Cell proliferation regulated by p38 MAPK activity. (a) The number of BrdU positive cells in 1,000. (b) Cell proliferation was evaluated by BrdU staining whereas all cell nuclei were stained by Hoechst 33258 dye. *P < 0.05 versus control. Each bar represents mean ± standard deviation of three experiments. Anti-CD95: treatment with a mAb anti-Fas CH 11 (100 ng/ml) in serum-free medium for 17 hours. SB: treatment with SB203580 (10 μmol/l) for 17 hours. SB+Anti-CD95: treatment with SB203580 for 2 hours followed by anti-Fas treatment for 17 hours. Control Ab: cells were treated with a mouse isotype control antibody IgM. Results are representative of three OA cartilage samples. BrdU, 5-bromo-2-deoxyuridine; mAb, monoclonal antibody; MAPK, mitogen-activated protein kinase; OA, osteoarthritis.