Cell behaviour is affected by the physical forces and mechanical properties of cells and their microenvironment. The viscosity of extracellular fluid—a component of the cellular microenvironment—can vary by orders of magnitude, but its effect on cell behaviour remains largely unexplored. Using biocompatible polymers to increase the viscosity of the culture medium, we characterize how viscosity affects cell behaviour. We find that multiple types of adherent cell respond in an unexpected but similar manner to elevated viscosity. In a highly viscous medium, cells double their spread area, exhibit increased focal adhesion formation and turnover, generate significantly greater traction forces and migrate nearly two times faster. We observe that when cells are immersed in a regular medium, these viscosity-dependent responses require an actively ruffling lamellipodium—a dynamic membrane structure at the front of the cell. We present evidence that cells utilize membrane ruffling to sense changes in extracellular fluid viscosity and to trigger adaptive responses.

细胞行为受到细胞及其微环境的物理力和机械特性的影响。细胞外液（细胞微环境的一个组成部分）的粘度可以有几个数量级的变化，但其对细胞行为的影响在很大程度上仍未被探索。使用生物相容性聚合物来增加培养基的粘度，我们表征了粘度如何影响细胞行为。我们发现多种类型的贴壁细胞以意想不到但相似的方式对粘​​度升高做出反应。在高粘度介质中，细胞的扩散面积加倍，粘着斑形成和周转增加，产生显着更大的牵引力，并且迁移速度几乎快两倍。我们观察到，当细胞浸入常规介质中时，这些依赖于粘度的反应需要一个活跃的褶皱片状足——细胞前部的动态膜结构。我们提供的证据表明，细胞利用膜波纹来感知细胞外液粘度的变化并触发适应性反应。