Experimental Study Of Fluid Shear Stress Inhibits Apoptosis Induced By TNF-α In Murine Osteoblastic MC3T3-E1 Cell

Objective To observe the effect of fluid shear stress (FSS) on TNF-a-induced apoptosis in murine osteoblastic MC3T3-E1 cells,an attempt was made at establishing the physiological stress to stimulate bone formation.Methods MC3T3-E1 cell is divided into two groups:TNF-a intervention group(four experimental group:0min,15min,30min,60min group) and non-TNF-a intervention group (control group).apoptosis induced by TNF-α(10ng/ml)×4H,then MC3T3-E1 cell were stimulated by the FSS in different time(0min,15min,30min,60min),MTT assay were applied to measure the cellular proliferation,and Fluorescence Microscope and flow cytometry (FCM) were used to detection cell apoptosis by qualitation and quantitation respectively,western blotting was used to measure the exprssion of Caspase9 and Apaf-1 protein.Statistical analysis was performed using SPSS16.0 software package for one way analysis of variance (ANOVO).multiple comparisons were applied using LSD. Spearman rank correlation of Nonparametric test were used for correlation analysis. P<0.05 was considered significant.Result MC3T3-E1 cell showed significant signs of apoptosis within 4H of exposure to TNF-α(10ng/ml),survival of osteoblasts increased and the number of apoptosis decreased in time dependment manner by FSS. correlation coefficient of Spearman rank correlation r=-0.986,p<0.05,the time of FSS and apoptosis ratio had significant nagative correlation.and application of FSS(12dyne/cm2) significantly attenuated this TNF-a-induced apoptosis and those influences, analysis of ANOVO(F=1.976,p<0.05) and pairing Comparison of LSD (P<0.05) indicated statistical significance.the expression of Caspase 9 and Apaf-1 protein also increased by TNF-α,after different time of FSS the expression of both proteins reduced.Conclusion As the key protein in mitochondrial pathway,the Caspase9 and Apaf-1 protein increased by TNFa-induced apoptosis and decreased by FSS indicated that the physiological FSS can decrease TNF-αinduced apoptosis and increase cell activity in murine osteoblastic MC3T3-E1,and at least in part by attenuating TNF-α-induced mitochondrial pathway of Apoptosis.