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Posted: Dec 18, 2013
Stretching living cell sheets
(Nanowerk News) Cell monolayers line most of the surfaces and cavities in the human body. During development and normal physiology monolayers sustain, detect, and generate mechanical stresses, yet little is known about their mechanical properties due to a lack of experimental testing techniques.
In a publication in Nature protocols ("Generating suspended cell monolayers for mechanobiological studies"), a team of researchers from the London Centre for Nanotechnology led by Dr Andrew Harris and Dr Guillaume Charras describe a novel cell culture and mechanical testing protocol for generating freely suspended cell monolayers and examining their mechanical and biological response to uni-axial stretch.
(a) Image of cell boundaries visualised using cells stably expressing E-Cadherin-GFP before application of stretch. Scale bar =10Ám. (b) Image of the same area as in (a) following application of 50% stretch along the horizontal axis (grey arrows). All cells become elongated in the direction of stretch. (c) Representative force relaxation curve. (d) Averaged force extension curve for an MDCK monolayer.
In this protocol, cells are cultured on temporary collagen scaffolds polymerised between two parallel glass capillaries. Once cells form a monolayer covering the collagen and the capillaries, the scaffold is removed with collagenase leaving the monolayer suspended between the test-rods. The suspended monolayers are subjected to stretch by prising the capillaries apart with a micromanipulator. The applied force can be measured for characterisation of monolayer mechanics. Monolayers can be imaged with standard optical microscopy to examine changes in cell morphology and subcellular organisation concomitant with stretch.
The team anticipates that this novel method will allow characterisation the mechanical properties of any cell type that forms strong intercellular junctions (such as epithelial cells, endothelial cells, or keratinocytes) paving the way for a broader understanding of how mechanical properties depend on differences in intercellular junction structure and composition across tissues.