The miracle cure with a catch

Scientists could be using a new technique to treat diseases of the heart, liver, brain, kidneys... the list is endless. So what's stopping them? It involves the controversial issue of cloning
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Bridget Connors was born with no immune system and was destined to spend a miserably short life in a sterile bubble. Today, at eight months of age, Bridget is a healthy baby leading a near-normal life. She is living testament to the power of stem cells, the elusive "mother cells" of the body that possess the almost supernatural ability to mend what would otherwise be irreparably damaged tissues and organs.

Bridget Connors was born with no immune system and was destined to spend a miserably short life in a sterile bubble. Today, at eight months of age, Bridget is a healthy baby leading a near-normal life. She is living testament to the power of stem cells, the elusive "mother cells" of the body that possess the almost supernatural ability to mend what would otherwise be irreparably damaged tissues and organs.

Bridget was once given just 12 months to live. Lacking an immune system meant she was vulnerable to just about every infection imaginable. However, at four months of age she was given a pioneering transplant of blood cells extracted, and then frozen, from the umbilical cord of a newborn child who had died two years previously. Today, those transplanted blood cells have restored a working immune system in Bridget's small body.

The success of the operation, carried out by Andrew Cant, a consultant paediatrician at Newcastle-upon-Tyne General Hospital, relied on the presence of stem cells within the cord blood. These stem cells were able to replicate continuously, shedding "daughter" cells that could develop into the specialised white bloods cells which form a major part of our immune defences. The transplant led to the stem cells repopulating Bridget's defective bone marrow, enabling her to produce the cells that help to fend off infections.

Bridget was lucky. It was pure chance that her tissue type matched that of the child who had donated the umbilical cord blood. Mr Cant says the odds of such a match between unrelated individuals is something like one in 18,000. For the other Bridgets who suffer from severe combined immune deficiency, the only viable treatment at present is either bone marrow transplantion, which again needs a matched donor, or gene therapy, which is neither simple nor proven.

There is another possible solution, however, which could soon be available if the Government agrees to a change in the law governing the use of human embryos for research. This involves taking stem cells at an even earlier stage of development - from an embryo a few days old - and using them directly to restore the function not only of defective bone marrow, but other diseased tissues.

It is generally accepted that the earlier in human development stem cells are taken, the greater the chance of them being able to develop into a wider set of tissues. A stem cell taken from the umbilical cord blood of a newborn can easily be made to generate specialised blood cells, but not brain or heart tissue. Yet a stem cell taken from an early embryo just a few days old could theoretically develop into any of the 200 to 300 specialised cells and tissues of the human body.

The potential for using embryonic stem cells to treat previously incurable conditions is vast. Harold Varmus, the former director of America's National Institutes of Health, recently told the US Congress: "There is almost no realm of medicine that might not be touched by this innovation."

If it were possible to create an unlimited source of embryonic stem cells, many of the problems associated with the shortage of organs for transplants may be overcome. Britain's Royal Society, our de facto national academy of sciences, has told the Government's inquiry into the issue: "Organs damaged by trauma or disease do not always need replacing, and repair often would be possible if a suitable source of cells was available. Stem cells are a potential source. Patients suffering from certain degenerative diseases of the brain, liver (hepatitis), pancreas (diabetes), blood (leukaemias), joints (rheumatoid arthritis), heart and kidneys are likely to benefit from stem cell therapy. Other diseases which might be alleviated thus include muscular dystrophy and cystic fibrosis."

As the law stands, scientists can only work with stem cells taken from an embryo less than 14 days old if the research is geared towards understanding fertility, reproduction or congenital disorders. Austin Smith, the only scientist in Britain with such a licence, says that the law should be relaxed to allow people like him to use them for treating other medical disorders. "They are a wonderful natural resource as they can develop into almost any kind of human cell, such as brain, bone or heart. They offer a unique opportunity to replace tissues damaged by disease," Dr Smith says.

So what's the problem? Why doesn't the Government change the law to allow scientists to exploit the obvious benefits of embryonic stem cells? The answer of course is that some religious groups perceive even the earliest embryo as a potential human being that cannot be treated as an expendable resource. But there is another ethical issue mixed up with the Government's deliberations. This concerns whether permission should be given to scientists to attempt a form of human cloning for therapeutic, as opposed to reproductive, purposes.

Bridget Connors, like all other patients who undergo transplant operations, faced the problem of tissue rejection. Bridget was one of the lucky ones who was able to find a precise tissue match. Many others are not so fortunate. If, however, it is possible to create a source of embryonic stem cells from their own bodies - which would constitute an exact tissue match - the problems of rejection would be no more.

Therapeutic cloning envisages that it should be possible to take a healthy cell from a patient in need of a transplant, extract the nucleus and transfer it to an unfertilised egg which has had its own nucleus removed. Using the cloning technology developed to create Dolly the sheep, it would then be possible to stimulate the division of this unfertilised egg, complete with its own mature nucleus, to create an early "embryo". In fact, the embryo at this stage is technically called a morula and consists of a solid, microscopic ball of undifferentiated cells, only some of which will eventually develop into the embryo proper.

After several cell divisions, the morula develops into a blastocyst, or hollow ball of cells. It is at this stage that embryonic stem cells can be extracted from what is called the "inner cell mass". Eventually, from day 14 onwards, this inner cell mass develops into the "primitive streak", the point at which the embryo proper can be identified (and the point at which it is illegal to use embryonic material for any purposes).

What nobody yet knows is whether it is indeed possible to generate an early embryo, or morula, from fusing an unfertilised human egg with a cell nucleus. Experiments on animals suggest there is nothing in theory to suggest this is not possible, but the practical problems are still enormous; the main one being the large number of eggs needed for the creation of one animal clone.

But the benefits of being able to create a steady source of embryonic stem cells from one's own body tissue would be immense. It could lead to the day when each of us has our own embryonic stem cells stored away ready for the day when we need them. Animal studies have already shown how effective stem cells are at incorporating themselves into complex organs such as hearts or brains and effectively repairing any damaged tissues. Julia Polak, a stem cell researcher at the Hammersmith Hospital in London, says: "We are beginning to see that stem cells will grow into the right cell types when they are transported into other tissues, for example, stem cells injected into bone will start making bone cells."

The Government's chief medical officer, Liam Donaldson, submitted his report on the the use of therapeutic cloning to produce embryonic stem cells three months ago. It has been widely touted as recommending a go-ahead, with the strong proviso that no one be allowed to transplant any human clone into a womb. So-called reproductive cloning, resulting in the birth of a cloned baby, will be strictly illegal.

Next week the Government is expected to make its decision, fully conscious of the medical benefits that could result. But its delay in responding to the Donaldson inquiry suggests it is equally sensitive to the ethical storm that will inevitably follow any relaxation of the laws governing human embryo research. Ministers may be damned if they do allow therapeutic cloning, but they will be more damned by the vast majority of medical scientists if they don't.

Anne McLaren, one of Britain's most eminent embryologists and principal research associate at the Wellcome Trust and Cancer Research Campaign Institute in Cambridge, says the critics of therepeutic cloning would be using familiar pro-life arguments. "There would of course still be people who believe that personhood is present from the very beginning of embryonic life, so that using an embryo for any purpose other than making a baby is tantamount to murder," Dr McLaren says.

"The stroke victim, the multiple sclerosis patient and the person crippled with rheumatoid arthritis may, on the other hand, believe that they have every right to use what are effectively their own cells."