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Prof. Dr. Joachim P. Spatz

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Cell Biology . Material Sciences . Structural Biology

Cells are extremely sensitive to mechanical stimuli

If you want to make cells work for you, you have to be able to communicate with them. That’s the challenge. However, the language that tissue cells use to keep in touch with their environment is still largely indecipherable, so the scientists in Stuttgart are concentrating on trying to decipher it. Cells communicate with their immediate environment through many subtle contacts, which they can actively switch on and off. In highly developed multicellular organisms like mammals, the environment we are talking about here consists of a complex network of stabilizing fibres in a basic aqueous substance. The latter contains all of the messenger substances necessary for life, such as hormones and molecular energy suppliers. Biologists call this protective zone around the cells the extracellular matrix.

Dipping in the service of science: A glass plate is dipped in a solution and Maria Sycha, institute technician, checks whether the glass plate is centered in the beaker. Zoom Image
Dipping in the service of science: A glass plate is dipped in a solution and Maria Sycha, institute technician, checks whether the glass plate is centered in the beaker. [less]

Researchers claim, with a bit of a wink, that there are four different scientific dialects in which to speak to cells: biochemical, electrical, mechanical and structural. Of course, the importance of biochemistry has long been apparent to researchers. After all, every vital function in a cell is based on biochemical processes. The effect of electrical stimuli has also been the subject of investigations for quite some time.

However, the cells’ enormous sensitivity to the subtlest of mechanical and structural stimuli on the nanometre scale is something scientists discovered only recently. And the interdisciplinary team of biologists, chemists and phys­icists brought together by Joachim Spatz at the Max Planck Institute for Metals Research made a key contribution to this discovery. That’s how the two video recordings with the relaxed and the stressed rat cell came about.

If cells are to move, they require components that act like muscles. The cell’s skeleton (the cytoskeleton) takes on this function. Like our own muscles, it contains relatively stiff, strong fibres made of the protein actin. These fibres serve as a molecular ladder for a so-called motor protein, a myosin, to climb. Depending on the direction in which it climbs, the myosin-actin motor pulls an area of the cell together in a certain direction, or stretches it. It is precisely this molecular mechanism that enables our muscle cells to contract particularly strongly.

The cytoskeleton becomes active as soon as the cell pushes out parts of its membrane to search the environment for suitable contact points, as in the video recording. In an electron microscopic image with a resolution in the nanometre scale, Joachim Spatz shows what the cell does on the synthetic surfaces made by the Stuttgart-based research group. It puts out tiny little feet, known as filopodia, which reach down to the peptide-coated gold nanoparticles.

If the cell likes its synthetic environment, it acts almost as it would if it were in its natural environment, the extracellular matrix. It begins with the job it performs in the living organism, producing the building blocks for tissue, for example. But if the environment does not suit it, then it initiates its suicide program. In our body, program­med cell death, known as apoptosis, prevents such things as uncontrolled tissue growth.

 
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