Mechanical communication between cells and substrates

Cells are sensitive to mechanical signals produced either by application of exogenous force, or by the resistance to cell-generated forces caused by the viscoelastic properties of the materials to which they adhere. The range of stiffness over which different cell types respond can vary over a wide range and generally reflects the elastic modulus of the tissue from which these cells were isolated. Many cell types can alter their own stiffness to match that of the substrate to which they adhere. The maximal elastic modulus that cells can attain is similar to that of crosslinked actin networks at the concentrations in the cell cortex. Mechanosensing appears to require an elastic connection between cell and substrate, mediated by transmembrane proteins. The viscoelastic properties of different extracellular matrices and cytoskeletal elements strongly influence the response of cells to mechanical signals, and the unusual non-linear elasticity of many biopolymer gels, characterized by strain-stiffening, leads to novel mechanisms by which cells alter their stiffness by engagement of molecular motors that produce internal stresses.