| Budget Amount *help |
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2003: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2002: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2001: ¥900,000 (Direct Cost: ¥900,000)
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| Research Abstract |
Occlusal trauma causes alveolar bone resorption around the root in healthy periodontal tissue. In periodontitis tissue, occlusal trauma is also considered to be a factor that accelerates alveolar bone resorption caused by bacterial infection. In an experimental occlusal trauma model using the beagle dogs, the occurrence of thrombosis in microcirculation of periodontal ligament was demonstrated histopathologically. Thereby, occlusal trauma may cause hypoxia in the periodontal ligament. In the present study, the effects of hypoxia on the production of bone-resorbing factors from cultured human periodontal ligament cells were examined. Periodontal ligament culture cells were divided into 2 groups. One group was cultured under the hypoxic condition in 1% O2 (Hypoxia group), and the other was cultured in 20% O2 (Normoxia group). The concentrations of bone resorbing factors, vascular endothelial growth factor (VEGF), interleukin (IL)-6, IL-1β, tumor necrosis factor -α (TNF-α), and prostaglan
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din E2 (PGE_2) in the cell culture supernatants were determined by use of enzyme-linked immunosorbent assay. Expressions of the mRNAs concerned with these bone resorbing factors were detected by performing the reverse transcription-polymerase chain reaction. Hypoxia group showed higher concentrations of VEGF and IL-6 in their culture media than Normoxia group (p<0.01), and the observed expression of mRNAs for these proteins in the Hypoxia group was also higher than that of them in the Normoxia group. The expression of IL-1β was observed in only in the Hypoxia group. TNF-α and PGE_2 were undetectable in culture medium from both Hypoxia and Normoxia groups, whereas COX-2 mRNA was detected from the Hypoxia group. However, production of PGE_2 became discernible 3 hours after the addition of recombinant human VEGF even under normoxic condition. Similarly, PGE_2 became detectable in the culture medium 9 hours after the oxygen level had been elevated from hypoxic to normoxic. These results suggest that hypoxia induced by occlusal trauma may stimulate the periodontal ligament to produce bone resorbing factors, resulting in resorption of alveolar bone. Less
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