Many cells in our body are moving and somehow seem to ‘know’ where to go. But how do they learn the location of their destination? This question is key to understanding phenomena such as the renewal of cells in our body, the transfer of cancer cells, and especially how wounds heal. Edouard Hannezo and his team at the Institute of Science and Technology Austria (IST Austria) in collaboration with Tsuyoshi Hirashima and his Kyoto University student proposed a new model of information transfer in which cells use long-distance travel in an organized manner. to close a wound. This study was recently published in the journal Nature Physics.
The researchers built a mathematical model to describe the interactions within a layer of cells on a substrate, similar to a layer of skin. These cells contain chemical signals ̵1; proteins – that allow them to understand the other cells around them, so as to push or pull, and to control their own movements. What scientists have found is the complex interaction of cell movement, environmental perception, and protein activation states within cells that combine to create mechanical and chemical wave currents where direction information is encoded.
Mechanical currents appear as denser areas and sparser cells alternate with space and time. The chemical wave appears as protein activity and is triggered by cell movement and mechanical feedback. Cell chemistry in turn drives changes in cell shape and the closing motion of a feedback loop in cell mechanics. In this affiliate system these mechanical and chemical currents spontaneously emerge due to feedback and amplification.
In a normal un layered layer of cells, these waves spread without the desired direction, but when an artificial wound is introduced to one side, the waves move again to exclusively spread away from the wound. Researchers thus thought that waves could serve as a communication tool, allowing cells far too far from the wound — and thus not “seeing” it directly — to understand which way to go.
A density wave causes the neighbors of a cell to push and pull it in the direction in which the wave travels. Because the forces exerted on the cell are equal and opposite between the peaks and troughs of each wave, the result is that the cell moves only a small distance back and forth without any net movement. As a result, the cell has no way of knowing the direction the wave originated and thus there is no information about the location of the wound.
This is where the second wave of protein activity enters. It hits the cell slightly after the density wave due to the delay required for proteins to activate. And because protein activity controls the speed of movement of cells, the delay between two waves allows the cells to move faster when pulled in the direction of the wound, and slowly when pushed. In this way, the cells can break the symmetry and begin to move in the desired direction towards the wound.
Researchers at Kyoto University observed this behavior that does not equilibrium wound healing during in vitro experiments with real cells on a substrate. They used a novel microscopy technique to allow them to measure protein activity within each cell: the protein is modified so that it is lit when activated thus exposing the protein activation waves that propagate whole cell layer. The researchers were able to predict the volume of wave patterns, which they then also followed experimentally. More notably, they also found that the delay between two waves was close to the theoretically predicted optimal for allowing cells to retrieve maximum information from the waves.
This mechanism of self-regulation is notable for allowing stable and spontaneous communication of direction over large distances within cell layers. It shows a way in which coordinated behaviors can appear in our bodies that help them heal and grow.
Discovery of a mechanism for determining the direction of collective cell migration
Daniel Boocock et al, The theory of mechanochemical pattern and optimal transfer in monolayer cells, Nature Physics (2020). DOI: 10.1038 / s41567-020-01037-7, www.nature.com/articles/s41567-020-01037-7
Provided by the Institute of Science and Technology Austria
Citation: Research reveals how ‘wave’ wounds heal (2020, September 28) obtained on September 28, 2020 from https://phys.org/news/2020-09-reveals-wounds.html
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