin from AMD eyes, but compacted and shifted spectrum over time to resemble lipofuscin from healthy aged human RPE. UAM accumulation mildly reduced transepithelial electrical resistance, ketogenesis, certain RPE differentiation markers, and phagocytosis efficiency, while inducing senescence and rare, focal pockets of epithelial-mesenchymal transition. However, it had no effects on mitochondrial oxygen consumption rate, certain other RPE differentiation markers, secretion of drusen components or polarity markers, nor cell death.

Conclusions

hfRPE demonstrates a remarkable resistance to UAM accumulation, suggesting mechanisms for efficient OS processing that may be lost in other RPE culture models. Furthermore, while UAM alters hfRPE phenotype, the effects are modest, consistent with conflicting reports in the literature on the toxicity of lipofuscin. Our results suggest that healthy RPE may adequately adapt to and tolerate lipofuscin accumulation.

Evaluation of retinal function improvement in neovascular age-related macular degeneration after intravitreal aflibercept injections with the use of the assessment of retinal sensitivity: The use of the assessment of retinal sensitivity in anti-VEGF treatment - a STROBE-compliant observational study

This study compares 2 methods of macular function evaluation: the microperimetric examination (mean central retinal sensitivity and fixation stability) and the distance best-corrected visual acuity (BCVA) examination, which is the most frequently used method of assessing macular function in patients with newly diagnosed wet age-related macular degeneration (AMD) who have been treated with anti-vascular endothelial growth factor (VEGF) drug (aflibercept).Prospective analysis was conducted on 44 eyes of 44 patients treated with intravitreal injection of anti-VEGF (aflibercept) because of newly diagnosed neovascular AMD. According to the research protocol, all patients had a 6-month follow-up. The response to treatment was monitored functionallybyMP-1 microperimetry, fixation, and distance BCVA assessment after injection. Improvement of retinal sensitivity and BCVA was found under aflibercept treatment. There was statistically significant improvement in retinal sensitivity in the MP-1 study 3 and 6 months from the beginning of anti-VEGF therapy. Moreover, a significant improvement in retinal sensitivity between 3 and 6 months of observation was demonstrated. At the same time, up to 3 months from the beginning of treatment, BCVA improved significantly compared to the baseline value. In the 6th month of the study BCVA remained stable without further significant improvement.Microperimetric examination with medium sensitivity and fixation stability assessment is a very valuable test determining the retinal function. It is clear that examining the macular morphology itself in modern diagnostics is not enough to assess retinal function. Microperimetry technique is a valuable tool for functional long-term evaluation of retinal function (also for a period of more than 3 months).

Diabetic retinopathy and age-related macular degeneration: a survey of pharmacoutilization and cost in Calabria, Italy

The aged population is constantly growing, thus fostering an increase in age-dependent diseases. Among these, diabetic retinopathy (DR) along with age-related macular degeneration entails progressive vision loss. Since such conditions are associated with the proliferation of novel vessels, their pharmacotherapeutic management consists of the intravitreal injection of anti-vascular endothelial growth factor drugs, able to hinder the driving of vascular proliferation prompted by vascular endothelial growth factor. The humanized anti-vascular endothelial growth factor monoclonal antibody ranibizumab provided evidence for efficacy in several trials, hence earning approval by the US Food and Drug Administration for therapeutic use in all the stages of DR. Due to the lack of epidemiologic and pharmacoeconomic evaluation in the local Calabria Region context, the present retrospective observational study focused on prevalence of DR and age-related macular degeneration, treatment and cost of therapy with ranibizumab in 870 patients arriving to clinical observation at the "Mater Domini" University Hospital in Calabria, Italy from January 2014 to June 2017. Data were extracted from the database of ophthalmology ward and subjected to statistical analysis. The results suggest that the most frequent retinal diseases are age-related macular degeneration and DR and that the use of ranibizumab has been decreasing over the 4-year study period together with the associated cost per patient which was similar for both disorders. Therefore, appropriateness of treatment with drugs other than ranibizumab needs to be assessed in this setting and deep monitoring of pharmacologic treatment for retinal diseases is necessary to prevent or delay visual acuity decrease and complete vision loss. Study procedures were performed in accordance with the "Mater Domini" University Hospital ethical standards of the responsible committee on human experimentation.

Confocal Shear Wave Acoustic Radiation Force Optical Coherence Elastography for Imaging and Quantification of the In Vivo Posterior Eye

Retinal diseases, such as age-related macular degeneration (AMD), are the leading cause of blindness in the elderly population. Since no known cures are currently present, it is crucial to diagnose the condition in its early stages so that disease progression is monitored. Recent advances show that the mechanical elasticity of the posterior eye changes with the onset of AMD. In this work, we present a quantitative method of mapping the mechanical elasticity of the posterior eye using confocal shear wave acoustic radiation force optical coherence elastography (SW-ARF-OCE). This technique has been developed and validated with both an ex-vivo porcine tissue model and a customized in-vivo rabbit model, which both showed the quantified elasticity variations between different layers. This study verifies the feasibility of using this technology for the quantification and diagnosis of retinal diseases from the in-vivo posterior eye.

Extended HLA-G haplotypes in patients with age-related macular degeneration

The study aims to determine if genetic polymorphisms in the human leukocyte antigen (HLA)-G gene are associated with age-related macular degeneration (AMD). HLA-G is important for immunological tolerance, and it is also known to have angiogenic effects. Polymorphisms in the 5'-upstream regulatory region (URR) and 3'-untranslated region (UTR) of HLA-G have been associated with a number of diseases, especially with respect to a 14 bp insertion/deletion (ins/del) polymorphism in the 3'UTR. Full gene sequencing was performed on a cohort of 146 AMD patients and 63 healthy controls aged 60 years or older and HLA-G haplotypes were determined. Analyses were performed on a publicly available gene expression dataset from the NCBI GEO database (accession number GSE29801) from which expression data for HLA-G, -C and -A were extracted. Analysis of the GEO dataset showed that both HLA-G and -C was expressed in the back of the eye and that expression was upregulated in the macular area of AMD. No differences were observed between patients and controls when analysing the distribution of haplotypes in the HLA-G promoter, coding region, 3'UTR or the 14 bp ins/del polymorphism of the 3'UTR. The increased expression of HLA-G in the macula of AMD patients indicates a role of HLA-G in the micro environment as part of the AMD pathogenesis. This is supported by the expression of HLA-C, which has previously been shown to play a role in AMD. The HLA-G haplotype distribution did not display any differences between AMD patients and controls. This article is protected by copyright. All rights reserved.

