How are our cells organized to give our bodies their final shape? The answer lies in morphogenesis, the set of mechanisms that regulate their distribution in space during embryonic development. A team from the University of Geneva (UNIGE) has just made an amazing discovery in this area: when tissue is bent, the volume of the cells that make it up increases, not decreases. This discovery opens up new avenues for in vitro organ culture, a partial alternative to animal experiments. It also offers new perspectives for the production of some materials. This study is published in the journal Developmental cell.
In biology, the mechanisms that determine the distribution of cells in space to form the shape and structure of our tissues and organs are called “morphogenesis”. These mechanisms work during embryonic development and explain how, for example, the folds of our intestines or the alveoli of our lungs are formed. In other words, these phenomena underlie our development and the development of all living things.
The cells swell and it’s unexpected
In a recent study, Professor Ru’s team investigated how the cells that make up tissue respond and adapt when it folds. By rolling a monolayer of cells in vitro, which is a compact flat assembly of cells located nearby, UNIGE scientists have made an unreasonable discovery. “We found that the volume of cells located in the curvature increased by about 50% after five minutes instead of decreasing and then returned to normal within 30 minutes,” explains Aurelien Roux, the latest author of the study. This is the opposite of what can be observed when bending an elastic material.
By bending this “sheet” of cells, similar to what our skin is made of, the researchers more accurately noticed that the latter swelled, taking the shape of small domes. “The fact that this increase in volume is gradual and transient also shows that it is an active and living system,” adds Ekaterina Tomba, the study’s lead author and former researcher at UNIGE’s Department of Biochemistry.
Mechanical and biological phenomenon
This increase in volume is due to a combination of two phenomena. “The first is a mechanical reaction to curvature, the second is due to the osmotic pressure it exerts on the cell,” says Aurelien Roux. Cells develop in an environment of salt water. The semi-permeable membrane that separates them from the environment is permeable to water, but not salt, which puts some pressure on the cell. The greater the concentration of salt on the outside – and thus the so-called osmotic pressure – the more water will pass through the cell membrane, increasing its volume.
“When a curvature is caused, the cells react as if it increases the osmotic pressure. Therefore, they absorb more water, which leads to their swelling, “- explains the researcher.
Useful for reducing animal experiments
Understanding how cells respond to bending is important progress for in vitro development of organelles. These three-dimensional multicellular structures, designed to mimic the microanatomy of an organ and its functions, can indeed allow large-scale research to be conducted without the need for animal experiments. “Our discovery is an active phenomenon that must be taken into account to control the spontaneous growth of organelles, ie. get the desired shape and size of the body – says Aurelien Roux. The long-term goal would be to be able to “grow” any replacement organ for specific patients.
These results are of interest to the industry as well. “Today, there are no materials that increase in volume in folded form. Engineers conceived this material without even realizing it, because its production was extremely complex. Therefore, our work also offers new clues to understanding the development of such materials,” concludes Aurellen. . Ру.
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