Figure 4: Adaptive osteoblast-regulated osteoclastic differentiation to compressive stress.
From: Magnitude-dependent response of osteoblasts regulated by compressive stress
In MC3T3-E1 cells, Rankl mRNA increased significantly only when a compressive stress of 2 g/cm2 was applied (a). Opg mRNA increased significantly in the groups exposed to 4 and 5 g/cm2 (b). The Rankl/Opg ratio increased significantly only in the group exposed to 2 g/cm2 (c). In POBs, Rankl mRNA increased significantly in the group exposed to 2 and 3 g/cm2 (d). Opg mRNA increased significantly in the group exposed to 5 g/cm2 (e). The Rankl/Opg ratio increased significantly in the groups exposed to 2 and 3 g/cm2 (f). The protein expression levels of RANKL and OPG in the culture medium of MC3T3-E1 cells were measured with ELISA. OPG expression showed a significant increase only in the cells exposed to 5 g/cm2 compressive stress (g). RANKL protein was not detected in the medium with ELISA. RAW264.7 cells were co-cultured with MC3T3-E1 cells exposed to compressive stress for 72 h with additions of 10−8 mol/L 1α,25(OH)2 D3 and 50 ng/mL M-CSF. TRAP activity increased significantly in the groups exposed to 1 and 2 g/cm2, but it was inhibited significantly in the group exposed to 5 g/cm2. Data are displayed as the mean ± SD from one representative of two (for ELISA) or three (for PCR and TRAP activity) independent experiments (n = 5 per group). “p” denotes the significance level compared with the group exposed to 0 g/cm2 (control). *p < 0.05.
