ABSTRACT
<p><b>OBJECTIVE</b>To investigate the expression of DNAX-activating protein 12 (DAP12) and tartrate-resistant acid phosphatase (TRAP) in mouse monocyte RAW264.7 subjected to compressive stress.</p><p><b>METHODS</b>Mouse monocyte RAW264.7 was subjected to four-point bending system. The expression of DAP12 and TRAP mRNA were examined by reverse transcription-polymerase chain reaction (RT-PCR) and the expression of DAP12 protein by Western Blotting after 0, 3, 6 and 12h's compressive stress.</p><p><b>RESULTS</b>After RAW264.7 cells were cultured by osteoclast cell culture fluid, the amount of the cells increased, and the volume enlarged, and the number of nuclei per osteoclast increased in vitro. The expression of DAP12 and TRAP mRNA and DAP12 protein of RAW264.7 cells subjected to compressive stress increased along with the time (P < 0.05).</p><p><b>CONCLUSION</b>The mouse monocyte RAW264.7 can differentiate into osteoclast in vitro, and high expression of DAP12 exists in the process of osteoclast differentiation.</p>