Testing possible adiponectin-mediated factors that may stimulate matrix metalloproteinase (MMP) expression in rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLSs). (a) Adiponectin-mediated interleukin (IL)-6 and IL-8 may stimulate MMP expression, but the levels of MMPs at 6 hours of stimulation are very low compared with that stimulated by IL-1β, which did not stimulate MMP expression in RA FLSs. (b) Recombinant adiponectin protein contaminated with lipopolysacchride (LPS) could stimulate MMP expression; however, LPS at 1 μg/mL did not strongly stimulate the expression of these proteins compared with adiponectin at 10 μg/mL. The data shown are representative of two independent experiments, which were performed in duplicate. Similar results were obtained from the two experiments.