Cellular activation products in osteoarthritis synovial fluid

In order to address the issue of the role of mast cells (MC) and nitric oxide (NO) in rheumatic synovial-fluid diseases, synovial fluid (SF) collected from the knee of patients with osteoarthritis (OA), articular chondrocalcinosis (ACC) or rheumatoid arthritis (RA) was examined for the levels of mast cells (MC), histamine, tryptase, phospholipase A2 and nitrite. MC counts were found to be elevated in the SF of OA patients as compared with RA patients. Histamine content in SF parallelled the number of MC. Tryptase levels were elevated in OA in comparison to RA and ACC, but the difference was not statistically significant. Identical PLA2 levels were recorded among the 3 groups. Nitrite concentrations were also higher in SF from OA patients as compared to RA patients. These results suggest that mast cells (MC), in association with various inflammatory cells, may contribute to inflammation and cartilage breakdown in osteoarthritis (OA).