Harris, A.R. et al. Proc. Natl. Acad. Sci. USA 109, 16449–16454 (2012).

Many body surfaces are lined by one-cell-thick sheets with complex intercellular junctions. Harris et al. describe an approach to study the mechanical properties of mature cellular monolayers in the absence of substrate. Cells are first seeded onto collagen suspended between a fixed and a flexible rod. When the monolayer has filled the space between the rods, the collagen is dissolved away. The viscoelastic properties of the monolayer are then probed by pulling the rods apart with micromanipulators and monitoring the displacement of the flexible rod. Experiments with this setup show that MDCK monolayers are almost twice as elastic as individual cells and that monolayer extension is due to cell extension without intercalation. The monolayer can be imaged during the mechanical experiments, permitting the behavior of subcellular components to be studied simultaneously.