The surprising way a tadpole regrows its tail

Scientists at the University of Manchester have discovered, to their surprise, that a tadpole’s ability to regrow its tail is dependent on a group of chemicals generally believed to be harmful to cells. Professor Amaya’s group at The Healing Foundation Centre in the Faculty of Life Sciences identified in an earlier study which genes were activated during tail regeneration. Surprisingly, many of the identified genes are linked to the production of reaction oxygen species (ROS) – chemically reactive molecules containing oxygen; a group of molecules commonly caricatured to be enemies to the cell.

Professor Amaya said: “We were very surprised to find these high levels of ROS during tail regeneration. Traditionally, ROS have been thought to have a negative impact on cells. But in this case they seemed to be having a positive impact on tail re-growth.”

Their new findings are due to published in Nature Cell Biology. To examine ROS during tail regeneration, the group measured the level of hydrogen peroxide (H₂O₂) -a common ROS in cells using a fluorescent molecule that changes colour in its presence. This advanced imaging technique showed a marked increase in H₂O₂ following tail amputation and additionally, that H₂O₂ levels remained elevated during the entire tail regeneration process, which lasts about a week.

To further test their theory about the role of ROS in tail regeneration, the group then performed techniques that would limit ROS production. By using antioxidants and removing a gene responsible for ROS production in the tadpoles, the team then repeated the amputation procedure and waited for regeneration. In this case however, that tadpole’s tail did not re-grow.

Professor Amaya said: “Our research suggests that ROS are essential to initiate and sustain the regeneration response. We also found that ROS production is essential to activate Wnt signalling which has been implicated in essentially every studied regeneration system, including those found in humans. It was also striking that our study showed that antioxidants had such a negative impact on tissue regrowth, as we are often told that antioxidants should be beneficial to health.”

These findings may have important implications in regenerative medicine. The next stage for the group at the Healing Foundation Centre will be to further study ROS and their role in regenerative processes. Eventually, the team hope to identify whether manipulating ROS levels in the body could improve our ability to heal and regenerate tissues better.

Love, Chen, Ishibashi, Kritsiligkou, Lea, Koh, Gallop, Dorey & Amaya. 2013. Amputation-induced reactive oxygen species are required for successful Xenopus tadpole tail regeneration. Nature Cell Biology http://dx.doi.org/10.1038/ncb2659