What forces do cells develop?

In order to ensure their mobility (migration of individual cells or collective migration), cells rely on their environment / culture substrate to propel themselves thanks to the forces that their cytoskeleton deploys. The measurement of these forces by the technique of Traction Force Microscopy (TFM) is evaluated by following the deformation of the polyacrylamide (PAA) substrates described above, under the cells. The PAA is distorted as when a hand on a sheet of paper crumples it slightly or, to choose another comparison in athletics, when the athlete's shoe distorts the tartan of the track with each impulse. The deformation is measured by following the movement of fluorescent beads present in the PAA gel. The displacement of the beads in the presence of cells will be calculated by an algorithm applied to the images acquired. The calculation of the forces is obtained by taking into account the physical parameters of the gel, in particular its rigidity (Figures 1 and 2).

Figure 1 : Scheme of the principle of Traction Force Microscopy (TFM) (Source : Suné-Aunon A BioInformatics 2017 18 365)

Figure 2 : Example of an experiment carried out on fibroblasts. A: superimposition of the image of the beads in false red color (in the presence of the cell) and the image of the beads in false green color (in the absence of the cell). In areas where the cell has not exerted traction on the gel, the superposition of the two bead images shows yellow beads (white squares). In areas where the cell has exerted traction, the same red and green beads are slightly shifted (green circles). B: the displacement of the beads is "translated" into a measurement of forces whose intensity is coded in false colors (in fraction of Newton). Source : BioMecan'IC