Slashdot Mirror
Scientists Demonstrate Mammalian Tissue Regeneration
telomerewhythere writes "A quest that began over a decade ago with a chance observation has reached a milestone: the identification of a gene that may regulate regeneration in mammals. The absence of this single gene, called p21, confers a healing potential in mice long thought to have been lost through evolution and reserved for creatures like flatworms, sponges, and some species of salamander. 'Unlike typical mammals, which heal wounds by forming a scar, these mice begin by forming a blastema, a structure associated with rapid cell growth and de-differentiation as seen in amphibians. According to the Wistar researchers, the loss of p21 causes the cells of these mice to behave more like embryonic stem cells than adult mammalian cells, and their findings provide solid evidence to link tissue regeneration to the control of cell division. "Much like a newt that has lost a limb, these mice will replace missing or damaged tissue with healthy tissue that lacks any sign of scarring," said the project's lead scientist.' Here is the academic paper for those with PNAS access."
Now I can finally start my restaurant (which specializes in mouse-tail delicacies) without PETA breathing down my neck. "Look: it's growing back!" Mouse-tail soup anyone?
Minus the Claws. And the Adamantite interior. And the Rugged good looks - in your case, anyways.
What the side effects are. One would(perhaps naively) assume that regeneration is an obvious survival advantage, and that losing regenerative capabilities would be a handicap. That being so, one would tend to suspect that an anti-regeneration gene would be fairly strongly selected against. Since this gene is, in fact, rampant in mammals, one is led to the suspicion that there must be some sort of upside.
Is it something more or less irrelevant to modern humans(at least those wealthy enough to ever be genetically engineered), something like "without any sort of medical care, most serious injuries were fatal before regeneration could occur, so the extra energy costs weren't worth it", or is it some kicker of the "Well, without a whole bunch of other adaptations possessed by certain amphibians and creepy-crawlies, you'll 'regenerate' yourself entirely full of tumors by age 20." flavor?
I have a feeling you should know something about the subject before weighing in.
p21 knockout mice don't appear to get cancer more than wild-type mice, interestingly enough...
It's interesting, because p53 is a major regulator of p21 expression, and p21 itself is a major player in regulating cell cycle progression into S-phase, thus controlling cell replication. p53 knockouts, on the other hand, are extremely prone to cancer, as p53 is one of the most important tumor-suppressor genes.
The paper is interesting because the authors demonstrate that two separate strains of mice that contain a p21 deficiency can both regenerate differentiated tissue (measured by looking at ear-hole closure), supporting the link between p21/cell cycle progression and tissue regeneration. Whether this is of consequence therapeutically is a different story, but I'd be very interested to see the same study repeated in wild-type mice being fed or injected a small molecule p21 inhibitor.
You are correct. In point of fact, around 90% of the time when you hear that "X gives you cancer" what you should instead read it as is "X causes cancer to happen sooner". Usually this means that exposure to risk factor X reduces your ability to fight off cancer. You've probably got a few carcinogenic cells in you right now that are going to be killed off before they do you any harm. Obviously this doesn't apply in every single case - ionizing radiation falls into that other 10% that really does cause cancer directly - but when you see cancer linked to, say, stress, that falls under the other 90%.
I don't think that tissue regeneration will cause cancer to happen more frequently, for two reasons. The first is that the healing process in humans already accelerates cancer. As do certain immune responses. Essentially, every bit of damage you pick up over your lifetime accelerates the inevitable rise of carcinogenesis by some tiny amount. Regeneration, done correctly, probably won't worsen this.
The second reason is that the reason mammals don't regenerate naturally has to do with speed, not safety. The healing process in mammals essentially slaps a quick patch over the damage in order to get you healthy sooner; we call this patch a scar. Regenerating vertebrates (amphibians, some reptiles) take longer to heal, but heal more completely, which is substantially more viable when you're cold blooded and can go a few days without more food. At some point in our distant evolutionary past, scarring became a more viable approach to damage, as it fixed us up sooner, so selection pressure favored the scarring over the regenerating. Lack of regeneration in humans is a matter of what worked in the wild for our ancestors, not what works today, where the injured have plenty of time to recuperate, and don't run the risk of starvation or predation.
Erotic is when you use a feather. Exotic is when you use the whole chicken.