Study on a Cell Mechanosensing System by Measuring Structural Deformation and Biochemical Response

Abstract

Mechanical stimulation induces new bone formation in vivo and promotes the metabolic activity and the gene expression of osteoblasts in vitro. It was reported that biochemical signals of osteoblasts to sense mechanical stimulation are activated according to their actin cytoskeletal deformation. However, there have been not so many researches on the relationship between cytoskeletal deformation and biochemical response. Here we show an original method to investigate a cell mechanosensing system and the quantitative relationship between the deformation of cytoskeletal structure and the change of intracellular calcium ion concentration as biochemical response in a living cell stimulated by a micropipette. Gene transfection of green fluorescent protein to osteoblastic cells enabled visualization of actin in cells. When local deformation was applied to a single osteoblastic cell by a micropipette, the displacement distribution of cytoskeletal structure in the whole cell was automatically obtained from the two images of the cell before and after deformation by using Kanade-Lucas-Tomasi (KLT) method. Intracellular calcium ion response to mechanical stimulation was measured as the spatial and temporal changes of intensity of Fura Red loaded to a cell. As a result, we obtained the quantitative relationship between structural deformation and biochemical response of a cell and found that the change of calcium ion concentration increases with increasing the displacement of actin cytoskeleton. It indicates that the deformation of actin cytoskeleton is highly related to the cell mechanosensing system.