Cells of our body deform under external forces. But how do they recover their shape once the force is removed? This important mechanism is now described by scientists from the Friedrich-Alexander University Erlangen-Nurnberg (FAU) together with international colleagues in Nature Materials.
The cells of our body are soft and deform easily when stretched, sheared or compressed under external forces. The relationship between force and cell deformation is altered in many diseases such as cancer, pulmonary and cardiovascular diseases, or muscular disorders. An accurate determination of cell mechanical properties is therefore important for understanding disease mechanisms and has long been of central interest in medicine and biology.
Current models can describe with high accuracy how cells deform under an external force, but they fail to predict how cells recover their shape once the force is removed. For example, after our blood cells are pressed through narrow capillaries, how quickly do they regain their original shape? What happens to our lung cells after they are stretched during yawning or a deep sigh, or to our muscle cells after being over-distended in an accident?
Biophysicists from the University of Erlangen-Nuremberg, the Max-Planck Institute for the Science of Light in Erlangen, and the University of Arizona have found a surprisingly simple answer to these questions: During application of an external force, the total cell deformation is the sum of two parts, a viscoelastic deformation that is fully reversible when the force is removed, and a plastic deformation that is long-lasting or permanent. The plastic deformation depends on the total deformation and the duration of force application, as probably will be confirmed by anyone who has attempted to stretch the earlobe for a fashionable tunnel. Interestingly, the viscoelastic and plastic deformations are indistinguishable during force application and follow the exact same time course.
The researchers could show that this coupling originates at the level of so-called cytoskeletal filaments that criss-cross the cell interior and carry most of the mechanical stress. With this knowledge at hand, cell biologists, trauma surgeons and body piercers can now quantitatively predict the level of permanent cell deformation after mechanical loading and stretching.