NAKANO Tamotsu Kanagawa Dental College, School of dentistry Research Associate, 歯学部, 助手 (80164250)
IMAI Kiyoshi Kanagawa Dental College, School of dentistry Research Associate, 歯学部, 助手 (10151656)
NISHIYAMA Katsuhiro Kanagawa Dental College, School of dentistry Research Associate, 歯学部, 助手 (20084783)
KAWASE Toshio Kanagawa Dental College, School of dentistry Assistant Professor, 歯学部, 助教授 (30084784)
The petiodantium, especially the periodontal ligament and alveolar bone, are tissues constantly subjected to physical stresses among which are occlusion, mastication and even gravity. These factors are inherent factors in the metabolism of these tissue cells. Saito et al recently reported that the alkaline phosphatase(ALPase) of human periodontal ligament fibroblasts(HPLF) showed remarkably high activity which was similar to that present in asteoblasts, and suggested that HPLF could be tersed as " osteoblastic fibroblast".
(1) ALPase synthesized on HPLF in relation to 1,25(OH)_2 D_3
The cell growth which was assayed by DNA contents and the incorporation of ^3H-TdR was decreased by D_3 From the separation of ALPase activity on SDS-PAGE, 110K and 120-130K ALPase were identified. The 110K ALPase, which was not changed by D_3, was converted to 100K, releasing 10K peptide after trypsin treatment. This 110K ALPase might be tightly associated with cell membrane structure. The 120-130K ALPase wa
s remarkably increased by D_3 on SDS-PAGE and completely digested with trypsin. The ALPase in the cultured HPLF might be located not only on the plasma membrane but also in the extracellular matrix.
Therefore, D_3, which regulates Ca^2 metabolism in bone, may control the cell cycle and also the gene expression of ALPase of HPLF.
(2) Effects of mechanical stress on the cell growth and differentiation
The protein content of cell layers of HPLF, HGF and HABC were more significantly decreased by stressed conditioned medium(S-CM) than by non-stressed conditioned medium(NS-CM). ALPase activity of HPLF was increased 1.71 fold by NE-CM and 2.63 fold by S-CM. The incorporation of ^3H-TdR into DNA incubated with S-CM was remarkably inhibited. On the other hand. S-CM stimulated cell spreading after cell inoculation and adhesion. The molecular size of one of the cell spreading factors was estimated 10K peptide which is heat labile and digested by proteolytic enzymes.
Therefore, mechanical stress may regulate cell metabolism of HPLF, stimulating secretion of a negative cellular autocrine growth factor, which might itself control cellular response. Less