GLOBAL ECONOMIC VIEWPOINT
STEM CELLS FROM CLONED EMBRYOS ARE KEY TO TREATING DISEASE
Ian Wilmut, a professor of reproductive science at the University of Edinburgh and a visiting scientist at the Roslin Institute in Edinburgh, was the leader of the team that cloned the sheep Dolly.
By Ian Wilmut
EDINBURGH, Scotland -- Extraordinary opportunities to study and treat human diseases are now possible thanks to the recently acquired ability by a team of South Korean scientists to derive stem cells from cloned human embryos. Because these cells form all of the tissues that make up an adult, they provide a chance to study normal human development in the laboratory, to define the abnormalities associated with inherited disease and, in time, perhaps to treat diseases that presently have no effective treatment.
In addition to providing new means to study inherited diseases, cloned stem cells will offer treatments for a large number of degenerative diseases. Parkinson's disease, diabetes, stroke, Alzheimer's disease and spinal cord injury, among many other conditions, all reflect damage to cells that are neither repaired nor replaced. There is no fully effective treatment for any of them. The hope of the next few decades is that treatments will become available by delivery of cells into the patient to replace those that are lost. The first trials can be expected within a few years, but it will take a long time to realize the full potential of this approach.
Cells derived from cloned embryos offer a unique advantage for such a therapy. If the cells are derived from an embryo donated at a fertility clinic, they would almost certainly be rejected by the patient unless he or she took immunosuppressive drugs. While these drugs are effective in preventing rejection, they have significant side effects, including an increased risk of infection. By contrast, if the genetic information from the patient is used to produce a cloned embryo from which the cells are derived, the cells would be immunologically matched to the patient.
In discussing stem cells, researchers face criticism from people for whom the idea of producing and using a human embryo is deeply offensive. Different, sincerely held views must be recognized and accepted. There is an urgent need for an informed debate about what we consider to be the critical human characteristics, just as there was an equivalent debate about the end of life when decisions were first made to remove healthy organs from accident victims who were brain dead. Guided by physicians, society came to accept that it is ethical to turn off machines that maintain some bodily functions if integrated brain function was no longer present in the patient.
The fundamental question concerns the nature of the blastocyst from which stem cells are derived. This early embryo is a ball of cells smaller than a grain of sand. It cannot be seen without the aid of a microscope. While it has the potential to become a person, it lacks the fundamental human characteristics of being conscious and aware. Indeed it will be several weeks before a nervous system develops that could allow the developing conceptus to feel pain or be aware. This is the reason why I, and others, propose to carry out research with cloned human embryos. A majority of people accept this view of early human development and support the use of cloning.
At the Roslin Institute, we have chosen to study amyotrophic lateral sclerosis ( ALS) —also known as Lou Gehrig's disease — but this is just one of many inherited diseases that can now be studied in this way. ALS is a family of related diseases that affect the nerve cells along which the brain sends instructions to the muscles. Degeneration of these motor neurons leads to weakness and wasting of muscles. This generally occurs initially in arms or legs — a patient just recently told me that he had now lost the use of his arms. Consider the effect of that situation. Someone would have to dress you, feed you, take you to the toilet; in fact you would require help for almost everything.
ALS is a relentlessly progressive disease for which there is no treatment. Typically, it first affects people around the age of 54 and is fatal within four years (the person becomes unable to breathe). Thousands of people die each year because of the disease. We propose to study ALS in human cells because, despite research in animals over several years, the way in which the disease develops is still not understood.
Researchers will be able to work with new cells in the laboratory that are identical to those of a patient, providing opportunities to study the development of the disease that are not available in any other way. To achieve this, cells will be derived from cloned embryos.
In approximately 10 percent of cases, ALS runs in families;that is, it is inherited. In 20 percent of these families, an error has been found in a specific gene, but the genetic error in the other 80 percent of inherited cases remains unknown. The genetic information from a cell of such a patient will be introduced into an egg from which the genetic information has been removed. This information confers almost all of the characteristics of the resulting stem cells, including the fact that they are vulnerable to ALS.
In this way, for the first time, motor neurons affected by ALS will become available for study. Comparison between the cells of an ALS patient and those not liable to this disease will provide new understanding of the differences between ALS and normal cells.
Testing of new drugs will be transformed by the availability of ALS cells. At present, it takes months and requires considerable cost to test a single drug in experimental animals that have a disease similar to ALS. By contrast, laboratory screening of drugs will be both quicker and cheaper, as hundreds of tests will be able to be carried out in the time taken for one animal test. The immediate hope is that drugs will be identified that can prevent further degeneration and allow patients to live full lives.
We should be excited by these opportunities as they have the potential to transform key aspects of medicine. Anyone who has cared for a person with any of these inherited or degenerative diseases knows only too well the great need for new treatments. The opportunities described above can — and can only — become available through stem-cell cloning.
(c) 2005, Global Viewpoint