Joint Location-Specific JAK-STAT Signaling in Rheumatoid Arthritis Fibroblast-like Synoviocytes

Deepa Hammaker; Gyrid Nygaard; Amanda Kuhs; Rizi Ai; David L Boyle; Wei Wang; Gary S Firestein

doi:10.1002/acr2.11093

Joint Location-Specific JAK-STAT Signaling in Rheumatoid Arthritis Fibroblast-like Synoviocytes

ACR Open Rheumatol. 2019 Oct 31;1(10):640-648. doi: 10.1002/acr2.11093. eCollection 2019 Dec.

Authors

Deepa Hammaker¹, Gyrid Nygaard¹, Amanda Kuhs¹, Rizi Ai², David L Boyle¹, Wei Wang², Gary S Firestein¹

Affiliations

¹ School of Medicine, Department of Rheumatology, Allergy and Immunology, University of California San Diego, La Jolla, California.
² Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California.

Abstract

Objective: 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.

Methods: 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.

Results: 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.

Conclusion: 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.

Abstract

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