Effect of TRAIL on differentiation of RAW264.7 cells into functional osteoclasts. RAW264.7 cells were left untreated (without cytokines) or cultured in the presence of TRAIL and with RANKL plus M-CSF with or without TRAIL for 10 days. (A) Representative fields of the cultures, treated as indicated, after TRAP staining (magnification, × 10; NA, 0.25). (B) The number of TRAP-positive multinucleated cells containing 3 or more nuclei was scored. Data represent the means ± SD of 7 different experiments.