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WASHINGTON -- Researchers from South Korea say they have cloned human embryos and extracted from them stem cells in a development that experts hope could spark a medical revolution.
The experiment, which is reported in Friday's edition of the respected American magazine Science, is viewed as a major advance towards growing patients' own replacement tissue to treat diseases.
Previous attempts to clone a human embryo to produce stem cells are believed to have failed -- despite claims to the contrary -- and the report is likely to revive controversy around the world over the technique.
Critics have attacked such experiments as unethical because of the destruction of the embryos, however tiny. The U.S. government is trying to outlaw all cloning both in America and around the world.
In the experiment, scientists from Seoul National University said they collected 242 human eggs and succeeded in creating the 30 blastocrysts -- early-stage embryos containing about 100 cells.
From these they harvested one colony of stem cells that have the potential to grow into any tissue -- without being rejected by a patient's immune system.
The technique raises the hope of revolutionary treatments for diabetes, Parkinson's and other diseases, but any therapy is years away from being tested in people.
"Our approach opens the door for the use of these specially developed cells in transplantation medicine," Dr. Woo Suk Hwang, who led the study, said in a statement.
Experts on cloning praised the work.
"It is a very impressive study. It obviously represents a major medical milestone," Dr. Robert Lanza, from Advanced Cell Technology, told Reuters on Thursday.
"I think it could help spur a medical revolution."
And stem-cell researcher Dr. Rudolf Jaenisch of the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts told The Associated Press the experiment proved the technique was possible using human cells.
"That's an important point to prove," he said.
Still, "it's not of practical use at this point," Jaenisch said, stressing that years of additional research were required.
The reports will renew debate over whether human cloning should be banned. The U.S. House last year voted to do that, but the Senate stalled over whether there should be an exception for research of this type.
Internationally, the U.S. is pushing for a United Nations ban of all human cloning, too. The U.N. General Assembly recently postponed a decision.
There is almost universal support for a global ban of reproductive cloning, but Britain and several other countries want cloning for medical experiments to be permitted.
Jaenisch said he regretted that most U.S. scientists could not experiment with the Seoul researchers' new stem-cell line.
Extracting stem cells from embryos kills them and U.S. President George W. Bush has banned any federally funded research on stem cells from embryos destroyed after August 9, 2001 -- making the South Koreans' recently developed line too new.
Further experiments in Seoul suggest the stem-cell colony could produce different types of body cells, AP reported. It began to form muscle, bone and other tissues in test tubes and when implanted into mice.
The team said it was now studying how to direct which tissues those cells form.
The experiment, which is reported in Friday's edition of the respected American magazine Science, is viewed as a major advance towards growing patients' own replacement tissue to treat diseases.
Previous attempts to clone a human embryo to produce stem cells are believed to have failed -- despite claims to the contrary -- and the report is likely to revive controversy around the world over the technique.
Critics have attacked such experiments as unethical because of the destruction of the embryos, however tiny. The U.S. government is trying to outlaw all cloning both in America and around the world.
In the experiment, scientists from Seoul National University said they collected 242 human eggs and succeeded in creating the 30 blastocrysts -- early-stage embryos containing about 100 cells.
From these they harvested one colony of stem cells that have the potential to grow into any tissue -- without being rejected by a patient's immune system.
The technique raises the hope of revolutionary treatments for diabetes, Parkinson's and other diseases, but any therapy is years away from being tested in people.
"Our approach opens the door for the use of these specially developed cells in transplantation medicine," Dr. Woo Suk Hwang, who led the study, said in a statement.
Experts on cloning praised the work.
"It is a very impressive study. It obviously represents a major medical milestone," Dr. Robert Lanza, from Advanced Cell Technology, told Reuters on Thursday.
"I think it could help spur a medical revolution."
And stem-cell researcher Dr. Rudolf Jaenisch of the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts told The Associated Press the experiment proved the technique was possible using human cells.
"That's an important point to prove," he said.
Still, "it's not of practical use at this point," Jaenisch said, stressing that years of additional research were required.
The reports will renew debate over whether human cloning should be banned. The U.S. House last year voted to do that, but the Senate stalled over whether there should be an exception for research of this type.
Internationally, the U.S. is pushing for a United Nations ban of all human cloning, too. The U.N. General Assembly recently postponed a decision.
There is almost universal support for a global ban of reproductive cloning, but Britain and several other countries want cloning for medical experiments to be permitted.
Jaenisch said he regretted that most U.S. scientists could not experiment with the Seoul researchers' new stem-cell line.
Extracting stem cells from embryos kills them and U.S. President George W. Bush has banned any federally funded research on stem cells from embryos destroyed after August 9, 2001 -- making the South Koreans' recently developed line too new.
Further experiments in Seoul suggest the stem-cell colony could produce different types of body cells, AP reported. It began to form muscle, bone and other tissues in test tubes and when implanted into mice.
The team said it was now studying how to direct which tissues those cells form.
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