Vitreomacular Adhesion and the Risk of Neovascular Age-Related Macular Degeneration

PURPOSE

To assess the prevalence of vitreomacular adhesion (VMA) in consecutive naïve eyes diagnosed with exudative age-related macular degeneration (AMD) in comparison with eyes with nonexudative AMD and age-matched controls, and to evaluate prospectively the incidence of vitreomacular interface changes over time and their influence on choroidal neovascularization (CNV) development.

DESIGN

Retrospective cross-sectional analysis and longitudinal cohort study conducted at Sacrocuore Hospital, Negrar, Verona, Italy.

PARTICIPANTS

A total of 1067 eyes examined at Sacrocuore Hospital between August 2008 and June 2015 met the inclusion criteria and were evaluated in this study.

METHODS

Eyes were classified into 3 groups: 403 eyes of 364 patients (mean [standard deviation; SD] age 77.8 [8.0] years) affected by exudative AMD; 350 eyes of 298 subjects (mean [SD] age 78.1 [8.2] years) with nonexudative AMD; and 314 eyes of 214 subjects (mean [SD] age 74.2 [8.2] years) with no signs of AMD enrolled as the control group. The vitreomacular interface status was evaluated by spectral-domain optical coherence tomography (OCT) and was graded according to the OCT-based International Classification System developed by the International Vitreomacular Traction Study Group by 2 independent masked observers.

RESULTS

VMA was present in 101 (25.1%) eyes with exudative AMD, 84 (24.0%) eyes with nonexudative AMD, and 84 (26.8%) eyes with no signs of AMD (no statistical difference was found; P = 0.3384). Spontaneous release of VMA (RVMA) was found in 15 (15.3%) eyes with exudative AMD, 21 (28.0%) eyes with nonexudative AMD, and 10 (24.4%) eyes with no signs of AMD over a mean follow-up of 25.5, 25.9, and 24.1 months, respectively. The incidence of RVMA in exudative AMD eyes was significantly lower compared with nonexudative (P = 0.0207) and lower, but not statistically significant, with respect to eyes with no signs of AMD (P = 0.1013). In eyes with nonexudative AMD, de novo development of CNV occurred in 91 eyes (30.6%). There was no significant difference regarding the rate of CNV development in the presence or absence of VMA (P = 0.0966).

CONCLUSIONS

The present study found no significant difference in the prevalence of VMA in eyes affected by AMD compared with age-matched controls and no difference in the rate of de novo CNV development in eyes with or without VMA. Conversely, a lower incidence of RVMA over time was found in eyes affected by exudative AMD. The results of this study suggest that VMA might be a consequence rather than a causative factor in the development of CNV.

Association between Vascular Endothelial Growth Factor Polymorphisms and Age-Related Macular Degeneration: An Updated Meta-Analysis

Age-related macular degeneration (AMD) is the most common cause of blindness in elderly people worldwide and the major degenerative disease of the retina that leads to progressive impairment of central vision. Several polymorphisms in different genes have been proposed as factors that increase the disease susceptibility. The aim of the present study is to carry out a systematic review and an updated meta-analysis in order to summarize the current published studies and to evaluate the associations between four common vascular endothelial growth factor (VEGF) polymorphisms (rs833061, rs1413711, rs3025039, and rs2010963) and AMD risk, also stratifying for AMD subtypes and ethnicity. A systematic literature search in the Medline database, using PubMed, was carried out for epidemiological studies, published before June 2016. Associations of VEGF polymorphisms with AMD were estimated by calculating pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) based on different models. Twelve articles were included in the analysis. The present meta-analysis constitutes a useful guide for readers to study AMD and adds new evidence to the growing literature on the role of VEGF polymorphisms in the risk of AMD. Significant associations with AMD risk were showed for rs833061, rs1413711, and rs3025039 polymorphisms but not for rs2010963.

Novel risk index for the identification of age-related macular degeneration using radon transform and DWT features

Age-related Macular Degeneration (AMD) affects the central vision of aged people. It can be diagnosed due to the presence of drusen, Geographic Atrophy (GA) and Choroidal Neovascularization (CNV) in the fundus images. It is labor intensive and time-consuming for the ophthalmologists to screen these images. An automated digital fundus photography based screening system can overcome these drawbacks. Such a safe, non-contact and cost-effective platform can be used as a screening system for dry AMD. In this paper, we are proposing a novel algorithm using Radon Transform (RT), Discrete Wavelet Transform (DWT) coupled with Locality Sensitive Discriminant Analysis (LSDA) for automated diagnosis of AMD. First the image is subjected to RT followed by DWT. The extracted features are subjected to dimension reduction using LSDA and ranked using t-test. The performance of various supervised classifiers namely Decision Tree (DT), Support Vector Machine (SVM), Probabilistic Neural Network (PNN) and k-Nearest Neighbor (k-NN) are compared to automatically discriminate to normal and AMD classes using ranked LSDA components. The proposed approach is evaluated using private and public datasets such as ARIA and STARE. The highest classification accuracy of 99.49%, 96.89% and 100% are reported for private, ARIA and STARE datasets. Also, AMD index is devised using two LSDA components to distinguish two classes accurately. Hence, this proposed system can be extended for mass AMD screening.

Advances in pharmacotherapy for wet age-related macular degeneration

INTRODUCTION

In developed countries, neovascular age-related macular degeneration (AMD) is the leading cause of irreversible central blindness. Although AMD pathogenesis is complex and still not fully understood, many involved mechanisms are already partially known and could be promising targets for future therapies. Currently, anti-VEGF drugs are the standard care of this condition.

