No excuse for human embryonic stem-cell research

UNDER THE MICROSCOPE:HUMAN EMBRYONIC STEM-CELL (HESC) research is back in the news in Ireland. On November 26th, a Stem Cell Bill was introduced in the Seanad aimed at preventing research in Ireland that would result in deliberate destruction of human embryos.

Whether or not you consider human embryonic stem-cell research to be permissible depends on your evaluation of the ethical status of the human embryo. Science alone cannot settle this question, but it does provide information essential to forming an informed opinion.

Biology tells us that an individual human life begins when the sperm unites with the egg to form the zygote, the genetically unique, complete and self-directing earliest embryonic stage. The zygote is the beginning of a continuum of development - zygote-foetus- baby-child-adult-older person - that ends in death. Each point on this continuum is human and has the properties appropriate to that point. Thus, the early embryo contains stem cells with the appropriate plasticity, enabling them to develop into the 200 specialised cells of the human adult. Such profound plasticity does not exist at later stages along the continuum.

The scientific facts are clear, but science does not deal in values and cannot assign a moral value to any point on the continuum. To decide this we must turn to ethics and this is where disagreements arise. I will give you my personal position. I allow biology to influence my thinking as much as possible. Since we are dealing with a unique human individual from the zygote stage, I believe we must assign him/her (the sex is specified) a basic moral value that applies at all stages of development. I believe that the minimum this can entail is the opportunity to develop normally along the continuum without deliberate intervention from adults to halt this development.

Others, including many biologists, look at the continuum of human development and apply a sliding scale of moral value. The human is considered to gradually increase in value as s/he develops from early embryo to baby. People who hold this position believe that, although the early embryo merits respect, this can be overridden by considerations of "greater good", in this instance the promise that human embryonic stem-cell research will cure disease. But, unfortunately, the process of obtaining embryonic stem cells for research kills the embryo.

Biology tells us the early human embryo is human, not partly human. Nevertheless, I can appreciate how some people feel that s/he, an undifferentiated little ball of cells, is not entitled to the same protection as a baby. But surely this is to discriminate on the basis of appearance and size. This is a wonderful "little ball of cells". The embryo is not sentient or conscious, but has great powers appropriate to its stage - the power to self- develop into the conscious and sentient. It is this fully human characteristic that makes the early embryo so valuable for research.

Now let me turn to the "greater good" that might be served by killing the embryo - curing human disease. The public is told that human embryonic stem-cell research is a reliable route to discovering early cures for many distressing diseases. This is an over-optimistic projection. Certainly HESC research has great potential, but this potential does not exceed the combined potential of two other types of stem-cell research that pose no ethical problems. I refer to adult stem-cell research and the new induced pluripotent stem-cell (IPSC) research.

Adult tissues contain stem cells. They are not as flexible as embryonic stem cells, but they are much more reliably manipulated. Almost all medical stem-cell advances to-date have come from adult stem-cell research. The most recent success reported was the woman who had a large section of her windpipe replaced by a new section grown from adult stem cells. On the other hand, no clinical trials are in progress worldwide using embryonic stem cells because researchers do not yet know how to reliably control them.

There has recently been a dramatic breakthrough in stem-cell research. Scientists have discovered how to make a new type of stem cell, the induced pluripotent stem cell (IPSC), that is just as potent as the embryonic stem cell. IPSCs are made by genetically reprogramming ordinary body cells, eg skin cells.

A few years ago it was possible to argue that HESC research alone had more potential than adult stem cells, then the only other stem-cell research, but the new IPSC research looks just as powerful as HESC research, and without any ethical problems. Doing HESC research now merely adds another option in addition to adult stem cells and IPSC. In these new circumstances is HESC research worth its heavy ethical baggage? I think not.

• William Reville is associate professor of biochemistry and public awareness of science officer at UCC - understandingscience.ucc.ie