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New York Times 4/3/13:
Scientists Fabricate Rudimentary Human
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 metabolized drugs as human livers do.Takanori TakebeResearchers from Japan used human stem cells to create "liver buds," rudimentary livers that, when transplanted into mice, grew and functioned. They and others caution that these are early days and this is still very much basic research. The liver buds, as they are called, did not turn into complete livers, and the method would have to be scaled up enormously to make enough replacement liver buds to treat a patient. Even then, the investigators say, they expect to replace only 30 percent of a patient's liver. What they are making is more like a patch than a full liver.But the promise, in a field that has seen a great deal of dashed hopes, is immense, medical experts said."This is a major breakthrough of monumental significance," said Dr. Hillel Tobias, director of transplantation at the New York University School of Medicine. Dr. 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 on Wednesday in the journal Nature.Although human studies are years away, said Dr. Leonard Zon, director of the stem cell research program at Boston Children's Hospital, this, to his knowledge, is the first time anyone has used human stem cells, created from human skin cells, to make a functioning solid organ, like a liver, as opposed to bone marrow, a jellylike organ. Ever since they discovered how to get human stem cells — first from embryos and now, more often, from skin cells — researchers have dreamed of using the cells for replacement tissues and organs. The stem cells can turn into any type of human cell, and so it seemed logical to simply turn them into liver cells, for example, and add them to livers to fill in dead or damaged areas. But those studies did not succeed. Liver cells did not take up residence in the liver; they did not develop blood supplies or signaling systems....