  The unique nonlinear mechanics of the fibrous extracellular matrix (ECM)
facilitates long-range cell-cell mechanical communications that would be
impossible on linear elastic substrates. Past research has described the
contribution of two separated effects on the range of force transmission,
including ECM elastic non-linearity and fiber alignment. However, the relation
between these different effects is unclear, and how they combine to dictate
force transmission range is still elusive. Here, we combine discrete fiber
simulations with continuum modeling to study the decay of displacements induced
by a contractile cell in fibrous networks. We demonstrate that fiber
non-linearity and fiber reorientation both contribute to the strain-induced
anisotropy of the elastic moduli of the cell local environment. This elastic
anisotropy is a parameter that governs the slow decay of the displacements, and
it depends on the magnitude of applied strain, either an external tension or an
internal contraction as a model of the cell. Furthermore, we show that
accounting for artificially-prescribed elastic anisotropy dictates the
displacement decay induced by a contracting cell. Our findings unify previous
single effects into a mechanical theory that explains force transmission in
fibrous networks. This work provides important insights into biological
processes that involve the coordinated action of distant cells mediated by the
ECM, such that occur in morphogenesis, wound healing, angiogenesis, and cancer
metastasis. It may also provide design parameters for biomaterials to control
force transmission between cells, as a way to guide morphogenesis in tissue
engineering.