AREAS COVERED

This review summarizes both the current available and the emerging pharmacological therapies for the management of neovascular AMD. At first, we briefly focused on anti-VEGF compounds that are commonly used. Then, we reviewed the mechanisms of action and potential advantages of new candidate drugs that are being evaluated in clinical trials.

EXPERT OPINION

Although anti-VEGF drugs have shown mild-term good efficacy and safety profile in the treatment of neovascular AMD, they are far away from being a perfect therapy. Pharmacological research should focus on finding new molecular targets in the AMD pathogenetical pathway and on developing longer lasting agents or new drug delivery systems. Besides the development of new drugs, a better characterization of patients is also needed, taking into account variables such as choroidal neovascularization subtypes and genetic factors, in order to identify a tailored treatment for each patient.

Early and exudative age-related macular degeneration is associated with increased plasma levels of soluble TNF receptor II

PURPOSE

We have recently identified homeostatic alterations in the circulating T cells of patients with age-related macular degeneration (AMD). In cultures of retinal pigment epithelial cells, we have demonstrated that T-cell-derived cytokines induced the upregulation of complement, chemokines and other proteins implicated in AMD pathogenesis. The purpose of this study was to test whether increased plasma levels of cytokines were present in patients with AMD.

METHODS

We conducted a case-control study. Age-related macular degeneration status was assessed using standardized multimodal imaging techniques. Plasma was isolated from freshly drawn peripheral venous blood samples and analysed for interleukin (IL)15, IL18, interferon (IFN)γ, soluble tumour necrosis factor (TNF) receptor II (sTNFRII) and complement factor H (CFH) Y402H genotype.

RESULTS

We included 136 individuals with early or late forms of AMD and 74 controls. Significantly increased levels of sTNFRII were observed in patients with early or exudative AMD (p < 0.01). After adjusting for CFH Y402H genotype, age, sex and smoking history, the level of sTNFRII remained a significant predictor for prevalence of AMD with odds ratios at 3.0 in the middle and 3.6 in the highest tertiles. Levels of IL15, IL18 and IFNγ were low and not associated with AMD.

CONCLUSIONS

Increased plasma level of sTNFRII is found to be associated with AMD. The data supports the observations of low-grade, systemic inflammatory alterations in patients with AMD. However, it remains to be determined whether increased levels of TNFα can be found, which directly reflects an increased activity of macrophages and T cells.

AAV2 delivery of Flt23k intraceptors inhibits murine choroidal neovascularization

Long-term inhibition of extracellular vascular endothelial growth factor (VEGF) in the treatment of age-related macular degeneration (AMD) may induce retinal neuronal toxicity and risk other side effects. We developed a novel strategy which inhibits retinal pigment epithelium (RPE)-derived VEGF, sparing other highly sensitive retinal tissues. Flt23k, an intraceptor inhibitor of VEGF, was able to inhibit VEGF in vitro. Adeno-associated virus type 2 (AAV2)-mediated expression of Flt23k was maintained for up to 6 months postsubretinal injection in mice. Flt23k was able to effectively inhibit laser-induced murine choroidal neovascularization (CNV). VEGF levels in the RPE/choroid complex decreased significantly in AAV2.Flt23k treated eyes. Neither retinal structure detected by Heidelberg Spectralis nor function measured by electroretinography (ERG) was adversely affected by treatment with AAV2.Flt23k. Hence AAV2.Flt23k can effectively maintain long-term expression and inhibit laser-induced CNV in mice through downregulation of VEGF while maintaining a sound retinal safety profile. These findings suggest a promising novel approach for the treatment of CNV.

Aflibercept for intravitreal injection: in neovascular age-related macular degeneration

Aflibercept is a recombinant human fusion protein that acts as a soluble decoy receptor for vascular endothelial growth factor (VEGF) family members VEGF-A, VEGF-B and placental growth factor, thereby preventing these ligands from binding to, and activating, their cognate receptors. The efficacy of intravitreal aflibercept in the treatment of wet (neovascular) age-related macular degeneration has been compared with that of intravitreal ranibizumab, the current gold standard for this indication, in two pivotal phase III studies of virtually identical design (VIEW 1 and 2). In both trials, the recommended regimen of aflibercept [2 mg every second month (after three initial monthly doses)] was shown to be noninferior to the recommended regimen of ranibizumab (0.5 mg every month) in terms of the primary endpoint of the proportion of patients who maintained their vision after 1 year of treatment; similar results were seen when monthly dosing with aflibercept (0.5 or 2 mg) was compared with ranibizumab. Over a period of 96 weeks in the VIEW studies, patients receiving the recommended regimen of aflibercept during the first year followed by modified quarterly treatment during the second year had a similar visual acuity gain to those receiving the recommended regimen of ranibizumab during first year followed by modified quarterly treatment during the second year, but on average required five fewer injections. Aflibercept was generally well tolerated in the VIEW studies; the ocular and non-ocular adverse event profile of the drug was similar to that of ranibizumab.

Aflibercept in wet AMD: specific role and optimal use

Background

Vascular endothelial growth factor (VEGF) is a naturally occurring glycoprotein in the body that acts as a growth factor for endothelial cells. It regulates angiogenesis, enhances vascular permeability, and plays a major role in wet age-related macular degeneration. The consistent association between choroidal neovascularization and increased VEGF expression provides a strong reason for exploring the therapeutic potential of anti-VEGF agents in the treatment of this disorder. Blockade of VEGF activity is currently the most effective strategy for arresting choroidal angiogenesis and reducing vascular permeability, which is frequently the main cause of visual acuity deterioration. In recent years, a number of other molecules have been developed to increase the efficacy and to prolong the durability of the anti-VEGF effect. Aflibercept (EYLEA®; Regeneron Pharmaceutical Inc and Bayer), also named VEGF Trap-eye, is the most recent member of the anti-VEGF armamentarium that was approved by the US Food and Drug Administration in November 2011. Because of its high binding affinity and long duration of action, this drug is considered to be a promising clinically proven anti-VEGF agent for the treatment of wet maculopathy.

