Axolotls are a part of the salamander family, which makes them one of very few animals in the world that are able to fully regenerate their limbs and tails when injured or lost. During a talk on Oct. 29, Dr. Prayag Murawala discussed the differences between cell regeneration of axolotl limbs and tails and what that means for the future of biological research.
“If there were no regeneration, there would be no life. If everything regenerated, there would be no death,” Richard J. Goss said in his 1969 work about regeneration. Dr. Murawala used this definition to start the lecture, along with showing the wide array of animals that are capable of regeneration, ranging from earthworms to starfish. Murawala defined the axolotl as the champion of regeneration because of its effective and quick acting abilities.
Regeneration occurs in two methods; the expansion of stem cells that already existed in the body part being regenerated and the dedifferentiation of a cell intended for another use into a cell intended for regeneration. In axolotls, the regeneration method depends on which part of the body you are looking at: on the primary body axis, like a tail, or on the secondary body axis, like limbs.
Murawala’s team’s research, which took place as a part of his post doctoral research, found that limb regeneration, like all regeneration in axolotls, requires the formation of blastema cells, a group of undifferentiated progenitors that carries the code for limb regeneration. Through a series of experiments and tracings, they were able to discover that uninjured limbs had no pre-existing blastema cells, meaning that the cells in the limbs differentiate to form those blastema. They also discovered that fibroblasts, a cell specialized in creating structural frames, are progenitors that create cells of multiple lineages.
The research team found that tail regeneration, however, takes on the other method of regeneration. Through the same tracing methods they used on axolotl limbs, they discovered that through the process of somitogenesis, an evolutionary process that all vertebrates have undergone, progenitors are formed from preexisting stem cells. They then differentiate into the lineages needed to regenerate a fully functioning tail.
The main differences between the two regenerative processes are the methods and the amount of heterogeneity of the cells post regeneration. In axolotl limbs, the new connective tissue cells formed post-regeneration homogenize a lot more than those post-regeneration in tails, and it takes a good amount of time for those connective tissue cells to be fully heterogeneous again, if ever.
In humans, we are rarely able to fully regenerate lost appendages, like fingers and toes, let alone limbs. Being able to regenerate something on the primary body axis, like a tail, is unique to salamanders and other lizards, which is what makes this research so groundbreaking.
Murawala’s research team hopes to tackle the question of how different the cells found in axolotl limbs and tails really are in further research. For more information about Murawala’s team and where his research has taken him, you can visit https://calendar.umaine.edu/event/community-engagement-to-enhance-research-in-maine-2/.