Many lower animals are capable of great feats of regeneration, and researchers are working to understand the mechanisms by which this occurs. There is the possibility that the ability to regenerate lost body parts is something that lies dormant in mammals, rather than being completely lost. Finding out whether or not this is the case requires a far better understanding of regeneration than presently exists. Here, researchers investigate the biochemistry of tail regeneration in tadpoles:
It is generally appreciated that frogs and salamanders have remarkable regenerative capacities, in contrast to mammals, including humans. For example, if a tadpole loses its tail a new one will regenerate within a week. In an earlier study, [researchers] identified which genes were activated during tail regeneration. Unexpectedly, that 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.
[The researchers] were able to show 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. To assess how vital the presence of ROS are in the regeneration process, [the scientists] 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. 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."