Serum concentrations of cartilage oligomeric matrix protein, fibrinogen and hyaluronan distinguish inflammation and cartilage destruction in experimental arthritis in rats

Objectives. We investigated if changes in serum/plasma fibrinogen (FIB), hyaluronan (HA) and cartilage oligomeric matrix protein (COMP) levels can be used to differentiate between inflammation and cartilage involvement during arthritis. Methods. Collagen-induced arthritis (CIA), oil-induced arthritis (OIA) and for comparison, experimental autoimmune encephalitis (EAE) induced in DA rats were investigated. Results. Elevations of FIB concentrations were apparent at days 4-7 post-immunization in both arthritis models reaching a maximum on day 20-21, i.e. before peak arthritis. Elevations of HA in both models were seen shortly before macroscopically apparent arthritis, and peaked at or just before maximal arthritis, i.e. later in CIA than in OIA. COMP levels increased only after onset of arthritis and peaked late in disease (days 34-37), being significantly higher in the more destructive CIA compared with the less destructive OIA. During EAE flares, only FIB levels increased. Conclusions. FIB is a general inflammation marker, HA appears to be a marker for synovitis and changes in COMP levels appear to reflect the cartilage destruction process.