Medical scientists routinely grow human cells in plastic culture dishes and these cells, often derived from human cancers, are a mainstay of biomedical research. But such cells do not have the same genetic makeup as cells in our body. Remarkable exceptions are human stem cells, particularly those derived from early-stage embryos. These cells have the potential to develop into any human tissue, offering possibilities for cell-replacement therapy for diseases like Parkinson's, Alzheimer's, diabetes, degeneration of heart, muscle and brain cells and many others.
These cells were first reported in 1998, a very short time ago in medical research. Since then, comparatively little work with these cells has occurred. The conditions to convert them into specific tissue types, such as insulin-producing cells, are now only beginning to be elucidated. Careful and often frustratingly slow laboratory studies are needed. Treating infectious diseases like HIV is a far simpler concept than the idea of treating human disease like diabetes with stem cells. Yet it took about 15 years to begin to treat AIDS, and there is still much to do. Stem-cell research has many years to go before we may reap benefits.
The moral path is to continue research, not prevent it. Human stem cells come from fertilized eggs that otherwise would be discarded. Interestingly, they are products of another remarkable medical advance called in vitro fertilization that also was very controversial when it first started. By now we tend to forget that the first test-tube baby was born in 1978 in England and, although now an accepted medical practice, such treatment was controversial until the public understood the medical need and the nature of the procedure. IVF was developed to treat human reproductive dysfunction that affects about 10 percent of individuals at reproductive age, both male and female, and is now in great demand.
In this procedure, sperm and eggs are isolated from the donor parents and the eggs fertilized in a laboratory. The fertilized egg begins to divide once every day to produce initially two cells, then four and so on. After five to seven days, a tiny mass of cells (about 32) called a blastocyst is implanted in the woman. Often multiple implantations are required to obtain a successful pregnancy. Thus, for any given couple, IVF clinics save more fertilized eggs than they need. Most of these cells are stored and will never be used.
Before implantation, a few cells from the blastocyst stage of development are destined to become the developing fetus, the remaining contributing to the placenta. The few cells obtained from the inner part of the blastocyst that are destined to become the fetus can be placed in special culture conditions and go on to divide forever. They have the unique properties of having normal, unperturbed full set of chromosomes and the capacity to be converted into virtually any tissue type. Pancreas cells that produce insulin for diabetics, brain cells that produce dopamine for those with Parkinson's, or brain cells for those who have suffered a stoke are but a few possibilities.
Excess blastocysts that have not been implanted but stored for very long periods in IVF clinics will undoubtedly lose their ability to be viable for human reproduction. The choice comes down to using this valuable material for medical research and maybe treating a now incurable disease, versus throwing out the blastocysts for no gain.
Some who believe that destroying a blastocyst is equivalent to aborting a fetus propose using stem cells derived from adult tissues, rather than embryonic stem cells. The problem is we do not know enough about either embryonic or adult stem cells to bet the farm and future on adult stem cells. So research on both must continue.
Many opponents also mistakenly equate stem-cell research with human cloning. There is a big difference. The material inside of stem cells that has developed into a particular tissue type and been placed into a patient will not be passed on to the patient's children. Your pancreas that produces insulin does not appear in the next generation. In cloning, as occurred with Dolly the sheep, embryonic or adult cells are used to produce a whole individual that can reproduce. Human cloning is a separate issue for which there is virtually no support in the scientific community.
Religious opposition to embryonic stem cell research is primarily based on the arguments about sanctity of human life. Clearly, however, human life comes in many forms. I suggest that people and families with horrible, but potentially treatable diseases are far more important than frozen blastocysts with little or no potential to become viable human beings. Their only potential is only by being successfully implanted. Unused blastocysts in IVF clinics, obtained with informed consent from the donors, can provide all the stem cell lines needed to continue important and morally justifiable research. There is a need to make more stem cell lines, as there are a limited number that have been developed.
The very nature of research is probing the unknown. Sometimes new scientific developments seem to go far beyond what people are willing to accept. But now most of us are comfortable with in vitro fertilization. In the United States alone, IVF has helped parents bring over 45,000 babies into the world since 1981. Stem-cell research has the potential to help millions of people each year. But without research we will never get there.
Bruce Stillman
Editorial appeared as written in 7/15/2001 issue of Newsday.