THE decision to grant Newcastle University a licence to clone the embryos of human beings for research brings Britain closer to a medical breakthrough that has tantalised scientists since Dolly, the cloned sheep, was born in 1996.

That success, by Ian Wilmut’s team at the Roslin Institute, suggested a new approach to treating conditions such as Parkinson’s disease, diabetes and spinal paralysis, which researchers have been striving to follow since.

It also opened an ethical controversy over the possibility of creating a cloned human being, and over the use of cloned embryos in medical therapies and research. The medical potential of cloning rests on the way it can be employed alongside another technology — the production of embryonic stem cells (ES cells) — to make spare-part tissue for treating disease.

ES cells, which were first isolated by Jamie Thomson of the University of Wisconsin a year after Dolly’s birth, are found in early embryos. They are master cells with the potential to develop into any tissue type. This means that if a way can be found to coax them into forming particular tissue cells, these could be used to cure diseases that are caused by a shortage of that tissue.

In diabetes, the Newcastle team’s target, insulin-producing islet cells in the pancreas are faulty. Parkinson’s patients lack neurons that make the signalling chemical dopamine.

ES cells offer a possible source of replacements. While this technology is exciting enough in its own right, cloning adds another dimension. When foreign tissue is transplanted into a patient, the body’s immune system will often reject it. Even if islet cells were grown from ES cells of a reasonably good match to the recipient, the rejection risk would still be high.

Cloning could solve this problem. If the ES cells were genetically identical to the patient they would be accepted.

A marriage between Professor Wilmut’s and Thomson’s breakthroughs has thus become a medical research Holy Grail. The idea is to clone an embryo from the patient who needs a transplant, and then harvest ES cells for therapy. But this strand of research has met widespread opposition. The isolation of ES cells requires the destruction of an embryo, to which many religious groups object. They favour research into adult stem cells, which are considered less promising by some scientists and cannot be cloned.

The cell nuclear transfer method that would be employed to produce cloned embryos is identical to that needed to clone a person. Genetic material is cleared from a donated egg and replaced with an adult cell’s nucleus from the person to be cloned. The resulting embryo could then be allowed to develop for a few days before being split into stem cells, but it could also be implanted into a womb and left to develop.

This has fed arguments that allowing “therapeutic” cloning would inevitably be the start of a slippery slope that would lead inexorably to the birth of a cloned human being While most scientists support the idea of therapeutic cloning, they reject reproductive cloning as unethical and unsafe. The overwhelming majority of cloned animals, including Dolly, have suffered developmental abnormalities, and hundreds of attempts are needed to produce even a moderately healthy infant.

This has not stopped mavericks from trying to produce a human clone. In 2002 the Raelian cult claimed the birth of one, but it produced no evidence and the claim was dismissed by scientists. Teams led by Panayiotis Zavos and Severino Antinori are pursuing the same goal.

This year, a Korean team announced the creation of the first confirmed cloned human embryo. They accepted that their technique could be used for reproductive or medical purposes, and called for strict laws to control its use. Most developed countries have outlawed reproductive cloning, but they have different attitudes to its use in medical research. Germany and the United States have banned therapeutic cloning, and make it difficult for scientists to use ES cells. Britain, however, has taken a more liberal approach in both fields.

In 2001 Parliament voted to allow ES cell research and therapeutic cloning for research approved by the Human Fertilisation and Embryology Authority. The Newcastle team has now become the first to be granted a cloning licence.

The Newcastle group and a team at King’s College London also hold licences for ES cell research, and have produced colonies or “lines” of these cells, which have been deposited in the UK national stem cell bank, the first of its kind in the world.

The bank was set up by the Government, which actively encourages ES cell and therapeutic cloning research. It is keen to establish Britain as the leading centre for ES cell and therapeutic cloning research. This support has attracted leading scientists to Britain.

CLONING PROGRESS

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