Effect of continuous compressive force on the expression of RANKL, OPG, and VEGF in osteocytes.

The present study aimed to investigate the effect of a compressive force (CF) on the expression of receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegerin (OPG), and vascular endothelial growth factor (VEGF) in murine osteocytes (MLO-Y4) as well as animal study. After application of a CF for 1, 3, 6, and 12 h, gene and protein expression of RANKL, OPG, and VEGF in MLO-Y4 cells were determined by real-time PCR and enzyme-linked immunosorbent assay (ELISA). Furthermore, the effect of a stretch-activated (S-A) channel was examined by gadolinium (Gd) administration. In an animal experiment, the expression of these factors in osteocytes of alveolar bone was examined after experimental tooth movement in rats. After CF application, significant increases in RANKL, VEGF and RANKL/OPG ratio were shown. The upregulated gene and protein levels of these factors were reduced by Gd administration. After tooth movement, upregulated RANKL and VEGF were imunohistochemically shown in osteocytes of alveolar bone. These findings suggest that CF application on osteocytes elevates expression of osteoclast-inducing factor and angiogenesis factor in vivo and vitro.