January 14, 2013
Tadpole And The Tail: Studying The Secrets Of Human Healing
Brett Smith for redOrbit.com - Your Universe Online
Humans have the capacity to regenerate tissue after suffering an injury, but many animals have the ability to regenerate whole limbs after an amputation.A group of UK researchers decided to look into this ability in tadpoles, which can regrow a tail that has been severed. Their results proved to be somewhat counter intuitive–showing that a molecule previously thought to be harmful to cells is involved in the process.
According to their report in the latest edition of Nature Cell Biology, the research team´s latest findings were based on their previous work that identified genes that were activated during the tail regeneration process. The earlier study showed that several metabolism genes are activated, including those responsible for the production of reactive oxygen species (ROS) — chemically-reactive, oxygen-containing molecules.
"We were very surprised to find these high levels of ROS during tail regeneration,” said the study´s lead author Enrique Amaya, a professor at the University of Manchester. “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."
First, the team investigated the prevalence of ROS during tail regeneration. To do so, they measured the level of hydrogen peroxide, a common ROS in cells, using a molecule that fluoresces in its presence. Amaya and his colleagues were able to demonstrate that a marked increase in hydrogen peroxide occurs in the tadpoles after tail amputation. The levels remained higher during the entire regeneration process, which lasts several days, according to the team´s report.
After positively identifying the elevated levels of ROS, the team looked to see how the concentration of ROS played a role in the regeneration process. Using a chemical or a genetic inhibiting mechanism, Amaya´s team was able to block the effectiveness of ROS in two separate experiments. The researchers were able to show that when ROS was effectively inhibited, a tadpole´s tail did not grow back.
"When we decreased ROS levels, tissue growth and regeneration failed to occur,” Amaya said in a statement. “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,” he added. “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."
Amaya also noted that the chemical mechanism for inhibiting ROS included antioxidants and a recent study from the iconic geneticist James Watson suggested antioxidants could be harmful to people in the later stages of cancer.
"It's very interesting that two papers suggesting that antioxidants may not always be beneficial have been published recently,” Amaya said. “Our findings and those of others are leading to a reversal in our thinking about the relative beneficial versus harmful effects that oxidants and antioxidants may have on human health, and indeed that oxidants, such as ROS, may play some important beneficial roles in healing and regeneration."