Objective

This article reviews the current literature and clinical trial data regarding the efficacy and the pharmacological properties of VEGF-Trap eye and describes the possible advantages of its use over the currently used “older” anti-VEGF drugs.

Methods

For this review, a search of PubMed from January 1989 to May 2013 was performed using the following terms (or combination of terms): vascular endothelial growth factors, VEGF, age-related macular degeneration, VEGF-Trap eye in wet AMD, VEGF-Trap eye in diabetic retinopathy, VEGF-Trap eye in retinal vein occlusions, aflibercept. Studies were limited to those published in English.

Results and conclusion

Two Phase III clinical trials, VEGF Trap-eye Investigation of Efficacy and Safety in Wet AMD (VIEW) 1 and 2, comparing VEGF Trap-eye to ranibizumab demonstrated the noninferiority of this novel compound. The clinical equivalence of this compound against ranibizumab is maintained even when the injections are administered at 8-week intervals, which indicates the potential to reduce the risk of monthly intravitreal injections and the burden of monthly monitoring.

Age-related macular degeneration is associated with increased proportion of CD56(+) T cells in peripheral blood

PURPOSE

To examine the association between age-related changes in the T-cell compartment and prevalence of age-related macular degeneration (AMD).

DESIGN

Case-control study.

PARTICIPANTS

A total of 117 AMD cases and 106 controls were included prospectively.

METHODS

Fresh-drawn peripheral blood samples were processed for flow cytometric analysis of T-cell populations. Plasma samples were analyzed for anti-cytomegalovirus (CMV) immunoglobulin (Ig)G and complement factor H (CFH) Y402H genotype. The diagnosis of AMD was made according to the Clinical Age-Related Maculopathy Staging System.

MAIN OUTCOME MEASURES

Association between frequency of aged T cells and prevalence of AMD.

RESULTS

The prevalence of AMD was associated with distinct age-related changes in the T-cell compartment. Specifically, the patients with AMD had an increased frequency of CD28(-) T cells that expressed the CD56 surface marker (patients, 34.9% vs. aged controls, 25.8%; P = 0.002). Participants in the highest tertile of CD56(+) CD28(-) T cells had an odds ratio (OR) for the presence of AMD of 3.2 (95% confidence interval [CI], 1.2-8.8) after adjustment for CFH genotype, anti-CMV IgG positivity, age, sex, and smoking history. The adjusted OR of the presence of AMD for persons having at least 1 CFH H402 risk allele increased from 3.5 (95% CI, 1.5-8.1) to 13.3 (95% CI, 3.3-53.6) for persons with at least 1 CFH H402 risk allele and above the median level of CD56(+) CD28(-) T cells.

CONCLUSIONS

We found increased levels of circulating aged CD56(+) CD28(-) T cells in patients with AMD. Although this supports the notion of AMD as a systemic disease, it also suggests that the adaptive immune system is implicated in its pathogenesis.

Complement factor H deficiency results in decreased neuroretinal expression of Cd59a in aged mice

PURPOSE

The complement system is closely linked to the pathogenesis of AMD. Several complement genes are expressed in RPE, and complement proteins accumulate in drusen. Further, a common variant of complement factor H (CFH) confers increased risk of developing AMD. Because the mechanisms by which changes in the function of CFH influence development of AMD are unclear, we examined ocular complement expression as a consequence of age in control and CFH null mutant mice.

METHODS

Gene expression in neuroretinas and RPE/choroid from young and aged WT and Cfh(-/-) C57BL/6J mice was analyzed by microarrays. Expression of a wide range of complement genes was compared with expression in liver.

RESULTS

An age-associated increased expression of complement, particularly C1q, C3, and factor B, in the RPE/choroid coincided with increased expression of the negative regulators Cfh and Cd59a in the neuroretina. Young mice deficient in CFH expressed Cd59a similar to WT, but failed to upregulate Cd59a expression with age. Hepatic expression of Cd59a increased with age regardless of Cfh genotype.

CONCLUSIONS

While the connection between CFH deficiency and failure to upregulate CD59a remains unknown, these results suggest that expression of CD59 is tissue-specific and that neuroretinal regulation depends on CFH. This could contribute to the visual functional deficits and morphological changes in the Cfh(-/-) mouse retina that occur with age.

Retinal pigment epithelium response to oxidant injury in the pathogenesis of early age-related macular degeneration

Age-related macular degeneration (AMD) represents the leading cause of vision loss in the elderly. Accumulation of lipid- and protein-rich deposits under the retinal pigment epithelium (RPE) heralds the onset of early AMD, but the pathogenesis of subretinal deposit formation is poorly understood. Numerous hypothetical models of deposit formation have been proposed, including hypotheses for a genetic basis, choroidal hypoperfusion, abnormal barrier formation, and lysosomal failure. This review explore the RPE injury hypothesis, characterized by three distinct stages (1) Initial RPE oxidant injury, caused by any number of endogenous or exogenous oxidants, results in extrusion of cell membrane "blebs," together with decreased activity of matrix metalloproteinases (MMPs), promoting bleb accumulation under the RPE as basal laminar deposits (BLD). (2) RPE cells are subsequently stimulated to increase synthesis of MMPs and other molecules responsible for extracellular matrix turnover (i.e., producing decreased collagen), affecting both RPE basement membrane and Bruchs membrane (BrM). This process leads to progression of BLD into basal linear deposits (BLinD) and drusen by admixture of blebs into BrM, followed by the formation of new basement membrane under the RPE to trap these deposits within BrM. We postulate that various hormones and other plasma-derived molecules related to systemic health cofactors are implicated in this second stage. (3) Finally, macrophages are recruited to sites of RPE injury and deposit formation. The recruitment of nonactivated or scavenging macrophages may remove deposits without further injury, while the recruitment of activated or reparative macrophages, through the release of inflammatory mediators, growth factors, or other substances, may promote complications and progression to the late forms of the disease.

