How do Axolotls regrow amputated limbs?

Author: Alicia Ma

Editors: Emily Chen and He-Hanson Xuan Artist: Serena Yung

Legend has it that the axolotls are descendants of an ancient Aztec god. These incredible creatures are found exclusively in Lake Xochimilco outside of Mexico City, near the ancient Aztec city of Tenochtitlan The axolotl has many biological superpowers, ranging from never aging out of its juvenile tadpole form to being able to regrow limbs, organs, and even parts of its brain. How is it biologically possible for this to happen?

To understand how the axolotl regenerates its amputate limbs, it’s necessary to understand the regeneration process itself. Regeneration is actually a fairly common process that occurs throughout many species, including humans In humans, regeneration is limited to skin or scar tissue However, for many invertebrates, regrowing an entire limb, or even its whole body is not unusual The axolotl, and a few other salamanders, are the only vertebrates that have the ability to regrow limbs and organs throughout their whole life.

The secret to this unique vertebrate’s ability to regrow limbs centers around its ability to transform mature bone, cartilage,

immortality: endless vitality

And Muscle Cells Back Into Stem Cells

When an axolotl loses a limb, a blood clot will rapidly form over the injured area, creating a thin protective layer. This process is similar to how humans and other vertebrates heal similar wounds. However, unlike humans, the axolotl will grow new cells from the cells underneath the epidermis (i e the outermost layer of skin) over the next few days to form the blastema The blastema, also known as a regeneration bud, is a cone-shaped structure that grows over the area where the limb was last. Inside the blastema, a fascinating phenomenon occurs. The axolotl’s normal bone, cartilage, and muscle cells go through a dedifferentiating process, transforming back into stem cells From here, these stem cells will divide and reform the lost bone and tissue This process is similar to how an animal first develops in an embryo or egg

As the cells in the blastema continue to multiply, existing nerves and blood vessels start to connect the newly formed areas to

The Rest Of The Body

The axolotl’s incredible regeneration abilities do not end with limbs. Contrasting all other known processes of life, the axolotl is also able to regrow parts of its brain. The brain is composed of neurons, which normally only grow in embryonic stages for mammals and vertebrates. Thereafter, the neuron enters a G0 phase in which cell division is permanently paused, making nerve growth and repair impossible However, this salamander’s capacity to de-differentiate various cells back into stem cells allows it to grow back neurons, and thus, parts of its brain. Perhaps the most intriguing fact is that the axolotl has no special genes that allow it to regenerate its limbs and brain. The axolotl merely regulates its genes differently Therefore, scientists hope to one day be able to uncover the secrets behind the axolotl’s ability to dedifferentiate cells, and recreate its biological superpowers in humans where millions of lives could be saved or improved.