ABSTRACT
OBJECTIVE: Cartilage oligomeric matrix protein (COMP) has been identified as a prognostic marker of progressive joint destruction in rheumatoid arthritis. In this population based study we evaluated associations between plasma concentrations of COMP, disease activity, and growth velocity in patients with recent-onset juvenile idiopathic arthritis (JIA). COMP levels in JIA and healthy children were compared with those in healthy adults. Plasma levels of insulin-like growth factor I (IGF-1), which has been associated with COMP expression and growth velocity, were studied in parallel. METHODS: 87 patients with JIA entered the study, including oligoarticular JIA (n = 34), enthesitis-related arthritis (n = 8), polyarticular rheumatoid factor (RF)-positive JIA (n = 2), polyarticular RF-negative JIA (n = 27), systemic JIA (n = 6), and undifferentiated JIA (n = 10). Plasma levels of COMP were measured by ELISA and IGF-1 by a radioimmunoassay. RESULTS: Significantly higher COMP levels [mean 18.9 U/l (95% CI 17.3-20.5)] were found in healthy children compared with healthy adults [mean 10.7 U/l (95% CI 9.4-12.1)] (p < 0.0001). COMP levels in the JIA patients [mean 13.5 U/l (95% CI 12.4-14.7)] were significantly reduced compared to healthy children (p < 0.0001), and correlated negatively with C-reactive protein (CRP; r = -0.29, p = 0.01) and thrombocyte count (r = -0.28, p = 0.02). COMP levels in the JIA patients correlated positively with growth velocity (cm/yr) (r = 0.38, p = 0.0003) and growth velocity (SDS) (r = 0.29, p = 0.007). CONCLUSION: We found reduced COMP levels in children with JIA compared with healthy children. COMP levels in JIA correlated negatively with inflammatory activity as evaluated by CRP and the thrombocyte counts, and were associated with reduced growth rate.
Subject(s)
Arthritis, Juvenile/blood , Arthritis, Juvenile/physiopathology , Extracellular Matrix Proteins/blood , Glycoproteins/blood , Growth Disorders/blood , Growth Disorders/physiopathology , Adult , Arthritis, Juvenile/complications , Blood Platelets/cytology , C-Reactive Protein/metabolism , Cartilage Oligomeric Matrix Protein , Cartilage, Articular/physiology , Child , Child Development/physiology , Cohort Studies , Extracellular Matrix/physiology , Female , Growth Disorders/etiology , Humans , Insulin-Like Growth Factor I/metabolism , Male , Matrilin Proteins , PrognosisABSTRACT
INTRODUCTION: Tumour necrosis factor (TNF)-alpha and TNF-beta, also called lymphotoxin (LT), are bound by soluble truncated TNF receptors (sTNFRI and II) that are released from cell surfaces and act as natural inhibitors of TNF-induced inflammation. We investigated the plasma levels of sTNFRI and II in parallel with LT binding capacity (LTBC) in 44 patients with juvenile chronic arthritis (JIA). METHODS: LTBC was determined by spiking diluted plasma samples with 1000 pg/ml of human recombinant LT. Detectable LT was measured by an in-house ELISA and LTBC was expressed in arbitrary units (AU) as the percentage value of bound LT to added LT. The levels of sTNFRI and-II were measured by ELISA (R&D). RESULTS: We found slightly reduced sTNFRI and II levels in JIA patients (n=44) compared with healthy controls sTNFRI: 1118 pg/ml (656-2074) [mean (range)] vs. 1262 pg/ml (819-2280) p=0.015; sTNFRII: 1953 pg/ml (889-4476) vs. 2311 pg/ml (1309-4186) p=0.008. The sTNFRI levels correlated positively with morning stiffness (r=0.30, p=0.044), physician's global assessment (r=0.39; p=0.009) and CRP (r=0.43; p=0.0048). sTNFRII did not correlate with measures of disease activity. In contrast, patient LTBC values were elevated compared to controls: 44 AU (36-52) vs. 31 AU (13-41) [mean (range)], p<0.0001, but did not correlate with disease activity. CONCLUSION: Despite overall slightly reduced plasma levels of sTNFRI and II, the capacity to bind TNF appeared to be increased in plasma samples from JIA patients.
