A continuous-discrete model of cell contraction incorporating actin and intermediate filaments

Cell contractility is driven largely by actin filaments (AFs), while intermediate filaments (IFs) contribute to mechanical stability and help maintain cellular architecture. Here, we present a continuous-discrete finite element model that represents AFs and IFs as one-dimensional elements embedded within a two-dimensional cell domain. AFs generate contractile forces, move toward regions of maximum mean strain, and align with the major principal strain, whereas IFs move toward regions of minimum mean strain and align with the minor principal strain. Model predictions agree with experimental measurements of membrane curvature and the spatial distribution of F-actin and IFs across cells cultured on different adhesion patterns and substrates. Simulations reveal that AFs accumulate near focal adhesions (FAs) and the plasma membrane and also assemble into cable-like bundles that cross the cytoplasm, while IFs resist excessive deformation and reduce membrane curvature. This framework provides a mechanistic approach for studying how cytoskeletal organization regulates cell contraction.