South Koreans Streamline Cloning of Human Embryos<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office"
By GINA KOLATA
Published: <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smartt
In what scientists say is a stunning leap forward, a team of South Korean researchers has developed a highly efficient recipe for producing human embryos by cloning and then extracting their stem cells.
Writing today in the journal Science, they report that they used their method to produce 11 human stem cells lines that are genetic matches of patients aged 2 to 56.
Previously, the same group, led by Dr. Woo Suk Hwang and Dr. Shin Yong Moon of
Now things have changed.
"It is a tremendous advance," said Dr. Leonard Zon, a stem cell researcher at
The method, called therapeutic cloning, is one of the great hopes of the stem cell field. It produces stem cells, universal cells that are extracted from embryos, killing the embryos in the process, and, in theory, can be directed to grow into any of the body's cell types. And since the stem cells come from embryos that are clones of individuals, they should be exact genetic matches. Scientists want to obtain such stem cells from patients to study the origin of diseases and to develop replacement cells that would be identical to ones a patient has lost.
Dr. Zon cautioned that "it will take a lot of work" before stem cells fulfill those promises, but said the new finding would bring scientists significantly closer to the goals.
"It will spearhead the effort, for sure," Dr. Zon said.
Until now, scientists have been studying human embryonic stem cells they extracted from embryos that were created for that purpose or from embryos created at fertility clinics and donated by couples who no longer needed them. They also are studying mouse stem cells, working on the extraordinarily difficult task of directing them to develop into specific tissue types.
But researchers wanted embryos that were genetic matches of patients. The only way to do that is to use embryos that were clones of patients. And human cloning had seemed all but impossible.
To produce a clone, scientists slip the genetic material from a patient's cell into an unfertilized egg from another person whose genetic material has been removed. The genes from the patient's cell take over, directing the egg to divide and develop into an embryo that is genetically identical to the patient, rather than the egg donor. About five days later, when the cloned embryo contains about 100 cells, stem cells appear, looking like a ball of cells encased in a sphere.
The process, however, fails more often than it succeeds and in humans it seemed to fail almost all the time. In their previous report, published in February, Dr. Hwang and Dr. Moon used 248 human eggs to produce a single stem cell line.
But this time, with a handful of technical improvements that mostly involved such things as methods for growing cells and breaking open embryos, they used an average of 17 eggs per stem cell line and could almost guarantee success with a single woman's eggs obtained in a single month. And it did not matter if the patient whose cells were being cloned was young or middle aged, male or female, sick or well - the process worked.
"You almost have no reason not to do it," said Dr. Davor Solter, the director of the Max Planck Institute for Immunobiology in
In fact, Dr. Solter added, it now looks like it is much more efficient to clone and obtain human stem cells than it is to do the same experiment in animals.
Seven states ban cloning for any reason and 11 have laws that prevent embryonic stem cell research, said Lori B. Andrews, a law professor at Chicago-Kent College of Law. And the federal government will not pay for the creation of new stem cell lines. But where such work is legal, increasing numbers of scientists, including Dr. Zon, say they have private financing and plan to go forward using cloning to produce stem cells.
The new paper, said Dr. John Gearhart, a stem cell researcher at
But not everyone is excited.
Dr. Leon Kass, chairman of the President's Council on Bioethics, said in an e-mail message that "whatever its technical merit, this research is morally troubling: it creates human embryos solely for research, makes it much easier to produce cloned babies, and exploits women as egg donors not for their benefit. "
The United States Conference of Catholic Bishops shares those concerns, said Richard Doerflinger, director of pro-life activities there. He added that he also worried that a cloned baby might be next.
"Up until now, people were beginning to wonder whether human cloning for any purpose was feasible at all," Mr. Doerflinger said. "This development makes it feasible enough to be a clear and present danger."
The South Korean study participants wanted only to advance medicine, Dr. Hwang said. They included 18 women who provided eggs, including one of the study's patients, who provided her own eggs. Eleven patients participated - eight adults with spinal cord injuries and three children, consisting of a 10-year-old boy with a spinal cord injury, a 6-year-old girl with diabetes, and a 2-year-old boy with congenital hypogamma-globulinemia, a genetic disorder of the immune system.
Dr. Gerald Schatten of the University of Pittsburgh School of Medicine, who visited the South Korean lab and helped the scientists, whose English is limited, write their paper, said the results were partly the product of extraordinary dedication.
"They work 365 days a year except for leap year, when they work 366 days," Dr. Schatten said. "They have lab meetings at every morning except Sunday, when they have them at ."
Scientists say they know the word "cloning" raises fears of actual babies that are clones, but say they have no intention of doing such work. The South Korean government, which paid for the new study, has made it a criminal offense to implant a cloned embryo into a woman's uterus, Dr. Hwang said. "It should be banned throughout the world," he added.
Few would venture into the cloning arena if the science were not so promising, researchers say.
Of course, they add, there is a long way to go from stem cells to therapy. "It's going to take a lot of work," said Dr. Ronald McKay, a stem cell researcher at the National Institutes of Health. "But we want this to work - it's not a theory. My technical and professional judgment tells me this is really important."
But Dr. Kass of the President's Council on Bioethics says that cloning and extracting stem cells from the embryos are not the only ways to do such work. He notes that the majority of the council called for a moratorium on cloning for research. And, he said, the council recently suggested other ways of getting stem cells that could develop into the desired tissue types and that would match a patient's own cells, "without these violations and moral hazards."
Opinion polls have had varied results, often depending on the words that are used to describe the work. In one recent
Dr. Hwang's paper goes a step further, using "S.C.N.T." instead of "somatic cell nuclear transfer" and then dropping the first two letters and calling the process "N.T."
Some, like Dr. Ruth Faden, the executive director of the bioethics center at Johns Hopkins, say the moral debate will change if stem cell research leads to new treatments with dramatic benefits for some patients. "That could really shake it up," she said.
But Dr. Richard Land, the president of the Southern Baptist Convention's ethics and religious liberty commission, said his group, for one, would not be assuaged.
"We believe a cloned embryo is a human being," he said. "We should not be the kind of society that kills our tiniest human beings in order to seek a treatment for older and bigger human beings."