Effect of atorvastatin on osteoclast formation. (A) Osteoclast formation was assayed with tartrate-resistant acid phosphatase (TRAP) staining and counting positive cells containing three or more nuclei under a light microscope (original magnification, ×100). (B) Peripheral blood mononuclear cells (PBMCs; 2 × 105 cells/well) from a healthy donor were cocultured with fibroblast-like synoviocytes from a rheumatoid arthritis patient (RA FLSs; 2 × 104 cells/well, patients 1, 4, and 5) in the presence of macrophage colony-stimulating factor, 1,25-dihydroxyvitamin D3, and different concentrations (0.001 to 0.1 μM) of atorvastatin in 96-well plates for 3 weeks. Cell viabilities were assayed in separate cultures of FLSs and PBMCs. (C) PBMCs were cultured for 3 weeks in the presence of 10-7 M 1,25-dihydroxyvitamin D3 and different concentrations of atorvastatin. (D) RA FLSs were cultured for 3 weeks in the presence of 2 ng/ml macrophage colony-stimulating factor and different concentrations of atorvastatin (0.001 to 0.1 μM). Bars represent means and SDs. All experiments were carried out 3 times in triplicate. *P < 0.01 versus control.