Our previous studies found that the C-X-C motif chemokine receptor 5 (CXCR5) loss leads to retinal pigment epithelium (RPE) dysfunction and AMD pathogenesis. The current study aimed to characterize the G protein-coupled receptor (GPCR) structure of CXCR5 and analyze its interactions with AMD-related risk genes. The sequence alignments, homology model of CXCR5 and structural assessment analysis were performed. Data and text mining were then performed to identify AMD-related risk genes and their interaction with CXCR5 using statistical and mathematical algorithms. Sequence alignment and phylogenetic tree analysis revealed that human CXCR5 was highly similar (85.4839%) to the rabbit. The least similarity (33.871%) was found to be in zebrafish compared to the other species. The CXCR5 model structural assessment and secondary structure analysis exhibited an excellent model. Network analysis revealed that IL10, TNF, ICAM1, CXCL1, CXCL8, APP, TLR4, SELL, C3, IL17A and CCR2 were the most connected genes CXCR5. These findings suggest that CXCR5 signaling may regulate the biological function of RPE and modulate AMD pathophysiology via GPCR signaling and interacting with identified AMD risk genes. In summary, the data presented here provide novel and crucial insights into the molecular mechanisms of CXCR5 involvement in AMD.Communicated by Ramaswamy H. Sarma.
Stem cell-based disease modeling is an emerging technology for the mechanistic study and therapeutic screening of complex ocular pathologies. In this issue of Cell Stem Cell, Saini et al. (2017) show that iPSC-derived RPE cells from age-related macular degeneration patients express increased levels of pro-inflammatory factors that can be normalized by the anti-aging drug nicotinamide.
We conducted a nested candidate gene study and pathway-based enrichment analysis on data from a multi-national 77,000-person project on the molecular genetics of age-related macular degeneration (AMD) to identify AMD-associated DNA-sequence variants in genes encoding constituents of a netrin-1 (NTN1)-based signaling pathway that converges on DNA-binding transcription complexes through a 3'-5'-cyclic adenosine monophosphate-calcineurin (cAMP-CN)-dependent axis. AMD-associated single nucleotide polymorphisms (SNPs) existed in 9 linkage disequilibrium-independent genomic regions; these included loci overlapping NTN1 (rs9899630, P ≤ 9.48 x 10-5), DCC (Deleted in Colorectal Cancer)-the gene encoding a primary NTN1 receptor (rs8097127, P ≤ 3.03 x 10-5), and 6 other netrin-related genes. Analysis of the NTN1-DCC pathway with exact methods demonstrated robust enrichment with AMD-associated SNPs (corrected P-value = 0.038), supporting the idea that processes driven by NTN1-DCC signaling systems operate in advanced AMD. The NTN1-DCC pathway contains targets of FDA-approved drugs and may offer promise for guiding applied clinical research on preventive and therapeutic interventions for AMD.
