This experiment was designed to study possible roles of interleukin-Iβ, interleukin-6 and tumor necrosis factor-α in bone remodeling by measuring their effects on PGE², LTB4 and collagenase production when they were administered to human periodontal ligament fibroblasts. Human periodontal ligament fibroblasts were collected from first premolars extracted for orthodontic treatment. They were incubated in the environment of 37°C, 5% CO², and 100% humidity. They were treated with 0.25% trypsin-EDTA solution and centrifuged. PDL cells in the fifth to seventh passage were used for the experiment. Cells were seeded onto the culture dishes and when they were successfully attached, human recombinant interieukin-lβ, interleukin-6, and tumor necrosis factor-α were administered, alone or in combination. They were incubated for 4, 8 and 24 hours and the levels of PGE², LTB4 and collagenase released into the culture media were assessed by enzymeimmunoassay and collagenase activity assay. The conclusions are as follows: 1. IL-1β and TNF-a were very active in stimulating the production of PGE² and collagenase by human periodontal ligament fibroblasts, while IL -6 increased LTB4 production. 2. IL-1β significantly increased PGE² , but LTB4 production was not increased. IL-1β is thought to act mainly via the cyclooxygenase pathway of arachidonic acid metabolism. 3. IL-6 tended to inhibit IL- 1β in the production of PGE² and collagense whereas IL-6 and TNF-α showed additive effect in the level of PGE². The above cytokines increased the release of at least one of PGE², L TB4 and collagenase. It suggests that cytokines are involved in bone remodeling process by stimulating PDL fibroblasts to produce various bone-resorptive agents. The roles of cytokines in bone remodeling as a whole would need further study.
