A multiscale investigation of reconstituted intermediate filament hydrogels under compression

Cell migration is an essential process in many biological functions, including tissue maintenance and disease progression. The mechanical forces behind these functions are mediated through the cells via the cytoskeleton, a complex network of (semi-) flexible biopolymers that include actin, microtubules (MTs), and intermediate filaments (IFs). What role IF mechanics have in cell motility is yet to be fully understood. Here, we first study the mechanical response of reconstituted polymer networks comprised of the IF proteins vimentin and keratin using a parallel-plate rheometer. We investigate the mechanical response of these IF networks to uniaxial compression, knowing that cells stiffen under compression and this function may protect cells during migration. We first demonstrate that vimentin and keratin networks also stiffen under axial compression, in contrast to actin and MTs which soften. Further, we demonstrate this stiffening is divalent cation concentration dependent, a property regulated by the cell. We further investigate the microscopic compression behavior of these IF gels by real-time imaging their compression and directly analyzing network motion.