Why can't humans regenerate body parts?

THAT'S THE WHY:Some animal species have a neat trick up their sleeves, so to speak. Many marine animals that lack a backbone can regenerate body parts if they are lost, and when it comes to backboned animals, salamanders and lizards can regenerate amputated tails and limbs if needed.

Humans are not so well endowed in the regenerative department. Some tissues are good at self-repair: if you get a paper cut, it might smart, but it will most likely heal. If you break a bone, with the right care, it can also heal.

But if you injure cartilage or parts of your nervous system, their regenerative powers are limited. As for spontaneously regrowing a severed limb, forget about it.

Why is that? One school of thought is that we lack superpowers of regeneration as a trade-off to help protect against cancer.

“The things that make tumours grow are very often the same things that make limbs or tissues grow,” says Frank Barry, professor of cellular therapy and a principle investigator in the Science Foundation Ireland-funded Regenerative Medicine Institute (Remedi) at NUI Galway.

“Humans, by virtue of their longevity, need tumour suppression, but perhaps by having cancer-protection systems we have lost the ability to regenerate.”

A goal in regenerative medicine is to use tools such as genes and stem cells to boost our capacity for self-repair without increasing cancer risk.

And maybe there are things we can learn from those enterprising creatures that can sprout new body parts if needed. “A lot of what is being talked about in regenerative medicine now comes from animals like the salamander,” says Prof Barry.

“These species have incredible capacity to regenerate fully a limb that has been completely amputated, and there’s a lot of work going on to understand the biology behind that.”