Age-related Macular Degeneration

Ratnapriya R, Zhan X, Fariss RN, Branham KE, Zipprer D, Chakarova CF, Sergeev YV, Campos MM, Othman M, Friedman JS, Maminishkis A, Waseem NH, Brooks M, Rajasimha HK, Edwards AO, Lotery A, Klein BE, Truitt BJ, Li B, Schaumberg DA, Morgan DJ, Morrison MA, Souied E, Tsironi EE, Grassmann F, Fishman GA, Silvestri G, Scholl HPN, Kim IK, Ramke J, Tuo J, Merriam JE, Merriam JC, Park KH, Olson LM, Farrer LA, Johnson MP, Peachey NS, Lathrop M, Baron RV, Igo RP, Klein R, Hagstrom SA, Kamatani Y, Martin TM, Jiang Y, Conley Y, Sahel J-A, Zack DJ, Chan C-C, Pericak-Vance MA, Jacobson SG, Gorin MB, Klein ML, Allikmets R, Iyengar SK, Weber BH, Haines JL, Léveillard T, Deangelis MM, Stambolian D, Weeks DE, Bhattacharya SS, Chew EY, Heckenlively JR, Abecasis GR, Swaroop A. Rare and common variants in extracellular matrix gene Fibrillin 2 (FBN2) are associated with macular degeneration. Hum Mol Genet 2014;23(21):5827-37.Abstract

Neurodegenerative diseases affecting the macula constitute a major cause of incurable vision loss and exhibit considerable clinical and genetic heterogeneity, from early-onset monogenic disease to multifactorial late-onset age-related macular degeneration (AMD). As part of our continued efforts to define genetic causes of macular degeneration, we performed whole exome sequencing in four individuals of a two-generation family with autosomal dominant maculopathy and identified a rare variant p.Glu1144Lys in Fibrillin 2 (FBN2), a glycoprotein of the elastin-rich extracellular matrix (ECM). Sanger sequencing validated the segregation of this variant in the complete pedigree, including two additional affected and one unaffected individual. Sequencing of 192 maculopathy patients revealed additional rare variants, predicted to disrupt FBN2 function. We then undertook additional studies to explore the relationship of FBN2 to macular disease. We show that FBN2 localizes to Bruch's membrane and its expression appears to be reduced in aging and AMD eyes, prompting us to examine its relationship with AMD. We detect suggestive association of a common FBN2 non-synonymous variant, rs154001 (p.Val965Ile) with AMD in 10 337 cases and 11 174 controls (OR = 1.10; P-value = 3.79 × 10(-5)). Thus, it appears that rare and common variants in a single gene-FBN2-can contribute to Mendelian and complex forms of macular degeneration. Our studies provide genetic evidence for a key role of elastin microfibers and Bruch's membrane in maintaining blood-retina homeostasis and establish the importance of studying orphan diseases for understanding more common clinical phenotypes.

Yonekawa Y, Kim IK. Clinical Characteristics and Current Treatment of Age-Related Macular Degeneration. Cold Spring Harb Perspect Med 2014;Abstract

Age-related macular degeneration (AMD) is a multifactorial degeneration of photoreceptors and retinal pigment epithelium. The societal impact is significant, with more than 2 million individuals in the United States alone affected by advanced stages of AMD. Recent progress in our understanding of this complex disease and parallel developments in therapeutics and imaging have translated into new management paradigms in recent years. However, there are many unanswered questions, and diagnostic and prognostic precision and treatment outcomes can still be improved. In this article, we discuss the clinical features of AMD, provide correlations with modern imaging and histopathology, and present an overview of treatment strategies.

