Cytokine secretion of periodontal ligament fibroblasts derived from human deciduous teeth: effect of mechanical stress on the secretion of transforming growth factor-beta 1 and macrophage colony stimulating factor.

The periodontal ligament may play an important role in tooth eruption, root development and resorption. The tissue physiologically receives mechanical force during mastication. We focused on the effects of intermittent mechanical strain on the cytokine synthesis of periodontal ligament (PDL) fibroblasts in vitro. The cells were derived from human periodontal ligament of deciduous teeth (HPLF-Y) and permanent teeth (HPLF). The two kinds of PDL cells and human gingival fibroblasts (HGF) were cultured in flexible bottomed culture plates. The cells were mechanically stretched at 5% elongation, 3-cycles/min for 24 h on d 7 in culture using a Flexercell strain unit. After the stretching, we measured DNA content and alkaline phosphatase activity in the cell layer, transforming growth factor beta 1 (TGF-beta 1) and macrophage colony stimulating factor (M-CSF) contents in the conditioned medium. The TGF-beta 1 level in the conditioned medium of HPLF was significantly higher than that of HPLF-Y and HGF. It was stimulated by mechanical stretching only on HPLF, whereas no significant effect was observed on HPLF-Y and HGF. M-CSF secretion was inhibited by the stretching on all of HPLF, HPLF-Y and HGF. 1 alpha, 25 dihydroxy vitamin D3 (D3) stimulated M-CSF secretion into the culture medium of both HPLF and HPLF-Y, but the stretching inhibited M-CSF secretion and completely blocked the enhancement by D3. These data suggest that periodontal ligament cells synthesize and secrete the molecules as autocrine or paracrine factors that affect bone remodelling and root resorption and the level of those factors change in response to mechanical stress.