Project description:Diabetic retinopathy (DR) and age-related macular degeneration (AMD) are leading causes of visual impairment and blindness in people aged 50 years or older in middle-income and industrialized countries. Anti-VEGF therapies have improved the management of neovascular AMD (nAMD) and proliferative DR (PDR), no treatment options exist for the highly prevalent dry form of AMD. To unravel the biological processes underlying these pathologies and to find new potential biomarkers, a label-free quantitative (LFQ) method was applied to analyze the vitreous proteome in PDR (n=4), AMD (n=4) compared to idiopathic epiretinal membranes (ERM) (n=4). Post-hoc tests revealed 96 proteins capable of differentiating among the different groups, whereas 118 proteins were found differentially regulated in PDR compared to ERM and 95 proteins in PDR compared to dry AMD. The pathway analysis indicates that mediators of complement and coagulation cascades and acute phase responses are enriched in PDR vitreous, whilst proteins highly correlated to the extracellular matrix (ECM) organization, platelet degranulation, lysosomal degradation, cell adhesion, and central nervous system development were found underexpressed. According to these results, 35 proteins were selected and validated by MRM (multiple reaction monitoring) in a larger cohort of patients with ERM (n=21), DR/PDR (n=20), AMD (n=11), and retinal detachment (n=13). Of these, 26 proteins were validated and were capable of differentiating between vitreoretinal diseases under study. Based on Partial least squares discriminant and multivariate exploratory receiver operating characteristic (ROC) analyses, a panel of 15 discriminatory biomarkers was defined, which includes complement and coagulation components (CO2 and prothrombin), acute-phase mediators (alpha-1-antichymotrypsin), adhesion molecules (e.g., myocilin, galectin-3-binding protein), ECM components (opticin), and neurodegeneration biomarkers (beta-amyloid, amyloid-like protein 2).

Project description:Reduced oxygenation of photoreceptors and the RPE in the ageing eye may be a risk factor for the development of both neovascular and dry AMD. Chronic activation of the molecular response to hypoxia in RPE or photoreceptors leads to retinal degeneration that depends on hypoxia inducible transcription factors. For approaching the identification of accessible markers characteristic for photoreceptors with an activated hypoxic response, we used a proteomics approach to determine the protein composition of the vitreous humor in mice. To discriminate between rod and cone-specific effects we used genetically modified mice that had the hypoxic response activated specifically in rods of a rod-dominant retina (rodΔVhl) or a genetically engineered all-cone retina (coneΔVhl). For comparison, we used wild-type mice exposed for 6 hours to acute hypoxia. We identified 1,357 unique proteins in the vitreous of mice after acute hypoxia, 1,624 in rodΔVhl and 1,895 in coneΔVhl mice. Of these, 1,043 proteins were common to all three types of mice. Of the identified proteins, 257 were significantly regulated by a factor of 1.5 or more in hypoxic mice, 258 in rodΔVhl and 356 in coneΔVhl mice in at least one of the three analyzed time points. Only 51 of the significantly regulated proteins were common to the vitreous of rodΔVhl and coneΔVhl mice, suggesting different consequences of the activated hypoxic response for rods and cones. Guanylate binding protein 2 (GBP2) was found at increased levels in the vitreous of both rodΔVhl and coneΔVhl mice at all time points tested. This was also reflected by increased gene expression in the retina. Although retinal expression of the AMD-associated gene alpha-2 macroglobulin (A2M) appeared increased in both types of mice, the protein was only found elevated in the vitreous of rodΔVhl mice. Other proteins found increased included Serpina3n, synaptosome associated protein 25 (SNAP25) and others. The distinct protein compositions present at early and late time points, suggest a well-regulated process in our models. We hypothesize that some of the proteins identified at early time points may potentially be used as markers for the chronic hypoxic response of photoreceptors.

