The Effect of Mechanical Vibration on Osteogenesis of Periodontal Ligament Stem Cells

Introduction: Appropriate occlusal forces can prevent ankylosis after tooth replantation or transplantation. However, the “proper occlusal forces” on periodontal ligament (PDL) healing have not yet been defined due to insufficient in vitro studies and uncertain in vitro models. Herein, we presented a mechanical vibration device as an in vitro model to determine such favorable occlusal forces. Methods: Human periodontal ligament stem cells (hPDLSCs) were exposed to mechanical vibration force with 4 frequencies (30, 90, 150, and 210 rpm). Cell viability and the expression of osteogenic differentiation-related genes and proteins were tested in vitro. The calvarial transplantation experiment was performed to assess the bone formation ability of 150 rpm mechanical vibration stimulation (MVS). Results: MVS at 150 and 210 rpm significantly reduced cell viability in the early stages. The 150-rpm MVS decreased osteogenic marker expression at the early time point (3 days) but had no harmful effects at the late time point (14 days). Furthermore, hPDLSC cell sheets treated with 150-rpm MVS had potential to decrease bone formation in rat calvarial defects serendipitously and facilitated functional PDL-like tissue formation. Conclusions: We found that MVS at a frequency of 150 rpm could provide a strategy for a transient reduction in the osteogenic potential of hPDLSCs and promote PDL-like tissue formation. Thus, 150-rpm MVS could be used as a controllable proper occlusal force to prevent ankylosis and promote PDL healing after tooth replantation or transplantation.