Effects of various factors produced by mechanically stressed human periodontal ligament fibroblasts (HPLF) on bone-related cells

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Various studies in vitro have shown that the physically stressed human periodontal ligament fibroblasts (HPLF) may have an important role in the regulation of bone remodeling evoked by orthodontic tooth movement. To determine whether conditioned medium (S-CM) obtained from the mechanically stressed HPLF would affect the osteoblastic function or activity, we investigated ALPase activity and cAMP production in clonal mouse osteoblast-like cells (MC3T3-E1), after an addition of S-CM.HPLF and MC3T3-E1 were routinely cultured in Dulbecco's Modified Eagle's Medium (D-MEM) containing 15% fetal bovine serum (FBS) at 37ﾟC under 5% CO_2 in air. At the confluent phase, continuously compressive stress of 1.0 g/cm^2 was applied to HPLF for 1,3,6,12 and 24 h. Each conditioned medium was gathered, and then added to MC3T3-E1. At the end of each experimental period, ALPase activity and cAMP production were measured by a modification of the method of Puzan and Brand, and the use of enzyme immunoassay kit for cAMP,respectively.The results obtained in this project were as follows :1.Addition of S-CM induced increases in both ALPase activity and cAMP production in MC3T3-E1, time-dependently, as observed in directly stressed MC3T3-E1.2.Especially in the presence of S-CM,significant increase in ALPase activity and cAMP production in MC3T3-E1 was recognized after 12h and 6h, respectively (p<0.01).3.S-CM in the presence of Indomethacin, an inhibitor of PGEs, increased neither ALPase activity nor cAMP production in MC3T3-E1.These findings suggest that several factors produced by HPLF subjected to continuously compressive stress might affect differentiation and/or cellular responses of MC3T3-E1. In addition, PGEs appear to be one of these factors and to act as a modulator of cellular activities of MC3T3-E1.