[Effect of Biaxial Tensile Strain on Expression of Osteogenic Specificity Markers of Rat Bone Marrow-derived Mesenchymal Stem Cells in Vitro].

The purpose of this study was to investigate the effect of biaxial tensile strain on the osteogenic differentiation of rat bone marrow mesenchymal stem cells(rBMSCs)in vitro.The rBMSCs were isolated from tibia and femur of 4weeks-old Sprague-Dawley(SD)rats.The rBMSCs were cultured in DMEM-LG complete culture medium and grew to subconfluence in the cell culture device for loading tensile strain.The biaxial tensile strain was applied to the rBMSCs for periods of 2,4and 6hours every day,respectively,lasting 3days.The amplitude of biaxial tensile strain applied to the rBMSCs were 1%,2% and 5%respectively,at a frequency of 1Hz.Unstrained rBMSCs were used as blank control(control group).The rBMSCs cultured with DMEM-LG complete culture medium containing100nmol/Lβ-Estradiol(E2)were used as positive control.The mRNA expression of alkaline phosphatase(ALP),collagen typeⅠ(ColⅠ),Runt-related transcription factor 2(Runx2)and osteocalcin(OCN)was examined with real-time quantitative PCR and the protein expression of ALP,ColⅠ,Runx2 and OCN was detected with Western blot method.The results showed as follws:(1)The mRNA and protein expression of the ALP,ColⅠ,Runx2,OCN were significantly higher in rBMSCs of the E2 group than those in the control group(P<0.05).(2)The mRNA and protein expression level of the ALP,Runx2 were higher markedly in the 1% tensile strain groups than those in the control group(P<0.05),but lower than those in the E2group(P<0.05).(3)The mRNA and protein expression level of the ALP,ColⅠ,Runx2,OCN were significantly higher in the 2% tensile strain groups than those in the control group(P<0.05),and the mRNA and protein expression level of ColⅠ and Runx2 in the group applied with2% amplitude of tensile strain for 4h/d was significantly higher than those in E2group(P<0.05).(4)The mRNA and protein expression level of the ALP,ColⅠ,Runx2 were significantly higher in the groups applied with 5% amplitude of tensile strain for 2h/d or for 4h/d than those in the control group(P<0.05).In our study,E2 and mechanical stimulation played an important role in the regulation of differentiation of rBMSCs into osteoblasts,and the manner applied with the 2%amplitude of tensile strain for 4h/d,lasting 3days was an optimal stimulus for up-regulating the mRNA and protein expression of ALP,ColⅠ,Runx2,OCN of rBMSCs.