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Cloned human cells spell embryonic first


Injection of a human donor cell, a vital step in therapeutic cloning (Image: WS Hwang)

The first published report of cloned human stem cells means so-called therapeutic cloning is no longer a theory but a reality, say the Korean and U.S. researchers who announced their results today.

The researchers cloned several human embryos and extracted from one sought-after cells called embryonic stem cells. They published their results online in the journal Science.

But the researchers, led by Professor Woo Suk Hwang of Seoul National University, said their achievement showed an immediate need for a global ban on cloning to make babies, or reproductive cloning.

Their technique is an example of therapeutic cloning. Scientists hope one day this type of cloning could be used to grow replacement tissue such as brain cells, skin, a liver or a kidney. They hope this tissue could then be used for human transplants or to treat diseases such as diabetes, Alzheimer's and Parkinson's.

Hwang's team was the first to publish the development of versatile 'pluripotent' human embryonic stem cells, potentially capable of becoming any cell in the body, from a cloned human blastocyst.

The researchers created several clones using eggs and cumulus cells donated by Korean women who had independently approached the researchers.

Cumulus cells are found in the ovaries and surround an egg while it is developing. Researchers have shown these cells work especially well in cloning experiments.

The researchers removed the nuclei from the egg cells and replaced them with nuclei from the cumulus cells, matching each woman's egg cell with her own cumulus cell. The nucleus contains 99% of a person's DNA.

Then they used a chemical trigger to start the eggs growing as if they had been fertilised by sperm.

Hwang stressed the difficulty of the experiment. Out of more than 200 tries, they got only 30 blastocysts, the hollow balls of 100 to 200 cells that can be used as the source of stem cells.

When they tried to clone men using a piece of skin from the ear, they failed. They also failed when they tried to clone one woman using the hollowed-out egg of another woman.

Scientists welcomed the work as a breakthrough but stressed it would be years before any patient benefited from the technique.

"I emphasise that it is long-range, not short-range promise," said Science edtior Dr Donald Kennedy. "It represents, I think, an extraordinary series of technological accomplishments."

Professor Ian Wilmut, who led the team that created Dolly the world's first mammal to be cloned from an adult cell, called the research "very encouraging".

"The ability to derive cells from cloned embryos would have several potential benefits that cannot be obtained in any other way," he said.

Professor Richard Gardner, chair of a Royal Society group in the U.K. working on stem cells and cloning, welcomed the news but warned:

"This announcement does not make attempts at human reproductive cloning any more desirable, ethical or safe."

Professor Shin Yong Moon of Seoul National University, director of the centre where the research was done, called for a ban on reproductive cloning.

"To prevent reproductive cloning we would like to ask every country or every nation to have a law to prohibit reproductive cloning," he said.

Tags: health, biology, cloning-and-dna