This micrograph shows the cross-section of the spinal cord of an axolotl. The reddish and green colored stem cells in the middle have a special property: If the spinal cord is injured, they can divide synchronously so that the spinal cord can regenerate.
The axolotl (Ambystoma mexicanum) is a Mexican tailed amphibian that we normally hardly get to see. Because it lives at the bottom of water and is nocturnal. What makes the axolotl special is that it reaches sexual maturity without losing its larval characteristics. Another special feature of the bizarre animal is its ability to fully and properly restore limbs and organs after an injury or amputation. For this purpose, a tissue is initially formed, which causes the underlying tissue layers to heal. After a few days, a kind of regeneration bud emerges from which the new body part grows.
This even applies to the vital spinal cord: while damage to it in humans and other animals is usually irreparable, the axolotl can regenerate its spinal cord. For example, if the tail of the amphibian is amputated, after four days the neural stem cells in the middle of the spinal cord divide at the injury site – which can be seen on our photo. They replace lost neurons and thus rebuild the nerve connection to the newly growing tail.
Researchers led by Emanuel Costa from the University of La Plata in Argentina have investigated exactly how this new formation of the spinal cord takes place in the axolotl. To do this, they simulated the regeneration process in a mathematical model and tested its predictions in the axolotl tissue. It was noticed that the stem cells of an injured axolotl spinal cord do not divide asynchronously as usual, but adapt their cell cycles in such a way that most of the cells in the vicinity of the injury multiply in “lock step”. This synchronous regeneration is presumably made possible by a messenger substance that spreads in the tissue in the first few days after the wounding and reprograms the stem cells.
“The next step now is to identify the molecules that promote the regeneration of the spinal cord – this could have enormous therapeutic potential for patients with spinal cord injuries,” explains team member Elly Tanaka from the Research Institute for Molecular Pathology in Vienna.