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Dying cells emit molecular signals that protect their neighbors
Recently, two independent groups of scientists have discovered the same molecular mechanism that supports the integrity of body tissues. These results are a vivid example of the abilities of living tissues to self–organization and autonomous, independent of the central "conductor" work on survival
In any organism, there is a constant process of renewal, when some cells, old and worn out, die and are replaced by new ones. This process is especially active in "barrier" tissues that are constantly exposed to environmental factors: the integumentary epithelium of the skin, the keratinized cells of which are continuously exfoliated, and the mucous membranes of the digestive tract.
Thus, millions of cells are continuously dying in our body, but surprisingly, all tissues retain their integrity! At the same time, the mechanisms involved in its maintenance are poorly understood, but their violation can play an important role in the development of pathologies such as chronic inflammation.
Scientists from the Pasteur Institute (France) the process of tissue renewal was studied using the example of the epithelial cells of the pupae of drosophila flies, the structure of which is very similar to human. Using an optogenetic tool that allows using blue light to start the process of "suicide" (apoptosis) in cells, they found that the integrity of the epithelium is violated only if at least three neighboring cells die within half an hour. Such damage is then "repaired" in a process similar to wound healing.
However, in natural conditions, such a situation, i.e. a "hole" in the tissue, rarely occurs. And the researchers found out why: it turns out that any dying cell emits chemical signals that activate a cascade of molecular events in neighboring cells - the so–called EGFR-ERK signaling pathway that promotes cellular survival. Its activation protects from the death of the neighbors of the dying cell for about an hour.
The same protective mechanism was independently discovered by a Swiss research team in human breast epithelial cell cultures. Studying the spatio-temporal organization of the apoptosis process, they found that molecular "impulses" emanate from dying cells, activating the same EGFR-ERK signaling pathway, which radially propagate to about three neighboring cell layers. This gives the cells that are dying in the immediate vicinity protection from apoptosis for 3-4 hours.
Thus, scientists conclude that the process regulating the integrity of epithelial tissue in animals is very conservative – it proceeds in a similar way in flies and in humans, organisms separated by hundreds of millions of years of evolution. "Postponement", which allows the neighbors of the dying cell to survive, allows the body to maintain the integrity of tissues, which, by the nature of their activity, have to be constantly updated.
The second conclusion is more practical: violations of this mechanism can lead to the development of chronic inflammation of the intestinal mucosa and such immuno-inflammatory diseases as ulcerative colitis and Crohn's disease. And if warned, it means armed.
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