Membrane ruffling is a mechanosensor of extracellular fluid viscosity

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. Living cells change their behaviour in response to the viscosity of the medium surrounding them. An in vitro study shows that cells spread wider and move faster in a highly viscous medium, provided they have an actively ruffling lamellipodium.

Automated summary

Cell behaviour is influenced by the physical forces and mechanical properties of both cells and their microenvironment. This study explores the effect of viscosity, an important component of the cellular microenvironment, on cell behaviour. The results show that cells respond in a similar manner to elevated viscosity, with increased spread area, focal adhesion formation and turnover, traction forces, and migration speed. Cells utilize membrane ruffling to sense changes in extracellular fluid viscosity and trigger adaptive responses.