Stem cell breakthrough

Using stem cells from a mouse embryo, Japanese scientists say they have generated functioning kidneys in three mice, an advance applauded by U.S. scientists Monday who see the development as a significant step toward stem cell-derived kidneys for humans.

Hiromitsu Nakauchi, of the University of Tokyo, presented his studies Monday in Australia at the International Society for Stem Cell Research.

Mouse embryos engineered to lack a critical gene needed to grow their own kidneys were injected with stem cells before implantation into surrogate mothers. When the mice were born, they had functioning kidneys, Nakauchi told the meeting. Only one mouse had minor abnormalities.

Stem-cell-derived kidneys for humans are at least a decade away, researchers said.

For years, scientists in the field of regenerative medicine have been struggling to produce “off-the-shelf” organs and other body parts for people who’ve lost vital tissues to accidents and disease. New organs coaxed from stem cells are a genuine possibility, scientists say.

“This is terrific science,” said Dr. Ronald Crystal, chairman of the department of genetic medicine at Weill Cornell Medical Center in Manhattan. “All of the things coming out about stem cells are exciting, but there are several caveats, and the biggest one is that humans are not big mice.”

“We have to remember that when we work with mice, the mice are all genetically similar,” Crystal said. “The ones in this experiment were all missing a critical gene. The stem cells filled that niche.”

Nakauchi’s report has yet to be published in a peer-reviewed journal allowing scientists to study it. Data released at the meeting reveal the kidneys look like the twin bean-shaped organs. They are said to possess nephrons, the basic units within kidneys that regulate water and soluble substances by filtering blood and excreting urine.