Circulating surfactant protein -D is low and correlates negatively with systemic inflammation in early, untreated rheumatoid arthritis

Anne Friesgaard Christensen, Grith Lykke Sørensen, Kim Hørslev-Petersen, Uffe Holmskov, Hanne Merete Lindegaard, Kirsten Junker, Merete Lund Hetland, Kristian Stengaard-Pedersen, Søren Jacobsen, Tine Lottenburger, Torkell Ellingsen, Lis Smedegaard Andersen, Ib Hansen, Henrik Skjødt, Jens Kristian Pedersen, Ulrik Birk Lauridsen, Anders Svendsen, Ulrik Tarp, Jan Pødenphant, Aage VestergaardAnne Grethe Jurik, Mikkel Ostergaard, Peter Junker

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ABSTRACT: INTRODUCTION: Surfactant protein D (SP-D) is a collectin with immuno-regulatory functions, which may depend on oligomerization. Anti-microbial and anti-inflammatory properties have been attributed to multimeric SP-D variants, while trimeric subunits per se have been suggested to enhance inflammation. Previously, we reported low circulating SP-D in early rheumatoid arthritis (RA), and the present investigation aims to extend these data by serial SP-D serum measurements, studies on synovial fluid, SP-D size distribution and genotyping in patients with early RA. METHODS: One-hundred-and-sixty disease-modifying antirheumatic drug (DMARD) naïve RA patients with disease duration less than six months were studied prospectively for four years (CIMESTRA (Ciclosporine, Methotrexate, Steroid in RA) trial) including disease activity measures (C-reactive protein, joint counts and Health Assessment Questionnaire (HAQ) score), autoantibodies, x-ray findings and SP-D. SP-D was quantified by enzyme-linked immunosorbent assay (ELISA) and molecular size distribution was assessed by gel filtration chromatography. Further, SP-D Met11Thr single nucleotide polymorphism (SNP) analysis was performed. RESULTS: Serum SP-D was significantly lower in RA patients at baseline compared with healthy controls (P < 0.001). SP-D increased slightly during follow-up (P < 0.001), but was still subnormal at four years after adjustment for confounders (P < 0.001). SP-D in synovial fluid was up to 2.5-fold lower than in serum. While multimeric variants were detected in serum, SP-D in synovial fluid comprised trimeric subunits only. There were no significant associations between genotype distribution and SP-D. Baseline SP-D was inversely associated to CRP and HAQ score. A similar relationship was observed regarding temporal changes in SP-D and CRP (zero to four years). SP-D was not associated to x-ray findings. CONCLUSIONS: This study confirms that circulating SP-D is persistently subnormal in early and untreated RA despite a favourable therapeutic response obtained during four years of follow-up. SP-D correlated negatively to disease activity measures, but was not correlated with x-ray progression or SP-D genotype. These observations suggest that SP-D is implicated in RA pathogenesis at the protein level. The exclusive presence of trimeric SP-D in affected joints may contribute to the maintenance of joint inflammation. TRIAL REGISTRATION: ( NCT00209859).
Original languageEnglish
JournalArthritis Research & Therapy
Issue number2
Pages (from-to)R39
Publication statusPublished - 8. Mar 2010


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