Hasegawa E, Sweigard H, Husain D, Olivares AM, Chang B, Smith KE, Birsner AE, D'Amato RJ, Michaud NA, Han Y, Vavvas DG, Miller JW, Haider NB, Connor KM. Characterization of a spontaneous retinal neovascular mouse model. PLoS One 2014;9(9):e106507.Abstract

BACKGROUND: Vision loss due to vascular disease of the retina is a leading cause of blindness in the world. Retinal angiomatous proliferation (RAP) is a subgroup of neovascular age-related macular degeneration (AMD), whereby abnormal blood vessels develop in the retina leading to debilitating vision loss and eventual blindness. The novel mouse strain, neoretinal vascularization 2 (NRV2), shows spontaneous fundus changes associated with abnormal neovascularization. The purpose of this study is to characterize the induction of pathologic angiogenesis in this mouse model. METHODS: The NRV2 mice were examined from postnatal day 12 (p12) to 3 months. The phenotypic changes within the retina were evaluated by fundus photography, fluorescein angiography, optical coherence tomography, and immunohistochemical and electron microscopic analysis. The pathological neovascularization was imaged by confocal microscopy and reconstructed using three-dimensional image analysis software. RESULTS: We found that NRV2 mice develop multifocal retinal depigmentation in the posterior fundus. Depigmented lesions developed vascular leakage observed by fluorescein angiography. The spontaneous angiogenesis arose from the retinal vascular plexus at postnatal day (p)15 and extended toward retinal pigment epithelium (RPE). By three months of age, histological analysis revealed encapsulation of the neovascular lesion by the RPE in the photoreceptor cell layer and subretinal space. CONCLUSIONS: The NRV2 mouse strain develops early neovascular lesions within the retina, which grow downward towards the RPE beginning at p15. This retinal neovascularization model mimics early stages of human retinal angiomatous proliferation (RAP) and will likely be a useful in elucidating targeted therapeutics for patients with ocular neovascular disease.

Scotti F, Maestroni A, Palini A, Introini U, Setaccioli M, Lorenzi M, Zerbini G. Endothelial progenitor cells and response to ranibizumab in age-related macular degeneration. Retina 2014;34(9):1802-10.Abstract

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.

