Characterization of OCs. Osteoclasts (OCs) were generated from monocytes with macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor κB ligand (RANKL) for 14 days. Dendritic cells (DCs) were derived from monocytes with the addition of granulocyte-macrophage colony-stimulating factor and IL-4 for 5 days. (A) Tartrate-resistant acid phosphatase (TRAP) staining to detect the TRAP activity in monocytes, OCs, and DCs. TRAP activity appears as purplish to dark red granules in the cytoplasm of the cells. (B) Bone resorption assay of OCs and DCs. OCs and DCs were generated from monocytes in 96-well plates with dentine discs in the wells. Dentine discs were stained with toluidine blue, and the blue area indicates the resorption of the dentine. (C) Phenotype of OCs and immature DCs. OCs and DCs were harvested and stained with antibodies and analyzed by flow cytometry. Shown are representative results of 3 independent experiments.