Abstract: Objective： To analyse knocking down Runx3 on BMP9-induced osteogenic differenciation of iMEFs. Methods：iMEFs were infected with ad-BMP9 and then the expression of endogenous Runx3 was determined by RT-PCR and Western blot. iMEFs were treated with ad-siRunx3 and BMP9,then the alkaline phosphatase( ALP) activity was detected by quantitative and staining assay; calcium deposition was detected by Alizarin Red S staining ; the gene expression levels of Id1,Id2,Id3 and Runx2 were determined by RT-PCR and the protein expression level of DLX5 was determined by western blot. iMEFs were transfected with p(12SBE)- Luc and detected by quantitative. Results BMP9 can inhibit the expression of Runx3.Ad-siRunx3 can inhibit the expression of ALP, which is early osteogenic marker, and the expression of calcium deposition, which is late osteogenic marker . Ad-siRunx3 can inhibit the expression of Id1,Id2, Id3, Runx2 and DLX5 induced by BMP9. Conclusion Knocking down Runx3 can inhibit the BMP9-induced Osteogenic differentiation of iMEFs.

Key words: iMEFs , Runx3 , BMP9 , osteogenic differentiation