The Hindu : Opinion / Leader Page Articles : Stem cells, cloning, and ethics

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Thursday, Dec 09, 2004

Opinion

Opinion - Leader Page Articles

Stem cells, cloning, and ethics

By Lewis Wolpert

There is no moral justification for banning research using embryonic stem cells. It offers great hope to all those suffering from a wide variety of illnesses.

WHY SHOULD the idea of making stem cells from human embryos lead to passionate opposition and attempts to ban it? Is it dangerous? And why would anyone want to create such cells in the first place?

Stem cells are cells that have the capacity for renewal as well as the capacity to give rise to specialised cells, such as nerve and muscle and blood cells. We have in our bodies a number of stem cells, which are present in very small numbers in certain tissues. There are stem cells at the base of our skin which divide and one of the two daughter cells can differentiate to replace the skin cells that we lose daily, while the other remains a stem cell. Again, there is a continual loss of cells in our gut, and these are replaced by dividing stem cells one of whose daughters differentiate into functioning gut cells. In our bone marrow there are stem cells that give rise to blood cells. These stem cells multiply and replace lost throughout our lives. But in the body their potential to give rise to cells other than those for the renewal of the local tissue is totally restricted. By contrast stem cells derived from the early embryo have a much greater potential.

We all have our origin in the fertilised egg, a single cell. The egg divides to give rise, eventually, to many billions of cells. At an early stage there are only a few hundred cell. Some of these cells are pluripotent, which means that they can give rise at later stages to any of the specialised cells of our bodies such as skin, nerve, blood and muscle cells. It is possible to separate the cells at this stage and place them in a culture dish where they are very happy, and grow and multiply. Under certain conditions these cells can be made to differentiate, that is change, into cells of a variety of different types such as muscle, nerve and skin. Since they can both multiply and give rise to different kinds of cells they are referred to as stem cells, and since they come from the early embryo, they are called embryonic stem cells.

The current excitement about embryonic stem cells is their ability to give rise to different cell types — this might provide a powerful means to repair damage to tissue in the body such as the heart, brain, spinal cord or pancreas. It should be possible, it is hoped, to so engineer stem cells that they could replace damaged cells in the pancreas that normally secrete insulin, and whose damage results in diabetes. Again could stem cells replace damaged cells in the spinal cord that have led to paralysis? Both pancreatic and nerve cells have been made from stem cells in culture, but making them functional in the right place in the body is a very difficult problem. One of the major problems in using embryonic stem cells to cure a patient comes from the body mounting an immune response to the foreign cells — they were taken from someone else's embryo — and so rejecting and destroying the implanted cells. One solution to this problem is to use therapeutic cloning so the DNA in the transplanted cells comes from the patient.

Cloning hit the headlines with the sheep Dolly being created from an unfertilised egg into which the nucleus of a cell from a mammary gland culture was injected. It is the nucleus in the cell that contains the DNA and genes that code for the proteins that determine the behaviour of cells. In normal development the sperm brings in the genes from the father to join with those of the mother, but a nucleus from some adult cells of the patient might support development of the embryo. Then embryonic stem cells would be taken from that early embryo, and used to treat the patient, and since these cells have the same genes as the patient there would be no immune rejection. This therapeutic cloning only lets the early embryo develop, and is never intended to give rise to a person.

Another approach is not to use embryonic stem cells with their immunological problems but to try to use adult stem cells, which may have greater potential than previously thought. A much-investigated stem cell is that found in the bone marrow; it replaces blood cells continuously. These stem cells from mice can be grown in culture, and there have been reports that when injected into adult mice could give rise to several cell types such as muscle and nerve cells. But later reports questioned this and showed that the stem cells merely fused with normal cells from those tissues giving the illusion that they had actually given rise to either muscle or brain. Similarly, reports that stem cells from the nervous system could give rise to blood cells have been questioned. However, there are reliable reports that embryonic stem cells can rescue the development of embryos that would give rise to animals with severe heart defects.

In spite of the technical difficulties, there is still great hope that the problems could be overcome as more is understood about the nature and behaviour of stem cells. One possible danger is that stem cells not under proper control could give rise to cancer cells, and this has to be studied with great care. But are there ethical issues?

In the United States it is forbidden to use Government funds to make human embryonic stem cells. The reason given for this is that in order to isolate the stem cells from the early human embryo the embryo has to be broken up and effectively destroyed. Since it is believed by several religious groups and the American Government that the fertilised egg is already a human being this destruction of the early embryo is effectively killing a person. But what is the justification for believing that the fertilised egg or the early embryo is already a human being? This is a religious belief for which there has never been any justification based on biblical or other religious writings, and which does not have any scientific justification. For example, one does not know if the early embryo will develop into one or two persons as twinning is possible at a later stage.

There is also a fundamental inconsistency in the reasoning of those who would ban stem cells being made from early embryos while at the same time supporting assisted reproduction by in vitro fertilisation (IVF). IVF, which is widely used in the U.S., involves the destruction of many early embryos. There is no moral justification for banning stem cell research using embryonic stem cells. On the contrary, it offers great hope to all those suffering from a wide variety of illnesses. It is necessary to understand stem cells better — the difficulty is that they are both very complicated and very clever. We must be patient.

But there is another ethical issue related to these new techniques for altering the behaviour of cells and embryos. Does reproductive cloning really open up a slippery slope that could lead us to real dangers? With reproductive cloning a woman would donate her egg to the person who would want to be cloned, either a man or a woman. Cells would be taken from suitable tissue and the nucleus from one of them put into the egg, which would then have to be put back into some woman so that it could develop in her womb. If the child developed normally — it is a very big if — it would effectively be an identical twin of the donor of the nucleus, but clearly many years younger. I fail to see what possible ethical issues this raises as the child will be exposed to a quite different environment as it grows up compared to its older twin. That the child would grow up to have the identical personality to the older twin is just nonsense. Claims that there would be excessive pressure on the child to be like the twin raises no new issue, as there are many different pressures on children. Much more serious is that all the evidence that shows that if the cloned embryo did give rise to a baby, the child would almost certainly suffer from severe and disabling abnormalities. There is not a single reliable report of any animal close to humans, like apes, having been cloned. It just does not work, and the embryos fail to develop. Claims from certain groups that they have actually cloned a human should be dismissed out of hand.

Why the possibility of human reproductive cloning should have raised so much discussion is really puzzling. Perhaps it is the fear of interfering too much with natural birth. Perhaps, too, it is linked to the image of Mary Shelley's Frankenstein creating a monster. But there are humans whose behaviour is monstrous and has nothing to do with cloning. If cloning could be demonstrated to be safe, in that the child would be normal, then there are no new ethical issues I can identify.

(The writer is Professor of Biology, Department of Anatomy and Developmental Biology, University College, London.)

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