Objective:To investigate the inhibition effect of small interfering RNA(siRNA)on the expression of vitamin D receptor(VDR),and observe the effects of down-regulation of VDR on the expression of dentin matrix protein 1(Dmp1),core binding factorα1(Cbfa1)and bone morphogenesis protein 2(BMP-2)mRNA in mouse osteoblast mc3t3-E1cells. Methods:Four pairs of 21 nucleotide VDR siRNAs directed to mouse VDR mRNA 144,594,852 and 3 628 targets were transfected into mc3t3-E1cells with LipofectamineTM 2000,while untreated and transfected scramble siRNA served as the blank control and nonspecific siRNA control separately. Total RNA of the cells were extracted after 24 h of transfection while protein extracted after 72 h. The expression of VDR in mRNA and protein levels were assessed by semiquantitive RT-PCR and Western blot respectively,according to ascertainment of the effective siRNA sequences. The expression of the functional gene of osteoblast,Dmp1,Cbfa1 and BMP-2 mRNA in mc3t3-E1 cells were detected by quantitive SYBR Green real-time PCR. Results:Compared with the blank control group,the expression of VDR mRNA and protein were significantly down-regulated by siRNA directed to 852 and 3628 target of mouse VDR mRNA(P < 0.01),while siRNA directed to 144 and 594 targets showed no effect on the expression of VDR(P > 0.05). According to the results of real-time PCR the expression of Dmp1,Cbfa1 and BMP-2 mRNA were down-regulated in mc3t3-E1 cells transfected with siRNAs directed to 852 and 3628 targets(P < 0.01). Conclusion:VDR siRNA can effectively inhibit the mRNA and protein mRNA expression of VDR. Inhibition of VDR expression down-regulates the mRNA expression of Dmp1,Cbfa1 and BMP-2 in mouse osteoblastic mc3t3-E1 cells. VDR may play some role in the maintenance of osteoblast functions.