Effects of fluid shear stress on apoptosis of osteoblasts and expression of bcl-2,Bax and caspase-3.

PURPOSE: The aim of the present investigation is to evaluate the effects of fluid shear stress on the cells of osteoblasts and to determine the mechanisms involved. METHODS: The fluid shear stress with a magnitude of 0(control group), 0.6, 1.0, 2.0, 3.0, 4.0, 5.0 Pa was exerted on the third passage of osteoblasts for 1 hour, and incubation in static condition for 24 hours. The cell apoptotic index was tested by the terminal transferase dUTP nick end-labeling (TUNEL) method. The expression of bcl-2, Bax and caspase-3 were detected by immunohistochemical method. Statistical analysis was performed using SPSS11.5 software package for one-way ANOVA. RESULTS: The apoptosis of osteoblasts and the expression of bcl-2, Caspase-3 were not affected significantly by the fluid shear stress with a magnitude from 0 to 2.0 Pa (P>0.05). But in the 3.0,4.0 and 5.0 Pa groups, the number of apoptotic cells and the expression of caspase-3 increased while the expression of bcl-2 decreased (P<0.05).There was no significant difference in expression of Bax in all groups. CONCLUSIONS: The physiological fluid shear stress does not affect apoptosis of osteoblasts. However, the fluid shear stress of over-magnitude may lead to the decrease the expression of bcl-2, which results in activation of caspase-3 and apoptosis of osteoblasts. [ABSTRACT FROM AUTHOR]