Effects of Compressive Stress Combined with Mechanical Vibration on Osteoclastogenesis of RAW 264.7 Cells

Abstract

The effects of mechanical stimulation on osteoclastic differentiation differ depending on the pattern of mechanical loading. However, there is still no knowledge about mechanical vibration combination with compressive force applied on osteoclast precursor cells. Objectives This study purposed to investigate the effects of compressive force combined with mechanical vibration or mechanical vibration alone on osteoclastogenesis in RAW 264.7 cells, a murine osteoclastic-like cell line. Materials and Methods Murine monocyte/macrophage RAW 264.7 cells were used as model osteoclast precursor cells. To determine the optimal compressive force and mechanical vibration. Various compressive force (0.3, 0.6 or 0.9 g/cm2) was applied to RAW 264.7 cells and induced with either 30 Hz or 60 Hz at 0.49 g. To determine the effects of compressive force combination with mechanical vibration, RAW 264.7 cells were subjected to suitable compressive force or mechanical vibration for 20 min every 24 h for 4 days or combination of compressive force and vibration. Cell viability was assessed using Prestoblue assay. NFATc1, DC-STAMP and CTSK gene expression were measured by quantitative realtime reverse transcription polymerase chain reaction (RT-PCR) and the numbers of TRAP-positive multinucleated cells (MNCs) were counted and analyzed Results: Compressive force combination with mechanical vibration significantly increased the numbers of TRAP-positive multinucleated cells when compared with compressed or vibrated group (P<0.05). Application of force on RAW 264.7 cells did not significantly affect cell viability. The combination of compressive force and vibration significantly increased NFATc1, DC-STAMP, and CTSK mRNA expression, compared to compressive force or vibration alone (P<0.05). Conclusions: Compressive force combined with mechanical vibration induces osteoclastogenesis and upregulates the expression of NFATc1, DC-STAMP and CTSK gene on RAW 264.7 cells. These results provide more insight into the mechanisms by which vibratory force accelerates orthodontic tooth movement.