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Axolotl (Ambystoma mexicanum)
Photo: Paul Starosta/Getty Images
In its native Mexico, the axolotl has become rare.
On the other hand, it thrives in research laboratories.
Because the salamander has long fascinated laypeople and experts alike - especially its ability to regenerate severed limbs or even organs such as parts of the heart.
They just grow back within a few weeks.
Researchers have once again tracked down this amphibian's wondrous ability to regenerate.
In one study, they created a cell map of parts of his brain.
Because there, too, it was found that eight weeks after an injury to the forebrain, which is also responsible for processing smells, all the lost nerve cells in the test animals had been replaced.
Some of them have rebuilt their old connections to neighboring cells, said Katharina Lust from the Vienna Research Institute of Molecular Pathology (IMP).
She is co-author of the study published in the journal Science.
"But we don't yet know whether the restored neural network will actually work as before," says Lust.
In search of the secret of regeneration
Led by Elly Tanaka (IMP) and Barbara Treutlein from ETH Zurich, the research team mapped cell types in the axolotl forebrain and characterized the cells that give the newt its extraordinary ability to regenerate.
They also compared the cells with those of turtles and mice.
In the evolutionary tree, amphibians split off from the rest of the vertebrates about 350 million years ago.
Until now it was not known how similar the axolotl brain is to other vertebrate brains.
The researchers also identified clusters of neurons in the axolotl brain that correspond to the mouse and turtle hippocampus, a region responsible for memory and learning.
"Mapping cell types in the axolotl brain not only brings evolutionary insights into the vertebrate brain, but also paves the way for innovative research on brain regeneration," says Tanaka.
The aim is to understand what brain stem cells do after an injury - which genes they activate, how they interact and how they restore neurons that reconnect the lost connections.
The question is how each cell knows what to do, says Lust.
In earlier studies, scientists had already investigated which cells in the axolotl are responsible for the regrowth of limbs.
According to a 2018 paper, they are ordinary connective tissue cells.
They just rewind in their development.
Highly specialized body cells, so-called fibroblasts, become progenitor cells that can form different types of connective tissue - whether skin, bones or tendons.
Human fibroblasts cannot do this.
When we are injured, they transform into so-called myofibroblasts, which form scar tissue.
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