Neutrophils from G-CSF–mobilized blood can be induced to acquire osteoclast phenotype. Neutrophils from G-CSF–mobilized donors were stimulated with GM-CSF (10 ng/mL)/TNFα (25 ng/mL)/IL-1β (10 ng/mL) for 5 days, followed by a culture period in osteoclast-promoting conditions (M-CSF, 25 ng/mL; RANKL, 100 ng/mL). TRAP (lower left; original magnification ×10) and immunofluorescence (upper right; nuclei, blue; actin, red; original magnification ×40) at day 21 of osteoclast culture identify cells with osteoclast phenotype (arrowheads). Lower right: Secondary cultures were initiated on bovine bone discs, and lacunae formation was assessed by scanning electron microscopy (bar = 100 µm). The insert shows a single osteoclast (bar = 10 µm) with several lacunae in its surrounding area. Data are representative of 3 experiments.