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."
Honestly, I don't think that calling a tooth an organ is very much of a stretch. Teeth have their own blood vessels and nerves, and consist of a large proportion of living tissue. This little blurb provides what I think is a convincing, if hardly exhaustive, argument that teeth are organs.