Morpholino-mediated increase in soluble Flt-1 expression results in decreased ocular and tumor neovascularization

Background

Angiogenesis is a key process in several ocular disorders and cancers. Soluble Flt-1 is an alternatively spliced form of the Flt-1 gene that retains the ligand-binding domain, but lacks the membrane-spanning and intracellular kinase domains of the full-length membrane bound Flt-1 (mbFlt-1) protein. Thus, sFlt-1 is an endogenous inhibitor of VEGF-A mediated angiogenesis. Synthetic mopholino oligomers directed against splice site targets can modulate splice variant expression. We hypothesize that morpholino-induced upregulation of sFlt-1 will suppress angiogenesis in clinically relevant models of macular degeneration and breast cancer.

Methods and Findings

In vivo morpholino constructs were designed to target murine exon/intron 13 junction of the Flt-1 transcript denoted VEGFR1_MOe13; standard nonspecific morpholino was used as control. After nucleofection of endothelial and breast adenocarcinoma cell lines, total RNA was extracted and real-time RT-PCR performed for sFlt-1 and mbFlt-1. Intravitreal injections of VEGFR1_MOe13 or control were done in a model of laser-induced choroidal neovascularization and intratumoral injections were performed in MBA-MD-231 xenografts in nude mice. VEGFR1_MOe13 elevated sFlt-1 mRNA expression and suppressed mbFlt-1 mRNA expression in vitro in multiple cellular backgrounds (p<0.001). VEGFR1_MOe13 also elevated sFlt/mbFlt-1 ratio in vivo after laser choroidal injury 5.5 fold (p<0.001) and suppressed laser-induced CNV by 50% (p = 0.0179). This latter effect was reversed by RNAi of sFlt-1, confirming specificity of morpholino activity through up-regulation of sFlt-1. In the xenograft model, VEGFR1_MOe13 regressed tumor volume by 88.9%, increased sFlt-1 mRNA expression, and reduced vascular density by 50% relative to control morpholino treatment (p<0.05).

Conclusions

Morpholino oligomers targeting the VEGFR1 mRNA exon/intron 13 junction promote production of soluble FLT-1 over membrane bound FLT-1, resulting in suppression of lesional volume in laser induced CNV and breast adenocarcinoma. Thus, morpholino manipulation of alternative splicing offers translational potential for therapy of angiogenic disorders.

The influence of cortical, nuclear, subcortical posterior, and mixed cataract on the results of microperimetry

PURPOSE

Microperimetry is a useful instrument for evaluating sensitivity threshold due to retinal pathologies. The aim of the study is to assess the impact of different forms of cataract on microperimetry results.

METHODS

In a prospective design, patients were recruited for cataract surgery at the Department of Ophthalmology, Medical University of Vienna. Exclusion criteria were any other ophthalmic disease except cataract, that is, macular pathology. Using the Lens Opacities Classification System III classification, patients were classified into four groups: nuclear, cortical, subcapsular posterior, and mixed cataract. Then patients underwent microperimetry: results were analyzed for magnitude of retinal sensitivity loss and correlated to the forms and density of the cataract.

RESULTS

Mean density of cataract was LOCS 3.2-3.5 in the four groups. Differences were not statistically significant. The best-corrected visual acuity (BCVA) was LogMAR 0.5 ± 0.13 in nuclear, LogMAR 0.49 ± 0.21 in cortical, and LogMAR 0.58 ± 0.12 in mixed cataract patients, and significantly worse in patients with subcapsular posterior cataract (LogMAR 0.64 ± 0.12). Microperimetry shows a mean sensitivity of 11.4-12.6 dB without significant group differences. The BCVA is correlated with microperimetry in patients with nuclear and cortical cataract. Density of cataract is highly correlated with microperimetry results in all groups.

CONCLUSION

The present study shows a good correlation of microperimetry results with the BCVA of patients with nuclear and cortical cataract. In patients with subcapsular posterior cataract, microperimetry results were better than estimated by BCVA. Density of cataract is highly correlated with macular sensitivity. A reduction of 1 dB in microperimetry per 1 posterior capsule opacification score increase can be estimated for these patients.

Chloroquine treatment of ARPE-19 cells leads to lysosome dilation and intracellular lipid accumulation: possible implications of lysosomal dysfunction in macular degeneration

Background

Age-related macular degeneration (AMD) is the leading cause of vision loss in elderly people over 60. The pathogenesis is still unclear. It has been suggested that lysosomal stress may lead to drusen formation, a biomarker of AMD. In this study, ARPE-19 cells were treated with chloroquine to inhibit lysosomal function.

Results

Chloroquine-treated ARPE-19 cells demonstrate a marked increase in vacuolation and dense intracellular debris. These are identified as chloroquine-dilated lysosomes and lipid bodies with LAMP-2 and LipidTOX co-localization, respectively. Dilation is an indicator of lysosomal dysfunction. Chloroquine disrupts uptake of exogenously applied rhodamine-labeled dextran by these cells. This suggests a disruption in the phagocytic pathway. The increase in LAMP protein levels, as assessed by Western blots, suggests the possible involvement in autophagy. Oxidative stress with H₂O₂ does not induce vacuolation or lipid accumulation.

Conclusion

These findings suggest a possible role for lysosomes in AMD. Chloroquine treatment of RPE cells may provide insights into the cellular mechanisms underlying AMD.

Genetic basis of inherited macular dystrophies and implications for stem cell therapy

Untreatable hereditary macular dystrophy (HMD) presents a major burden to society in terms of the resulting patient disability and the cost to the healthcare provision system. HMD results in central vision loss in humans sufficiently severe for blind registration, and key issues in the development of therapeutic strategies to target these conditions are greater understanding of the causes of photoreceptor loss and the development of restorative procedures. More effective and precise analytical techniques coupled to the development of transgenic models of disease have led to a prolific growth in the identification and our understanding of the genetic mutations that underly HMD. Recent successes in driving differentiation of pluripotent cells towards specific somatic lineages have led to the development of more efficient protocols that can yield enriched populations of a desired phenotype. Retinal pigmented epithelial cells and photoreceptors derived from these are some of the most promising cells that may soon be used in the treatment of specific HMD, especially since rapid developments in the field of induced pluripotency have now set the stage for the production of patient-derived stem cells that overcome the ethical and methodological issues surrounding the use of embryonic derivatives. In this review we highlight a selection of HMD which appear suitable candidates for combinatorial restorative therapy, focusing specifically on where those photoreceptor loss occurs. This technology, along with increased genetic screening, opens up an entirely new pathway to restore vision in patients affected by HMD.

