Guess what? Scientists have found the Wolverine gene. That's right. The ability to regenerate! A Harvard researcher thinks he might have found it.

Apparently, George Daley of Harvard Medical School stumbled upon this somewhat accidentally. While using an identification technique for his lab mice by clipping their ears or the tips of their toes, he noticed that they would grow back their ears and toes in a few days.

Turns out, the mice had been genetically engineered so that a gene that helps them grow in the womb, would continue to function even after birth. It would never turn itself off. Essentially, this is Wolverine. The gene is called Lin28a, and by boosting metabolism, it can trick the body into thinking it's younger than it actually is.

Daley and his fellow researchers confirmed that the gene could regrow parts of body parts, but his method has some limitations. According to Scientific American:
The power of Lin28a appeared to only extend so far. When mice were no longer babies—at five weeks—the scientists were not able to regenerate their limbs, even if the gene was stimulated. And mice with Lin28a activation were never able to repair damage to the heart, suggesting that the protein is not equally effective everywhere in the body.
Lin28a works but not forever and not everywhere. But now that scientists know that bodily healing is possible by controlling or manipulating certain metabolic processes, they can probably do some hocus pocus with other genes that might be involved.

We're still far off from limb regeneration for now, so we're guessing 3D printing them is still the way to go.

[Scientific American]