Observations of the life of elderly mice revealed an interesting fact - their skin heals cuts and other wounds faster and "better" than that of young individuals. This is the conclusion reached by biologists who published an article in the journal Cell Reports.
The cells of the embryo and embryonic stem cells are virtually immortal from the point of view of biology - they can live almost indefinitely in an adequate environment, and divide an unlimited number of times. In contrast, cells in the adult body gradually lose their ability to divide after 40-50 division cycles, entering the aging phase, which presumably reduces the chances of developing cancer.
Why do cells do this? As scientists today believe, in a similar way, cells protect themselves and the body as a whole from the development of cancer, stopping division at a time when the likelihood of developing mutations in their genome reaches some critical point. The decrepitude of the body, in turn, is a side effect of this process, associated with the accumulation of "aged" cells in the organs.
Thomas Leung of the University of Pennsylvania in Philadelphia (USA) and his colleagues discovered a big exception to this rule by observing how the skin of young and old mice heals small cuts, and how their cells behave when such damage occurs.
“Plastic surgeons and dermatologists often notice that scars are less common on the skin of older people, but the causes and mechanisms of this unusual phenomenon remained a mystery to us. Understanding why this is happening will pave the way for skin regeneration technologies,”says Lyng.
To answer this question, scientists have acted in an unusual way. They "stitched" the circulatory systems of two mice - an elderly and a young rodent, and tracked which genes and signaling molecules present in their skin changed the most and how these changes affected the regeneration process when a hole was pierced in their ears.
Ear piercing of "ordinary" young mice, not connected to elderly companions, led to the formation of scar tissue at the edges of the wound and the formation of a permanent "hole" in their shell. If they were "connected" to the circulatory system of elderly rodents, this did not happen - the hole slowly but tightened and the damage disappeared without a trace.
The reason for this, as Lyng and his colleagues found, was that the blood of young mice contained large amounts of SDF1, special signaling molecules that, as biologists previously believed, are responsible for the regeneration of the liver, kidneys and some other organs.
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This protein is practically absent in the body of elderly rodents, since its work is blocked by changes in the structure of the DNA envelope containing instructions for the synthesis of SDF1, and by the increased activity of the EZH2 gene, which controls the application of such labels to the protein wrapper of DNA. Its deactivation in the cells of elderly rodents drastically impaired its regeneration, forcing it to form scars and scars more often.
Having discovered this unusual phenomenon, scientists tested whether human skin works in a similar way. As observing skin wounds in young and elderly volunteers, aging altered the behavior of their cells in a similar way, suggesting that the skin actually starts to work "better" as they get older.
“This behavior of the skin makes sense from an evolutionary point of view. The faster the wound heals, the easier it will be for a young animal to survive, even if the treatment process is not too high-quality,”concludes the geneticist.