Off-label use of bevacizumab for the treatment of age-related macular degeneration: what is the evidence?

There is an active and controversial debate about the role of intravitreal bevacizumab versus approved drugs in the treatment of neovascular age-related macular degeneration (AMD). Because bevacizumab was available prior to the launch of ranibizumab, off-label use of the former became widespread and the cancer drug bevacizumab is the most commonly used medication in ophthalmology nowadays. This review considers every publication identified in MEDLINE using the keywords 'bevacizumab' and 'Avastin' between 1 June 2005 and 31 July 2008. The search identified 511 papers that were evaluated. In 33 studies, there was consistent and clear evidence for the efficacy of bevacizumab in neovascular AMD. However, the highest grade studies (three prospective, randomized, controlled trials) did not attain better than grade 2b level of evidence, and objective evaluation of the benefit of bevacizumab relative to representative controls was therefore not possible. Certainly, the available evidence is inferior to that obtained from the approval studies of ranibizumab and this should influence treatment selection and guidance of patients. These considerations indicate that important quality criteria need to be included in future studies to ensure more meaningful conclusions can be drawn. These include clearly defined inclusion criteria, information about the recruitment procedure (including data on withdrawals, excluded patients, concealed treatment allocation, use of intention-to-treat analyses and blinded assessment procedures). Although preclinical studies have almost exclusively found bevacizumab to be safe, the design utilized in clinical case series cannot rule out a possible increase in adverse events, which already show a high spontaneous incidence in elderly AMD patients. The superior evidence level for ranibizumab and the limited safety data for bevacizumab must be taken into consideration when evaluating the costs that a healthcare system is willing to spend. However, the superior grade of evidence for ranibizumab should not be confused with the (still missing) evidence for superior efficacy. The results of ongoing randomized, controlled, comparative trials will provide further data on the efficacy and cost effectiveness of bevacizumab and ranibizumab in the treatment of AMD. In the meantime, patients should be informed about the alternatives, the price differences and the restricted liability issue when off-label use of bevacizumab is offered.

Designing photosensitizers for photodynamic therapy: strategies, challenges and promising developments

Photodynamic therapy (PDT) and photodynamic antimicrobial chemotherapy (PACT) are techniques that combine the effects of visible light irradiation with subsequent biochemical events that arise from the presence of a photosensitizing drug (possessing no dark toxicity) to cause destruction of selected cells. Despite its still widespread clinical use, Photofrin® has several drawbacks that limit its general clinical use. Consequently, there has been extensive research into the design of improved alternative photosensitizers aimed at overcoming these drawbacks. While there are many review articles on the subject of PDT and PACT, these have focused on the photosensitizers that have been used clinically, with little emphasis placed on how the chemical aspects of the molecule can affect their efficacy as PDT agents. Indeed, many of the PDT/PACT agents used clinically may not even be the most appropriate within a given class. As such, this review aims to provide a better understanding of the factors that have been investigated, while aiming at improving the efficacy of a molecule intended to be used as a photosensitizer. Recent publications, spanning the last 5 years, concerning the design, synthesis and clinical usage of photosensitizers for application in PDT and PACT are reviewed, including 5-aminolevulinic acid, porphyrins, chlorins, bacteriochlorins, texaphyrins, phthalocyanines and porphycenes. It has been shown that there are many important considerations when designing a potential PDT/PACT agent, including the influence of added groups on the lipophilicity of the molecule, the positioning and nature of these added groups within the molecule, the presence of a central metal ion and the number of charges that the molecule possesses. The extensive ongoing research within the field has led to the identification of a number of potential lead molecules for application in PDT/PACT. The development of the second-generation photosensitizers, possessing shorter periods of photosensitization, longer activation wavelengths and greater selectivity for diseased tissue provides hope for attaining the ideal photosensitizer that may help PDT and PACT move from laboratory investigation to clinical practice.

Photodynamic therapy with verteporfin in age-related macular degeneration: a systematic review of efficacy, safety, treatment modifications and pharmacoeconomic properties

Photodynamic therapy (PDT) with verteporfin has been used less comprehensively in the treatment of exudative age-related macular degeneration (AMD), and specifically of choroidal neovascularization (CNV), since the advent of antiangiogenic therapies. Recently, there has been a renewed interest in PDT as an adjunct to these and other agents in the treatment of neovascular AMD. In light of this new development and the European Medicines Evaluation Agency's (EMEA) recent labelling decision to rescind approval for the use of PDT in occult CNV lesions, the present systematic review was undertaken to revisit the evidence supporting its clinical application. Photodynamic therapy provided the first pharmacological treatment for patients suffering from subfoveal CNV, the major cause of severe vision loss in AMD. Key clinical trials evaluating efficacy and safety have examined patients with all lesion subtypes, with the primary labelled indication (i.e. lesions containing a classic component of > or = 50% ) deriving from the results of the Treatment of Age-related Macular Degeneration with Photodynamic Therapy (TAP) Study. The subsequent TAP Study Group post hoc categorization of lesions as predominantly classic is open to question, however, as it appears that the overall efficacy in this group only may have reflected the especially strong response in 100% classic lesions. Based on a subgroup analysis of the Verteporfin in Photodynamic Therapy Study, the indication for PDT subsequently was expanded in some jurisdictions, including that of the EMEA, to include occult lesions with no classic component. However, the subsequent Visudyne in Occult Study found no benefit in 100% occult lesions, resulting in the EMEA rescinding its approval for this indication.