Chen J, Smith LEH. Altered cholesterol homeostasis in aged macrophages linked to neovascular macular degeneration. Cell Metab 2013;17(4):471-2.Abstract
Abnormal lipid metabolism has been linked to age-related macular degeneration (AMD); choroidal neovascularization in late AMD commonly causes blindness. Sene et al. (2013) now demonstrate that in aged macrophages decreased ABCA1 expression, regulated by liver X receptor and miR-33, impairs export of intracellular cholesterol, which promotes neovascular AMD.
Yonekawa Y, Andreoli C, Miller JB, Loewenstein JI, Sobrin L, Eliott D, Vavvas DG, Miller JW, Kim IK. Conversion to aflibercept for chronic refractory or recurrent neovascular age-related macular degeneration. Am J Ophthalmol 2013;156(1):29-35.e2.Abstract
PURPOSE: To explore the visual and anatomic outcomes of patients with refractory or recurrent neovascular age-related macular degeneration (AMD) who were converted from bevacizumab and/or ranibizumab to aflibercept. DESIGN: Two-center, retrospective chart review. METHODS: Treatment history, visual acuity (VA), and central macular thickness (CMT) on spectral-domain optical coherence tomography were collected. Patients were divided into "refractory" (persistent exudation despite monthly injections) or "recurrent" (exudation suppressed, but requiring frequent injections). RESULTS: One hundred and two eyes of 94 patients were included; 68 were refractory and 34 were recurrent. Eyes received a mean of 20.4 prior bevacizumab/ranibizumab injections and a mean of 3.8 aflibercept injections. Mean follow-up was 18 weeks. Mean VA was 20/50-1 before conversion, 20/50-2 after 1 aflibercept injection (P = .723), and 20/50+2 after the final injection (P = .253). Subgroup analysis of refractory and recurrent cases also showed stable VA. Of the refractory cases, mean CMT had improved after 1 injection (P < .001) and the final injection (P < .001). Intraretinal (P < .001) and subretinal (P < .001) fluid decreased after 1 injection, and the mean injection interval was extended from 5.2 to 6.2 weeks (P = .003). Of the recurrent cases, mean CMT improved after 1 injection (P < .001) and the final injection (P < .001). Intraretinal (P = .003) and subretinal (P = .046) fluid decreased after 1 injection, and the mean injection interval was extended from 7.2 to 9.5 weeks (P = .001). CONCLUSIONS: Converting patients with chronic neovascular AMD to aflibercept results in stabilized vision and improved anatomic outcomes, while allowing injection intervals to be extended.
Miller JW. Age-related macular degeneration revisited--piecing the puzzle: the LXIX Edward Jackson memorial lecture. Am J Ophthalmol 2013;155(1):1-35.e13.Abstract
PURPOSE: To present the current understanding of age-related macular degeneration (AMD) pathogenesis, based on clinical evidence, epidemiologic data, histopathologic examination, and genetic data; to provide an update on current and emerging therapies; and to propose an integrated model of the pathogenesis of AMD. DESIGN: Review of published clinical and experimental studies. METHODS: Analysis and synthesis of clinical and experimental data. RESULTS: We are closer to a complete understanding of the pathogenesis of AMD, having progressed from clinical observations to epidemiologic observations and clinical pathologic correlation. More recently, modern genetic and genomic studies have facilitated the exploration of molecular pathways. It seems that AMD is a complex disease that results from the interaction of genetic susceptibility with aging and environmental factors. Disease progression also seems to be driven by a combination of genetic and environmental factors. CONCLUSIONS: Therapies based on pathophysiologic features have changed the paradigm for treating neovascular AMD. With improved understanding of the underlying genetic susceptibility, we can identify targets to halt early disease and to prevent progression and vision loss.
Kanoff J, Miller J. Pharmacogenetics of the treatment response of age-related macular degeneration with ranibizumab and bevacizumab. Semin Ophthalmol 2013;28(5-6):355-60.Abstract
INTRODUCTION: Age-related macular degeneration is a major cause of blindness among people aged 50 and older in industrialized countries. Anti-VEGF therapy has been tremendously successful in the treatment of neovascular macular degeneration. Examining the pharmacogenetics of patients' response to the anti-VEGF molecules could allow for a tailored treatment strategy based on patients' underlying genetics rather than the "one-size fits all" approach currently used. METHODS: Review of the English literature for papers examining the pharmacogenetics of treatment response of neovascular macular degeneration to either ranibizumab or bevacizumab. Polymorphisms in CFH, ARMS2, HTRA1 and VEGF A were examined and reviewed. RESULTS: Patients with the high-risk CC genotype in complement factor H (CFH) had a worse response to therapy with ranibizumab and bevacizumab. No clear trends were found with ARMS2, HTRA1 and VEGF A. CONCLUSIONS: The goal of personalized medicine is to craft a treatment program that is ideally suited to an individual patient's disease and genetic make-up rather than simply what works for a large population who share similar disease characteristics. Continued research is needed to achieve this goal for the treatment of age-related macular degeneration.
