Celecoxib reduces viability and proliferation of synovial fibroblasts extracted from patients with rheumatoid arthritis (RA). (a) Fibroblast-like synoviocytes (FLSs) of patients with RA were cultured for 24 hours in the presence of the cyclooxygenase inhibitors celecoxib, valdecoxib, or indomethacin at the indicated concentrations. Metabolic activity was determined by means of the MTS assay. Untreated cells (Co) and cells treated only with solvent served as controls. The graph presents relative cell viability toward cells treated only with solvent as the mean ± standard error of the mean (SEM) of three individual experiments. (b) Celecoxib strongly inhibits RA FLS proliferation in a dose-dependent manner. RA FLSs were stimulated for 24 hours with the indicated concentrations of celecoxib, and proliferation was assessed using [3H]thymidine incorporation. The graph presents relative cell viability toward cells treated only with solvent as the mean ± SEM of three individual experiments.