Study on relationship between BMP9-induced osteogenicdifferentiation and COX-2/PI3K/Akt in stem cells / 中国药理学通报

ABSTRACT

Aim To investigated the possible effect of COX-2 on the BMP9-induced activation of PI3K/Akt signal in progenitor cells.Methods The activity of alkaline phosphatase(ALP) was measured using histochemical staining or chemiluminescence.The mRNA level of ALP was determined using real-time PCR assay.The protein levels of osteopontin(OPN), osteocalcin(OCN), COX-2, Akt1/2 and phosphorylated Akt1/2 were detected by Western blot.The mRNA level of COX-2 was assayed with RT-PCR, and the mineralization was measured with Alizarin Red staining.Results The ALP activity was apparently increased by BMP9 in C2C12 cells, as well as the protein level of OPN and OCN.The mineralization was also markedly induced by BMP9 in C2C12 cells.BMP9 increased the level of phosphorylated Akt1/2 greatly, although no substantial effect was observed on total protein level of Akt1/2.The BMP9-induced ALP activity was dramatically decreased by the inhibitor of PI3K.The mRNA and protein level of COX-2 were both increased by BMP9 in C2C12cells, and the BMP9-induced ALP activity and mineralization were greatly attenuated by the inhibitor of COX-2.The BMP9-induced phosphorylation level of Akt1/2 was increased by the exogenous expression of COX-2, but decreased by the inhibitor of COX-2.Conclusion Activation of PI3K/Akt signaling may be a critical event in BMP9-induced osteogenic differentiation, and this process may be mediated by the BMP9-upregulated COX-2 in stem cells at least.