Why Stem Cells Are Used in Medicine

1. Many diseases are caused by a particular type of cell dying or failing to work.
2. Type 1 diabetes follows the loss of the insulin producing cells in the pancreas, and Parkinson's disease follows the loss of certain nerve cells in the brain.
3. Ordinary drugs treat the symptoms, because a damaged cell cannot be repaired by medication.
4. Stem cells offer a different approach, because they can differentiate into the missing cell type and replace what has been lost.

The Benefits of Using Stem Cells

1. Damaged tissue can be replaced rather than simply managed, so the treatment addresses the cause of the disease.
2. Conditions that currently have no cure, including paralysis after a spinal injury and some forms of blindness, could be treated.
3. Stem cells grown from a patient's own cells are not rejected, so there is no need for lifelong immunosuppressant drugs.
4. Organs could be grown from stem cells, which would remove the shortage of donor organs and the wait for a matched donor.
5. Embryonic stem cells taken from spare embryos from fertility clinics use tissue that would otherwise be destroyed.
6. New drugs can be tested on human tissue grown from stem cells before they are given to people, which makes early trials safer.

The Risks of Using Stem Cells

1. Tissue rejection. Stem cells from a donor carry different antigens, so the patient's immune system may destroy them.
2. Uncontrolled division. Stem cells divide readily, and cells that keep dividing after transplant can form a tumour.
3. Infection. Stem cells are grown in culture, and a culture contaminated with a virus or bacterium would pass that infection to the patient.
4. Unpredictable results. Transplanted cells may differentiate into the wrong cell type or fail to differentiate at all.
5. Long term effects are unknown, because most stem cell treatments are still at the trial stage and patients have not been followed for decades.
6. Cost. The procedures are expensive and specialised, so an overstretched health service can treat only a small number of patients.

The Ethical Issues

1. Taking stem cells from an embryo destroys that embryo.
2. Some people believe that an embryo is a potential human life from the moment of fertilisation, so destroying it is destroying a life.
3. Others argue that a few day old ball of cells has no nervous system and cannot feel anything, so its potential does not outweigh the suffering of a living patient.
4. The embryo cannot give consent, and the donors of the egg and sperm must consent to its use in research.
5. Religious and cultural beliefs lead different people to weigh these arguments differently, and there is no single agreed answer.
6. Adult stem cells avoid the objection entirely, but they can only differentiate into a limited range of cell types.

How the Use of Stem Cells Is Controlled

1. Stem cell research in the United Kingdom is regulated by law and licensed by a national authority.
2. Embryos used in research must be spare embryos from fertility treatment, donated with the informed consent of both donors.
3. An embryo used in research cannot be grown beyond 14 days, the point at which the nervous system starts to form.
4. Regulation is what allows the research to continue while setting limits that most people find acceptable.

Reaching a Judgement

1. A good evaluation weighs the benefit to patients against the status of the embryo and the medical risks.
2. The strength of an argument depends on the source of the cells, so adult stem cells and embryonic stem cells should be judged separately.
3. The evidence base also matters, because bone marrow transplants are established while brain repair is still experimental.
4. A conclusion should state a position and give the reason for it, rather than listing points on both sides and stopping.