Effect of IRAK-4 on BMP-Smad pathway in osteoblast differentiation

Objective To study the mechanisms of the effect of IRAK-4 on BMP-Smad pathway in osteoblast differentiation. Methods C2C12 are muscle satellite cells isolated from the muscle tissue, which shows a different differentiation potential under different culture conditions. C2C12 cells have the potential of osteoblast cells, and can serve as an ideal model for experiment of osteoblast differentiation. C2C12 cells were cultured in plates and randomly divided into 3 groups; each group was treated with different stimuli to imitate the stimuli in osteoblast differentiation. Cell ALP osteoblastic activity was analyzed by PNNP, Smad1 mRNA expression was detected by RT-PCR, the expression level of P-Smad1 protein was determined by immunohistochemistry and Western blot, to observe the effects of different stimulation on osteoblast differentiation. Results The differentiation of osteoblast ALP activity showed that in the group treated with BMP-2 was significantly higher than that in the control group, the group treated with BMP-2 and IRAK-4siRNA was significantly higher than that treated with BMP-2. RT-PCR results showed that compared with the group that treated with BMP-2, the expression of smad1 mRNA in the group that treated with BMP-2and IRAK-4siRNA was only slightly increased,but the protein expression was significantly increased.Conclusions BMP-2 can enhance C2C12 cell osteogenic effect. IRAK-4 could inhibit osteogenic effect,which could possibly be the result of reduced BMP-2,Smad1 phosphorylation.