Urokinase-type plasminogen activator (u-PA)/u-PA receptor (u-PAR)-dependent chemoinvasion in healthy (H) and rheumatoid arthritis (RA) synoviocytes. (a) Cell invasion of Matrigel-coated filters by H and RA synoviocytes as a function of u-PA concentration. Migration was stimulated by increasing concentrations of u-PA (5 to 250 ng/ml) in the lower well of the migration chamber. (b) Percent increase of Matrigel invasion in H and RA synoviocytes treated with Raloxifene (RAL) or neutralizing antibodies. Basal, invasion of H and RA synovial cells in the presence of 0.2% FCS in the lower well; C+, invasion stimulated by conditioned medium of A431 cell line, used as a sure chemotactic agent; RAL 0.5 and RAL 1, invasion challenged with 0.5 μM and 1 μM RAL in the lower well; u-PA, invasion challenged with 100 ng/ml of u-PA in the lower well; u-PA+RAL 0.5 and u-PA+RAL 1, invasion challenged with 100 ng/ml u-PA in the presence of 0.5 and 1 μM RAL in the lower well; u-PA+5B4 and u-PA+3936, invasion challenged with 100 ng/ml u-PA in the presence of 1.5 μg/ml of monoclonal antibodies 5B4 and 3936 in the lower and upper well, respectively. In (a) and (b), each point represents the mean ± standard deviation of three experiments performed in triplicate on four normal and four RA synovial cell lines. § = p < 0.01 versus basal (0.2% FCS); # = p < 0.001 versus u-PA, for both H and RA.