Circulating Aggrecan, Biglycan, and Decorin as Biomarkers of Osteoarticular Alterations in Juvenile Idiopathic Arthritis—A Preliminary Study

Proteoglycans and their fragments have potential as diagnostic or theragnostic biomarkers to identify diseases characterized by dysregulated extracellular matrix remodeling, such as juvenile idiopathic arthritis (JIA). Therefore, our study aimed to evaluate the diagnostic utility of plasma proteoglycan profiles, namely, aggrecan, decorin, and biglycan, released from osteoarticular structures into the blood of children with juvenile idiopathic arthritis. These profiles are potential biomarkers of tissue destruction and/or indicators of the efficacy of therapy with the biologic agent etanercept (ETA). This study was conducted on 263 blood samples collected from 25 healthy children and 34 children at various stages of juvenile idiopathic arthritis disease: immediately after diagnosis, following treatment with disease-modifying antirheumatic drugs (DMARD) (methotrexate, sulfasalazine, and prednisone), and during 3, 6, 12, 18, and 24 months of therapy with etanercept. Quantitative levels of aggrecan, biglycan, and decorin were measured using ELISA kits. In children with JIA, plasma aggrecan levels were elevated at diagnosis, decreased after ineffective DMARD therapy, and increased again at 24 months of etanercept treatment despite clinical improvement. By contrast, biglycan levels were similar to those in healthy controls but decreased during etanercept therapy. Decorin levels were initially high in untreated and DMARD-treated patients but returned to normal after 24 months of biologic treatment. After considering these findings and the ROC analysis, we conclude that decorin appears to be a promising biomarker for diagnosing and monitoring etanercept therapy in JIA, and biglycan is a useful biochemical marker for assessing the effectiveness of ETA treatment.