EFFECT OF DIFFERENT MAGNITUDES OF TENSION FORCE ON PROSTAGLANDIN E(2) PRODUCTION BY HUMAN PERIODONTAL-LIGAMENT CELLS

Periodontal ligament (PDL) cells are known to produce prostaglandin E(2) (PGE(2)) in response to mechanical stress. However, the rate of PGE(2) production from PDL cells in response to different magnitudes of tension forces has not been examined. This study, therefore, was undertaken to determine the effect of different magnitudes of tension forces on PGE(2) production and inositol trisphosphate (IP3) levels in PDL cells in vitro. Human PDL cells were cultured on flexible-bottomed plates and placed on a Flexercell strain unit. Cells were flexed at six cycles (5-s strain, 5-s relaxation) at six steps of tension force (9, 12, 15, 18, 21, 24% increase in surface area) for 5 days. PGE(2) production and IP3 levels were determined by radioimmunoassay. There was a 6- and 25-fold increase in the rate of PGE(2) production by cells exposed to low (9%) and high (24%) tension forces, respectively, and these increases were tension force-dependent. Tension force also induced increases in the intracellular levels of IP3 that did not seem to be directly related to the production of PGE(2). The different rates of PGE(2) production by PDL cells in response to different magnitudes of mechanical stress may be of importance in PDL and alveolar bone metabolism.