Work & Dissipation in the Cell Cytoskeleton

Living cells generate and transmit mechanical forces over diverse time-scales and length-scales to determine the dynamics of cell and tissue shape during both homeostatic and pathological processes, from early embryonic development to cancer metastasis.  These forces arise from the cell cytoskeleton, a scaffolding network of entangled protein polymers driven out-of-equilibrium by enzymes that convert chemical energy into mechanical work.  However, how molecular interactions within the cytoskeleton lead to the accumulation of mechanical stresses that determine the dynamics of cell shape is unknown.  Furthermore, how cellular interactions are subsequently modulated to determine the shape and dynamics of the tissue is also unclear.  To bridge these scales, our group in collaboration with others, uses a combination of experimental, computational and theoretical approaches.  On the molecular scale, we use active gels as a framework to understand how mechanical work is produced and dissipated within the cell cytoskeleton.  On the scale of cells and tissues, we abstract mechanical stresses to surface tension in a liquid film and draw analogies between the dynamics of wetting and the dynamics of simple tissues.  Together, we attempt to develop comprehensive description for how cytoskeletal stresses translate to the physical behaviors of cells and tissues with significant phenotypic outcomes such as epithelial wound healing.