Axolotl: Regeneration secret revealed

Tissue repair according to salamander-type also possible in humans?

Regenerating artist Axolotl © MPI for Cellular Cell Biology
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If a leg is torn off, that does not mean that the axolotl will break his leg. Because this Mexican salamander grow lost limbs again completely. Scientists have now researched this amazing phenomenon - to derive perhaps benefit for humans, in which this ability to regenerate relatively limited, but may be only suppressed and therefore selectively targeted "detoxify".

The animals resemble their own wax casts. Yellowish, with pink-tipped gills on the head, the axolotl looks strangely unfinished - as if a huge tadpole had forgotten to become a frog. This salamander species, which is native to Mexico, has been an attractive object of biological research for nearly 200 years - ever since Alexander von Humboldt brought his first specimens to Europe. "These salamanders, " according to Elly Tanaka from the Max Planck Institute for Molecular Cell Biology and Genetics in Dresden, "are in terms of regeneration, the champions among the vertebrates": Even a full-length, full-length Axolotl is still able to regrow a cut leg, the entire tail, a piece of jaw, a lost eye or even parts of the heart within a few weeks allow.

New building also in humans?

The interest in this amazing amphibian regeneration capability is compounded by current research. According to this, people in many organs, from the liver to the brain, also have so-called stem cells that may be capable of regeneration - but they only have a very limited potential. And so the question: If a "new building" of limbs or organs in animals like the axolotl works - why not in humans as well?

Therefore, researchers interested in human stem cells are following closely the findings that Tanaka's Dresdner Group is working on together with a small community from a dozen laboratories around the world to the salamander relatives. Because even if the Axolotl has apparently not changed significantly for 350 million years, there are some indications that certain basic principles of tissue repair represent old "inventions" of nature, which also continue to run in the human body - or better : could not have humans and other mammals eventually gave up the ability to regenerate largely. The question then is whether this potential is finally lost or merely suppressed in the mammals and perhaps could be aroused again.

Mechanism decrypted

In the meantime Axolotl has identified a number of messenger substances that give the cells the signal for regeneration in the environment of an injury. These include a hormone that emanates from blood clots, alerts cells in the surrounding healthy tissue, and lures them to the site of the injury - a signal that largely resembles a substance found in calves. Whether it is present in humans and what function it fulfills here is still to be determined. display

In addition, the scientists around Tanaka have now gained insight into the temporal "choreography" of cellular processes in the vicinity of an injury and found that although most cells preserve a memory of their descent, but some also to a "role change "Able to do so: For example, cells from the nervous system can be transformed into muscle or cartilage cells.

The understanding of these mechanisms should and will ultimately help to understand why the ability to regenerate certain tissues or organs in sucklers is much weaker than that of salamanders. In the case of suckers, as has long been known, a certain signal substance inhibits its regeneration after injuries to the spinal cord; but if this substance is blocked by antibodies, the injuries heal much better. In the Axolotl, as first experiments show, a molecularly similar signal substance plays a role in the regeneration - here, however, apparently with a different function. The future will show how much of the regenerative powers of the Axolotl are in sucklers and thus in the human organism.

(MPG, 30.07.2004 - NPO)