Previously developed models for the cytoskeletal network in stationary cells (that is, ignoring cell spreading and motility) have been based on the assumption that the cytoskeleton is a structure of passive filaments. However, such models ignore the biochemical reactions within the cell that generate, support and respond to mechanical forces. Deshpande et al. now present a biochemically inspired model for the dynamic rearrangement of the cytoskeleton that addresses important challenges in the field of cell biomechanics.

The authors considered recent observations of the forces that are exerted by mammalian cells on a compliant substrate — for example, spatial correlations have been observed between the force vectors that operate on the substrate and the organization of the stress fibres. A model was then developed to capture the reorganization of the cytoskeleton in response to mechanical perturbations.

Experiments, for example, measure the forces that are exerted by cells on a bed of microneedles, with the stress fibres revealed by actin staining. So, how can one model such experiments? The model is based on three important biological processes: an activation signal that triggers actin polymerization and myosin phosphorylation; the tension-dependent assembly of actin and myosin into stress fibres; and the cycling between actin and myosin filaments that generates the tension. Because the precise details of these biochemical processes are still unclear, the authors have developed a model that does not depend on the details and serves as a framework that can be appropriately modified when these biochemical processes are better understood.

Deshpande et al. propose that simple relationships simulate these coupled phenomena and show that their model can be used to predict experimentally verified data, such as the influence of cell shape and boundary conditions, on the orientations of the fibres as well as the high concentration of the stress fibres at the focal adhesions. Most importantly, this model can measure the mechanical characteristics of living cells that react to the measurement tools and, therefore, can be used as a framework to design and interpret experiments.