Aging stimulates cyclooxygenase‐2 expression and prostaglandin E2 production in human periodontal ligament cells after the application of compressive force

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Some clinical studies show that alveolar crestal bone loss is higher in adults than in young patients during orthodontic treatment, but the causes of such a phenomenon have not been elucidated. It is known that prostaglandin E2 (PGE2) is a proinflammatory agent and one of the potent osteoclast-inducing factors, and is produced by human periodontal ligament cells in response to orthodontic force. The aim of this study was to investigate age-related change in the biosynthetic capacity of PGE2 and its regulatory gene, cyclooxygenase 2 (COX-2) from periodontal ligament cells in response to mechanical stress. Compressive force of 2 g/cm2 was applied for 3-48 h to periodontal ligament cells obtained from human donors aged 9-50 years, and COX-2 mRNA expression in and PGE2 production by the periodontal ligament cells in response to the compressive force were examined. Application of a compressive force of 2 g/cm2 for 3-48 h significantly stimulated these factors in both time- and age-dependent manners. Furthermore, these increases were dramatically larger in periodontal ligament cells obtained from donors over the age of 35. Periodontal ligament cells obtained from old donors have significantly greater COX-2 expression and PGE2 production in response to compressive force than those from younger donors. The turning point of aging, where significantly larger amounts of theses factors begin production, appears to be around the age of 35. These results may be positively related to the acceleration of alveolar crestal bone loss during orthodontic treatment in adult patients.