Cloned human embryos could help cure diseases

SCIENTISTS in South Korea have become the first to successfully clone a human embryo and extract from it master stem cells that may hold the key to creating cures for diabetes, Parkinson's and other diseases.

This is not cloning to make babies, but to create medicine.

It's almost guaranteed to revive international controversy over whether to ban all human cloning, as the Bush administration in the US wants, or to allow this "therapeutic cloning" that might eventually let patients grow their own replacement tissue.

Embryonic stem cells are the body's building blocks, cells from which all other tissue types spring. They're present in an embryo only days after conception and are ethically sensitive because culling stem cells destroys the embryo.

Scientists have used therapeutic cloning to partially cure laboratory mice with an immune system disease. And they know how to cull stem cells from human embryos left over in fertility clinics. But attempts to clone human embryos so resulting stem cells would be genetically identical to the patient who needs them have failed until now.

Scientists from Seoul National University say they succeeded largely because of using extremely fresh eggs donated by South Korean volunteers and gentler handling of the genetic material inside them.

They acknowledge the ethical sensitivity of the work. "We continually agonised over whether there was an alternative to this research, but decided to go ahead with it to give hope to suffering patients and open a new epoch in science and technology," Dr Moon Shin-yong, a research team leader, said in a statement yesterday.

But years of additional research are required before embryonic stem cell transplants could be considered in humans, he stressed.

US scientists almost universally want a ban on cloning for reproduction, because the high rate of birth defects in cloned animals shows the technique is too dangerous. The Seoul researchers collected 242 eggs from 16 unpaid volunteers. Each woman also donated some cells from her ovary.

Using the same process as is used to clone animals, they removed the gene-containing nucleus of each egg and replaced it with the nucleus from the donor's ovarian cell.

Chemicals jump-started cellular division, resulting in 30 blastocysts, early-stage embryos that contain a mere 100 cells. From those, they harvested just one colony of stem cells a small success rate.

But those stem cells were a genetic copy of the donor, and began forming muscle, bone and other tissues in test tubes and when implanted into mice, the Seoul team reported.

The team is studying how to direct which tissues those cells form, said Woo, who pledged to make the new cell line available to other interested scientists. The team says it sought approval for its work from an ethical review board and obtained informed consent from its women donors before proceeding.

The stated intention is to study human embryonic stem cells to see how they could be used as a therapeutic tool in the treatment of disorders such as Parkinson's disease, diabetes and osteoarthritis, among others, in which tissues in the body have begun to fail.

Editor-in-chief of the journal Science, Donald Kennedy, said: "The potential for embryonic stem cells is enormous, but researchers still must overcome significant scientific hurdles."

He added: "These results seem promising. But remember that cell and tissue transplantation and gene therapy are still emerging technologies, and it may be years before embryonic stem cells can be used in transplantation medicine."

He called for a global ban on activities which would seek to use this technology to create living children.