In the second of two articles on the opportunities and ethical dilemmas raised for medicine by the fast-developing world of genetics, Prof Peter Whittaker looks at questions Ireland will have to ask itself in the debate about the use of embryonic stem cells
'Medical revolution to 'eradicate infertility within decades'". "Human cells to make paralysed rats walk." "Blood brothers: how newly-born Jamie offers hope to Charlie." "Israeli scientists grow human kidney in mice." just some of recent newspaper headlines illustrating the medical revolution promised by stem cell research. However, some of this research poses serious moral and ethical questions.
The scientific basis of stem cell research is complex. It is nevertheless vital that we understand what is happening if we are to balance the possible health benefits and the moral considerations.
Stem cells are present in our bodies from the early embryo stage until we die. They can grow and divide to give new stem cells identical to themselves or to give the specialised (differentiated) cells that make up our bodies.
They play a critical part in our development, providing for each tissue of the body the particular types of cells that are needed.
An early embryo (blastocyst), just prior to implantation in the womb, comprises a sphere of cells surrounding a compartment containing a group of cells known as the inner cell mass.
The latter are embryonic stem cells (ESC) which can be cultured in a laboratory, and, given particular treatments, can be made to differentiate into muscle cells, blood cells, etc.
These stem cells are said to be pluripotent, meaning that they have the potential to give rise to any kind of cell found in the human body.
Adult human bodies are made up of something of the order of 50 million cells, only a minute proportion of which are stem cells. There are over 20 different kinds of adult stem cell. Blood stem cells will normally only give rise to the various types of blood cell, brain stem cells to the various kinds of brain cell and so on.
In comparison with embryonic stem cells therefore, these are more limited - they are consequently referred to as multipotent.
It is not easy to isolate adult stem cells and perhaps the best sources are bone marrow and umbilical cord blood. (Stem cells from infants or children are also considered to be "adult" stem cells.)
It is the capacity for stem cells to differentiate into cells typical of the various bodily tissues and organs that gives them their tremendous medical potential. The idea is that stem cells will repair tissues or organs that have degenerated or been injured.
There is every reason to be optimistic that this type of therapy will become a reality in the future.
Bone marrow transplants have been used for a number of years to treat some leukaemias. The patient's own bone marrow has first to be destroyed using X-rays. Then the donor marrow acts as a source of stem cells to replace the patient's own.
Similarly, foetal brain tissue, a source of brain stem cells, has, in clinical trials, been used with some success to treat Parkinson's disease. While these treatments are using donated tissues containing stem cells, it is probable that cultured stem cells will ultimately be used. For a single treatment of Parkinson's disease brain tissue from 4-6 aborted foetuses is required.
Other conditions for which stem cell therapy is also seen as potential treatment include Alzheimer's disease, heart disease, some types of diabetes, auto-immune diseases and spinal injuries. Current research indicates that pluripotent ESCs are likely to be the most successful type of stem cells to achieve these various therapies.
To establish an embryonic stem cell culture, destruction of a blastocyst stage embryo is necessary. There are hundreds of thousands of such embryos surplus to requirements for in vitro fertilisation (IVF) frozen in hospitals and clinics around the world.
The vast majority of these are destined for destruction as they reach an age where it is considered to be risky to use them for reproductive purposes.
It is possible to argue that it is ethically more desirable to use these embryos to make stem cells that might alleviate suffering or save lives than to destroy them unproductively.
On the other hand, for those who believe that human life starts at conception, the act of destroying a human life, even when the objective is good, is an immoral act.
The constitutional protection of the unborn in the Republic makes destruction of an embryo to establish a stem cell culture illegal. On the other hand, the use of imported ESCs could possibly be legal although still ethically questionable.
Ireland faces an important time of decision here. If all kinds of embryonic stem cell treatments are precluded in Ireland, we are going to have to face the possibility that therapies available elsewhere in the world will not be available here.
There is, however, a possible way around this. Recent research suggests that adult stem cells might be less restricted in their potential than previously thought. There is evidence that, treated appropriately, it may be possible to induce multipotent adult stem cells to revert towards pluripotency.
It would make very good sense if research into adult human stem cells were to be strongly encouraged in Ireland. Unless good, ethically sound therapeutic strategies based on adult stem cells can be established, the pressure will be on people to travel abroad for therapies based on not-so-ethically sound embryonic stem cells.
As well as the core issue of the status of the early human embryo, some current and some future developments in the stem cell field raise other ethical questions.
Just a few weeks ago, a British couple gave birth through IVF to a son, Jamie Whitaker, whose umbilical cord blood stem cells are to be used to treat an elder brother Charlie, who is suffering from a rare and possibly fatal type of anaemia.
Jamie's embryo was selected for implantation in his mother on the basis of tests of single cells removed from a number of early embryos, one of which provided excellent tissue match for Charlie.
It is probable that most people in the position faced by Charlie's parents would go down a similar road to save their child's life.
However, the necessary embryo selection procedure was turned down by the Human Fertilisation and Embryology Authority (HFEA), the body that regulates such procedures in Britain. The parents went to a Chicago clinic for the embryo selection.
The HFEA turned down the Whitakers' application because Charlie's anaemia was not genetically based and so it was very unlikely that any subsequent baby would suffer from the anaemia. Embryos would be rejected, not because they would suffer from a disease but solely because they had an unsuitable tissue type.
In principle, this procedure could not be carried out in the Republic, as there is a requirement to implant all IVF embryos formed.
The fear in Britain is that allowing selection of embryos on any basis other than serious genetically determined disease would open the door to "designer babies", babies selected on the basis of parents' wishes and whims.
One of the most amazing developments in the stem cell field is the recent demonstration that mouse embryonic stem cells can be made to develop into eggs and sperm. If these prove to be fertile and if the techniques work with human stem cells, this promises to play a major role in future human infertility treatments.
The source of the embryonic stem cells is again an ethical issue, but that is not all. With mice, it has been possible to convert male embryonic stem cells into egg cells, giving the prospect of babies with both a male father and a male mother.
O Brave New World . . .
• Prof Peter Whittaker is a member of the Irish Council on Bioethics and a researcher in the ESRC Centre for Economic and Social Aspects of Genomics (CESAGen) at Furness College, Lancaster University
His first article, on the ethics of gene therapy, was carried on Saturday, July 19th.