Limb Regeneration is Really Cool (and Really Difficult)

Humans have come a long way in prosthetics technology. Herodotus, the ancient Greek historian, documented a prisoner who escaped his captors by sawing off his foot and replacing it with a wooden substitute, marking the first written evidence of an artificial limb, and the first of many entries in the Saw movie franchise.

These days, thanks to robotics, we’re developing some pretty amazing, Six-Million-Dollar-Man-style mechanical arms and legs. But here’s the bad news: we’re still getting our cyborg asses handed to us by the animal kingdom. And I’m not talking about worms and insects. I’m talking about salamanders. Turns out, those little guys you used to terrorize in the pond behind your uncle’s house have regenerative superpowers that make Wolverine look like… well, like someone who can’t regenerate limbs so well.

 127 hours

Here’s how it works: when a salamander loses an arm, cells near the site of the dismemberment—including those from “muscle, bone, cartilage, nerve sheath, and connective tissues”—lose their characteristic qualities and become progenitors, essentially blank slates which can be turned into any type of cell. Through a process called redifferentiation, these blank slates become the cells in a newly-formed arm. It’s the salamander equivalent of the surgeries Kim Kardashian gets to move fat from her stomach to her butt, only it occurs naturally and wouldn’t frighten small children if they showed it on Discovery.

And salamanders aren’t the only animals who could rip off the limbs and play appendage-Jenga if they wanted. Starfish, swallow-chicks, and lizards like geckos and chameleons have all demonstrated their regenerative abilities. There’s even a species of mouse that regenerates hair follicles and ear tissue. So what about humans? We’re supposed to be at the top! We can’t let lizards and amphibians and rodents get the best of us! We’re the species that saw how bats echolocate and invented radar, because screw bats!

 batman

Well, of course we’re working on it. But the prognosis isn’t good for now. The more scientists study limb regeneration in creatures like the axolotl, a kind of Mexican salamander, the more we’re realizing just how complex the process really is, which is saying a lot considering no one ever said, “Oh yeah, the Calc test? It was as easy as regrowing a leg from out of a disfigured, bloodied stump.” No one that passed the Calc test, anyway. So for now it looks like we’re just going to have to live with our limbs as they are, and maybe stay away from wood chippers for a while.

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