IMPORTANCE: The CX3CR1 gene is implicated as a candidate gene for age-related macular degeneration (AMD) through several lines of evidence. There is uncertainty, however, as to whether common genetic variants in CX3CR1 alter risk of AMD, since prior studies have been inconsistent and mostly limited to evaluation of 2 nonsynonymous variants, T280M (rs3732378) and V249I (rs3732379). OBJECTIVE: To determine if common variants in CX3CR1 predict future risk of AMD. DESIGN, SETTING, AND PARTICIPANTS: Prospective nested case-control study within 5 large study populations with long-term follow-up. We measured genotypes for T280M, V249I, and 13 other common single-nucleotide polymorphisms (SNPs) of the CX3CR1 gene among people who developed AMD (n = 1110, including 369 with neovascular AMD) and 2532 age- and sex-matched controls. MAIN OUTCOMES AND MEASURES: We determined the incidence rate ratios (RR) and 95% CIs for incidence of AMD for each variant and examined interactions with other AMD-associated variants and modifiable risk factors. RESULTS: In additive genetic models, we identified nonsignificant associations with AMD for T280M (RR, 0.87; P = .07) and 3 other SNPs, rs2853707 (RR, 0.88; P = .07), rs12636547 (RR, 0.85; P = .10), and rs1877563 (RR, 0.84; P = .06), 1 of which, rs2853707, is positioned in the CX3CR1 promoter region and was associated with neovascular AMD (RR, 0.75; P = .03). We observed that a recessive model was a better fit to the data for some SNPs, with associations between rs11715522 and AMD (RR, 1.27; P = .03) and between rs2669845 (RR, 3.10; P = .04), rs2853707 (RR, 0.48; P = .050), and rs9868689 (RR, 0.31; P = .02) and neovascular AMD. Moreover, in exploratory analyses, we identified a number of possible interactions including between V249I and rs2669845 and dietary intake of ω-3 fatty acids (P = .004 and P = .009, respectively) for AMD; between rs2669845 and obesity (P = .03) for neovascular AMD; between T280M and complement component 3 (C3) R102G for AMD (P = .03); between rs2669845 and Y402H in complement factor H for AMD (P = .04); and between rs2669845, rs2853707, and V249I and C3 R102G for neovascular AMD (P = .008; .04; and .002, respectively). CONCLUSIONS AND RELEVANCE: This study failed to identify significant associations between common CX3CR1 variants and AMD after considering the number of SNPs analyzed and multiple comparisons. However, we observed evidence consistent with recessive modes of association and that an effect of CX3CR1 variants may depend on other factors including dietary intake of ω-3 fatty acids, obesity, and genotypes at CFH Y402H and C3 R102G. If replicated in other populations, these findings would support a role for CX3CR1 in AMD but also suggest that its role may involve mechanisms that are independent of the T280M/V249I variations.
BACKGROUND: Since they were first derived more than three decades ago, embryonic stem cells have been proposed as a source of replacement cells in regenerative medicine, but their plasticity and unlimited capacity for self-renewal raises concerns about their safety, including tumour formation ability, potential immune rejection, and the risk of differentiating into unwanted cell types. We report the medium-term to long-term safety of cells derived from human embryonic stem cells (hESC) transplanted into patients. METHODS: In the USA, two prospective phase 1/2 studies were done to assess the primary endpoints safety and tolerability of subretinal transplantation of hESC-derived retinal pigment epithelium in nine patients with Stargardt's macular dystrophy (age >18 years) and nine with atrophic age-related macular degeneration (age >55 years). Three dose cohorts (50,000, 100,000, and 150,000 cells) were treated for each eye disorder. Transplanted patients were followed up for a median of 22 months by use of serial systemic, ophthalmic, and imaging examinations. The studies are registered with ClinicalTrials.gov, numbers NCT01345006 (Stargardt's macular dystrophy) and NCT01344993 (age-related macular degeneration). FINDINGS: There was no evidence of adverse proliferation, rejection, or serious ocular or systemic safety issues related to the transplanted tissue. Adverse events were associated with vitreoretinal surgery and immunosuppression. 13 (72%) of 18 patients had patches of increasing subretinal pigmentation consistent with transplanted retinal pigment epithelium. Best-corrected visual acuity, monitored as part of the safety protocol, improved in ten eyes, improved or remained the same in seven eyes, and decreased by more than ten letters in one eye, whereas the untreated fellow eyes did not show similar improvements in visual acuity. Vision-related quality-of-life measures increased for general and peripheral vision, and near and distance activities, improving by 16-25 points 3-12 months after transplantation in patients with atrophic age-related macular degeneration and 8-20 points in patients with Stargardt's macular dystrophy. INTERPRETATION: The results of this study provide the first evidence of the medium-term to long-term safety, graft survival, and possible biological activity of pluripotent stem cell progeny in individuals with any disease. Our results suggest that hESC-derived cells could provide a potentially safe new source of cells for the treatment of various unmet medical disorders requiring tissue repair or replacement. FUNDING: Advanced Cell Technology.
