Objective To investigate the expression of DNAX-activating protein 12（DAP12） and tartrate-resistantacid phosphatase（TRAP） in mouse monocyte RAW264.7 subjected to compressive stress.Methods Mouse monocyteRAW264.7 was subjected to four-point bending system. The expression of DAP12 and TRAP mRNA were examined byreverse transcription-polymerase chain reaction（RT-PCR） and the expression of DAP12 protein by Western Blottingafter 0, 3, 6 and 12 h’s compressive stress.Results After RAW264.7 cells were cultured by osteoclast cell culturefluid, the amount of the cells increased, and the volume enlarged, and the number of nuclei per osteoclast increasedin vitro. The expression of DAP12 and TRAP mRNA and DAP12 protein of RAW264.7 cells subjected to compressivestress increased along with the time（PConclusion The mouse monocyte RAW264.7 can differentiate intoosteoclast in vitro, and high expression of DAP12 exists in the process of osteoclast differentiation.
