Stem cell research is one of the most controversial topics in modern society, yet many do not know the basic facts about it. Stem cells may be key to possible cures for a wide range of diseases. However, the research also poses thorny ethical questions that make us confront the basic meaning of human life and human value.
Why the excitement about stem cells? The diseases that plague us most in modern society are degenerative diseases such as heart disease, stroke, chronic lung disease, Parkinson's, and diabetes. In these diseases, only part of an organ is damaged. Stem cells might repair or replace the damaged part of the organ, thus restoring full function; the term used is regenerative medicine.
The unique properties of stem cells make this regeneration possible. A stem cell can grow and replenish itself, maintaining a pool of undifferentiated cells, and it can respond to specific signals-hormones, for example-to produce a specialized cell type, such as a heart or brain cell. This would allow stem cells to repair damage from disease, replacing damaged tissue.
There are numerous sources for stem cells, and this is the basis of the debate. Embryonic stem cells are taken from early embryos, 5 to 7 days after conception. In normal development, embryonic stem cells go on to form all of the tissues of the adult body. In a laboratory culture, the cells can be grown for extended periods of time. However, extracting embryonic stem cells destroys a human embryo, hence the ethical qualms about this source. Despite the enthusiasm surrounding them, embryonic stem cells have significant disadvantages for potential treatment of disease, including the tendency for tumor formation, immune rejection, and genetic instability. They also are difficult to grow and difficult to guide into forming a single desired cell type; they have shown poor success at treating animal models of disease, and have not been used for a single patient. As a side issue, some propose producing cloned human embryos for matched transplant cells. This theory is not supported by any scientific literature however; and it actually has failed to work in mice.
Another source, called adult stem cells, includes cells found in most or all tissues from birth onward, as well as in umbilical cord blood and placenta. It was previously thought that adult stem cells were few in number, difficult to isolate and grow, and could form only a few tissues. However, a wealth of research in the last few years has disproved all of these dogmas. Although the public has heard little about their successes, adult stem cells have already shown effectiveness in treating disease. In animal models, adult stem cells have successfully treated conditions such as diabetes, Parkinson's, stroke, heart disease, and spinal cord injury. Moreover, adult stem cells already have successfully treated human patients-against cancer, multiple sclerosis, lupus, immune deficiencies, and sickle cell anemia. They have repaired cartilage damage, grown new corneas to restore sight to blind patients, grown new blood vessels to rescue legs from gangrene, repaired stroke and heart damage, and successfully treated patients with Parkinson's disease. The adult stem cells do not produce tumors and have little problem with transplant rejection, especially when using the patient's own cells.
The ethical question forms the real root of the stem cell debate, specifically the question of the moral status of the human embryo. Scientifically and genetically, the embryo is a human being, its species is Homo sapiens, and the organism already has a gender. But how do we as a society view this tiny entity? Is the young human a person or a piece of property? Views on embryo status range from considering it simply a clump of cells, to the idea that it is a form of human life deserving of profound respect. Some believe it is only a potential person; others that it should receive the benefit of the doubt with the full ethical consideration given any other human being.
When considering use of human embryos as raw materials, careful deliberation is required. Factors to consider include the patients who might benefit from research, the embryos that might be destroyed, the facts versus the claims, research alternatives that might actually be more promising, and even the economics of the research and its potential availability to all patients. Another consideration is the potential slippery slope-will use of human embryos for research potentially lead to use of other humans? The possibility of forming embryonic stem cells via parthenogenesis, or generating eggs, sperm, or whole new embryos from embryonic stem cells, only increases the number of ethical questions regarding formation of embryos.
The debate poses basic questions that all of us must address, not just in terms of human embryos but in our view of any human life. What does it mean to be human? To whom do we choose to assign value? Who will decide, and who will benefit? The decisions made now can affect the future of humanity.