The secret of salamander regeneration has been revealed - they grow new organs from memory. Instead of returning to an embryonic state, the cells of the salamanders remember the lost organ and reconstruct it exactly as it was before
The mechanism of regeneration of lost limbs by salamanders has nothing to do with the action of stem cells, scientists have found.
The magical abilities of salamanders
The ability of these tailed amphibians to grow paws, lungs, and a brain has worried mankind for thousands of years - it was studied by Aristotle, Voltaire, Darwin.
When the animal loses a part of the body, the cells of the superficial layer of the skin quickly cover the wound with the so-called epithelial cover, fibroblasts break the bonds with the connective tissue and form a blastema (an accumulation of specialized cells) at the site of the wound, from which a new limb is formed. For example, it takes only three weeks to get a new paw.
At the end of the 20th century, scientists assumed that salamander cells are similar to stem cells, that is, they can turn into any organ.
Martin Kragl of the German Max Planck Institute found that this is not the case. Together with his American colleagues, he studied how the Mexican salamander, the axolotl Ambystoma mexicanum, grows limbs and tissues. Kragl took advantage of the discoveries of the University of California, who proved that salamander blastema cells are similar to cells in the developing limbs of mammalian embryos, which are able to renew their limbs, but lose these skills before birth.
Experiment in ultraviolet
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Based on the idea that the development of limbs from the blastema practically repeats in a brief form their natural development in growing creatures, German and American scientists divided the animals into two groups. The first to be injected was the GFP protein derived from the fluorescent jellyfish. In ultraviolet light, this protein highlights cells in green, which allows scientists to trace the origin of various cells and their purpose. The second group included both adult axolotls and larvae. Scientists introduced them to cells with protein taken from genetically modified individuals. The substance was injected into the larvae where, as biologists knew, various tissues and organs, in particular the nervous system, should have grown. Adults were first injected cells with protein, and then cut off from the body piece by piece.
After observing the wards for several weeks, biologists found that the cells behave very conservatively - they grow only in those organs and tissues from which they originated. “The main conclusion of the researchers is that new muscle cells only produce old muscle cells, new skin cells only produce old skin cells, new neurons only produce old nerve cells,” writes Science Daily. This process was most clearly observed in the larvae: injected into the area from which the nervous system was supposed to grow, the cells highlighted in green spread along the growing axolotl exactly according to the scheme of the nervous system.
"In all likelihood, cells near the amputated organ are reprogrammed, which allows them to start embryonic tissue formation programs without returning to the original polypotential cell," the researchers noted in an article published in the prestigious journal Nature.
In other words, salamander cells behave in a fundamentally different way than stem cells. If the latter are able to receive specialization and develop into practically any organs, then in the cells of salamanders there is a mechanism of clear continuity.
From salamander to superman
The advantage of salamander cells is that they do not need to reach an embryonic state to start the regeneration process - they work great as adults. Revealing the secret of "active cells", doctors will be able to grow a person's severed arm or leg, following the example of a salamander.
“One day we will be able to regenerate human tissue,” says one of the study's authors, Malcolm Meden. The hopes of American scientists are largely due to the personality of those who ordered the study: it was sponsored by the US Department of Defense, whose representatives want to help amputated veterans of Iraq and Afghanistan.