In a paper published in Proceedings of the National Academy of Sciences (PNAS) this week, researchers at the Institute of Bioengineering of Catalonia (IBEC) –located at the barcelona Scientific Park– have uncovered a crucial mechanism by which cells probe their environment, taking them a step closer to understanding how they interact with their surroundings; in turn, this opens doors to being able to predict or control cell behaviour.

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The rigidity of the cellular environment is so important that it can be the determining factor of whether a stem cell will differentiate into bone or fat, for example – or whether a cell behaves normally or turns cancerous. “How a cell measures rigidity has long been a mystery,” explains Pere Roca-Cusachs, senior researcher in IBEC’s Cellular and Respiratory Biomechanics group, which carried out the research alongside collaborators in the US.

To answer these questions, the scientists placed cells on a bed of flexible nanometric pillars. “By tracking the movement of these pillars, we were able to map how cells exert forces on their environment with a resolution never achieved before,” says the researcher. “Using this technique, we found that the rigidity sensor in cells is a small complex of not more than one micrometre (1/1000th of a millimetre) long.” The researchers saw, too, that the cell does indeed possess multiple copies of this complex, all of which apply a constant displacement of 60 nanometers – less than 1/10000th of a millimeter. The sensors then measure the applied force to deduce the rigidity of the environment.

“These findings represent a very important step towards understanding how cells interact with their environment, knowledge which is crucial to fabricate organs like lungs or hearts in vitro or treat diseases such as cancer,” says Pere Roca-Cusachs.

Reference article:
Saba Ghassemi, Giovanni Meacci, Shuaimin Liu, Alexander A. Gondarenko, Anurag Mathur, Pere Roca-Cusachs, Michael P. Sheetz, and James Hone. Cells test substrate rigidity by local contractions on submicrometer pillars. PNAS 2012 [published ahead of print], March 19, 2012, doi:10.1073/pnas.1119886109.

Image: A cell spreading on the nanometric pillars