Clinical and histological aspects of CNV formation: studies in an animal model

The purpose of the present thesis was to develop an animal model of CNV in order to study the early formation of CNV and to test the effects of an anti-angiogenic treatment. Porcine eyes were chosen as a substrate for CNV induction, since they are similar to human eyes in terms of both macroscopic and microscopic morphology. However, a major difference is that pigs lack a fovea; instead they have a visual streak, with a relatively stable and high concentration of cones. By surgical perforation of Bruch's membrane we were able to induce formation of CNV membranes. The morphology and cellular composition of these membranes varied with the surgical technique employed. When RPE cells were locally removed at the time of perforation, the resulting CNV was thinner, contained fewer blood vessels and was less prone to leak on fluorescein angiography than when RPE cells were left intact at induction. The neuroretina overlying the perforation site was not damaged by any of the surgical techniques, thus allowing the subsequent retinal damage to be ascribed to the actual process of CNV formation. Using this animal model allowed us to directly map histological findings onto fluorescein angiograms and thereby perform meaningful correlations between histopathologic and photographic features. Such correlations have been hampered in human subjects, since human eyes are not enucleated as a consequence of CNV and are therefore only available for post-mortem studies. In such studies there often is a considerable time-gap between the death of the patient and the latest available fluorescein angiogram, thereby allowing macular pathology to evolve in the interim. Histological examination of the porcine membranes demonstrated that they were composed of RPE cells, glial cells, macrophages, endothelial cells, collagen and smooth muscle fibres, which are the same cellular and fibrillar elements that dominate human CNV membranes. The porcine model was applied to test the effects, in a randomized and masked fashion, of intravitreally injected bevacizumab. Bevacizumab, a pan VEGF A antibody, was found to reduce both the proliferation of endothelial cells in CNV membranes and the propensity to leak in fluorescein angiograms. Immunohistochemically, bevacizumab was detected in the inner limiting membrane, in retinal blood vessels and binding uniformly to the entire CNV membrane without any cellular predisposition. Based on the above findings we believe that the porcine CNV model shows a bearing to human disease and therefore might be used as a tool to obtain improved treatments for this debilitating condition.

The role of abnormal vitreomacular adhesion in age-related macular degeneration: spectral optical coherence tomography and surgical results

PURPOSE

To assess the incidence of vitreomacular adhesion and traction in age-related macular degeneration (AMD), and to evaluate surgical treatment in a subset of patients with choroidal neovascularization (CNV) nonresponsive to anti-neovascular growth factor (anti-VEGF) treatment.

DESIGN

Retrospective observational case-control and interventional case series.

METHODS

Spectral optical coherence tomography, combined with simultaneous scanning laser ophthalmoscope (Spectral OCT/SLO), was performed in 170 eyes of 94 elderly patients, 61 with exudative AMD, 59 with nonexudative AMD, and 50 control eyes. The presence of hyaloid adhesion to the posterior pole, and vitreomacular traction (VMT) were determined. Five patients with VMT underwent surgical hyaloid removal. Best-corrected visual acuity (BCVA) and retinal thickness were evaluated as outcomes.

RESULTS

Hyaloid adhesion was present in 17 eyes with exudative AMD (27.8%), 15 eyes with nonexudative AMD (25.4%), and eight control eyes (16%). Significant difference was found among the groups (P = .002). Among the eyes with hyaloid adhesion, VMT was shown in 10 eyes (59%) with exudative AMD, two eyes (13%) with nonexudative AMD, and one control eye (12%). VMT was associated with the severity of AMD (P = .0082). The area of hyaloid adhesion was significantly smaller than and concentric to the area of CNV complex in eyes with exudative AMD. Eyes with VMT that underwent surgery experienced a modest improvement of BCVA and decrease of retinal thickness.

CONCLUSIONS

Hyaloid adhesion to the macula is associated with AMD, and frequently causes VMT in eyes with CNV. Tractional forces may antagonize the effect of anti-VEGF treatment, and cause pharmacological resistance in a subpopulation of patients. Future studies are needed to define the role of vitreoretinal surgery in such cases. Spectral OCT/SLO allows careful diagnosis and follow-up.

HTRA1 variants in exudative age-related macular degeneration and interactions with smoking and CFH

PURPOSE

Mapping the genes for age-related macular degeneration (AMD) had not been successful until recent genome-wide association studies revealed Tyr402His in CFH and rs11200638 in HTRA1 as AMD-related genetic variants. This study was conducted to identify other critical factors in HTRA1 that are associated with exudative AMD.

METHODS

The promoter, splice regions, and coding exons of HTRA1 were sequenced in 163 patients with exudative AMD and 183 sex- and age-matched control subjects. Also documented were the CFH genotype and smoking status.

RESULTS

Four significant SNPs were found in the promoter and the first exon of HTRA1: rs11200638 (-625G>A), rs2672598 (-487T>C), rs1049331 (102C>T, Ala34Ala), and rs2293870 (108G>T, Gly36Gly) with respective P = 1.7 x 10(-14), 3.0 x 10(-10), 3.7 x 10(-12), and 3.7 x 10(-12). Among them, rs11200638 is the most significant associated SNP with a high odds ratio (OR) of 7.6 (95% CI: 3.94-14.51). One risk haplotype block across the promoter and exon 1, ACCTT, significantly predisposes to AMD (P = 6.68 x 10(-14)). In both models, significant independent additive effects were identified with smoking and rs800292 (184G>A, Val62Ile) of CFH. Smoking and rs11200638 (HTRA1) combined caused a 15.7-fold increased risk, whereas combined rs800292 and rs11200638 caused a 23.3-fold increased risk. An extremely high population attributable risk (PAR) of 78% was also found.

CONCLUSIONS

A high impact of the additive effect of CFH and HTRA1 in the development of exudative AMD was shown. The HTRA1-smoking additive effect found in this study further suggests the importance of this environmental risk factor in AMD.

Murine ccl2/cx3cr1 deficiency results in retinal lesions mimicking human age-related macular degeneration

PURPOSE

Senescent Ccl2(-/-) mice are reported to develop cardinal features of human age-related macular degeneration (AMD). Loss-of-function single-nucleotide polymorphisms within CX3CR1 are also found to be associated with AMD. The authors generated Ccl2(-/-)/Cx3cr1(-/-) mice to establish a more characteristic and reproducible AMD model.