Jacobo SMP, Deangelis MM, Kim IK, Kazlauskas A. Age-related macular degeneration-associated silent polymorphisms in HtrA1 impair its ability to antagonize insulin-like growth factor 1. Mol Cell Biol 2013;33(10):1976-90.Abstract
Synonymous single nucleotide polymorphisms (SNPs) within a transcript's coding region produce no change in the amino acid sequence of the protein product and are therefore intuitively assumed to have a neutral effect on protein function. We report that two common variants of high-temperature requirement A1 (HTRA1) that increase the inherited risk of neovascular age-related macular degeneration (NvAMD) harbor synonymous SNPs within exon 1 of HTRA1 that convert common codons for Ala34 and Gly36 to less frequently used codons. The frequent-to-rare codon conversion reduced the mRNA translation rate and appeared to compromise HtrA1's conformation and function. The protein product generated from the SNP-containing cDNA displayed enhanced susceptibility to proteolysis and a reduced affinity for an anti-HtrA1 antibody. The NvAMD-associated synonymous polymorphisms lie within HtrA1's putative insulin-like growth factor 1 (IGF-1) binding domain. They reduced HtrA1's abilities to associate with IGF-1 and to ameliorate IGF-1-stimulated signaling events and cellular responses. These observations highlight the relevance of synonymous codon usage to protein function and implicate homeostatic protein quality control mechanisms that may go awry in NvAMD.
Hagstrom SA, Ying G-S, Pauer GJT, Sturgill-Short GM, Huang J, Callanan DG, Kim IK, Klein ML, Maguire MG, Martin DF, of Group CAMDTTR. Pharmacogenetics for genes associated with age-related macular degeneration in the Comparison of AMD Treatments Trials (CATT). Ophthalmology 2013;120(3):593-599.Abstract
PURPOSE: To evaluate the pharmacogenetic relationship between genotypes of single nucleotide polymorphisms (SNPs) known to be associated with age-related macular degeneration (AMD) and response to treatment with ranibizumab (Lucentis; Genentech, South San Francisco, CA) or bevacizumab (Avastin; Genentech) for neovascular AMD. DESIGN: Clinical trial. PARTICIPANTS: Eight hundred thirty-four (73%) of 1149 patients participating in the Comparison of AMD Treatments Trials (CATT) were recruited through 43 CATT clinical centers. METHODS: Each patient was genotyped for SNPs rs1061170 (CFH), rs10490924 (ARMS2), rs11200638 (HTRA1), and rs2230199 (C3), using TaqMan SNP genotyping assays (Applied Biosystems, Foster City, CA). MAIN OUTCOMES MEASURES: Genotypic frequencies were compared with clinical measures of response to therapy at one year, including mean visual acuity (VA), mean change in VA, 15-letter or more increase in VA, retinal thickness, mean change in total foveal thickness, presence of fluid on OCT, presence of leakage on fluorescein angiography (FA), mean change in lesion size, and mean number of injections administered. Differences in response by genotype were evaluated with tests of linear trend calculated from logistic regression models for categorical outcomes and linear regression models for continuous outcomes. To adjust for multiple comparisons, P≤0.01 was considered statistically significant. RESULTS: No statistically significant differences in response by genotype were identified for any of the clinical measures studied. Specifically, there were no high-risk alleles that predicted final VA or change in VA, the degree of anatomic response (fluid on OCT or FA, retinal thickness, change in total foveal thickness, change in lesion size), or the number of injections. Furthermore, a stepwise analysis failed to show a significant epistatic interaction among the variants analyzed; that is, response did not vary by the number of risk alleles present. The lack of association was similar whether patients were treated with ranibizumab or bevacizumab or whether they received monthly or pro re nata dosing. CONCLUSIONS: Although specific alleles for CFH, ARMS2, HTRA1, and C3 may predict the development of AMD, they did not predict response to anti-vascular endothelial growth factor therapy.
Chen J, Smith LEH. Protective inflammasome activation in AMD. Nat Med 2012;18(5):658-60.Abstract
Age-related macular degeneration (AMD) is the most common cause of blindness in the elderly. AMD progression is associated with alterations in inflammatory pathways and the immune system. A new study identifies a protective role for inflammasomes in AMD, suggesting that inflammasome activation might be manipulated as a potential therapeutic strategy for this condition (pages 791-798).
Sobrin L, Ripke S, Yu Y, Fagerness J, Bhangale TR, Tan PL, Souied EH, Buitendijk GHS, Merriam JE, Richardson AJ, Raychaudhuri S, Reynolds R, Chin KA, Lee AY, Leveziel N, Zack DJ, Campochiaro P, Smith TR, Barile GR, Hogg RE, Chakravarthy U, Behrens TW, Uitterlinden AG, van Duijn CM, Vingerling JR, Brantley MA, Baird PN, Klaver CCW, Allikmets R, Katsanis N, Graham RR, Ioannidis JPA, Daly MJ, Seddon JM. Heritability and genome-wide association study to assess genetic differences between advanced age-related macular degeneration subtypes. Ophthalmology 2012;119(9):1874-85.Abstract
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.

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