You can think of skin as a city where worker cells are constantly repairing streets and buildings. With age, the city hall, that is, the basal stem cells (the progenitor cells in the lower layer of the epidermis), starts to function poorly. In it, levels of the protein ATF3, which controls youth genes, decline. This protein turned out to be the key official who gets fired from city hall with age.
To bring back the fired official, scientists created mRNA, a temporary instruction for the cell to produce the needed protein. It was delivered into cells, skin samples, and mice. In skin samples from a 62-year-old donor, the thickness of the basal layer increased by a factor of 1.8, and collagen increased 10-fold. In mice with wounds, ATF3 treatment reduced scarring. City hall began sending out orders again, and the workers returned to the construction site.
To deliver the mRNA, they used a microneedle patch with needles 600 micrometers tall, thinner than a human hair. It painlessly pierces the stratum corneum and delivers the drug directly to living cells.
The idea of rejuvenation through stem cell activation brings to mind the film 'Paragraph 78' or the series 'Altered Carbon,' where bodies can be renewed. But here, instead of futuristic capsules, it's a simple mRNA injection that works on the principle of a vaccine.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.