Effect of PGE2 induced by compressive and tensile stresses on cementoblast differentiation in vitro

Objective m of the study was to clarify the mechanisms underlying orthodontically induced root resorption by characterizing the role of PGE2 induced by compressive stress (CS) and tensile stress (TS) on cementoblast metabolism in vitro. cementoblast cell line OCCM-30 was continuously stimulated with 0.2 KPa CS or 5.0 KPa TS. COX-2 mRNA expression and PGE2 production were thus quantified. In addition, cells were treated with COX-2 inhibitor and the role of PGE2 induced by CS or TS on the expression of genes related to cementoblast differentiation was examined. PGE2 receptors mRNA expression induced by CS or TS was also evaluated. Moreover, cells were treated with exogenous PGE2 and the role of PGE2 concentration on matrix mineralization was verified. s TS enhanced COX-2 mRNA expression and PGE2 production. PGE2 synthesis, however, was markedly induced by CS. Gene expression of bone morphogenetic protein 2 (BMP-2), osteocalcin (OCN) and receptor activator for nuclear factor kappaB ligand (RANKL) was enhanced by CS on an endogenous PGE2-mediated manner. Osteoprotegerin (OPG) expression was not affected by CS. Meanwhile, TS up-regulated the expression of BMP-2 and alkaline phosphatase (ALP) on an endogenous PGE2-mediated manner. TS down-regulated RANKL mRNA expression, whilst OPG expression was not affected. Moreover, EP4 mRNA expression was considerably enhanced by TS. Regarding PGE2 concentration, only cells treated with low concentration presented anabolic response. sions xpression was differentially regulated according to the type of mechanical stimulation applied to cementoblasts. In addition, it is shown that PGE2 plays an important role on mediating cementoblast mechanosensitivity.