METHODS

Single Ccl2- and Cx3cr1-deficient mice were crossbred to obtain Ccl2(-/-)/Cx3cr1(-/-) mice. Funduscopy, histopathology, retinal A2E quantification, proteomics, RT-PCR gene expression assay, immunochemistry, and Western blotting were used to examine the retina and to evaluate gene expression within the retinal tissue.

RESULTS

By 6 weeks of age, all Ccl2(-/-)/Cx3cr1(-/-) mice developed AMD-like retinal lesions, including drusen, retinal pigment epithelium alteration, and photoreceptor degeneration. Furthermore, choroidal neovascularization occurred in 15% of the mice. These degenerative lesions progressed with age. A2E, a major lipofuscin fluorophore that accumulated during AMD progression, was significantly higher in the Ccl2(-/-)/Cx3cr1(-/-) retina than in the wild-type retina. Complement cofactor was higher in the Ccl2(-/-)/Cx3cr1(-/-) RPE. Proteomics data indicated that four proteins were differentially expressed in Ccl2(-/-)/Cx3cr1(-/-) retina compared with control. One of these proteins, ERp29, an endoplasmic reticulum protein, functions as an escort chaperone and in protein folding.

CONCLUSIONS

The authors concluded that Ccl2(-/-)/Cx3cr1(-/-) mice develop a broad spectrum of AMD abnormalities with early onset and high penetrance. These observations implicate certain chemokines and endoplasmic reticulum proteins in AMD pathogenesis. Similar to the mechanism of neurodegeneration caused by dysfunction of endoplasmic reticulum proteins, decreased chaperoning may cause misfolded protein accumulation, leading to drusen formation and retinal degeneration.

Age-related macular degeneration: a perspective on genetic studies

AIM

Age-related macular degeneration (AMD) is a common macular disease in the developed world and recent studies have shown that specific genes may be associated with it and may contribute to a higher risk of developing AMD.

OBJECTIVE

Our objective was to review systematically recent publications related to the genetics of AMD and provide relevant information that would help both scientists and clinicians in advising patients.

METHOD

A systematic search was performed on PubMed, Medline, and National Library of Medicine as well as ARVO abstracts using key words relevant to the genetic associations of AMD.

RESULTS

The most important genetic associations in AMD involved the complement factor H (CFH) gene, which showed that possession of the variant Y402H polymorphism significantly increases the risk for AMD. Protective genes have also been identified such as those on either factor B (BFor complement factor B (CFB)) or complement component 2 (C2) genes. The genes involved in inherited macular dystrophies such as ATP-binding cassette, subfamily A (ABC1), member 4 (ABCA4), vitelliform macular dystrophy (VMD2), tissue inhibitor of matrix metalloproteinase-3 (TIMP3), and EFEMP1have yielded some important information but further confirmatory work has yet to establish a clear association with AMD.

CONCLUSION

Patients with AMD possess specific genetic variants of the CFHgene, which put them at a higher risk of developing the disease. Other unaffected individuals may possess certain protective genetic variants, which could prevent them from developing AMD. Further research will no doubt shed light on other such mechanisms and these will be useful in identifying possible direct targets for drugs or indirectly through modulation of the genes responsible for disease presentation.

An apolipoprotein E variant may protect against age-related macular degeneration through cytokine regulation

Age-related macular degeneration (AMD) is the leading cause of visual impairment and blindness among the elderly in Western countries. Genetic factors, age, cigarette smoking, nutrition, and exposure to light have been identified as AMD risk factors. In this study, we investigated the association between ApoE C112R/R158C single nucleotide polymorphisms (which determine the E2, E3, and E4 isoforms) and age-related macular degeneration (AMD), and the mechanism underlying the association. Genomic DNA was extracted from 133 clinically screened controls, 94 volunteers with a younger mean age, 120 patients with advanced AMD, and 40 archived ocular AMD slides for single nucleotide polymorphism typing. The effects of recombinant ApoE isoforms on CCL2 (a chemokine), CX3CR1 (a chemokine receptor), and VEGF (a cytokine) expression in cultured human retinal pigment epithelium (RPE) cells were tested and serum cholesterol profiles of the clinically screened subjects were analyzed. ApoE112R (E4) distribution differed significantly between AMD patients and controls. ApoE112R allele frequency was 10.9% in the AMD group when compared with 16.5% in the younger controls and 18.8% in the clinically screened controls. The pathologically diagnosed archived AMD cases had the lowest allele frequency of 5%. No significant differences in ApoE158C (E2) distribution were observed among the groups. A meta-analysis of 8 cohorts including 4,289 subjects showed a strong association between AMD and 112R, but not 158C. In vitro studies found that recombinant ApoE suppresses CCL2 and VEGF expression in RPE cells. However, the E4 isoform showed more suppression than E3 in both cases. These results further confirm the association between ApoE112R and a decreased risk of AMD development. The underlying mechanisms may involve differential regulation of both CCL2 and VEGF by the ApoE isoforms.

Consumption of one egg per day increases serum lutein and zeaxanthin concentrations in older adults without altering serum lipid and lipoprotein cholesterol concentrations

Lutein and zeaxanthin accumulate in the macular pigment of the retina, and are reported to be associated with a reduced incidence of age-related macular degeneration. A rich source of lutein and zeaxanthin in the American diet is the yolk of chicken eggs. Thus, the objective of the study was to investigate the effect of consuming 1 egg/d for 5 wk on the serum concentrations of lutein, zeaxanthin, lipids, and lipoprotein cholesterol in individuals >60 y of age. In a randomized cross-over design, 33 men and women participated in the 18-wk study, which included one run-in and one washout period of no eggs prior to and between two 5-wk interventions of either consuming 1 egg or egg substitute/d. Serum lutein 26% (P < 0.001) and zeaxanthin 38% (P < 0.001) concentrations increased after 5-wk of 1 egg/d compared with the phase prior to consuming eggs. Serum concentrations of total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides were not affected. These findings indicate that in older adults, 5 wk of consuming 1 egg/d significantly increases serum lutein and zeaxanthin concentrations without elevating serum lipids and lipoprotein cholesterol concentrations.