Measuring Three-Dimensional Traction Force of Mesenchymal Stem Cells on a Two-Dimensional Compliant Substrate by the Finite Element Method

To understand cell adhesion and migration, it is crucial to have information on cellular traction stress. Most traction force microscopy only measures shear stress. Recently a few group developed develop methods to measure normal stress and mostly based on finite element method. We report our finite element-method to compute three-dimensional (3D) traction stress exerted by human mesenchymal stem cells on a two-dimensional compliant polyacrylamide substrate embedded with fluorescent nanoparticles. The images of nanoparticles are acquired by confocal microscopy. We tracked the displacement of nanoparticles and computed strain, stress and strain energy by ANSYS. We examined both experimental factors and calculation that affect the resolution of the force measurement, especially in z direction. The stress measurement of the third dimension provides complete information on traction stress.