German scientists are ripping cells apart to study their elasticity.

Elasticity allows a cell to perform many fundamental processes, such as migration, adhesion and interaction. Investigating how a cell's individual components contribute to its overall elasticity is therefore of vital interest for scientists trying to understand how these processes work. However, gauging the membranes' contribution has proved to be difficult, in particular at smaller than micrometre length scales.

Andreas Janshoff at the University of Gottingen and colleagues have now developed a method to trap cell membranes so that their elastic properties can be mapped. The researchers attach epithelial cells to a surface before placing a polymer-coated porous chip on top of the cells. On lifting off the chip, the membranes stick to its poly-D-lysine coating, leaving behind the rest of the cell. The group can then perform atomic force microscopy experiments on the membranes to obtain quantitative stress-strain measurements. 

Importantly, the membrane fragments are from the apical side of the cells. Since epithelial cells are polar, the two membrane segments - apical and basolateral - may behave differently. But whilst in earlier work the researchers were able to isolate membranes from the basolateral side, this is the first time they have been able to study the apical membrane away from the rest of the cell.

Janshoff suggests that the method is an improvement over existing elasticity measuring techniques. 'To assess the properties of lipid bilayers, mainly non-local methods have been used,' he says. These include indentation and aspiration of giant liposomes, a method in which cell membrane models are poked to measure their response. 'Now, mechanical information can be accessed from cell membrane fragments on nanometre length scales,' Janshoff explains.

Markus Deserno, associate professor of physics at Carnegie Mellon University, Pittsburgh, US, agrees that this is a step forward. 'Cell membranes are fascinating objects that keep surprising us,' he says. 'This work shows how suspected links between chemistry, thermodynamics and elasticity can be probed quantitatively. Such experiments are challenging, both in terms of execution and analysis, but they promise deeper and more quantitative insights than existing indentation tests'.

Edward Morgan

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