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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."
This reminds me of that godawful late Beowulf Shaeffer story by Larry Niven "Procrustes" (collected in Crashlander ) where someone loses their head and an autodoc manages to grow one back. I mention this not hoping anyone would go read the story, but to provide a forum where other people who lost hours of their lives to late Niven can express their feelings and frustrations to a sympathic audience of people who did the same.
FYI, as I guess this is not going to be obvious to everyone reading the article - microRNAs are a type of small RNA that are currently very popular in biology because they allow to "turn off" genes. Basically, microRNAs as well as related types of small RNA molecules switch off the synthesis of the product of a gene. Obviously, Wikipedia is going to offer more detail... Look up "RNA interference".
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.
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.