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Stem Cell Research

Part of the debate – in the House of Lords at 12:13 pm on 3rd May 2007.

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Photo of Baroness Greenfield Baroness Greenfield Crossbench 12:13 pm, 3rd May 2007

My Lords, I congratulate the noble Lord, Lord Patel, on bringing forward this timely and wide-ranging debate. I shall focus on just one aspect: the potential application of stem cell therapy in my own particular area of research, which is neurodegeneration. While other conditions such as heart disease and cancer are devastating, we all fear in particular the disorders that destroy the brain. They target the ability to stand up, to smile, to converse, to relate to others and to cherish memories of those relationships; indeed, to enjoy the full experience of being a unique individual. Yet the big problem is that we do not yet know why certain key brain cells embark on the pernicious cycle of self-destruction that we call neurodegeneration. The best we can do is combat the symptoms.

Current strategies consist of using drugs to replace the dwindling levels of the chemical messengers that result from the dwindling numbers of brain cells. But there are problems. First, inevitably, drugs will permeate into areas of the brain or body where they are not needed, and these cause side effects. In Parkinson's disease, for example, treatment with a drug that will promote the chemical messenger in the area that is degenerating will also increase erstwhile normal levels of that same chemical elsewhere in the brain, so that the now excessive amounts risk psychotic side effects, such as hallucinations. Even where such treatment offers a temporary alleviation in the patient's basic condition or a slowing down of the deterioration, it is hard to convince organisations such as the National Institute for Health and Clinical Excellence that the costs are worth while.

The situation is made even worse when we consider how many more of us will need such treatment in the future. At the moment, 700,000 people in the UK are suffering from Alzheimer's and 120,000 from Parkinson's, at a cost of £25,000 per year per patient. A study commissioned by the Motor Neurone Disease Association, to be completed by the summer of 2007, puts the cost of caring for someone with motor neurone disease in their final year of life at around £170,000. With around 1,600 people dying of MND each year, the total cost to the NHS and the social services is estimated to be more than £270 million a year.

More insidious than the economics is the human cost. For every one person suffering from degenerative disorders, let us say that there are 10 who care about that individual. Hence, by the middle of this century, as the numbers in the UK climb to around 2 million, we could be looking at 20 million lives that are completely devastated. So there is a huge and growing need—a need that is unmet by current treatments.

Stem cell therapy offers an exciting and realistic alternative. Stem cells can also offer a very valuable tool to gain a better understanding of the diseases themselves. The rationale is completely different from conventional treatments. The idea is not to treat the symptoms but to harness regenerative biological mechanisms, so that new cells are produced and ailing cells are supported by the natural chemicals they produce. This would amount to a true cure. It would not merely replace the chemicals that are lost as a result of cell death but actually replace the cells themselves, from the microscopic ball of some 200 that make up the early stage embryo.

Embryonic stem cells are extraordinary as they have the capacity to produce every single type of cell in the body. Many of the chemical and micro-environmental signals that determine their fate are now known. Thus we are able to make the type of cells that degenerate in Parkinson's disease, and the different type of cells that are lost, in a different part of the brain, in Alzheimer's. By introducing such cells into the appropriate environment within the brain, they will become those lost neurons.

What are the potential arguments against this approach? I shall restrict my comments to the often overlooked technical aspects. On the potential for immune rejection, this hazard can be overcome, as is being researched in Oxford, by immunotolarising patients or by immunosuppression. Such therapies have side effects but the risk-benefit ratio compared with that seen with conventional drugs is greatly shifted in favour of the therapeutic benefit.

A further potential problem is that stem cells in an uncontrolled state will proliferate and thereby constitute a tumour. To date, there is no clinical evidence that this has occurred with stem cell therapy and, in any event, strategies to overcome this problem are well advanced. For example, you can manipulate stem cells so that they only divide at a few degrees hotter than would normally be the case in the living brain. Another way would be to initiate cellular suicide genes if the implant attempts division.

Another issue is that the chemical messenger produced by the implanted stem cells may be excessive or not appropriate compared with the normal levels that will be produced. Again, this anxiety could be offset by considering the likelihood that brain cells, once they are in place, will behave like their naturally occurring predecessors and release chemicals at normal levels, as and when they are stimulated and interacting in their normal micro-environment. In any event, the excessive amounts of chemical messenger released as a result of drugs will be far more likely to go beyond the normal range seen with stem cells, and be far more widespread.

Finally, some might say that the method of delivery could be problematic, involving major brain surgery. In fact, this is not the case: with so-called stereotaxic neurosurgery, the procedure can be performed under local anaesthetic. Only a small hole is made in the skull and a fine needle is introduced, using precise three-dimensional co-ordinates—it is a little like drilling for oil. The diseased area can then be specifically targeted and the injection of cells kept as strictly localised as required.

In summary, we have reason to be confident that, although not without risks and downsides, stem cell therapy could be not just a treatment of choice but a chance to turn the clock back to a situation where we are harnessing the nervous system's natural mechanisms. For an ever-growing number of individuals condemned to a severely compromised lifestyle and an even bleaker future, there is, for the first time—and not just for those suffering from neurodegeneration but for everyone who cares about them—the very real prospect of hope.