In vitro effects of low-intensity ultrasound stimulation on the bone cells

Mechanical perturbations serve as extracellular signals to a variety of cel ls, including bone cells. Low-intensity pulsed ultrasound produces signific ant multifunctional effects that are directly relevant to bone formation an d resorption. Ultrasound stimulation has been shown to accelerate bone-defe ct healing and trabecular bone regeneration. In this study, we use an in vi tro bone cell culture model to investigate the effect of low-intensity puls ed ultrasound. The rat alveolar mononuclear cell-calvaria osteoblast cocult ure system was used in this study. Before treatment, the bone cells were cu ltured for 3 days to facilitate their attachment and differentiation. Then, ultrasound exposure (frequency = 1 MHz, intensity = 0.068 W/cm(2)) or sham exposure for 20 rain per day was applied until the end of the experiment. Half of the culture media were obtained on the 4th, 5th, 6th, 7th, 8th, 9th , and 10th days for the analysis of cytokines and biochemical parameters. A t the end of the experiment, cells were fixed and stained for identificatio n and quantification of the osteoblast and osteoclast cells. After low-inte nsity pulse ultrasound stimulation, the osteoblast cell counts were signifi cantly increased, whereas the osteoclast cell counts were significantly dec reased. The total alkaline phosphatase amount in the culture medium was inc reased after 7 days of ultrasound stimulation, and tumor necrosis factor-al pha in ultrasound-stimulated bone cells was significantly increased after t he 7th day of culture and reached 474.77%. of the control medium on the 10t h day of culture. The results of this study suggest that low-intensity ultr asound treatment may have a stimulatory effect on bone-healing processes. ( C) 2001 John Wiley & Sons, Inc.