Vibrational stimulation induces osteoblast differentiation and the upregulation of osteogenic gene expression in vitro.

Vibrational stimulation is an accepted non-invasive method used to improve bone remodeling. However, the underlying mechanisms of this phenomenon remain unclear. In this study, we developed a new vibration-loading system to apply vibrational stimulation to cells based on a previously reported in vivo study. We hypothesized that osteoblasts respond to vibrational strain by expressing osteogenic marker genes, such as alkaline-phosphatase (ALP), Runx2, and Osterix. To test our hypothesis, we developed a vibration-loading system to apply a precise vibrational force to an osteoblast culture on a silicone membrane. The system regulated frequency and acceleration of the vibration, and strain on the silicone membrane culture surface was measured using the strain gauge method. After vibrational stimulation, cellular gene expression was analyzed using real-time polymerase chain reaction. We obtained clear strain signals from the culture surface at vibrational ranges of 1.0-10 m/s2 acceleration and frequencies of 30, 60, and 90 Hz, respectively. The strain increased in a linear fashion, depending on the acceleration magnitude. Vibrational stimulation also significantly upregulated expression of the osteogenic marker genes Runx2, Osterix, type I collagen, and ALP. In conclusion, we developed a new vibration-loading system that can precisely regulate frequency and acceleration, and we established the presence of dynamic cellular strain on a culture surface. Our findings suggest that vibrational stimulation may directly induce osteoblast differentiation.