The aim of this study was to investigate interleukin 37 (IL-37) levels in the serum and synovial fluid of patients with juvenile idiopathic arthritis (JIA), its expression in peripheral blood mononuclear cells, and correlation with disease activity and angiogenesis.
Seventy JIA patients and 50 control subjects were examined. The Juvenile Arthritis Disease Activity Score in 27 joints (JADAS-27) was calculated. Immunoassays were used to measure the serum and synovial fluid levels of IL-37, vascular endothelial growth factor (VEGF), soluble VEGF receptor 1 (sVEGF-R1), and sVEGF-R2. Relative expression of IL-37 mRNA in peripheral blood mononuclear cells and the power Doppler ultrasound score of the affected joint were measured.
Patients with JIA were subdivided as 20 systemic-onset, 20 polyarticular, and 30 oligoarticular (10 persistent, 20 extended) cases. Serum levels of IL-37, VEGF, VEGF-R1, and VEGF-R2 and relative IL-37 mRNA expression were significantly higher in JIA patients when compared with the control subjects (p < 0.001). These concentrations were significantly higher in systemic-onset JIA compared with those in polyarticular and oligoarticular JIA, and in polyarticular JIA when compared with oligoarticular JIA (p < 0.001). Serum, synovial, and mRNA expression levels of IL-37 were positively correlated with C-reactive protein, erythrocyte sedimentation rate, Juvenile Arthritis Disease Activity Score in 27 joints, power Doppler ultrasound score (p < 0.001), and the serum and synovial VEGF and VEGF-RI and -R2 levels (p < 0.05).
Our results demonstrate that IL-37 levels and mRNA expression were significantly increased in JIA patients, and their levels were positively correlated with disease activity and markers of angiogenesis (VEGF and VEGF receptors), suggesting that IL-37 may be correlated with angiogenesis.