Low-magnitude high-frequency vibration inhibits RANKL-induced osteoclast differentiation of RAW264.7 cells.

Osteoclasts are the key participants in regulation of bone mass. Low-magnitude high-frequency vibration (LMHFV) has been found to be anabolic to bone in vivo. This study aimed to investigate the effect of LMHFV on osteoclast differentiation in vitro. Murine monocyte cell line RAW264.7 cells in the presence of receptor activator of nuclear factor-kappaB ligand (RANKL) were treated with or without LMHFV at 45 Hz (0.3 g) for 15 min day(-1). Tartrate resistant acid phosphatase (TRAP)-positive multinucleated cells (MNCs) and actin ring formation were evaluated. Expression of the osteoclast-specific genes, such as cathepsin K, matrix metallopeptidase-9 (MMP-9) and TRAP, were analyzed using real time-PCR. c-Fos, an osteoclast-specific transcription factor, was determined using Western blot. We found that LMHFV significantly decreased the number of RANKL-induced TRAP-positive MNCs (P<0.01), and inhibited the actin ring formation. The mRNA expression of the cathepsin K, MMP-9 and TRAP were down-regulated by LMHFV intervention (all P<0.001). Furthermore, LMHFV also inhibited the expression of c-Fos protein in the RANKL-treated RAW264.7 cells (P<0.05). Our results suggest that LMHFV can inhibit the RANKL-induced osteoclast differentiation of RAW264.7 cells, which give some new insight into the anabolic effects of LMHFV on bone.