Effects of frequency on osteoblast apoptosis induced by tensile strain / 医用生物力学

ABSTRACT

Objective To investigate the effect of frequency on osteoblast apoptosis induced by tensile strain.Methods MC3T3-E1 cells were applied with 1％ biaxial tensile strain at the frequency of 1,2,3,4,5 Hz,re spectively for 1 hour per day in 8 days.The survival rate of the cells was determined by activity of lactate dehydrogenase (LDH).Annexin V-FITC/ PI Flow cytometry was used to test cell apoptosis.Real-time RT-PCR was used to detect the gene level of apoptosis markers caspase-3,-9 as well as Bcl-2 and Bax,and Western blotting was used to test protein expressions of caspase-3,-9.Results Different loading frequencies had no effect on osteoblast activity of LDH.There was no significant difference in the total apoptosis rate of flow cytometry at different frequencies.However,the frequency of 2 Hz could induce early osteoblast apoptosis.Tensile strain at the frequency of 2 Hz could significantly increase the expression of caspase-3,-9 gene and protein,and induce cell apoptosis with the up-regulation of the Bax/Bcl-2.Conclusions Osteoblast apoptosis and death cannot be induced by 1％ biaxial tensile strain at the frequency of 1-5 Hz,but the frequency of 2 Hz can induce the early apoptosis of osteoblasts by up-regulating the expression of Bax/BCI-2.