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Fully Functional Bioengineered Tooth Grown In a Mouse
A couple of weeks back the Wall Street Journal reported on the first organ grown in vivo from stem cells — a tooth in the mouth of a mouse. Reader cdrpsab spotted the news on the MedGadget blog; the research had been reported earlier in the PNAS. From the WSJ: "The researchers at the Tokyo University of Science created a set of cells that contained genetic instructions to build a tooth, and then implanted this 'tooth germ' into the mouse's empty tooth socket. The tooth grew out of the socket and through the gums, as a natural tooth would. Once the engineered tooth matured, after 11 weeks, it had a similar shape, hardness and response to pain or stress as a natural tooth, and worked equally well for chewing. The researchers suggested that using similar techniques in humans could restore function to patients with organ failure."
Solid. References. Now. (For the statement that a majority of growth to maturity just involves enlarging existing cells.) BTW, have you ever heard of osteoblasts and osteoclasts? Those cells are actively renewed and renewing bone throughout life, although they decline with age. You are certainly right that extremely rapid and "deep" division is limited in most organs, as you only need a few divisions and the wonderful gift of exponential growth to get just about any number of cells. The problem of organ regeneration is of course that the respecialization requires a number of "cell generations" in itself. There are some risks involved here, but the current techniques are not simply hardwiring the "on" mode for cell division. In fact, to get any real organ you need the natural "stop" modes and directed apoptosis just as much as you need the ability to start cell division in the first place.
Well, not entirely, but seriously - they've come up with a way to grow new teeth for mammals.
Personally, I would love it if I could go to the dentist and have him replace some of my bad teeth with new ones. One or two at a time would be fine.
Instead of getting fake teeth or fillings when you've abused your teeth to the point where the enamel on the outside of the tooth has worn away, exposing the dentine ... if I could get those replaced? I'd almost be willing to kill for that.
Sure, it'd take time to regrow a new tooth, but I could live with that.
So yeah, screw growing new organs - get me some new teeth!