Quantifying force transmission through fibroblasts: changes of traction forces under external shearing

Abstract

Mammalian cells have evolved complex mechanical connections to their microenvironment, including focal adhesion clusters that physically connect the cytoskeleton and the extracellular matrix. This mechanical link is also part of the cellular machinery to transduce, sense and respond to external forces. Although methods to measure cell attachment and cellular traction forces are well established, these are not capable of quantifying force transmission through the cell body to adhesion sites. We here present a novel approach to quantify intracellular force transmission by combining microneedle shearing at the apical cell surface with traction force microscopy at the basal cell surface. The change of traction forces exerted by fibroblasts to underlying polyacrylamide substrates as a response to a known shear force exerted with a calibrated microneedle reveals that cells redistribute forces dynamically under external shearing and during sequential rupture of their adhesion sites. Our quantitative results demonstrate a transition from dipolar to monopolar traction patterns, an inhomogeneous distribution of the external shear force to the adhesion sites as well as dynamical changes in force loading prior to and after the rupture of single adhesion sites. Our strategy of combining traction force microscopy with external force application opens new perspectives for future studies of force transmission and mechanotransduction in cells.

A multi-modal microscope for integrated mapping of cellular forces and Brillouin scattering with high resolution

“…With the interferometer in place, integrated ERISM and Brillouin measurements of cells cultured on a ZrO 2 based microcavity were now possible. Figure 4 shows proof of principle measurements of NIH-3t3 fibroblasts, a cell line that is well characterized in terms of the forces they exert on their surroundings [67,68]. The ERISM measurements are free of artefacts and resolve deformations of the microcavity down to the nm-scale, similar to ERISM measurements recorded on conventional ERISM microcavities.…”

Traction Force Microscopy with DNA FluoroCubes

“…A wide range of sample sizes can be studied, from very small cells to large multicellular systems 39 . Sophisticated analysis methods make it possible to study cellular forces in three-dimensional geometries or on complex topographies 7 , as well as in the presence of external perturbations 55 . Other advantages of classical TFM are that the method produces vectorial traction results and is able to detect force magnitudes in a very wide range, starting from a few pN measured for bacterial appendages on soft substrates to forces of up to 600 nN for platelet adhesions that are important for blood clot formation [40][41][42] .…”

Extracting, quantifying, and comparing dynamical and biomechanical properties of living matter through single particle tracking

“…TFM has been successfully used to measure stresses/forces in: rat cardiac cells grown on substrates mimicking normal and diseased tissue, 22 human induced pluripotent stem cells under a variety of conditions, 23 and mouse embryonic fibroblasts (MEFs) under applied shear stresses. 24 Alternatively, traction forces can be calculated from the bending of micro-scale 25,26 or nano-scale 27 pillars grown on cell culture substrates, see Fig. 2(b).…”

“…TFM has been successfully used to measure stresses/forces in: rat cardiac cells grown on substrates mimicking normal and diseased tissue, 22 human induced pluripotent stem cells under a variety of conditions, 23 and mouse embryonic fibroblasts (MEFs) under applied shear stresses. 24…”