Abstract
The periodontal ligament is exposed to mechanical stress such as occlusion, so periodontal ligament cells may have defenses against mechanical stress. We searched for the influence of mechanical stress on differentiation in HPDL cells, which were subjected to cyclic tension.
When HPDL cells were cultured under mechanical stress in normal medium, their ALP activity in stress groups was more inhibited than in control groups. The gene expression of periostin and Twist was an increased response to mechanical stress. BSP gene expression, a marker of osteoblasts, was not confirmed in stress or control groups. The calcium content in calcified materials produced after long-term culture was low. Results suggest that mechanical stress may accelerate differentiation of HPDL cells into periodontal ligament fibroblasts in normal medium.
BSP gene expression was firmed regardless of whether HPDL cells were cultured or not under mechanical stress in osteoblast differentiation medium. We thus expected that HPDL cells might differentiate into osteoblasts regardless of mechanical stress. When HPDL cells were subjected to mechanical stress in osteoblast differentiation medium, however, ALP activity increased and calcium content, a marker of calcification, increased more significantly in stress than in control groups. TGF-β1 gene expression was detected continuously in stress groups and the gene expression of periostin and Twist gradually decreased. This shows that HPDL cells under mechanical stress in osteoblast differentiation medium progress into differentiated osteoblasts.
These results show that when HPDL cells were differentiated into fibroblasts, mechanical stress may accelerate fibroblast differentiation, and when HPDL cells differentiated into osteoblasts, mechanical stress also may accelerate osteoblast differentiation. Nihon Shishubyo Gakkai Kaishi (J Jpn Soc Periodontol) 48: 113-122, 2006.