BACKGROUND: Choroidal neovascularization (CNV) is the main cause of vision loss in age-related macular degeneration (AMD). In experimental CNV, endothelial progenitor cells (EPCs) contribute to the formation of new vessels. The aim of this study was to investigate whether the behavior of EPCs in patients with AMD supports a role for EPCs in human CNV. METHODS: The number of circulating EPCs that are considered pure endothelial precursors and EPCs with monocytic characteristics, and the plasma levels of regulatory cytokines were evaluated in 23 patients with AMD with active CNV and 20 matched controls. In the patients, this profile was re-evaluated after ranibizumab. RESULTS: When compared with controls, the patients with AMD showed a lower number of both EPC types (P = 0.03) and higher plasma levels (P = 0.03) of stromal cell-derived factor 1. Three monthly injections of ranibizumab returned to control levels the number of circulating EPCs considered pure endothelial precursors and of stromal cell-derived factor 1, but not of monocytic EPCs. CONCLUSION: The observations indicate responsiveness of circulating EPCs to the CNV process in AMD. They suggest the hypothesis that increased stromal cell-derived factor 1 production at the CNV site (reflected in higher plasma levels) recruits EPCs from the circulation, and that antivascular endothelial growth factor therapy selectively decreases the recruitment of cells to be incorporated into new vessels.
Epithelial-mesenchymal transition (EMT) and endothelial-mesenchymal transition (EndMT) are physiological processes required for normal embryogenesis. However, these processes can be hijacked in pathological conditions to facilitate tissue fibrosis and cancer metastasis. In the eye, EMT and EndMT play key roles in the pathogenesis of subretinal fibrosis, the end-stage of age-related macular degeneration (AMD) that leads to profound and permanent vision loss. Predominant in subretinal fibrotic lesions are matrix-producing mesenchymal cells believed to originate from the retinal pigment epithelium (RPE) and/or choroidal endothelial cells (CECs) through EMT and EndMT, respectively. Recent evidence suggests that EMT of RPE may also be implicated during the early stages of AMD. Transforming growth factor-beta (TGFβ) is a key cytokine orchestrating both EMT and EndMT. Investigations in the molecular mechanisms underpinning EMT and EndMT in AMD have implicated a myriad of contributing factors including signaling pathways, extracellular matrix remodelling, oxidative stress, inflammation, autophagy, metabolism and mitochondrial dysfunction. Questions arise as to differences in the mesenchymal cells derived from these two processes and their distinct mechanistic contributions to the pathogenesis of AMD. Detailed discussion on the AMD microenvironment highlights the synergistic interactions between RPE and CECs that may augment the EMT and EndMT processes in vivo. Understanding the differential regulatory networks of EMT and EndMT and their contributions to both the dry and wet forms of AMD can aid the development of therapeutic strategies targeting both RPE and CECs to potentially reverse the aberrant cellular transdifferentiation processes, regenerate the retina and thus restore vision.
PURPOSE: To investigate whether the 2 subtypes of advanced age-related macular degeneration (AMD), choroidal neovascularization (CNV), and geographic atrophy (GA) segregate separately in families and to identify which genetic variants are associated with these 2 subtypes. DESIGN: Sibling correlation study and genome-wide association study (GWAS). PARTICIPANTS: For the sibling correlation study, 209 sibling pairs with advanced AMD were included. For the GWAS, 2594 participants with advanced AMD subtypes and 4134 controls were included. Replication cohorts included 5383 advanced AMD participants and 15 240 controls. METHODS: Participants had the AMD grade assigned based on fundus photography, examination, or both. To determine heritability of advanced AMD subtypes, a sibling correlation study was performed. For the GWAS, genome-wide genotyping was conducted and 6 036 699 single nucleotide polymorphisms (SNPs) were imputed. Then, the SNPs were analyzed with a generalized linear model controlling for genotyping platform and genetic ancestry. The most significant associations were evaluated in independent cohorts. MAIN OUTCOME MEASURES: Concordance of advanced AMD subtypes in sibling pairs and associations between SNPs with GA and CNV advanced AMD subtypes. RESULTS: The difference between the observed and expected proportion of siblings concordant for the same subtype of advanced AMD was different to a statistically significant degree (P = 4.2 × 10(-5)), meaning that in siblings of probands with CNV or GA, the same advanced subtype is more likely to develop. In the analysis comparing participants with CNV to those with GA, a statistically significant association was observed at the ARMS2/HTRA1 locus (rs10490924; odds ratio [OR], 1.47; P = 4.3 × 10(-9)), which was confirmed in the replication samples (OR, 1.38; P = 7.4 × 10(-14) for combined discovery and replication analysis). CONCLUSIONS: Whether CNV versus GA develops in a patient with AMD is determined in part by genetic variation. In this large GWAS meta-analysis and replication analysis, the ARMS2/HTRA1 locus confers increased risk for both advanced AMD subtypes, but imparts greater risk for CNV than for GA. This locus explains a small proportion of the excess sibling correlation for advanced AMD subtype. Other loci were detected with suggestive associations that differ for advanced AMD subtypes and deserve follow-up in additional studies.
