Cellular contractile forces are non-mechanosensitive

Cells’ ability to apply contractile forces to their environment and to sense its mechanical properties (e.g. rigidity) are among their most fundamental features. Yet, the interrelations between contractility and mechanosensing, in particular whether contractile force generation depends on mechanosensing, are not understood. We use theory and extensive experiments to study the time evolution of cellular contractile forces and show that they are generated by time-dependent actomyosin contractile displacements that are independent of the environment’s rigidity. Consequently, contractile forces are non-mechanosensitive. We further show that the force-generating displacements are directly related to the evolution of the actomyosin network, most notably to the time-dependent concentration of F-actin. The emerging picture of force generation and mechanosensitivity offers a unified framework for understanding contractility. One Sentence Summary Cellular contractile forces are generated by rigidity-independent displacements that are determined by the time evolution of F-actin assembly.