Breakthrough as human liver grows from stem cell

Researchers in Japan have used human stem cells to create tiny human livers like those that arise early in fetal life. When the scientists transplanted the rudimentary livers into mice, the little organs grew, made human liver proteins, and metabolised drugs as human livers do.

They and others caution that these are early days and this is still very much basic research. The liver "buds" did not turn into complete livers, and the method would have to be scaled up enormously to treat a patient. Even then, the investigators say, they expect to replace only 30 per cent of a patient's liver. What they are making is more like a patch than a full liver.

But the promise is immense, medical experts say.

"This is a major breakthrough of monumental significance," said Dr Hillel Tobias, director of transplantation at the New York University School of Medicine. Tobias is chairman of the American Liver Foundation's national medical advisory committee.

"Very impressive," said Eric Lagasse of the University of Pittsburgh, who studies cell transplantation and liver disease. "It's novel and very exciting."

The study was published in the journal Nature.