Age-related macular degeneration (AMD) is a common cause of irreversible visual loss and the disease burden is rising world-wide as the population ages. Both environmental and genetic factors contribute to the development of this disease. Among environmental factors, smoking, obesity and dietary factors including antioxidants and dietary fat intake influence onset and progression of AMD. There are also several lines of evidence that link cardiovascular, immune and inflammatory biomarkers to AMD. The genetic etiology of AMD has been and continues to be an intense and fruitful area of investigation. Genome-wide association studies have revealed numerous common variants associated with AMD and sequencing is increasing our knowledge of how rare genetic variants strongly impact disease. Evidence for interactions between environmental, therapeutic and genetic factors is emerging and elucidating the mechanisms of this interplay remains a major challenge in the field. Genotype-phenotype associations are evolving. The knowledge of non-genetic, modifiable risk factors along with information about heritability and genetic risk variants for this disease acquired over the past 25 years have greatly improved patient management and our ability to predict which patients will develop or progress to advanced forms of AMD. Personalized medicine and individualized prevention and treatment strategies may become a reality in the near future.
We present a novel fully automated algorithm for the detection of retinal diseases via optical coherence tomography (OCT) imaging. Our algorithm utilizes multiscale histograms of oriented gradient descriptors as feature vectors of a support vector machine based classifier. The spectral domain OCT data sets used for cross-validation consisted of volumetric scans acquired from 45 subjects: 15 normal subjects, 15 patients with dry age-related macular degeneration (AMD), and 15 patients with diabetic macular edema (DME). Our classifier correctly identified 100% of cases with AMD, 100% cases with DME, and 86.67% cases of normal subjects. This algorithm is a potentially impactful tool for the remote diagnosis of ophthalmic diseases.
PURPOSE: The purpose of this study was to develop an algorithm to automatically standardize the brightness, contrast, and color balance of digital color fundus photographs used to grade AMD and to validate this algorithm by determining the effects of the standardization on image quality and disease grading. METHODS: Seven-field color photographs of patients (>50 years) with any stage of AMD and a control group were acquired at two study sites, with either the Topcon TRC-50DX or Zeiss FF-450 Plus cameras. Field 2 photographs were analyzed. Pixel brightness values in the red, green, and blue (RGB) color channels were adjusted in custom-built software to make the mean brightness and contrast of the images equal to optimal values determined by the Age-Related Eye Disease Study (AREDS) 2 group. RESULTS: Color photographs of 370 eyes were analyzed. We found a wide range of brightness and contrast values in the images at baseline, even for those taken with the same camera. After processing, image brightness variability (brightest image-dimmest image in a color channel) was reduced 69-fold, 62-fold, and 96-fold for the RGB channels. Contrast variability was reduced 6-fold, 8-fold, and 13-fold, respectively, after adjustment. Of the 23% images considered nongradable before adjustment, only 5.7% remained nongradable. CONCLUSIONS: This automated software enables rapid and accurate standardization of color photographs for AMD grading. TRANSLATIONAL RELEVANCE: This work offers the potential to be the future of assessing and grading AMD from photos for clinical research and teleimaging.
