After outlandish claims, a few media circuses, and some near misses by legitimate researchers, a team of South Korean researchers reports the production of cloned human embryos. The findings, to be published today (February 12) in Science, were released Wednesday after a Korean newspaper broke an embargo (Science, DOI:10.1126/science.1094515, February 12, 2004).

Wook Suk Hwang and Shin Yong Moon of Seoul National University used somatic cell nuclear transfer to produce 30 human blastocysts and a single embryonic stem cell line; SCNT-hES-1. Using 242 oocytes and cumulus cells from 16 unpaid donors, the group achieved a cloning efficiency of 19 to 29%, on par with that seen in cattle (25%) and pigs (26%).

“They have obtained an efficiency that is really amazing,” said Hans Robert Scholer, a professor of reproductive medicine at the University of Pennsylvania. Although several groups have claimed to have grown cloned human embryos to the six-, eight-, or even 16-cell stage, the South Korean group has published the first controlled report, Scholer told The Scientist.

“Definitely it's the first one that got beyond the eight-cell stage, and definitely the first one that got a blastocyst, and the first one that got a stem cell line derived from a blastocyst that was basically the product of the cloning process,” he said.

After obtaining the stem cell line, the team passaged the cells more than 70 times, maintaining both a normal XX karyotype and embryonic stem cell surface markers. When injected into the testis of SCID mice, the cells form teratomas with endoderm-, mesoderm- and ectoderm-derived tissue.

“It's a long road before we get to clinic, but this is a good first step,” said study coauthor Jose B. Cibelli, a professor of animal biotechnology at Michigan State University.

Although boosting the prospect of the use of therapeutic cloning in the treatment of spinal cord injury, Parkinson disease, and other ailments, Cibelli urged caution. “We have to be careful on the promises because people that need those kinds of therapies are listening and they want to have it today, so perhaps we should think in terms of my kids, or the next generation, which may benefit,” he told The Scientist.

The findings may spur those on the scientific fringe to become more vocal on the subject of reproductive cloning, Scholer said. Several groups have claimed—often in elaborately staged publicity stunts—to have used cloned human embryos to achieve a pregnancy or birth.

“They are going to come out of their holes or corners or wherever they are right now and say we knew it all the time and we can think about cloning humans” said Scholer. “The thing is these people can talk, but they can't do the experiments; the people who can do those experiments wouldn't do them.

“I would say there is nothing to fear except for the response of the public to them,” he said. “They listen too much to these people.”

The achievement should serve as a “wake-up call” to those in the United States, said Michael D. West, president and chief executive officer of Advanced Cell Technology, the biotechnology company that in 2001 reported using cloning to produce a six-cell human embryo.

“The work should have been done in the US, it should have been published by researchers in the US first,” West told The Scientist. “It wasn't.”

The field is underfunded because the pharmaceutical industry is “waiting in the side lines because of the Bush administration's strong position on this. It has dramatically contracted the amount of research being done in the United States,” West said.

The “ramifications could be serious for the US scientific community,” said Bernard Siegel, executive director of the Genetics Policy Institute. “There currently exists a Europe–US brain drain due to better funding/remuneration packages and career prospects for stem cell scientists. Future advances made in countries like South Korea and the UK, which support therapeutic cloning, will lead to those countries becoming more attractive for scientists due to the opportunities the research produces.”