Stem Cells Spawn Kidneys in Mice

Using stem cells from a mouse embryo, Japanese scientists say they have generated functioning kidneys in three mice, an advance applauded yesterday by American scientists 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 yesterday 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 still 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, who chairs 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.

"Just how exciting this is depends on the kind of [embryonic] stem cells they used," said Dr. Alan Russell, director of the McGowan Institute for Regenerative Medicine at the University of Pittsburgh.

Because mouse stem cells were involved, that means kidneys can be generated in specially bred mice. The real test, Russell said, is producing kidneys from human-derived stem cells.

Dr. Michael West, chief executive of Advanced Cell Technology, a biotech firm in California and Massachusetts, said the Japanese research advances work conducted by scientists at his company. In 2002, Advanced Cell Technology announced the development of kidneys grown from stem cells derived from cloned cow embryos.

The tissue functioned for about a month in genetically identical cows.

West said the company is no longer pursuing the development of kidneys but emphasized the importance of such work.

"This is of inestimable importance to people with renal disease," West said.

Of all people awaiting transplantable organs, the largest number — about 100,000 — are in need of kidneys.