Effect of THR0921 on osteoclast differentiation. Mouse bone marrow cells were incubated for 8 days in the presence or absence of macrophage colony-stimulating factor (M-CSF; 10 ng/ml), soluble receptor activator of nuclear factor κB ligand (sRANKL; 30 ng/ml), and THR0921 at the concentrations shown. After incubation, cells were stained with the tartrate-resistant acid phosphatase (TRAP) staining kit and enumerated under 40× magnification. The mean ± standard error of the mean of TRAP-positive multinuclear cells containing three or more nuclei from four randomly selected fields is shown. The hash symbol indicates p < 0.01; the dagger symbol indicates p < 0.05 versus cells stimulated with M-CSF + sRANKL without THR0921.