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-

牙周膜韧带在牙齿萌出、牙根发育、牙根吸收中可能起重要作用。组织在咀嚼期间生理地接收机械力。本研究旨在探讨间歇性机械牵张对牙周膜成纤维细胞生长和细胞因子合成的影响。根据Kawase的方法（Adv.Dent.Res.2：234- 239，1988），细胞来源于人恒牙牙周膜（PDL-P）和乳牙牙周膜（PDL-D）。将两种PDL细胞在软底培养板中培养。在培养的第3天或第6天，使用Flexercell真空系统以50，000微应变（5%伸长率）、3个循环/分钟机械拉伸细胞24小时。拉伸后测定细胞层DNA含量、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β 1（TGF-β 1）含量。PDL-P的条件培养基中的TGF-β 1水平显著高于PDL-D（高2至3倍），并且在生长期结束时（在第7天）通过机械拉伸刺激（20至30%，p<0.01）。PDL-D的M-CSF分泌显著高于PDL-P的M-CSF分泌（1.3至1.8倍），并且在生长期结束时（在第7天）机械拉伸抑制了PDL-D的M-CSF分泌（-20%，p <0.01）。这些数据表明，牙周膜细胞合成和分泌影响骨重建和牙根吸收的因子，并且这些因子的水平响应于机械应力而改变。

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.