MOLECULAR MECHANISMS OF HOMEOSTASIS AND MECHANICAL STRESS-RESPONSE IN PERIODONTAL LIGAMENT

牙周膜的再生和动态平衡在牙周组织再生中具有非常重要的作用。牙周膜成纤维细胞具有较高的成骨和成牙骨质能力，并具有较高的碱性磷酸酶活性。用骨形态计量蛋白(BMP)、地塞米松诱导牙周膜成骨。这项综合性研究的目的是阐明咀嚼过程中牙周膜动态平衡的分子机制。以FX-4000T/FLEXCEL/USA为实验材料，在FX-4000T/FLEXCEL/USA细胞应变装置中，以6次/分钟的频率拉伸原代培养的大鼠牙周膜细胞，观察细胞反应、细胞增殖、细胞分化和细胞功能的变化。I型胶原(Coll-I)纤维蛋白…的表达采用荧光定量聚合酶链式反应(RT-PCR)技术检测牵张后骨组织中粘连蛋白(FN)、碱性磷酸酶(ALP)、碱性成纤维细胞生长因子(b-FGF)、骨形态蛋白-2(BMP-2)、骨形态蛋白-4(BMP-4)的表达，结果表明：(1)牵张后12小时，牵张组大鼠骨钙素、碱性磷酸酶、碱性成纤维细胞生长因子、骨形态发生蛋白-2、骨形态发生蛋白-4的表达均较对照组有明显变化，并出现峰值。(2)与对照组相比，所有牵张组大鼠牙周韧带细胞中b-FGF、BMP-2、BMP-4的mRNA表达均发生改变，并在24小时后达到峰值。这些机械应力影响培养的牙周膜成纤维细胞的分化，引起细胞增殖和细胞密度的改变。因此，机械应力或咀嚼力促进了牙周膜的再生，影响了牙周膜的动态平衡。较少

Regeneration and homeostasis of the periodontal ligament are highly significant functions in relation to periodontal tissue regeneration. Fibroblasts of periodontal ligament have high potency of osteogenesis and cementogenesis, and also, indicate high alkaline phosphatase activity. Bone formation of periodontal ligament was induced by bone morphmetric protein(BMP), dexamethazone. The aim of this comprehensive study is to elucidate the molecular mechanisms of homeostasis in the periodontal ligament during mastication. Cell reaction, cell proliferation, cell differentiation and cell function in mRNA level, were examined in established primally cultured rat periodontal ligament cells, under the artificial mechanical stretching stress condition in vitro.Third passage primally cultured rat periodontal ligament cells were stretched in a Flexer cell Strain Unit (FX-4000T/FLEXCELL/USA) to 9 and 18 % elongation, at a frequency of 6 cycles/min. mRNA expression of the Type I collagen(Coll-I), Fib … More ronectin(FN), Alkaline phosphatase(ALP), Basic fibroblast growth factor(b-FGF), Bone morphologic protein2 (BMP-2), Bone morphologic protein4 (BMP-4) were examined by Real time Polymerase Chain-Reaction(RT-PCR) using Light Cycler system.Followings results were obtained in this project, (1)mRNA expression of Coll-I, FN, ALP were altered in all stretching experimental group compare with control group, and peak of mRNA quantity was recognized after 12 hrs. (2)mRNA expression of b-FGF, BMP-2,BMP-4 were altered in all stretching experimental group compare with control group, and peak of mRNA quantity was recognized after 24 hrs.In conclusion, we demonstrated that, primally cultured rat periodontal ligament cells, undergo osteoblastic differentiation upon receiving mechanical cyclic stretch. The cell differentiations of the cultured periodontal ligament fibroblasts were influenced by these mechanical stresses, and generated alteration of cell proliferation and cell density. So that reason, mechanical stress or mastication force accelerate the periodontal ligament regeneration, and influenced to the homeostasis of periodontal ligament. Less