Inhibition of osteoclastogenesis by DC-STAMP siRNAs and by anti–DC-STAMP. (A) Effects of the siRNAs on the formation of osteoclast-like TRAP positive MNCs in RAW-D cells stimulated with RANKL and TNF-α for 3 d. Specific reduction of DC-STAMP mRNA and DC-STAMPΔT7mRNA by #6 siRNA was evaluated by RT-PCR (right). *, P < 0.05; **, P < 0.01; ***, P < 0.001. (B) Inhibition of osteoclast-like TRAP positive MNC formation in RAW-D cells by anti–DC-STAMP. RAW-D cells were treated with RANKL and TNF-α for 3 d without or with indicated concentrations of anti–DC-STAMP. **, P < 0.01; ***, P < 0.001. IgG, control IgG (20 μg/ml). (C) Inhibition of osteoclastogenesis in mouse BM cells by anti–DC-STAMP. BM cells were cultured in the presence of 1α,25(OH)2D3 for 6 d without or with indicated concentrations of anti–DC-STAMP. *, P < 0.05; **, P < 0.01. (D) Anti–DC-STAMP inhibits osteoclast function. Rat osteoclast-like cells formed in BM cultures were seeded on dentin slices and cultured for 3 d in the presence of 10 μg/ml of control IgG or anti–DC-STAMP. *, P < 0.05.