Hydraulics of active tissues

From interstitial space to luminal cavities, fluid pressure and flow can remodel, reshape and even redefine a biological tissue. These hydraulic forces both govern and react to mechanical interactions between cells, but difficulties of measuring flows at cellular scales make understanding tissue hy- draulics challenging. Here, we demonstrate a theoretical approach that models cellular mechanics and hydraulics simultaneously, and find that fluid flux can drastically alter tissue behavior. We show that perturbations to a tissue’s permeability in the presence of active noise can decrease cell mobility to the point of fracture, where a hydraulic ratchet drives fluid out of cells and nucleates microlumina. We find evidence that part of our theoretical results, that fluid permeability affects tissue dynamics, explains experimental observations of cell motion in zebrafish embryos injected with a thickening agent, indicating that hydraulics may generally affect any multicellular system.