This study aimed to investigate the effect and mechanisms of Exendin-4 mediated-Hedgehog/Gli1 signaling pathway on the differentiation of osteoblasts in mouse. The alkaline phosphate activity, alizarin red staining and expression of Gli1, GLP-1R, Hedgehog, Runx2 and osteocalcin were analyzed using PCR and Western blot analysis after treating the osteoblastic cell line MC3T3-E1 with Exendin-4. Osteoblasts were treated with Gli1-siRNA and Hedgehog receptor antagonist Cyclopamine (Cy) and analyzed for their impact on the Hedgehog/Gli1 signaling pathway. Our results showed that optimal treatment of Exendin-4 was 7 days at 10-7 mol/L. Exendin-4 significantly promoted osteoblast formation in the cell line in a dose-dependent manner and up-regulated the expression of GLP-1R, Hedgehog and Gli1. Gli1-siRNA significantly down regulated the expression of Gli1 and Runx2, and offset Exendin-4-induced osteoblast differentiation. Similarly, Cy offset Exendin-4-induced Gli1 up-regulation. It is clear that Exendin-4 can promote the osteogenic differentiation of osteoblasts through Hedgehog/Gli1 signaling pathway.
Keywords: Exendin-4; Gli1; Hedgehog signaling; differentiation; osteoblast.