Basic Study on the Relationship Between Remodeling of Periodontal Tissue and Mastication -Effects of Mechanical Force on Cytokins Synthesis of the Cells Derived from Periodontal Ligament-

牙周膜在牙萌出、牙根发育和牙根吸收中可能起重要作用。在咀嚼过程中，组织在生理上会受到机械力。本实验研究了间歇性机械张力对体外培养的牙周膜成纤维细胞生长和细胞因子合成的影响。细胞来源按Kawase方法(Adv.Dent.Result.2：234-239,1988)，分别取自人恒牙牙周膜(PDL-P)和乳牙(PDL-D)。两种PDL细胞均在柔性底培养板中培养。在培养的第3天或第6天，用Flexcell真空系统将细胞以50000微应变(伸长率为5%)、3个循环/分钟的机械拉伸24小时。拉伸后检测细胞DNA含量和碱性磷酸酶活性，条件培养液中巨噬细胞集落刺激因子(M-CSF)和转化生长因子-β1(TGF-β1)含量。PDL-P条件培养液中的转化生长因子-β1水平显著高于PDL-D(2~3倍)，并在生长末期(第7天)被机械拉伸刺激(20~30%，p&lt；0.01)。PDL-D的M-CSF分泌量显著高于PDL-P(1.3~1.8倍)，并在生长末期(第7天)被机械拉伸抑制(-20%，p&lt；0.01)。这些数据表明，牙周韧带细胞合成和分泌影响骨改建和牙根吸收的因子，这些因子的水平随着机械应力的变化而变化。

Periodontal ligament may play an important role on tooth eruption, development of root, and root resorption. The tissue physiologically receives mechanical force during mastication. We focused on the effects of the intermittent mechanical strain on the growht and cytokine synthesis of periodontal ligament (PDL) fibroblasts in vitro. The cells were derived from human periodontal ligament of permanent teeth (PDL-P) and deciduous teeth (PDL-D) according to the method of Kawase (Adv.Dent.Res.2 : 234-239,1988). The two kind of PDL cells were cultured in flexible bottomed culture plates. The cells were mechanically stretched at 50,000micro Strain (5% elongation), 3cycles/minute for 24 hours on the day 3 or day 6 in culture using Flexercell Vacuum System. After the stretching we measured DNA content and alkaline phosphatase activity of the cell layr, macrophage colony stimulating factor (M-CSF) and transforming growth factor beta 1 (TGF-beta1) contents in the conditioned medium. TGF-beta1 level in the conditioned medium of PDL-P was significantly higher than that of PDL-D (2 to 3 fold higher) and it was stimulated (20 to 30%, p<0.01) by the mechanical stretching in the end of growth phase (on the day 7). M-CSF secretion of PDL-D was significantly higher (1.3 to 1.8 fold) than that of PDL-P and it was inhibited (-20%, p<0.01) by the mechanical stretching at the end of growth phase (on the day 7). These data suggest that periodontal ligament cells synthesize and secrete the factors that affect bone remodeling and root resorption and the level of those factors change in response to mechanical stress.