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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."
We can all be Wolverine now? Cool!
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?
Then I hope it doesn't involve having to amputate the penis first.
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?
The next step is to make some p21 specific RNA interference molecules and shut it down in an adult, non-regenerative mouse. Then clip its ear and see what happens.
Since it also increases apoptosis, would this make a good diet pill?
On the one hand you take life too seriously, and on the other, you do not take playful existence seriously enough. Seth
Well, they claim that they thought it was "lost to evolution"... I assume the fact that the gene is not active today is the result of evolution. So that implies the question Why is it inactive? I would think the ability to regenerate body parts on demand would be an evolutionary advantage, wouldn't it? So something must not work correctly (or there must be some kind of side effect)... It could be as simple as we didn't have enough nutrition at the time to be able to support it, and would die of malnourishment when we'd otherwise live with the injury... But I do agree, it does seem "too easy". They must be a negative here that we haven't figured out... I guess it's time to welcome our new self-healing mouse overlords...
If a man isn't willing to take some risk for his opinions, either his opinions are no good or he's no good
A lot of people are asking why evolution has taken away our regenerative capacities, and are guessing what the downside of this regeneration is.
P21 is involved with anti-cancer. It arrests the cell cycle when DNA damage occurs, allowing the damage to be repaired (so mistakes are not carried forward into new generations). Or if the damage is too severe, the cell is made senescent (they lose the ability to reproduce and instead lead out a gentle retirement, performing their normal job until they just die of old age)
P21 knockout mice show a lot of carcinomas and P21 is also up-regulated by and works to remedy excessive oxidative stress. It's very unlikely this research is going to lead to a pill that knocks out P21 and lets us grow limbs back. It will only lead to a greater understanding of how our pathways work.
Of course the caveat to using mice to judge how a gene affects long-term development of cancer is that there really is no "long-term" on a human scale in mouse studies, since they only live about 3 years at most.
I'm also not entirely familiar with the effect of p21-deficiency in cases where major tumor suppressors are deregulated or otherwise deficient. It is feasible that in the absence of further regulation, the absence of a major cell cycle checkpoint will lead to a more severe phenotype, whether in terms of being more tumor prone, or development of more aggressive tumors.
"I would think the ability to regenerate body parts on demand would be an evolutionary advantage"
What advantage could regeneration provide when survival rates for amputation were abysmal before modern medicine?
Maybe changes in bacteria made regeneration pointless in larger lifeforms (which take longer to heal)?
It's speculation, but I guess the only way we can know if it can be done is to experiment.
I can think of a couple reasons why this feature may have been dropped. nutrition (regrowing something is a hell of a lot more resource intensive than just closing the hole) and infection prevention (just closing the hole is a lot faster than regrowing something, so less chance of it getting infected). Both of these were relevant considerations very recently and evolution is pretty slow.
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Not necessarily. A lot of small animals are pretty much disposable: they're sufficiently fragile that there's only a very narrow boundary between a trivial injury and a fatal one. (And anyone who's kept small birds and animals will know that if they're hurt beyond a certain point they'll simply go into shock and die.)
So it's entirely plausible that the gene might have been caused by a spot mutation very early on while all mammals were basically mice, and it then had a sufficiently small effect on actual survivability that the trait didn't get bred out. Later, once the small, disposable animals turned into large, expensive ones, it was too late.
It is interesting that both birds and animals appear to lack this trait, though. We both descend from much the same sort of lizards but in different directions. Finding out exactly where this gene sequence appeared might be productive.
(Of course, I want to know when we'll be able to get gene therapy to suppress the gene. Assuming it works in humans, and that the gene doesn't do anything else critical, it might even be fairly straightforward! But probably won't happen soon and I'm certainly not volunteering to be the guinea pig...)
Darwinism is cruel... Nature does things for a reason.
Narture wants to be anthropomorphized ;)
It nature is so cruel and barbaric, then for what reason did it evolve human beings who feel sympathy, empathy, are able to learn, and practice healing arts?
Computers are useless. They can only give you answers.
-- Pablo Picasso
Here is the academic paper for those with PNAS access.
I have access to a PNAS. Sometimes I let my wife have access to it, too.