Abstract: Objective  To study the effect of low intensity ultrasound on osteoclast activity and osteolytic in the mouse skull dissolution model.Methods A total of 30 BALB/c mice were randomly divided into blank control group,grain group and ultrasound group,10 in each group.Improved wear particles were used to replicate mouse skull dissolution models,and the parietal bone samples of mice were obtained 15 d after operation.The number of inflammatory cells and osteolysis area were evaluated.A percentage of bone absorption lacuna area was detected by scanning electron microscope.The proliferation and differentiation of osteoclasts were observed by Tartrate-resistant acid  phosphatase(TRAP)   staining.The expression of osteoprotegerin (OPG) in damage bone tissues was observed by immunohistochemistry staining localization.Results The  HE staining results showed that  compared with blank control group,the exudation of inflammatory cells and osteolysis area  in  grain group and ultrasound group were increased significantly (P<0.01). Compared with grain group,the  osteolysis area in ultrasound group was decreased significantly (P<0.05);but the number of inflammatory cells in  two groups had no significant difference (P>0.05).The scanning electron microscope results showed  that the percentage of bone absorption lacuna area  in  ultrasound group was significantly lower than that in  grain group (P<0.01).The TRAP staining results showed that the number of osteoclasts in ultrasound group was significantly lower than that in grain group (P<0.01). The immunohistochemistry results showed that the number of  OPG positive cells in ultrasound group was significantly higher than those in grain group and blank control group (P<0.05).Conclusion Low intensity ultrasound can inhibit the proliferation and differentiation of osteoclasts in mouse skull dissolution model,and effectively reduce the  bone dissolution  induced by polyethylene wear particles.So the density and strength of bone around joint prosthetic are enhanced,and the incidence of joint mobilization is reduced.

Key words: skull dissolution, low intensity ultrasound, osteoprotegerin, wear particles, aseptic loosening, mice