Teeth have been grown from stem cell "seeds" and planted in the mouths of mice, scientists from Tokyo University reported in Proceedings of the National Academy of Sciences. They hope it could lead to replacing teeth in humans, or even to rebuilding whole organs.

The Japanese scientists developed a bioengineered "tooth germ" — a seed-like package containing all the cells and instructions necessary to form a tooth.

A number of these were implanted into the jaw bones of mice which had earlier had molar back teeth removed. The "tooth germs" sprouted fully formed teeth in the gaps left by the extractions.

To make them easier to see, they incorporated a green fluorescent protein which glowed under ultraviolet light. The engineered teeth were as hard as their natural counterparts and threaded with nerve fibres which responded to pain.

Dr Takashi Tsuji, from the Tokyo University of Science and colleagues wrote: "The bioengineered tooth. . . had the correct tooth structure, hardness of mineralised tissues for mastication, and response to noxious stimulations such as mechanical stress and pain."

"This study represents a substantial advance and emphasises the potential for bioengineered organ replacement in future regenerative therapies."

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