2.3. Rhodamine-phalloidin staining and tartrate-resistant acid phosphatase (TRAP) staining

After culturing was complete, the cells were fixed with 4% paraformaldehyde. A solution of 0.1% Triton X was added to the fixed cells and was replaced with a rhodamine-phalloidin solution after 5 min; the samples were then allowed to stand for 30 min in the dark to stain F-actin. The numbers of osteoclasts with fluorescent rings were determined using a confocal laser microscope (LSM700, Carl Zeiss, Germany). TRAP staining was performed by adding TRAP solution and incubating the osteoclasts at 37 °C for 15 min. The numbers of cells with 3 or more nuclei were measured under an optical microscope.