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Zebrafish Regenerative Ability May Lead To Help In Humans
esocid tips us to news out of Duke University Medical Center, where researchers have discovered a type of microRNA that is related to the ability of zebrafish to regenerate lost or damaged organs. This is the result of a study initiated after it was discovered that zebrafish were able to recover from "massive injury" to the heart through their own regenerative biology. The scientists hope to be able to use this information to bring about similar healing in humans. Zebrafish have also been helpful in cancer research.
"In zebrafish, one or more microRNAs appear to be important to keep regeneration on hold until the fish needs new tissue, the Duke researchers say. In response to an injury, the fish then damp down levels of these microRNAs to aid regrowth. Poss and many other cell biologists believe that mammals may have the same tissue regeneration capability as zebrafish, salamanders and newts, but that it is locked away somewhere in our genome, silenced in the course of evolution."
if i had a tail i'll play with it all day...
Human life expectancy is quite long by animal standards, so it seems like we probably just don't need this anymore. On the other hand, there are usually tradeoffs with these kinds of mechanisms, and turning it on again may have rather negative side-effects.
I'm reminded of a story from Analog in the 60s, where they figure out how to stimulate toot regeneration. Except that, once the technique has been in use for a while, they find out that it doesn't stop producing new teeth ...
Lacking <sarcasm> tags,
AGH! I have ears regenerating all over my body! Get them off!
Once you start despising the jerks, you become one.
In my fairly limited understanding of evolution theory, the features that help to survive are retained through the natural selection. Regeneration ability seems to help to survive - why would it be lost then? Could it be that the time required to naturally regenerate was so long that the animal weakened by the injury died anyway by natural (lack of food and/or water access, climatic factors) or violent (predators) death?
That would be my guess. There's a good bit of research where they tinkered with mouse genes to accelerate or slow telomere erosion, and found that the natural mouse is pretty close to the maximum lifespan possible. Faster erosion causes the mice die of old age sooner, but slower erosion results in more cancer deaths.
Regeneration may well have similar costs. Since all of the natural regenerators are poikilotherms, I would speculate that their overall lower metabolic rate has less risk of cancer. Giving up regeneration may well be the price we pay for warm blood.
Lacking <sarcasm> tags,
where someone loses their head and an autodoc manages to grow one back
...
Hmm
Quote: "But they got him into the autodoc anyway. It was a puppeteer-shaped coffin, form-fitted to Nessus himself, and bulky Puppeteer surgeons and mechanics must have intended that it should handle any conceivable circumstance. But had they thought of decapitation?
They had. There were two heads in there, and two more with necks attached, and enough organs and body parts to make several complete puppeteers. Grown from Nessus himself, probably; the faces on the heads looked familiar.
From Ringworld, by Larry Niven."
CC.
TaijiQuan (Huang, 5 loosenings)
With Puppeteers it's slightly more "believable", because a Puppeteer's brain is under its back. The "heads" hold only the eyes and the mouth, as well as serving to manipulate objects like hands.
The problem is cancer.
... massive and nearly unlimited cell growth ... massive and unlimited cell growth
... just cut the immune system to a very low level, and disable a few cancer prevention mechanisms. Of course, make one tiny mistake, say 100 viral particles, and your patient probably won't survive.
Regeneration is
Cancer is
A tiny mistake in regeneration will therefore cause cancer very reliably, and quite deadly. In order to let people get really old, cancer must be prevented (most dogs could easily live up to 25, with reduced bodily function, instead of 15 without cancer, but they have more chance of recovering from large injuries during those 15 years).
There is another problem. Another very important reason human bodies don't regenerate is the immune system blocking the regeneration process. (you can prevent cuts from becoming scars with a large dose of aspirin and making sure the wound is not in contact with air (by making sure it's soaked in warm liquid for example)).
You can make regeneration easily very effective in humans
Maximum age and regeneration are forces pushing in opposite directions. You can't have your cake and eat it, I guess. This research will, if it works, present a choice to people, a short, very robust life, or a long one where you'd probably best avoid any injuries. "Forever young" this is not.
"Forever young" this is not.
... but as another poster pointed out, if this capability were activated on a temporary basis solely for the purpose of regenerating lost or damaged tissue, it would prove invaluable. Hell, if this did become practical, one could chop out diseased parts of an organ and simply regenerate them. Transplants could become a thing of the past. Lose an extremity? Regrow it!
Maybe not
The higher the technology, the sharper that two-edged sword.
I always though it was because that it is simply faster and easier to let the body scab over the wound then to try to let the internal structure regenerate. So the human body developed the scabbing ability so that humans who did get injured could quickly escape whatever injured them.
GENERATION 25: The first time you see this, copy it into your sig on any forum and add 1 to the generation. Social exper
Evolution doesn't happen along cleanly defined lines; lots of people are trotting out cancer as an easy problem to relate to regeneration, but it doesn't need to be anywhere near that complex. It could be as simple as the developments leading to warm blooded metabolism accidentally turning off regeneration, so as those organisms took over niches where being exothermic was a big advantage, regeneration disappeared.
So the breakage of the regeneration mechanism could be completely incidental, even if was advantageous, if some species with broken regeneration evolved some other mechanism that conferred a larger advantage.
Nerd rage is the funniest rage.
The autodoc didn't grow his head back. It grew his body back, starting from only a head.
I recently contacted Ellen Heber-Katz, asking how the regenerating mice were progressing; they have not published anything about them in nearly two years. She replied that the mice are in fact still alive and breeding, which means that they have passed their life expectancy by at least half a year. She also said they will be releasing "lots of papers" in 2008.