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Comprehensive Epigenetic Landscape of Rheumatoid Arthritis Fibroblast-like Synoviocytes [ChIP-seq]

ABSTRACT: Epigenetics is important in the pathogenesis of immune-mediated diseases like rheumatoid arthritis (RA). Here we show the first complete epigenomic characterization of RA fibroblast-like synoviocytes (FLS) by profiling histone modifications (H3K27ac, H3K4me1, H3K4me3, H3K36me3, H3K27me3, H3K9me3), open chromatin, RNA expression and whole genome DNA methylation. To address the complex multidimensional relationship and reveal the epigenetic regulation of RA, we perform integrative analyses using a novel unbiased method to identify genomic regions with similar profiles. Epigenomically similar regions exist in RA cells are particularly associated with active enhancers and promoters as well as specific transcription factor binding motifs. Differentially marked genes are enriched for immunological and unexpected pathways, with “Huntington's Disease Signaling” identified as particularly prominent. We validate the relevance of this pathway to RA by showing that Huntingtin-interacting protein-1 regulates FLS invasion into matrix. This work establishes a high-resolution epigenomic landscape of RA and demonstrates the potential for integrative analyses to identify unanticipated therapeutic targets.

ORGANISM(S): Homo sapiens

PROVIDER: GSE112655 | GEO | 2018/04/30

REPOSITORIES: GEO

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Project description:Rheumatoid synoviocytes, which consist of fibroblast-like synoviocytes (FLS) and synovial macrophages (SM), are crucial for the progression of rheumatoid arthritis (RA). Particularly, FLS of RA patients (RA-FLS) exhibit invasive characteristics reminiscent of cancer cells, destroying cartilage and bone, although it remains unresolved how RA-FLS exhibit invasive phenotype. RA-FLS and SM originate differently from mesenchymal and myeloid cells, respectively, but share many pathologic functions. However, the molecular signatures and biological networks representing the distinct and shared features of the two cell types are unknown. Presently, we performed global transcriptome profiling of FLS and SM obtained from RA and osteoarthritis patients. By comparing the transcriptomes, we identified distinct molecular signatures and cellular processes defining invasiveness of RA-FLS and pro-inflammatory properties of RA synovial macrophages (RA-SM), respectively. Interestingly, under interleukin1β-stimulated condition, RA-FLS newly acquired pro-inflammatory signature mimicking RA-SM without losing invasive properties. We next reconstructed a network model that delineates the shared, RA-FLS-dominant (invasive), and RA-SM-dominant (inflammatory) processes. From the network model, we selected 13 genes, including POSTN and TWIST1, as novel regulator candidates responsible for FLS invasiveness. Of note, POSTN and TWIST1 expressions were elevated in independent RA-FLS and were further instigated by interleukin1β. In vitro functional assays demonstrated the requirement of POSTN and TWIST1 for migration and invasion of RA-FLS stimulated with interleukin1β. Taken together, our systems approach to rheumatoid synovitis provides a basis for identifying novel regulators responsible for pathological features of RA-FLS and RA-SM, demonstrating how a certain type of cells acquires functional redundancy under chronic inflammatory conditions. To identify molecular signatures of FLS and MLS in RA joints, we isolated FLS from synovial tissues of RA and osteoarthritis (OA) patients, obtained synovial macrophages from synovial fluid of RA patients, and differentiated control macrophages from peripheral blood of healthy subjects. Also, we stimulated FLS with IL1β, and then analyzed gene expression profiles of both IL1β-stimulated RA-FLS and OA-FLS

Project description:Rheumatoid arthritis (RA) fibroblast‐like synoviocytes (FLS) derived from hip and knee have distinctive DNA methylation and transcriptome patterns in interleukin (IL)‐6 signaling and Janus kinase (JAK)–signal transducers and activators of transcription (STAT) pathways. To determine the functional effects of these joint‐specific signatures, we evaluated how RA hip and knee FLS differ in their response to IL‐6.Hip or knee RA FLS were obtained after arthroplasty. Previously published datasets on epigenetic landscape of FLS were mined to identify joint‐specific IL‐6–related epigenomic differences. RNA sequencing was performed on five RA hip and five knee FLS treated with or without IL‐6. Differential gene expression was determined using edgeR software. STAT3 phosphorylation was measured using bead assays. Sensitivity to tofacitinib was evaluated by measuring CCL2 inhibition using quantitative polymerase chain reaction. Assay for Transposase‐Accessible Chromatin sequencing and histone chromatin immunoprecipitation sequencing datasets from RA FLS were analyzed to identify epigenomic differences between hip and knee. Differential chromatin accessibility was associated with IL‐6, IL‐6R, and JAK1 genes. H3K27ac was also differentially marked at other JAK‐STAT–related genes, including STAT3‐STAT5A region. Principal component analysis of RNA sequencing data confirmed segregation between RA hip and knee FLS under basal conditions, that persisted following IL‐6 treatment. STAT3 phosphorylation after IL‐6 was significantly higher in knee than hip FLS and was highly correlated with JAK1 protein levels. Knee FLS were less sensitive to the JAK inhibitor tofacitinib than hip FLS. RA hip and knee FLS have distinct transcriptomes, epigenetic marks, and STAT3 activation patterns in the IL‐6 pathway. These joint‐specific differences might contribute to a differential clinical response in individual joints to targeted therapies such as JAK inhibitors.

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Comprehensive Epigenetic Landscape of Rheumatoid Arthritis Fibroblast-like Synoviocytes [ChIP-seq]

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