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New Mouse Teeth, Whiskers Grown From Handful of Cells

Mason Inman
for National Geographic News
February 26, 2007
 
Someday soon dentists may not just pull teeth and fill cavities. They could also stick entirely new teeth back in your mouth—perhaps by dabbing just a couple of cells in an empty tooth socket.

That is, if recent research pans out.

Scientists in Japan have come up with a controversial method for growing teeth in the lab—and even in adult mice—using a couple of cells from an embryo.

The researchers did the same with mouse whiskers, regenerating them from a single cell.

These teeth and whiskers were implanted into other mice, where they took root and seemed to function normally.

The scientists reported their work this week in the journal Nature Methods.

They focused on teeth and whiskers because they're not essential for the animal's life, so they can be repeatedly removed or implanted in experiments that seek to understand when and how organs can regenerate.

In the long run, however, the researchers hope this line of work will help them create replacements for more necessary organs, such as hearts and kidneys. (Related: "Mice With Human Brain Cells Created" [December 14, 2005].)

Germ of the Matter

Previous groups have had some success with growing teeth in the lab. Their results, however, have been hit-or-miss, said Takashi Tsuji of the Tokyo University of Science.

But he and his colleagues, he said, have developed a method that is "simple, easy, and highly reproducible for many researchers."

The scientists took cells from the mouths of mouse embryos and inserted them into drops of collagen gel, which is similar to the material in the part of the jawbone that surrounds teeth.

There the cells multiplied and developed, arranging themselves into tooth germs—clumps of cells that give rise to teeth.

When surgically implanted into the belly of a mouse, the germs grew into primitive teeth within a couple weeks, the researchers showed.

These teeth could then be implanted into a mouse's mouth, where nearly every time they took root and nerves grew into them.

The researchers were even able to implant a tooth germ directly into the mouth of an adult mouse—in an empty socket where a tooth had been pulled—and grow a new tooth in the jaw.

Controversial Claims

Some scientists say the new work doesn't show much progress over existing techniques.

The teeth grown using Tsuji's method never develop beyond a very primitive stage, and there is no way to select what kind of tooth they develop into, the scientists point out—both huge obstacles to developing true replacement teeth.

(Read a National Geographic magazine story on the controversy over stem cells.)

But according to Jeremy Mao of New York's Columbia University, "this study represents an important contribution to the field of tooth regeneration.

"It is likely one of the many challenging milestones before a whole tooth can be bioengineered for patients," he said.

"The key advance of this study rests on the implantation of reconstituted embryonic tooth germ cells."

But, he added, there's still a lot of work to be done before this is ready for people, such as scaling up the method so it can be done efficiently for growing many teeth.

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