TRAP staining
TRAP staining of CD14+ monocytes and RAW264.7 macrophages was performed
after culturing with or without CXCL2 in the presence of M-CSF and
RANKL. TRAP staining was conducted using the TRAP kit (387A-1KT, Sigma)
in accordance with the manufacturer’s instructions. TRAP-positive
multinucleated cells containing more than 3 nuclei were identified as
osteoclasts and counted under a microscope.