| The periodontal ligament is always exposed to mechanical stress in the oral environment during normal functional activities including occlusion and mastication. The proper occlusion force is healthful to the periodontal tissue. If occlusal force exceeds the adaptive capacity of the tissues, the occlusal trauma will occur. Despite extensive research over many decades, the effect of trauma from occlusion in the progression of periodontal destruction is not clear yet. Recently, many clinical and laboratory studies have indicated the important role of periodontal ligament fibroblasts ( HPLF ) which are the predominant cells in the periodontium in this process.Transforming growth factor- β1 ( TGF-β1 ) is one of the important mediates that are believed to be involved in the normal space maintenance, repair and regeneration of the periodontal ligament, and it has the potential to induce extracellular matrix biosynthesis by HPLF.The purpose of the present study was to determine the effect of mechanical pressure on cell proliferation and TGF-β1 synthesis in cultured HPLF. It will help us better understanding the functionalchange of HPLF induced by mechanical stress. Methods and Results: Primary culture of HPLF by explants with enzymatic digestion.The cells were isolated by scraping the human periodontal ligament tissue from the middle third of the tooth root, mincing the tissue and digesting with 0.05 % collagenase. After that the tissue was anchored to the bottom of culture bottle until the cells grew out from the explants and reached confluence. The morphological and biological characteristics were observed.The success rate of primary culture of HPLF was 77.8%, and the morphological and biological characteristics of the culture cells were similar to those of typical HPLF. Growth of HPLF obtained by this method was satisfactory. The modified method was simple and feasible.Effects of pressure on the proliferation of HPLF. Cell proliferation was studied with MTT assay.1. The 1st experiment was to study the relationship of proliferation of HPLF to values of pressure. In vitro cultured HPLFs of passage 4-6 were incubated under continuous pressure of 0.25Mpa, 0.5Mpa and l.OMPa for 30min respectively. Cell proliferation was measured at 6h, 12h, 18h, 24h, 30h and 36h after stimulation. Our data suggested that cells subjected to 0.25Mpa and 0.5Mpa pressure had no difference in proliferation compared with control group, while l.OMpa group had remarkable difference. The proliferation of that group was decreased after 6h, reached the bottom at 12h, and returned to the original level at 24h after stimulation.2. The 2nd experiment was to investigate the relationship of HPLF proliferation to duration times of pressure. We treated cells for10min, 30min and 50min respectively with l.OMpa pressure. Cell proliferation was studied at 6h, 12h, 18h, 24h, 30h and 36h after stimulation. The results showed that that cells treated for 30min and 50min had statistical difference in proliferation compared with control group, while lOmin group had no difference. The character of proliferation change was as same as that of 1st experiment.The data revealed that cell proliferation of HPLF had certain relationship with the values and duration time of pressure. With the pressure values getting stronger and duration time longer, their proliferation inclined. But these reactions were reversible, and no pathologic damage occured.Effect of mechanical pressure on TGF-β1 synthesis in cultured HPLF. The level of TGF-β1 was measured by enzyme-linked immunosorbent assay ( ELISA).1. The 1st experiment was to study the relationship of TGF- β1 secreted by HPLF to values of pressure. HPLFs were incubated under continuous pressure of 0.25Mpa, 0.5Mpa and 1.0MPa for 30min respectively. TGF-P 1 in the supernant was checked at 6h, 12h, 18h and 24h after stimulation. Our data suggested that cells subjected to 0.25Mpa and 0.5Mpa pressure had no difference in TGF- P 1 synthesis compared with control group. The TGF-β1 of 1.0M... |
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