Posted on behalf of Penny Sarchet.

For over two hundred years, scientists have been lopping the limbs off newts and watching them re-grow. The Italian biologist and Catholic priest Lazzarro Spallanzani first discovered the animal’s ability to regenerate in 1768 and today, in Nature Communications, a research team has tried to answer a question as old as the experiment itself: how many times can a newt recover?

Over a period of 16 years, the team removed the lens from the eye of Japanese newts (Cynops pyrrhogaster) 18 times, until the newts were at least 30 years old. Each time, the lens was replaced by the transdifferentiation of cells from other tissues. Scientists like Darwin have long suggested that older animals might be less efficient at tissue regeneration, but the team found no change in the speed or the quality of the newts’ lens regeneration.

“We didn’t expect such robust regeneration after so many times,” says Panagiotis Tsonis, one of the researchers who worked on the project and director of the Centre for Tissue Regeneration and Engineering in Dayton, Ohio. Though they have now halted the experiment – the newts were getting to the end of their lifespan – Tsonis thinks they could go on regenerating their lenses for the rest of their lives.

As well as observing regeneration speed, the researchers also analysed the last two lenses produced by the newts for changes in both structure and gene expression. The 17th and 18th lenses to be generated were virtually identical to the first ones, with no significant alterations in lens quality or the expression levels of genes known to be important in lens development or eye homeostasis.

“The issue addressed by this report is one of very wide interest,” explains Jeremy Brockes (University College London), who did not contribute to this research. “The interaction, or lack of it, between regeneration and ageing has received more speculative comment than any other issue in regeneration research apart from the loss of regenerative ability in higher vertebrates.”

A main aim for scientists probing and slicing animals like these is to one day develop regenerative treatments for human diseases. As scientists attempt to engineer mammalian tissue regeneration (see here and here), amphibians like newts and salamanders continue to show us what animals are capable of when you know how.

Image: photo by raneko via Flickr under Creative Commons.