Release of cartilage macromolecules into the synovial fluid in patients with acute and prolonged phases of reactive arthritis

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Abstract
Objective. Extensive changes in articular cartilage metabolism occur during the acute phase of reactive arthritis, as indicated by altered release of cartilage macromolecules into synovial fluid (SF) demonstrated immunochemically. Nevertheless, permanent cartilage lesions are rare in this disease. To monitor specific events during the evolution of reactive arthritis, we investigated the content of cartilage macromolecules in sequentially obtained SF samples from 22 patients. Methods. Two groups of proteoglycan epitopes, the glycosaminoglycan‐rich region of aggrecan (referred to as proteoglycan) and its hyaluronan‐binding region (HABr), as well as one matrix protein, cartilage oligomeric matrix protein (COMP), were quantified by immunoassay. Results. SF proteoglycan concentrations, which were initially elevated, decreased significantly with prolonged arthritis, whereas COMP levels changed less markedly and levels of HABr remained stable. There was a positive correlation between SF and serum concentrations of COMP in samples obtained during the early phase of the disease. Conclusion. Cartilage involvement in reactive arthritis is transient, in contrast to findings in rheumatoid arthritis. Reactive arthritis should therefore be a suitable model for studies of repair processes in cartilage, which will facilitate understanding of the pathophysiology of cartilage involvement in arthritis.