title: DNA methylation analysis of the temporal artery microenvironment in giant cell arteritis.
abstract: To investigate the inflammatory response in giant cell arteritis (GCA) by characterising the DNA methylation pattern within the temporal artery microenvironment.
  
  
  
  Twelve patients with non-equivocal histological evidence for GCA and 12 age-matched, sex-matched and ethnicity-matched controls with normal biopsies were studied. DNA was extracted from the affected portions of temporal artery tissue in patients with GCA and from histologically confirmed normal arteries in controls. Genome-wide DNA methylation status was evaluated using the Illumina Infinium HumanMethylation450 BeadChip Array. Differentially methylated loci between affected and unaffected arterial tissues were identified, and subsequent bioinformatic analysis performed. Immunohistochemistry was used to examine tissue expression patterns in temporal artery biopsies.
  
  
  
  We identified 1555 hypomethylated CG sites (853 genes) in affected temporal artery tissue from patients with GCA compared with normal controls. Gene ontology enrichment analysis of hypomethylated genes revealed significant representation in T cell activation and differentiation pathways, including both TH1 and TH17 signatures. Our DNA methylation data suggest a role for increased activity of the calcineurin/nuclear factor of activated T cells (NFAT) signalling pathway in GCA, confirmed by immunohistochemistry showing increased expression and nuclear localisation of NFAT1. NFAT signalling downstream targets such as interleukin (IL)-21/IL-21R and CD40L were overexpressed in GCA-affected arteries. Further, proinflammatory genes including TNF, LTA, LTB, CCR7, RUNX3, CD6, CD40LG, IL2, IL6, NLRP1, IL1B, IL18, IL21, IL23R and IFNG were hypomethylated in the cellular milieu of GCA arteries.
  
  
  
  We characterised the inflammatory response in GCA-affected arteries using 'epigenetic immunophenotyping' and identified molecules and pathways relevant to disease pathogenesis in GCA.
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Coit
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Lindsey B
authors.initials: LB
authors.lastname: De Lott
authors.affiliation: Department of Biostatistics, School of Public Health, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Bin
authors.initials: B
authors.lastname: Nan
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan, USA Department of Pathology, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Victor M
authors.initials: VM
authors.lastname: Elner
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA Center for Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Amr H
authors.initials: AH
authors.lastname: Sawalha
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D016022:Case-Control Studies; D016207:Cytokines / Q000378:metabolism; D019175:DNA Methylation; D005260:Female; D005786:Gene Expression Regulation / Q000276:immunology; D013700:Giant Cell Arteritis / Q000235:genetics* / Q000276:immunology / Q000473:pathology; D006801:Humans; D016130:Immunophenotyping; D018836:Inflammation Mediators / Q000378:metabolism; D008213:Lymphocyte Activation / Q000235:genetics / Q000276:immunology; D008297:Male; D013601:T-Lymphocytes / Q000276:immunology; D013699:Temporal Arteries / Q000276:immunology / Q000378:metabolism* / Q000473:pathology
chemical_list: D016207:Cytokines; D018836:Inflammation Mediators
keywords: Cardiovascular Disease; Giant Cell Arteritis; Systemic vasculitis