Only in April last US scientists reported that sea squirts could correct abnormalities over a series of generations, suggesting that a similar regenerative process might be possible in humans.
Now, British researchers have found a key protein that helps newts regrow severed limbs and which may guide future research into human regenerative medicine.
Newts are members of the Salamandridae family in which the adult form is aquatic or semi-aquatic. In some species the larva leave the water as a brightly-colored terrestrial form called an eft, returning to the water when mature and changing to adult colors.
Newts have a remarkable ability to regenerate limbes, eyes, spinal cords, hearts, intestines, and upper and lower jaws. The cells at the site of the injury have the ability to de-differentiate, reproduce rapidly, and differentiate again to create a new limb or organ.
Biologists have long been intrigued by that regenerative ability of newts and salamanders.
Now the new British published on Thursday shows that a protein called nAG, secreted by nerve and skin cells, plays a central role in producing a clump of immature cells, known as a blastema, which regrows the missing part.
The importance of nAG was demonstrated by the fact that even when a nerve was severed below the stump tip, which would normally prevent regrowth, the scientists were able to coax regeneration by artificially making cells produce the protein.
Anoop Kumar and colleagues from University College London (UCL), writing in the journal Science, said the finding "may hold promise for future efforts to promote limb regeneration in mammals."
David Stocum of Indiana University-Purdue University Indianapolis said it could help explain why mammals have limited regrowth abilities and thus help direct the field of regenerative medicine.
A clear understanding of the molecular signals involved in blastema formation and limb regeneration could eventually allow medics to programme similar patterns into cells of non-regenerating body parts.
"How soon this might be possible, particularly in humans, is anyone's guess but the addition of nAG to the repertoire of necessary factors is an important step forward," Stocum said.
"It would be very desirable for regenerative medicine to understand the specification of the blastema and to try to recreate that in a mammalian context. But we are a long way away from being able to do that," Jeremy Brockes of UCL. said in an interview.
Regenerative medicine is a growing area of research, with much of it centred on stem cells, the master cells that act as a source for various cells and tissues in the body.