IMPORTANCE: Age-related macular degeneration (AMD) remains the leading cause of blindness in developed countries, and affects more than 150 million worldwide. Despite effective anti-angiogenic therapies for the less prevalent neovascular form of AMD, treatments are lacking for the more prevalent dry form. Similarities in risk factors and pathogenesis between AMD and atherosclerosis have led investigators to study the effects of statins on AMD incidence and progression with mixed results. A limitation of these studies has been the heterogeneity of AMD disease and the lack of standardization in statin dosage. OBJECTIVE: We were interested in studying the effects of high-dose statins, similar to those showing regression of atherosclerotic plaques, in AMD. DESIGN: Pilot multicenter open-label prospective clinical study of 26 patients with diagnosis of AMD and the presence of many large, soft drusenoid deposits. Patients received 80 mg of atorvastatin daily and were monitored at baseline and every 3 months with complete ophthalmologic exam, best corrected visual acuity (VA), fundus photographs, optical coherence tomography (OCT), and blood work (AST, ALT, CPK, total cholesterol, TSH, creatinine, as well as a pregnancy test for premenopausal women). RESULTS: Twenty-three subjects completed a minimum follow-up of 12 months. High-dose atorvastatin resulted in regression of drusen deposits associated with vision gain (+ 3.3 letters, p = 0.06) in 10 patients. No subjects progressed to advanced neovascular AMD. CONCLUSIONS: High-dose statins may result in resolution of drusenoid pigment epithelial detachments (PEDs) and improvement in VA, without atrophy or neovascularization in a high-risk subgroup of AMD patients. Confirmation from larger studies is warranted.
We evaluated the influence of an antioxidant and zinc nutritional supplement [the Age-Related Eye Disease Study (AREDS) formulation] on delaying or preventing progression to neovascular AMD (NV) in persons with age-related macular degeneration (AMD). AREDS subjects (n = 802) with category 3 or 4 AMD at baseline who had been treated with placebo or the AREDS formulation were evaluated for differences in the risk of progression to NV as a function of complement factor H (CFH) and age-related maculopathy susceptibility 2 (ARMS2) genotype groups. We used published genetic grouping: a two-SNP haplotype risk-calling algorithm to assess CFH, and either the single SNP rs10490924 or 372_815del443ins54 to mark ARMS2 risk. Progression risk was determined using the Cox proportional hazard model. Genetics-treatment interaction on NV risk was assessed using a multiiterative bootstrap validation analysis. We identified strong interaction of genetics with AREDS formulation treatment on the development of NV. Individuals with high CFH and no ARMS2 risk alleles and taking the AREDS formulation had increased progression to NV compared with placebo. Those with low CFH risk and high ARMS2 risk had decreased progression risk. Analysis of CFH and ARMS2 genotype groups from a validation dataset reinforces this conclusion. Bootstrapping analysis confirms the presence of a genetics-treatment interaction and suggests that individual treatment response to the AREDS formulation is largely determined by genetics. The AREDS formulation modifies the risk of progression to NV based on individual genetics. Its use should be based on patient-specific genotype.
PURPOSE: To study the association between periodontal disease (PD) and age-related macular degeneration (AMD). METHODS: For this cross-sectional analysis, 8,208 adults aged 40 years or older with retinal photographs graded for AMD were used from the National Health and Nutrition Examination Survey III. National Health and Nutrition Examination Survey III standardized dental measurements of PD status (defined as loss of >3 mm of attachment between the gum and tooth in at least 10% of sites measured). Participants were stratified into 60 years or younger and older than 60 years of age groups. Association between PD and AMD was assessed while controlling for sex, race, education, poverty income ratio, smoking, hypertension, body mass index, cardiovascular disease, and C-reactive protein. RESULTS: In this population, a total of 52.30% had PD, and the prevalence of AMD was 11.45%. Logistic regression model controlled for confounders and stratified by age 60 years or younger versus older than 60 years showed PD to be independently associated with an increased risk for AMD (odds ratio = 1.96, 95% confidence interval = 1.22-3.14, P = 0.006) for those aged 60 years or younger but not for subjects older than 60 years (odds ratio = 1.32, confidence interval = 0.93-1.90, P = 0.120). CONCLUSION: In this population-based study, PD is independently associated with AMD in those aged 60 years or younger.
