Human Limb Regeneration!

(image by: Sbocaj)

For a while now we've been, as a species, looking jealously at salamanders wondering how they can regrow chopped off limbs. I think it's safe to say that most of us assume that, though awesome, the complete regeneration of lost body parts isn't really for humankind.

Maybe one day, with nanomachines or cybernetics, we'll find a way to tell robots how to build us new arms and legs. But we can't do it the way that salamanders do it. Even healing simple wounds seems to almost defeat the human body's level of ingenuity, leaving pronounced scars made of tissue that doesn't match or serve a purpose other than sealing.

That view, however, is changing! Scientists are starting to learn more about the process salamanders use to regrow limbs, and it turns out, it's not quite as far from our own capabilities as we might have thought. Humans have the capacity to regrow "limb buds" during embryonic development and even as adults can still regrow their fingertips, if not the joint.

What's so special about the salamander healing process, that lets them regrow exactly the portion of the limb that they're missing, while humans are left with nothing but a scar and a stump? It's called a "blastema," a bunch of cells that behave much like stem cells, and are capable of regeneration. They apparently form from the fibroblasts around the wound site, which for humans just create clumps of functionless extracellular material to fill in the hole.

Although there are other complicating factors, the main reason animals that can regenerate early in life can't do it as adults seems to be that something called a "Fibroblast Growth Factor" circuit, or FGF, gets turned off at some point in the development of the organism. By turning it back on in frogs (which can regrow limbs as tadpoles) they were able to create amazing tragic frog monsters with malformed limbs sticking out of places they don't belong.

They're still working on it.