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

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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