Measurement of cartilage oligomeric matrix protein (COMP) in normal and diseased equine synovial fluids

Objective: This study was designed to assay cartilage oligomeric matrix pro tein (COMP) in equine synovial fluids and to compare the concentration in s ynovial fluids from normal horses with joint diseased horses. The relations hip between the COMP degradation and the matrix metalloproteinase activity in synovial fluids was also investigated. Design: Using COMP antigen prepared from equine articular cartilage and mur ine monoclonal antibody (12C4) raised against human COMP, an inhibition ELI SA was developed. COMP in equine synovial fluids from normal and diseased j oints was quantified. Metalloproteinase activities were evaluated in the sa me synovial fluids by a gelatin degradation ELISA. COMP fragments were eval uated qualitatively by Western blotting. Results: The COMP inhibition ELISA was reliable at concentrations of equine COMP between 62.5 and 2000 ng/ml. COMP values in joint fluids in both asep tic and septic joint disease (19.7+/-15.3 and 16.1+/-11.2 mug/ml, respectiv ely) were significantly (P<0.001) lower than normal (53.2+/-29.0 <mu>g/ml). The molecular sizes of COMP on immunoblots were different between normal a nd diseased synovial fluids; more fragments were seen in diseased fluids. T he aseptic (26.6 +/- 20.6%) and septic joint disease synovial fluids (36.1 +/- 37.5%) had significantly higher (P<0.02 and 0.002, respectively) gelati nolytic activities than normal (13.6+/-13.7%). There was a negative correla tion (R=-0.31, P<0.002) between COMP level and gelatinase activity. Conclusions: We conclude that the fragment pattern and the absolute COMP co ncentration maybe useful for monitoring joint disease, and that COMP degrad ation in synovial fluids from progressed joint disease may be due to MMP ge latinolytic activity. (C) 2001 OsteoArthritis Research Society Internationa l.