Over on Pharyngula, PZ Myers has a fascinating post up on some laboratory mice who have the remarkable ability of true regeneration!

One way to mark individual mice is by punching small holes in their ears (it sounds cruel, I know...fathers with teenage daughters also think it is a terrible thing to do). The mice of the MRL strain do something remarkable, though, as you can see to the right: they heal right up. There is no detectable scar tissue, either—these mice regenerate.

Regrowing ears might be a very big deal to a mouse, but not so much to us. However, their powers of regeneration go deeper. Damage their livers, their kidneys, and many other tissues, and they grow right back. They can regrow lopped off toes and tails. Here's the big one: take a fine wire, stick it in their heart, and burn a hole in it with extreme cold, a process called cryo-damage which mimics the damage of a myocardial infarction, and in the MRL mouse, heart tissue regenerates.

Whoa.

Whoa indeed. He's even got pictures! Man, we love science.

Of course, we're not going to be genetically modifying humans to exhibit these same powers any time soon. Apparently, this ability is a highly complex genetic puzzle that we aren't going to immediately figure out how to "turn on" in humans. Darn. But there are some promising concepts opened up by this avenue of research:

The authors also report improved ability of the MRL mouse to regenerate from spinal cord injury; again, one commonly reported obstacle to recovery from neural damage is the formation of scar tissue, and these mice have less of that. There are some suggestive observations here.

These spinal cord studies demonstrate that the scar plays a major role in blocking the regenerative response and that even in the C57BL/6 mouse, axonal regeneration occurs in its absence. Perhaps the same thing is true for humans. And perhaps, without the scar, the same type of healing and regeneration would be seen in the heart.

So apparently, Christopher Reeve didn't need to scarf down all those aborted fetuses after all. (For non-fans, that's a South Park joke — Christopher Reeve didn't really eat aborted fetuses. Not that we know of, anyway.)

PZ also points out the ramifications of this development in terms of evolutionary biology:

An evolutionary lesson from this animal is that it represents a more likely example of how advantageous novelties arise: not by abrupt transformations of single genes, but by fortuitous recombination of smaller, hardly noticeable variants that, when they come together in a single individual, interact to produce a new phenotype.

It's nice to know that evolutionary theory is good for something. You know, since it so obviously fails to account for biodiversity, adaptation, inheritance or the fossil record.