All living things are made up of cells of various types. The human body contains trillions of cells. A collection of similar cells specialised for a particular purpose is called a tissue. For example, skin tissue is made of skin cells, muscle tissue is made up of muscle tissue.
Inside a cell is a compartment called the nucleus. This contains the genetic information which determines our personal characteristics such as what we look like and how we grow.
Stem cells
Stem cells are unspecialised cells at an early stage of development, which have not yet differentiated into any specific type of tissue. Stem cells are found in embryos, some types of adult tissue (eg bone marrow), the umbilical cord and foetal tissue. In theory stem cells can be influenced to turn into specific types of tissue, and used to treat patients whose tissue is diseased or damaged. Examples of their potential use include the treatment of diseased nerve tissue in patients with Parkinson's disease, strokes, and Alzheimer's disease; damaged skin tissue in people with burns; blood tissue in cancer victims. In theory stem cells could be induced to grow into a replacement organ, but this is at best a very long term prospect. Scientists consider that stem cells can be derived from a number of sources:
| � | From early embryos (blastocysts) created by in vitro fertilization (IVF), or created specifically for research using donated eggs and sperm. |
| � | From early embryos created by REPLACEing the nucleus from an adult cell into an egg with its nucleus removed (cell nuclear replacement, a form of cloning). |
| � | From the tissues of an aborted foetus. |
| � | From the blood cells of the umbilical cord at the time of birth. |
| � | From some adult tissues eg bone marrow. |
| � | From mature adult cells reprogrammed to behave like stem cells. |
Stem cells derived from early embryos appear to have the greatest potential to develop into most types of tissue. At this stage stem cells from other sources (adult stem cells) appear to be more limited in this potential, but current research may change this view.
Cloning and Stem Cells
The creation of human embryos by cell nuclear replacement technology (cloning) is an attractive prospect to stem cell researchers. A cloned embryo can be created using nuclear DNA from a cell of the patient, and allowed to develop into a ball of cells called a blastocyst. Stem cells can then be removed from the embryo, and used to develop a cell line for treating the patient.
This method of obtaining stem cells is attractive to researchers because stem cells can be obtained which have the same nuclear genetic makeup as the patient, thus avoiding problems of rejection by the patient's immune system. However there are serious ethical issues associated with creating a human embryo by cloning and then destroying the embryo by extracting stem cells.
Ethical Issues
The use of cell nuclear replacement technology to create human embryos has been described as �therapeutic cloning, or non-reproductive cloning, because it is being investigated for use in the treatment of illnesses, rather than for reproduction. The use of the term therapeutic cloning disguises the fact that this form of cloning results in an embryo which is then destroyed when stem cells are removed.
The use of so-called "spare" embryos resulting from IVF processes has been seen by some as an alternative to creating embryos for stem cell research, a view that ignores the fact that all human embryos, regardless of origin, are the early and most vulnerable stages of human life, and thus deserving of protection. The Pontifical Academy for Life has identified the following ethical issues in relation to the creation and use of embryos for stem cell research:
| � | The living embryo is from the moment of conception a human subject with a well-defined identity. |
| � | The embryo has a right to its own life, and therefore every intervention which is not in favour of the embryo violates that right. |
| � | No end believed to be good, such as therapeutic uses of stem cells, can justify an intervention of this kind. A good end does not make right an action which is in itself wrong. |
| � | The rights of the person must be recognised from the moment of fertilization, with the first of those inviolable rights being the right to life. |
In the United Kingdom the Expert Advisory Group which reported on all aspects of stem cell research noted that "in the long term the scientific view is that it will be possible to re-programme adult cells to make them behave like stem cells with the full potential of embryonic stem cells but without the morally more contestable need to create an embryo". Although this route to the therapeutic use of stem cells may take longer, it avoids the serious moral issues surrounding the use of an embryo as a means to an end, and the creation of embryos by cloning. However the use of embryo research to speed the development of adult stem cell technology is morally unacceptable for the reasons set out above. If speed is needed to ensure the relief of those who suffer, then the allocation of substantive resources to adult stem cell research is the appropriate means of reaching the desired goal.
The Human Assisted Reproductive Technology Bill is currently being considered by a Parliamentary Select Committee, and is expected to report in November 2004. This Bill would prohibit cloning for reproductive purposes but allow cloning to create embryos for the purpose of obtaining stem cells.