Apr 22, 2009
Paired technique probes cell stiffness
Researchers at the University of Münster, Germany, are studying the stiffness of endothelial cells (cells that form the inner layer of blood vessels). Stiffening of these cells has been shown to reduce the production of the vasodilating gas nitric oxide (NO), which results in increased peripheral resistance and blood pressure.
In particular, the group wants to find out more about the cellular mechanisms that lead to an increase in the stiffness of endothelial cells and believes that the electrical potential difference across the plasma membrane might be involved.
To investigate the hypothesis, the team has devised an experimental approach that combines fluorescence-based electrical membrane potential- and atomic force microscope (AFM)-based stiffness measurements. In practise, the set-up is realized by integrating an AFM and an epifluorescence microscope.
Using this technique, the researchers can simultaneously measure the dynamics of the membrane potential and the mechanical stiffness in a living endothelial cell. The cellular stiffness is determined by nano-indentation using an AFM while the electrical membrane potential is measured with bis-oxonol, a voltage-reporting fluorescent dye.
The study reveals that fast (in the range of seconds) membrane potential and stiffness changes are not related to each other, whereas sustained (in the range of minutes) changes in the two parameters do correlate. This suggests a more indirect coupling mechanism between electrical and stiffness changes in endothelial cells.
The method allows the scientists to study any kind of dynamic fluorescence (for example, Ca2+, pH, Na+, NO or fluorophore-linked proteins) together with mechanical properties of living cells. Now it is possible to start finding answers to a wide range of questions such as the linkage between cell mechanics and cell function.
The researchers presented their work in Nanotechnology.
About the author
Chiara Callies studied biology in Münster, NRW, Germany. She is now a PhD student at the Institute of Physiology II at the University of Münster and a member of the Interdepartmental Graduate Program for Experimental Life Sciences (iGEL), which is now part of the CEDAD (Cell Dynamics and Disease) graduate school. Currently she is exploring whether endothelial cell stiffness is regulated by the plasma membrane potential using combined atomic force and fluorescence microscopy.