2 research outputs found
Traction force microscopy on soft elastic substrates: a guide to recent computational advances
The measurement of cellular traction forces on soft elastic substrates has
become a standard tool for many labs working on mechanobiology. Here we review
the basic principles and different variants of this approach. In general, the
extraction of the substrate displacement field from image data and the
reconstruction procedure for the forces are closely linked to each other and
limited by the presence of experimental noise. We discuss different strategies
to reconstruct cellular forces as they follow from the foundations of
elasticity theory, including two- versus three-dimensional, inverse versus
direct and linear versus non-linear approaches. We also discuss how biophysical
models can improve force reconstruction and comment on practical issues like
substrate preparation, image processing and the availability of software for
traction force microscopy.Comment: Revtex, 29 pages, 3 PDF figures, 2 tables. BBA - Molecular Cell
Research, online since 27 May 2015, special issue on mechanobiolog
Measuring cellular traction forces on non-planar substrates
Animal cells use traction forces to sense the mechanics and geometry of their
environment. Measuring these traction forces requires a workflow combining cell
experiments, image processing and force reconstruction based on elasticity
theory. Such procedures have been established before mainly for planar
substrates, in which case one can use the Green's function formalism. Here we
introduce a worksflow to measure traction forces of cardiac myofibroblasts on
non-planar elastic substrates. Soft elastic substrates with a wave-like
topology were micromolded from polydimethylsiloxane (PDMS) and fluorescent
marker beads were distributed homogeneously in the substrate. Using feature
vector based tracking of these marker beads, we first constructed a hexahedral
mesh for the substrate. We then solved the direct elastic boundary volume
problem on this mesh using the finite element method (FEM). Using data
simulations, we show that the traction forces can be reconstructed from the
substrate deformations by solving the corresponding inverse problem with a
L1-norm for the residue and a L2-norm for 0th order Tikhonov regularization.
Applying this procedure to the experimental data, we find that cardiac
myofibroblast cells tend to align both their shapes and their forces with the
long axis of the deformable wavy substrate.Comment: 34 pages, 9 figure