Stem Cell Breakthrough in Japan

Researchers have used stem cells to clone sheep, dogs, and monkeys. But cloning isn't the only application of stem cell research. Another big promise is that these building blocks of life could one day help doctors treat spinal cord injuries, replenish blood cells, and patch up damaged organs.

So when a Japanese research team headed by University of Tokyo professor Hiromitsu Nakauchi announced this week that it had turned human stem cells into platelets, it was a big deal.

Platelets can be found floating around in the blood and play a key role in the body's ability to repair itself. They stop bleeding by sticking to each other and the walls of blood vessels to form clots. But some people don't produce enough platelets on their own and need regular blood transfusions to avoid excessive bleeding. Nakauchi's research may hand doctors a more powerful tool for fixing that malfunction. "We think we are the first, but we haven't published it yet—nobody has published it yet," Nakauchi said by telephone from his lab at the university's Center for Stem Cell & Regenerative Medicine.

His team plans to submit a research paper to a U.S. science journal, possibly Blood. It's unclear whether the paper will be published, but submissions for similar research to Blood and the Journal of Experimental Medicine were accepted last year.

Custom-Made Platelets

If Nakauchi's work eventually passes safety testing and clinical trials with patients, doctors would be able to take a patient's own stem cells, grow platelets with genes that have been tweaked, and put them back into the patient's body—instead of relying on donated blood. That would get around a big problem when the recipient's body rejects the donor's blood that's there to help out. "For those patients it's best to use their own platelets," he said.

Still, don't expect this kind of treatment to be ready any time soon.

It may take another 10 years for Nakauchi's work to make an impact in hospitals. "We still have a number of hurdles," he said. One of them: producing cells efficiently. "If we really want to replace donated blood then we really have to have a mass-production system," he said. "Mass production is pretty difficult. I have no experience in doing that." And finding a company that can do it may prove challenging.

How did Nakauchi's team succeed where other had not? Years of experiments using mice, and luck, mainly. In 2002, Nakauchi and his team began doing experiments on mouse stem cells. One researcher in the lab, Koji Eto, was the first in the world to successfully make platelets from embryonic stem cells of mice. Three years ago, the team used what they had learned to grow platelets from human embryonic stem cells (ES cells). In the latest experiments, they used another type, called induced pluripotent stem cells, or iPS, made from human skin cells. "At first we used the same protocol on human stem cells that we had used for the mouse stem cells, but it didn't work," says Nakauchi. "So we modified it."

The difference was that human stem cells didn't require as much looking after—something they stumbled on by accident. "That's the case with any new discovery or new method: It's usually found by chance or by continuous trial and error," Nakauchi says. Once they succeeded using ES cells, iPS cells were easy because of the similarities between the two types.

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