Geckos can partially regenerate tails and sea stars their many limbs, but a human doesn't share this handy ability. The only vertebrate that can regenerate whole limbs is the salamander. Yet we can partially regenerate our liver or even the tip of a finger, and a new study now shows this ability can be improved, though it's tricky.
The study, which is being funded by the Department of Defense, involves controlling the amount of oxygen an amputated limb receives, as well as when. Mimi Sammarco, who is leading the study from Tulane University in New Orleans, found that, like a switch, the genes that excite the kind of regeneration we see in salamanders needs to be activated by something.
"What it boils down to is genes (that spur regeneration) don't just turn themselves on. They turn on because something signals them. So I thought, maybe it's oxygen that's turning them on," Sammarco said in a release. "Oxygen is often the primary signal that turns on various genes."
To test her hypothesis, Sammarco and her team have been experimenting on samples of bone from amputation sites, and then exposing them to high levels of oxygen: "What we found is that when you expose regenerating bone to 20 percent oxygen, it'll respond very favorably but only at a certain time. If you try it too early, like right after amputation, it doesn't do a whole lot."
That's pretty much where we're at right now. Using oxygen to flick these genes into an "on" position shows promise, but the fact that timing matters has made things interesting. While we won't see humans regenerating whole limbs any time soon, this could allow doctors to simulate growth in the stump of an amputated limb enough to add an extra inch or two, which can make all the difference.
That, and Sammarco is interested in the developing the technique to the point where it could be used to help soldiers on the battlefield, which adds a whole 'nother layer of complexity: "Further on down the line, how do we make that treatable in the field in the middle of the desert? How do you make it portable and usable? There's general public usable and there's where it is going to be most useful, and that's in the field — immediate treatment for a soldier so we can have maximal bone growth down the line."