Axolotls are renowned for their ability to regrow vital body parts. But according to recent research, these frilly-headed salamanders, which are native to the lakes and wetlands around Mexico City, can perform an even more extraordinary biological feat: They can completely regrow their thymus, a complex organ critical to the immune system in most vertebrates.
Previous work had suggested that some animals could partially regrow the thymus, but the co-authors of the new paper published In science immunologyIt was amazing to see that the axolotl completely rebuilt its intricately structured limb from scratch.
“Axolotls are famous for regenerating limbs and parts of the central nervous system,” says study co-author Maximina H. Yun, a biologist at the Chinese Institute for Medical Research in Beijing. “The realization that these animals can regrow their entire thymus from scratch is a watershed moment.”
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The thymus is responsible for producing the body’s T cells, which help target and destroy invading pathogens. “In humans and most other vertebrates, the thymus is well known for being one of the first organs to be destroyed,” says Mughala SıTKı Biologist and regeneration expert Turan Demircan says; Kocaman University in Türkiye which was not involved in the new research. “Until now, it was believed that once this tissue is depleted or removed, it cannot be completely regenerated.”
For the new study, Yoon and his colleagues removed the thymus from several juvenile axolotls. After seven days new thymus were already emerging in many animals. After 35 days, more than 60 percent of them had completely regenerated limbs. “I was really surprised,” says study co-author René Mehr, a biologist at the University of Massachusetts Chan Medical School. “Complete, functional regeneration of a complex immune organ was not something I expected.”
The team then transplanted the regenerated thymus into other axolotls and tested their function. “The remarkable thing is that the transplanted organs were completely integrated,” says Demirkan.
Further analysis identified two key features essential for the regeneration process: foxn1 the gene, which scientists already knew was involved in the development of the thymus, and a signaling molecule called midkine, which Demirkan says appears in human embryos but is largely inactive in adults. The results suggest that there may be a biological pathway involving these components that could be useful for treating thymus-related conditions in humans.
“Axolotls are essentially nature’s ‘master key’ for regeneration research,” Demircan says. “If we can rekindle this specific pathway in humans, we may be able to stimulate the thymus to grow again, potentially reversing immune aging or helping patients who have undergone thymectomy.”
According to Yun, researchers may someday replace human stem cells to simulate axolotls and recover thymus function. “We are laying the groundwork for transformative therapies that could redefine our approach to immune restoration.”
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