Abstract:

BACKGROUND: Studies have shown that low-intensity and short-time vibration with a certain frequency can reduce the absorption of bone tissue and increase the quantity and quality of bone through promoting the proliferation and differentiation of osteoblasts. 
OBJECTIVE: To investigate the effects of different frequencies of vibration strains on cycle, proliferation and differentiation potency of RAW264.7 cells cultured in vitro.
METHODS: Passage 6 RAW264.7 cells in good conditions were randomly divided into six groups, and each group was induced cultured with Dulbecco’s modified Eagle’s medium containing receptor activator of nuclear factor kappa B ligand. The final concentration of receptor activator of nuclear factor kappa B ligand was adjusted to 50 μg/L, and then kept without changes. The non-loading group did not loaded with vibration strain, and the other five groups were loaded with 3-10 Hz, 15-35 Hz, 35-45 Hz, 50-70 Hz and 70-90 Hz vibration strains on the RAW264.7 cells respectively. The other vibration parameters were consistent; the vibration time was 15 min/time with the vibration intensity of 0.3 g, twice per day. The cell cycle and cell proliferation were detected at 3 and 6 days after loading of vibration strains.
RESULTS AND CONCLUSION: After composite vibration loading for 6 days, the cell cycle phase in the vibration groups was changed to some extent when compared with the non-loading group. Compared with non-loading group, the cell number in the G1 phase of the vibration group was significantly increased (P< 0.01); the cell number in the S phase and G2+M phase of the vibration group was significantly decreased (P < 0.01); the vibration parameters in the vibration group were significantly decreased (P < 0.01). The results indicate that different frequencies of vibration strains can affect the cell cycle and proliferation, and can inhibit the proliferation and differentiation of osteoblasts. 

Key words: vibration, stress, mechanical, osteoclasts, cell cycle, osteoporosis