16. In Vitro Experimental Study for the Determination of Cellular Characteristics of Mesenchymal Stem Cells Using a Non-uniform Deformation Field

In the present study, relationship between cell orientation angle and strain value of membrane was comprehensively investigated using inhomogeneous strain field. And an axial strain threshold of cell, which corresponds to launch of cell orientation migration, was elucidated. One of the advantages in this study was that the inhomogeneous strain distribution was easily created by making a little improvement in a commonly-used uniaxial stretching device. The strains of two-dimensional stretched membrane were quantified position by position using digital image correlation (DIC) method. A 3D histogram of the cell frequency, which correlated with the cell orientation angle and normal strain of the membrane, made it possible to determine the axial strain threshold accurately. The value was 4.4 ± 0.3 %, which was reasonable compared with past study conducted by other researcher, although the past experiments were based on cyclic uniaxial stretch stimulation (homogeneous strain field). In addition, a preferential axial strain of the cell was achieved using the same technique of the determination of the axial strain threshold. This work has novel values at three points: (i) Determining axial strain threshold of the cells precisely. (ii) First suggestion of preferential axial strain of the cells. (iii) Investigating methodically cell behavior in inhomogeneous strain field.