Objectives Systemic sclerosis (SSc) is an autoimmune disease with unknown pathogenesis manifested by inflammation, vasculopathy and fibrosis in skin and internal organs. Type I interferon signature found in SSc propelled us to study plasmacytoid dendritic cells (pDCs) in this disease. We aimed to identify candidate pathways underlying pDC aberrancies in SSc and to validate its function on pDC biology.
Methods In total, 1193 patients with SSc were compared with 1387 healthy donors and 8 patients with localised scleroderma. PCR-based transcription factor profiling and methylation status analyses, single nucleotide polymorphism genotyping by sequencing and flow cytometry analysis were performed in pDCs isolated from the circulation of healthy controls or patients with SSc. pDCs were also cultured under hypoxia, inhibitors of methylation and hypoxia-inducible factors and runt-related transcription factor 3 (RUNX3) levels were determined. To study Runx3 function, Itgax-Cre:Runx3 f/f mice were used in in vitro functional assay and bleomycin-induced SSc skin inflammation and fibrosis model.
Results Here, we show downregulation of transcription factor RUNX3 in SSc pDCs. A higher methylation status of the RUNX3 gene, which is associated with polymorphism rs6672420, correlates with lower RUNX3 expression and SSc susceptibility. Hypoxia is another factor that decreases RUNX3 level in pDC. Mouse pDCs deficient of Runx3 show enhanced maturation markers on CpG stimulation. In vivo, deletion of Runx3 in dendritic cell leads to spontaneous induction of skin fibrosis in untreated mice and increased severity of bleomycin-induced skin fibrosis.
Conclusions We show at least two pathways potentially causing low RUNX3 level in SSc pDCs, and we demonstrate the detrimental effect of loss of Runx3 in SSc model further underscoring the role of pDCs in this disease.
- systemic sclerosis
- dendritic cells
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Handling editor Josef S Smolen
Contributors WM and TRDJR supervised the study. AJA, TC, JCAB, JAvR, WM and TRDJR designed the study and wrote the initial draft of the manuscript. AJA, TC, AO, JCAB, LB-C, RGT, LvB, EC, MR, JSM, SG, LMGdK, RBC and WM performed the experiments, acquired, analysed and interpreted the data. AP, JM and JAvR analysed and interpreted the data. AO, JCAB, LvB, JSM, RBC, JM and TRDJR collected, analysed and supplied clinical data. All authors have critically revised and approved the final version the manuscript for important intellectual content.
Funding AJA was supported by the Dutch Arthritis Association (Reumafonds grant NR-10-1-301) and the Netherlands Organisation for Scientific Research (Mosaic grant 017.008.014). TC is supported by a grant from the Portuguese national funding agency for science, research and technology: Fundação para a Ciência e a Tecnologia [SFRH/BD/93526/2013]. JCAB is supported by a VENI Award from the Netherlands Organisation for Scientific Research (NWO project number 91614041). WM obtained funding from Marie Curie Intra-European Fellowship (Proposal number: 624871) and from the NWO VENI (grant number 91919149). TRDJR and JAGvR received funding from ERC Starting Grant (ERC-2011-StG, Circumvent). We thanked Kei Yasuda, Mike DiMarzio (Boston University), Chiara Angiolilli, Aniek Meijers, Ana P Lopes, M Inês Ramos (UMC Utrecht), and Mascha Schijvenaars (Radboud University Nijmegen) for their advice and technical expertise.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The local ethical committee (Institutional Review Boards) from The Boston University Medical Center, University Medical Center Utrecht, Instituto de Parasitología y Biomedicina López-Neyra, and the University of São Paulo reviewed and approved the conduct of this study.
Provenance and peer review Not commissioned; externally peer reviewed.
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