Effect of dehydroxymethylepoxyquinomicin on human osteoclastogenesis and production of matrix metalloprotease-9 by human osteoclasts. (a) Peripheral blood monocytes were incubated in 96-well plates with macrophage colony-stimulating factor (M-CSF), receptor activator of NF-κB ligand (RANKL), and the indicated concentrations of dehydroxymethylepoxyquinomicin (DHMEQ). At day 7, the total number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNC) with three or more nuclei/well was counted. Representative data of three independent experiments are shown. *P < 0.01, DHMEQ versus dimethyl sulfoxide (DMSO). (b) Peripheral blood monocytes were incubated in 96-well plates with M-CSF and RANKL without DHMEQ. At day 7, the medium was replaced with fresh medium and the indicated concentrations of DHMEQ were added. The culture supernatant was collected at day 8, and the matrix metalloprotease-9 (MMP-9) concentration was measured by ELISA. Representative data of two independent experiments are shown. Data represent the mean ± standard error of the mean of triplicate wells, and were compared by Student's t test. *P < 0.05, DHMEQ versus DMSO.