A STUDY OF A MECHANISM OF CELL PROLIFERATION PROMOTION OF CULTURED OSTEOBLASTS BY MECHANICAL VIBRATION

摘要

This paper describes a mechanism of cell proliferation promotion of cultured osteoblasts by mechanical vibration focusing on β-catenin. 12.5 Hz and 0.5 G mechanical vibration was reported to promote the cell proliferation of cultured osteoblasts in plane culture. That is because the mechanical vibration weakens cell-cell adhesion, promotes to pile up cells, and allows cells to form multilayer structure. However, it has not been clarified why cells continue cell division after their monolayer confluent state. Here we show that mechanical vibration not only weakens cell-cell adhesion bound by β-catenin but also promotes to move β-catenin from the cytoplasm to the nuclei, where β-catenin associates with DNA-binding members of the Tcf/LEF family and other associated transcription factors including cell division. After osteoblastic cells were cultured under 12.5 Hz and 0.5 G mechanical vibration, cells were fractionated into nuclear and cytoplasmic fractions using a centrifugation method, β-catenin in each fraction was detected by a western blot experiment. The protein bands from western blot films were quantified with an image processing and analysis software, ImageJ. As a result, the vibration group gave higher expression of β-catenin in nuclear fraction than the non-vibration group just after the vibration group reached the saturated cell density. It indicates that 12.5 Hz and 0.5 G mechanical vibration may promote to move β-catenin into the nuclei and the cell division.