Prostaglandin E2 affects osteoblast biology in a dose-dependent manner: An in vitro study

Abstract

ObjectiveThis study aimed to determine in vitro how exogenous PGE2 affects the expression of genes in cultured osteoblasts by relative quantitation PCR. DesignCultured osteoblasts were exposed to 10−3M, 10−5M or 10−7M PGE2 over 5, 10, 15 and 20 days. ResultsRANKL expression was higher after 5 days of exposure (p<0.05), but thereafter reduced in those treated with the two lower doses of PGE2 (p<0.01). RANKL/OPG ratio reported in favour of OPG gene expression and alkaline phosphatase gene expression increased in osteoblasts exposed to the two lower doses of the eicosanoid after 15 days. Conversely, prostaglandin E synthase, a cytokine produced during PGE2 synthesis, gene expression was significantly reduced at 15 and 20 days (p<0.01 and 0.05 respectively). The results from this study add to the current knowledge of the mechanisms by which PGE2 modulates the osteoblast biology in a dose-dependent manner. ConclusionsIt is proposed that PGE2at a low dose switch osteoblast's biology in favour of bone apposition by: first, inducing a significantly higher OPG gene expression overwhelming RANKL gene expression; second, reducing PGEs synthesis; and third, increasing ALP gene expression. An opposite effect is expected when the concentration of the eicosanoid overpass certain levels.