Cell Biological Study on the Response Against Mechanical Stress on Periodontal Ligament Fibroblasts Derived from Human Deciduous Teeth.

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Periodontal ligament fibroblasts derived from human deciduous (HPLF-Y) and permanent (HPLF) teeth were established by means of explant method reported by Kawase and Saito. The effects of mechanical stress on cell growth and differentiation were studied on HPLF-Y and HPLF in culture. Those cells were loaded with intermittent mechanical strain at 5 or 10% elongation for 10 second with the resting for 10 or 50 second using the flexible bottomed culture plates and vacuum system in the presence or absence of retinoic acid (RA), 1,25 dihydroxy vitamin D_3 (D_3) or both of them. After the stretching for 24 hours, we measured alkaline phosphatase (ALPase) activity and DNA quantity of both cells. DNA synthesis of HPLF-Y and HPLF were suppressed by treatment with 0.1 mM RA for 8 days. The growth of both cells was more suppressed by RA treatment in the latter half of culture period than by D_3 or by RA and D_3 together. Alkaline phosphatase (ALPase) activity of HPLF-Y was increased by treatment w … More ith 0.1 mM RA for 8 days, however no significant change was observed on HPLF after treatment with RA at the same concentration. After the loading of intermittent stretching (5%, 3 cycle/min., 24 hr) on the day 5 in culture, cell growth of HPlF was stimulated, whereas that of HPLF-Y was suppressed. On the other hand, ALPase synthesis was stimulated on both HPLF-Y and HPLF.The mechanical stress (5%) caused significant increase of ALPase on HPLF-Y treated with D_3 or with RA and D_3 together at confluent phase. ALPase activity was increased by stretching at growth phase of HPLF treated with RA or D_3 separately or with RA and D_3 together. These data demonstrate that there are obvious differences between HPLF-Y and HPLF in terms of the response to RA or mechanical stress. The present study suggests that HPLF-Y and HPLF have different functions in the remodeling of periodontal tissue during development and that D_3 and RA are able to modify of the response to the mechanical strain on the cell growth and differentiation of HPLF and HPLF-Y. Less