Project description:Background Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in the elderly population worldwide. Recent studies have demonstrated strong genetic associations between AMD and single nucleotide polymorphisms (SNPs) within genes such as CFH and HTRA1. However, we have identified monozygotic twins discordant for AMD phenotypes (one with disease, the other without disease), suggesting that an epigenetic mechanism may also contribute to the pathogenesis of AMD. Methods We identified two twin pairs with phenotypic discordance of AMD. We obtained genomic DNA from their peripheral blood mononuclear cells (PBMCs) and subjected them to DNA methylation-chip analysis (MeDIP-chip) that profiled genome-wide DNA methylation patterns on promoters of all genes and microRNAs. We next utilized the Methyl-Profiler DNA methylation assays to detect the methylation status of selected promoters. Flow cytometry and quantitative real-time PCR were used to detect the expression of the selected gene in peripheral blood cells, as well as in retinal and choroidal tissues of AMD patients and non-AMD controls. Results Our MeDIP-chip analysis identified 256 genes with hypo-methylated promoters only in the twins with AMD and 744 genes with hyper-methylated promoters only in the twins with AMD. Importantly, the promoter region of IL17RC was associated with hypo-methylated CpG sites only in the twins with AMD but not in the twins without AMD. We also found the association of the hypo-methylated IL17RC promoter with AMD in 7 pairs of siblings with discordant AMD pathology (P=0.003), as well as an independent patient cohort (95 neovascular wet and 107 geographic atrophy dry AMD patients as well as 96 non-AMD controls (95% CI, 0.01-0.10, P=9.8x10-8 for wet AMD vs. control; 95% CI, 0.05-0.32, P=2.2x10-5 for dry AMD vs. control)). Interestingly, we did not find an association between the levels of methylation on the IL17RC promoter with the previously identified genetic risk alleles in CFH, HTRA1, and ARMS2. We demonstrated an elevated expression of the IL-17RC protein in CD14+ monocytes in the peripheral blood of AMD patients as compared to non-AMD controls. These IL-17RC+ monocytes have elevated expression of CXCR1, CXCR2, and CXCR4. In addition, IL17RC was expressed only in the retinal and choroidal tissues from AMD patients but not from age-matched controls. Conclusions We show an association of the hypo-methylated IL17RC promoter with AMD, which resulted in the elevated expression of IL-17RC in peripheral blood cells as well as the retinal and choroidal tissues of AMD patients. Our study suggests that the hypo-methylated IL17RC promoter and elevated expression of IL-17RC can potentially serve as biomarkers for the diagnosis of AMD, while IL-17RC can be a new therapeutic target for AMD. In addition, our results strongly suggest an epigenetic control mechanism of AMD pathogenesis. The Affymetrix MOE430 2.0 GeneChip was used to detect gene expression patterns within the whole eye of C57B/6 normal mice.

Project description:Background Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in the elderly population worldwide. Recent studies have demonstrated strong genetic associations between AMD and single nucleotide polymorphisms (SNPs) within genes such as CFH and HTRA1. However, we have identified monozygotic twins discordant for AMD phenotypes (one with disease, the other without disease), suggesting that an epigenetic mechanism may also contribute to the pathogenesis of AMD. Methods We identified two twin pairs with phenotypic discordance of AMD. We obtained genomic DNA from their peripheral blood mononuclear cells (PBMCs) and subjected them to DNA methylation-chip analysis (MeDIP-chip) that profiled genome-wide DNA methylation patterns on promoters of all genes and microRNAs. We next utilized the Methyl-Profiler DNA methylation assays to detect the methylation status of selected promoters. Flow cytometry and quantitative real-time PCR were used to detect the expression of the selected gene in peripheral blood cells, as well as in retinal and choroidal tissues of AMD patients and non-AMD controls. Results Our MeDIP-chip analysis identified 256 genes with hypo-methylated promoters only in the twins with AMD and 744 genes with hyper-methylated promoters only in the twins with AMD. Importantly, the promoter region of IL17RC was associated with hypo-methylated CpG sites only in the twins with AMD but not in the twins without AMD. We also found the association of the hypo-methylated IL17RC promoter with AMD in 7 pairs of siblings with discordant AMD pathology (P=0.003), as well as an independent patient cohort (95 neovascular wet and 107 geographic atrophy dry AMD patients as well as 96 non-AMD controls (95% CI, 0.01-0.10, P=9.8x10-8 for wet AMD vs. control; 95% CI, 0.05-0.32, P=2.2x10-5 for dry AMD vs. control)). Interestingly, we did not find an association between the levels of methylation on the IL17RC promoter with the previously identified genetic risk alleles in CFH, HTRA1, and ARMS2. We demonstrated an elevated expression of the IL-17RC protein in CD14+ monocytes in the peripheral blood of AMD patients as compared to non-AMD controls. These IL-17RC+ monocytes have elevated expression of CXCR1, CXCR2, and CXCR4. In addition, IL17RC was expressed only in the retinal and choroidal tissues from AMD patients but not from age-matched controls. Conclusions We show an association of the hypo-methylated IL17RC promoter with AMD, which resulted in the elevated expression of IL-17RC in peripheral blood cells as well as the retinal and choroidal tissues of AMD patients. Our study suggests that the hypo-methylated IL17RC promoter and elevated expression of IL-17RC can potentially serve as biomarkers for the diagnosis of AMD, while IL-17RC can be a new therapeutic target for AMD. In addition, our results strongly suggest an epigenetic control mechanism of AMD pathogenesis.

Dataset Information

The Proteomic Landscape in the Vitreous of Patients With Age-Related and Diabetic Retinal Disease

Publications

The Proteomic Landscape in the Vitreous of Patients With Age-Related and Diabetic Retinal Disease.

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