Teeth Can Yield Stem Cells, Scientists Say

Amitabh Avasthi
for National Geographic News

Dental pulp from wisdom teeth could be a new source of therapeutic stem cells, Japanese researchers announced recently. Like embryonic stem cells, the new cells—known as mesenchymal stem cells—are capable of developing into a variety of tissues, including bone, cartilage, and fat. These new lines of stem cells can be created without the use of an embryo—possibly sidestepping controversy.

In many countries adults routinely get minor surgeries to remove wisdom teeth.

"The [wisdom] tooth is usually discarded into trash, so there are no ethical concerns," said Hajime Ohgushi, principal research scientist at the National Institute of Advanced Industrial Science and Technology in the Hyōgo Prefecture, Japan.

However, unlike embryonic stem cells, the newfound cells cannot morph into almost any type of cell in the body.

(Related: "Stem Cell Breakthrough: No More Need to Destroy Embryos?" [August 23, 2005.])

The new research has also not been published or vetted by other scientists in the field.

Stifled

Work on embryonic stem cells has long been mired in controversy.

The cells could lead to breakthroughs in regenerative medicine by allowing certain tissues and diseased organs to be replaced.

But harvesting the cells typically requires the destruction of an embryo, which critics equate with the taking of a life.

Since 2001 the United States government has restricted public funding to a limited number of embryonic stem cell lines, a move many U.S. scientists say has stifled their work.

The race to create induced pluripotent cells—cells capable of developing into most types of cells in the body—in humans began in 2006, when scientists at Kyoto University in Japan announced they had inserted genes into cells from the tails of mice and reprogrammed them into cells with properties of embryonic stem cells.

In 2007 researchers from Kyoto University and the University of Wisconsin, Madison, separately announced that they had successfully applied the technique to human cells by using viruses to ferry four genes—OCT4, SOX2, NANOG, and LIN28—into skin cells.

Researchers from the two teams said they had given properties of stem cells to human cells taken from skin and connective tissues.

Now Ohgushi and his colleagues claim they used just three sets of genes—OCT4, SOX2, and KLF4—to program cells cultured from the center of a wisdom tooth into adult stem cells.

The researchers add that their success rate, about 10 stem cells for every 50,000 cells, matches that of the Kyoto researchers.

Better Source

Ohgushi said stem cells derived from wisdom teeth are not only easier to store—the tooth they used had been sitting in a freezer for three years—but also better than those extracted from bone marrow.

Stem cells found in bone marrow cannot express telomerase reverse transcriptase (TERT), a type of protein crucial to cell division and growth, Ohgushi explained.

"Our cells clearly express TERT and showed [more] extensive … activity than stem cells from bone marrow."

Though clinical trials are still years away, the researcher envisions banks where donors could store their wisdom teeth and access their own stem cells to treat potential diseases later in their lives.

Shinya Yamanaka, a researcher from Kyoto University who was not involved in the teeth research, agreed that the discovery could provide an alternative source of stem cells for use in regenerative medicine.

But he said it was odd that the discovery was apparently announced directly to the press and that the results did not seem to be backed by a peer-reviewed publication.

"I know venture companies do this to keep investors' interest," Yamanaka said. "It was surprising to me that government-backed scientists did this."

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