Korean and US researchers clone human embryo

WASHINGTON - South Korean and US researchers say they have cloned a human embryo and extracted sought-after embryonic stem cells.

The experiment, the first published report of cloned human stem cells, means so-called therapeutic cloning is no longer a theory.

Supporters of medical cloning say it can transform medicine, offering tailored and highly effective treatments for diseases ranging from Parkinson's to diabetes.

It could eventually lead to grow-your-own organ transplants.

The stem cells taken from tiny embryos, known as blastocysts, have the potential to develop into any kind of cell or tissue in the body.

"Our approach opens the door for the use of these specially developed cells in transplantation medicine," said study leader Woo Suk Hwang, of Seoul National University in Korea.

But critics say it involves destroying a human embryo, however tiny, and is thus unethical. US President George W. Bush and supporters in Congress are seeking to outlaw the technology in the United States and worldwide.

Writing in the journal Science, Hwang and colleagues said they created clones using eggs and cumulus cells donated by Korean women.

Cumulus cells are found in the ovaries and in some species have been found to work especially well in cloning experiments.

Scientists have cloned sheep, cattle, mice and other species but have had trouble cloning a human being.

Last year, Massachusetts company Advanced Cell Technology said it had created a human cloned embryo but it had not grown enough to become a source of stem cells.

The company is still trying but has not reported publicly on its progress.

Stem cells are found throughout the body and are a kind of master cell.

However, adult stem cells are difficult to find and to work with.

Many scientists believe blastocysts - stem cells taken from days-old embryos - have much greater potential. Each one, when grown correctly, can be directed to become any kind of cell or tissue.

Outside experts on cloning praised the work.

"It is a very impressive study. It obviously represents a major medical milestone," said Dr Robert Lanza, who has helped to lead cloning experiments at Advanced Cell Technology.

"I think it could help to spur a medical revolution."

Working with Hwang was Dr Jose Cibelli, formerly of Advanced Cell Technology and now a researcher at Michigan State University.

They used a process called nuclear transfer, which involves removing the nucleus from an egg cell and replacing it with the nucleus of a so-called adult cell - in this case a cumulus cells.

They cloned each woman using her own egg cell and cumulus cell, so the clone was a 100 per cent copy of the donor.

They activated the egg cells using a chemical process, which started the eggs growing as if they had been fertilised by a sperm.

Thirty 30 embryos grew to the blastocyst stage.

Stem cells were pulled from one of the blastocysts and the researchers managed to get them to grow into a variety of cells, including eye cells, muscle cells, bone and cartilage.

Lanza said it was now important that laws be passed banning reproductive cloning - using cloning to create a human baby.

He noted that some researchers, notably Kentucky fertility expert Dr Panos Zavos, had been trying to clone a baby.

"He's got the cookbook now. It's scary," said Lanza.

"We really need to move as soon as possible."

- REUTERS