Effect of cellular aging on the induction of cyclooxygenase-2 by mechanical stress in human periodontal ligament cells.

The production of prostaglandin (PGE2) in human periodontal ligament fibroblast (hPLF) cells is increased by mechanical stress, however, the age-related changes in the susceptibility of hPLF cells in response to mechanical stress remain unclear. The purpose of this study was to examine the influence of in vitro cellular aging on PGE2 production and the gene expression of cyclooxygenase (COX) in mechanically stressed hPLF cells. In vitro cellular aged hPLF cells were prepared by sequential subcultivations of hPLF cells from young healthy periodontal ligaments. In vitro cellular aged hPLF cells produced a significantly higher amount of PGE2, as compared with young hPLF cells, when the cells were exposed to cyclic tension force in a time- and magnitude-dependent manner. The COX-2 mRNA level in aged cells was higher than that in young cells, whereas COX-1 mRNA remained unchanged. Since PGE2 from hPLF cells was stimulated by in vitro aging as presented here, aging of hPLF cells may affect the severity of inflammation and bone resorption in the aged through the production of a large amount of PGE2 in response to an excessive force such as a traumatic occlusion.