Assay of mRNA levels of integrin-β1, integrin-β5, ALP, OCN, and OPG using real-time PCR. Pretreatment of integrin-β1 or ntegrin-β5 siRNA reduced mRNA level of integrin-β1 or β5 (A). The mechanical tensile strain of 2500 με enhanced mRNA levels of ALP, OCN, and OPG in MC3T3-E1 cells (the first and second column of B, C and D), pretreatment of integrin-β1 siRNA inhibited the mechanical induced the enhancement of the three mRNAs levels. Integrin-β5 siRNA had little effect on these mRNA levels, and pretreatments of both integrin-β1 siRNA and integrin-β5 siRNA simultaneously also attenuated the elevation, but the inhibitory effect was weaker than only integrin-β1 siRNA. *P < 0.05, **P < 0.01, between indicated groups.