Feb. 20 (HealthDay News) -- Using tissue regeneration technology, Japanese researchers have been able to grow a new tooth from single mouse tooth cells and use it to replace natural teeth in a mouse.

The achievement is "a breakthrough in the development of bioengineered organs and proposes a novel concept for the organ replacement in future regenerative therapies," lead researcher Takashi Tsuji, associate professor, Department of Biological Technology, Tokyo University of Science, said in a prepared statement.

Reporting in the Feb. 19 online issue of the journal Nature Methods, Tsuji's team started by using the two cell types that form teeth -- mesenchymal and epithelial cells. They grew sufficient quantities of each of these cells and then injected them into a drop of collagen. This eventually developed into a budding tooth, which they transplanted into the cavity left by an extracted tooth in a mouse.

The new tooth developed normally and had the same composition and structure as natural teeth, the researchers reported. Ultimately, such bioengineered teeth could be used instead of inlays or synthetic implants, they said.

In addition, the new method might be applied to re-growing other organs. In fact, the researchers used similar methods to re-grow a mouse hair follicle that would eventually form a whisker.

"This method would be able to adopt the reconstitution of a wide variety of organs such as whisker, hair follicle, kidney and liver," Tsuji said.

He said the study increases the understanding of principles by which organ reconstitution can be achieved using bioengineered tissues.

"Our results therefore make a substantial contribution to the development of bioengineering technologies and the future reconstitution of primordial organs," the Japanese researcher said. "Our present findings should also encourage the future development of organ replacement by regenerative therapy."

But one expert believes this approach is still in its infancy.

"The developed tooth doesn't develop very far. As far as generating a functional, full size tooth in humans, we still have the same limitations of getting there," said Pamela C. Yelick, the director of the Division of Craniofacial and Molecular Genetics and an associate professor in the Department of Oral and Maxillofacial Pathology at Tufts University in Boston.

Her team has attempted similar work, she said, but the Japanese tooth "doesn't develop any farther than our bioengineered teeth did."

According to Yelick, the problem with all bioengineered teeth is that, so far, they can't be made to form specific teeth. "The limitations are generating teeth of predetermined size and shape, which really is the big stumbling block," she said.

"Tooth root formation is a big problem," too, she said. Tsuji's group was able to develop preliminary root structures, she said, "but they are not the functional roots that are really required for a functional tooth to stay in place."

However, Yelick remains optimistic. She predicts that, one day, there will be tissues engineered to replace damaged parts of organs, and even whole organs will be grown outside the body for transplant. "Every day, progress is being made," she said

SOURCES: Takashi Tsuji, Ph.D., associate professor, Department of Biological Technology, Tokyo University of Science, Japan; Pamela C. Yelick, Ph.D., director, Division of Craniofacial and Molecular Genetics, associate professor, Department of Oral and Maxillofacial Pathology, Tufts University, Boston; Feb. 19, 2007, online edition, Nature Methods