The effect of prostaglandin E2 on differentiation of human periodontal ligament cells toward osteoblast-like cells

Abstract

Prostaglandin E2 (PGE2) has been shown to be able to influence both bone formation and resorption. The purpose of this study was to investigate the effect of PGE2 on osteogenic differentiation of human periodontal ligament (HPDL) cells. HPDL cells were cultured with 0.001-1 µM PGE2 in osteogenic medium. In vitro mineral deposition was determined by Alizarin Red S staining, while gene expression profile was determined by real-time polymerase chain reaction. The results indicated that PGE2 inhibited in vitro mineral deposition by HPDL cells in a dose dependent manner. PCR analyses showed that PGE2 upregulated the expression of RUNX2 but had no effect on osteocalcin expression. Upregulation of TWIST1, the functional antagonist of RUNX2 was also observed. In addition, PGE2 induced RUNX2 and TWIST1 protein synthesis was also detected by Western blot analysis. By using a chemical activator of EP receptors as well as siRNA against an EP receptor, it was shown that PGE2 regulated both RUNX2 and TWIST1 via the EP2 receptor. The role of PKA in the inductive effect of PGE2 was also demonstrated. In conclusion, the results of this study revealed that PGE2 modulated the osteogenic differentiation of HPDL cells via regulating the expressison of RUNX2 and TWIST1. The results suggest a possible role of PGE2 in regulation of the homeostasis of periodontal ligament tissue.