Tadpole tail could hold key to regeneration of human limbs

Updated: Jan 14, 2013, 13:52 PM IST

London: Scientists have discovered a chemical that helps tadpoles to re-grow their tail, which could also provide clues to regeneration of human limbs.

Researchers led by Enrique Amaya from the University of Manchester have been trying to better understand the regeneration process, in the hope of eventually using this information to find new therapies that will improve the ability of humans to heal and regenerate better.

Amaya`s group identified which genes were activated during tail regeneration.

Unexpectedly, their earlier study showed that several genes that are involved in metabolism are activated, in particular those that are linked to the production of reactive oxygen species (ROS) - chemically reactive molecules containing oxygen.

To examine ROS during tail regeneration, researchers measured the level of hydrogen peroxide (H2O2) - a common reactive oxygen species in cells - using a fluorescent molecule that changes light emission properties in the presence of H2O2.

Researchers found that a marked increase in H2O2 occurs following tail amputation and interestingly, they showed that the H2O2 levels remained elevated during the entire tail regeneration process, which lasts several days.

"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," Amaya said.

To assess how vital the presence of ROS are in the regeneration process, Amaya`s team limited ROS production using two methods. The first was by using chemicals, including an antioxidant, and the second was by removing a gene responsible for ROS production.

In both cases the regeneration process was inhibited and the tadpole tail did not grow back.

"When we decreased ROS levels, tissue growth and regeneration failed to occur. Our research suggests that ROS are essential to initiate and sustain the regeneration response," Amaya said in a statement.

"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," he said.