The interactive effects of mechanical stress and interleukin-1β on prostaglandin E and cyclic AMP production in human periodontal ligament fibroblasts in vitro: Comparison with cloned osteoblastic cells of mouse (MC3T3-E1)

Human period ontal ligament fibroblasts and a cloned osteogenic cell line (MC3T3-E1) were seeded (4 × 10 5cells) on 60 mm Petriperm dishes, which have a flexible plastic growth surface. Cells were stretched by placing the dish on top of a spheroidal convex template, equilibrated to 37 °C. The amount of stretch was varied by changing the curvature of the template and calculated as percentage stretch. Both types of cell responded to mechanical stress by elevated synthesis of PGE and cAMP; the addition of interleukin-1β to mechanically stretched cells produced further elevation. Synergism between mechanical stress and interleukin-1β was found at certain lengths of incubation. The production of cAMP was secondary and dependent on the newly synthesized PGE, as shown in the presence of indomethacin. The two cell types were also different in terms of the timing of their response to mechanical stress and interleukin-1β. In the absence of stimuli, periodontal fibroblasts tended to produce PGE continually over time, whereas the MC3T3-E1 cells did not. However, both cell types had elevated PGE levels in response to the stimuli used in this experiment. Periodontal fibroblasts responded to mechanical stress and interleukin-1β with significant elevations of PGE as early as 15 min, whereas the MC3T3-E1 cells required 2 h to produce significant elevations for mechanical stress and 15 min for interleukin-1β. These findings indicate that the chemical and mechanical signals on these cells are mediated by surface receptors. Locally produced autocrine or paracrine factors can modify the effect of mechanical stress on periodontal and bone cells via the cAMP pathway. The difference in response between periodontal and bone cells to mechanical and chemical stimuli may be related to the selective activation of these cells in vivo.