INTRODUCTION: Contrast sensitivity function (CSF) may better estimate a patient's visual function compared with visual acuity (VA). Our study evaluates the quick CSF (qCSF) method to measure visual function in eyes with macular disease and good letter acuity. METHODS: Patients with maculopathies (retinal vein occlusion, macula-off retinal detachment, dry age-related macular degeneration and wet age-related macular degeneration) and good letter acuity (VA ≥20/30) were included. The qCSF method uses an intelligent algorithm to measure CSF across multiple spatial frequencies. All maculopathy eyes combined and individual macular disease groups were compared with healthy control eyes. Main outcomes included area under the log CSF (AULCSF) and six CS thresholds ranging from 1 cycle per degree (cpd) to 18 cpd. RESULTS: 151 eyes with maculopathy and 93 control eyes with VA ≥20/30 were included. The presence of a maculopathy was associated with significant reduction in AULCSF (β: -0.174; p<0.001) and CS thresholds at all spatial frequencies except for 18 cpd (β: -0.094 to -0.200 log CS, all p<0.01) compared with controls. Reductions in CS thresholds were most notable at low and intermediate spatial frequencies (1.5 cpd, 3 cpd and 6 cpd). CONCLUSION: CSF measured with the qCSF active learning method was found to be significantly reduced in eyes affected by macular disease despite good VA compared with healthy control eyes. The qCSF method is a promising clinical tool to quantify subtle visual deficits that may otherwise go unrecognised by current testing methods.
Purpose: To characterize and compare choroidal neovascularization (CNV) secondary to white dot syndromes (WDS) and age-related macular degeneration (AMD) using optical coherence tomography angiography (OCT-A). Methods: This is a cross-sectional study in which we imaged patients with CNV secondary to WDS and AMD with either the Zeiss Angioplex OCT-A or Optovue AngioVue OCT-A. Relevant demographic and clinical characteristics were collected and analyzed. CNV area and vessel density (VD) were measured by three independent graders, and linear regression analysis was subsequently performed. Results: Three patients with multifocal choroiditis and panuveitis, one patient each with birdshot chorioretinopathy, presumed ocular histoplasmosis syndrome, and persistent placoid maculopathy, and eleven patients with AMD with sufficient image quality were included. CNV associated with WDS was significantly smaller than that secondary to AMD (0.56±0.32 vs 2.79±1.80 mm, =-2.22, =0.01), while no difference in VD was detected (0.46±0.09 vs 0.44±0.09, =0.02, =0.71). Conclusion: CNV networks secondary to WDS appear to be smaller than those secondary to AMD but have similar VD. OCT-A is a powerful tool to investigate properties of CNV from various etiologies. Larger studies are needed for further characterization and understanding of CNV pathogenesis in inflammatory conditions.
Choroidal neovascularization (CNV) is the major cause of vision loss in wet age-related macular degeneration (AMD). Current therapies require repeated intravitreal injections, which are painful and can cause infection, bleeding, and retinal detachment. Here we develop nanoparticles (NP-[CPP]) that can be administered intravenously and allow local drug delivery to the diseased choroid via light-triggered targeting. NP-[CPP] is formed by PEG-PLA chains modified with a cell penetrating peptide (CPP). Attachment of a DEACM photocleavable group to the CPP inhibits cellular uptake of NP-[CPP]. Irradiation with blue light cleaves DEACM from the CPP, allowing the CPP to migrate from the NP core to the surface, rendering it active. In mice with laser-induced CNV, intravenous injection of NP-[CPP] coupled to irradiation of the eye allows NP accumulation in the neovascular lesions. When loaded with doxorubicin, irradiated NP-[CPP] significantly reduces neovascular lesion size. We propose a strategy for non-invasive treatment of CNV and enhanced drug accumulation specifically in diseased areas of the eye.