  How cells move through the three-dimensional extracellular matrix (ECM) is of
increasing interest in attempts to understand important biological processes
such as cancer metastasis. Just as in motion on flat surfaces, it is expected
that experimental measurements of cell-generated forces will provide valuable
information for uncovering the mechanisms of cell migration. However, the
recovery of forces in fibrous biopolymer networks may suffer from large errors.
Here, within the framework of lattice-based models, we explore possible issues
in force recovery by solving the inverse problem: how can one determine the
forces cells exert to their surroundings from the deformation of the ECM? Our
results indicate that irregular cell traction patterns, the uncertainty of
local fiber stiffness, the non-affine nature of ECM deformations and inadequate
knowledge of network topology will all prevent the precise force determination.
At the end, we discuss possible ways of overcoming these difficulties.
