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 mechan ical strain on the cytokine synthesis of periodontal ligament (PDL) fibrobl asts in vitro. The cells were derived from human periodontal ligament of de ciduous teeth (HPLF-Y) and permanent teeth (HPLF). The two kinds of PDL cel ls and human gingival fibroblasts (HGF) were cultured in flexible bottomed culture plates. The cells were mechanically stretched at 5% elongation, 3-c ycles/min for 24 h on d 7 in culture using a Flexercell(R) strain unit. Aft er the stretching, we measured DNA content and alkaline phosphatase activit y in the cell layer, transforming growth factor beta 1 (TGF-beta 1) and mac rophage colony stimulating factor (M-CSF) contents in the conditioned mediu m. 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 stretc hing 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 D-3 (D-3) Stimulated M-CSF secretio n into the culture medium of both HPLF and HPLF-Y, but the stretching inhib ited M-CSF secretion and completely blocked the enhancement by D-3 These da ta suggest that periodontal ligament cells synthesize and secrete the molec ules as autocrine or paracrine factors that affect bone remodelling and roo t resorption and the level of those factors change in response to mechanica l stress.