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OP0078 Synovial Myofibroblasts from Spondyloarthritis Patients Produce IL-26 Spontaneously and The Production Is Enhanced upon IL-1, TNF-α and LPS Stimulation
  1. L.D. Heftdal1,
  2. M. Hvid1,2,
  3. B. Deleuran1,3,
  4. T.W. Kragstrup1,3
  1. 1Department of Biomedicine
  2. 2Department of Clinical Medicine, Aarhus University
  3. 3Department of Rheumatology, Aarhus University Hospital, Aarhus C, Denmark

Abstract

Background New bone formation in spondyloarthritis involves myofibroblasts [1]. IL-26 is part of the IL-10 cytokine family and was recently reported to increase Th17 differentiation [2]. It was first discovered in herpesvirus saimiri–transformed T cells and thus suspected to be a T-cell cytokine [3]. However, more recent studies of RA patients show IL-26 expression in synoviolin-postive cells harvested from the synovia [2]. The knowledge about IL-26 is compromised by lack of IL-26 in mice and no studies of IL-26 in spondyloarthritis (SpA) and its regulation have been conducted.

Objectives In the present study we aim to characterize IL-26 producing cells in spondyloarthritis (SpA).

Methods IL-26 was measured by ELISA in plasma and synovial fluid (SF) of 14 SpA patients attending the clinic with a swollen joint and in plasma samples from 7 age and gender matched healthy controls. Synovial-fluid-mononuclear-cells (SFMC) and fibroblast-like-synoviocytes (FLS) were cultured and stimulated for 48 hours with IL-1β, TNFα, TGF-β, IL-17A and LPS. The supernatants were harvested and analyzed for IL-26 by ELISA. Tissue samples of inflamed synovial membrane were stained with a fluorochrome conjugated rabbit IL-26 antibody for immunofluorescence. Imaging of the sections was performed by confocal microscopy. For flow cytometry analysis, FLS were surface stained for CD90 and a live-dead marker, and subsequently permeabilized and stained intracellularly for α-Smooth-Muscle-Actin (αSMA) and IL-26. Samples were run on the flow cytometer within 24 hours of staining. Data are expressed as mean ± SD.

Results IL-26 levels were significantly higher in synovial fluid compared with plasma; this applied to plasma from the healthy controls (HC) as well as SpA patients. (HC plasma: 5.8 ± 3.3 pg/ml, SpA plasma: 6.6 ± 1.8 pg/ml, SpA SF: 41.6 ± 6.8 pg/ml - P-values HC vs. SF: 0.0020, P-value SP vs. SF: <0.0001.) Staining of synovial membrane revealed IL-26 presence in synovial cells with fibroblast-like morphology. ELISA analysis of the supernatants from culturing and stimulation of FLS and SFMC showed a high level of IL-26 in both cell populations as well as drastic increase in IL-26 production after stimulation with IL-1, TNF-α and LPS. The vast majority of the IL-26 producing FLS were αSMA+ and CD90+ myofibroblasts by flow cytometry.

Conclusions IL-26 levels in synovial fluid are significantly higher than in plasma, suggesting a local production of IL-26 in the inflamed joint. We found IL-26 positive cells in the synovial membrane with fibroblast morphology and FLS from the inflamed joints of SpA patients produce high amounts of IL-26. By flow cytometry we established that these IL-26 producing fibroblasts seem to be myofibroblasts primarily.

  1. Beyer C, et al: Changing paradigms in spondylarthritis: The myofibroblast signature. Arthritis Rheum. 2012;65:24–7

  2. Corvaisier M, et al: IL-26 is overexpressed in rheumatoid arthritis and induces proinflammatory cytokine production and Th17 cell generation. PLoS Biol 2012;10:e1001395

  3. Knappe A, et al: Induction of a novel cellular homolog of interleukin-10, AK155, by transformation of T lymphocytes with herpesvirus saimiri. J Vi- rol 2000;74:3881–3887

Disclosure of Interest None declared

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