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Sunday, 25 November, 2001, 20:14 GMT
Cloning still to prove itself
Clone e-biomed
A human embryo clone as featured in the journal e-biomed
The research that has yielded the world's first human embryo clone will no doubt prompt a major ethical debate right around the world.

There seems little doubt also that the work, published online in an electronic journal, will be read avidly by a great many scientists who believe this type of cell manipulation could revolutionise medical treatment.

They will note that the American team, from Advanced Cell Technology (ACT) in Massachusetts, not only managed to make embryo clones using a technique developed in mice, but also got unfertilised human eggs to start dividing as though they were embryos.

This second approach, known as parthenogenesis, is particularly interesting because it may provide an ethically more acceptable - and just as effective - route to achieving the therapeutic goals claimed for the new cell technologies.

Mice clones

Jose Cibelli and colleagues made their first human clone on 13 October, 2001. They used eggs from women volunteers in the Boston area. These women were all aged between 24 and 32, and had had at least one child.

At first, the researchers attempted to make the clones by injecting their donated eggs, which had had their nuclei removed, with the genetic material taken from the nuclei of skin cells.

This did not work very well and so the ACT team then injected enucleated eggs with the genetic material from cumulus cells - the tiny clouds of support cells that surround and nourish a developing egg in the ovaries.

This is how the world's first mice clones were made, and the technique, which differs slightly from the one that produced Dolly the sheep, was pioneered at the University of Hawaii.

It took 71 eggs to make the first clone. ACT says it actually produced three clones using the Hawaii method. Two divided to form early embryos of four cells, and one progressed to at least six cells before growth stopped.

Chemical 'trigger'

The ACT team also attempted something known as parthenogenesis. This makes eggs divide into early embryos, even though they have not been fertilised by a sperm, or been enucleated and injected with the genetic material from a donor cell in "traditional" cloning.

Parthenogenesis has been done in mice and rabbits, and it depends on being able to obtain immature eggs that still maintain a full set of genes (mature eggs would normally have half the necessary genetic complement to create an embryo; the other half would normally come from a sperm).

ACT treated 22 immature human eggs with a chemical "trigger" and got six of them to start dividing like embryos.

The stated aim of all this research is the creation of human embryos that can be mined for stem cells, the "master" cells that have the ability to form nearly all the body's tissues.

If the development of these cells can be carefully controlled, many scientists believe, they could be used to replace the failing cells that cause degenerative diseases.

Two sperm

If the transplanted cells are derived from a patient's own clone, they are less likely to be rejected by his or her immune system - in other words, the therapy is more likely to work.

Stem cells derived from parthenogenetically activated eggs would also be unlikely to be rejected after transplantation.

And this slightly different route to the stem cells could raise fewer moral dilemmas for some people than would stem cells derived from straight-forward cloning.

It is not difficult to imagine how such treatment might work in a women: the sick, female patient would have her own eggs collected and activated in the laboratory to yield up the therapeutic cells.

But in a man, the route is less obvious given that he produces sperm not eggs. The ACT team speculates it may be possible one day to transfer two nuclei from the man's sperm into a donated egg - stripped of its own nucleus - which is then activated and harvested.

However, all this may not be possible for many years - if at all. In the experiments detailed by ACT on Sunday, in none of the embryos were the researchers able to isolate the all important stem cells.

The BBC's Fergus Walsh
"It is not normal fertilisation"
Michael West, Advanced Cell Technology
"We think the future can be quite bright"
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