Bill of Rights in Action
Fall 2006 (22:4)
Stem-cell research promises someday to develop cures for currently incurable medical conditions. Does this noble goal justify research that involves destroying human embryos?
In 1978, the first so-called "test-tube baby" was born. This baby was conceived in a laboratory petri dish, not a test tube. An egg taken from the ovary of the mother was fertilized with the sperm of the father. When the fertilized egg divided into more cells to form a tiny, days-old embryo, a doctor implanted it into the mother’s womb. The embryo developed naturally to a fetus and finally a baby was born.
Called "in vitro (in glass) fertilization," this procedure allowed couples who were not able to conceive a child naturally to give birth to their own children. Since 1978, in vitro fertilization has been widely accepted throughout the world (although not by some religions).
In vitro fertilization has a significant "byproduct." Usually, a couple supplies enough eggs and sperm to create a number of embryos. As they divide into more cells in the lab, some embryos are healthier than others. After a few days, a doctor selects one or more of the embryos to implant into the mother. The rest are "spares" or surplus.
In some cases, parents have given their consent for researchers to conduct experiments on their unused embryos. In 1998, researchers were able to remove "stem cells" from donated fertility clinic embryos.
In young embryos (about 3–7 days old), two layers of cells form into a hollow ball called a blastocyst. The outer layer is destined to become the placenta, which attaches to the mother’s uterus and provides a means for nutrients to pass to the growing fetus. The inner layer consists of stem cells.
Stem cells are pluripotent. This means they have the remarkable capability of forming all the specialized cells of the body such as skin, muscle, nerves, and bone.
The Promise of Stem-Cell Research
Researchers discovered that when they removed stem cells from an embryo and put them in a petri dish with nutrients (called a culture), the individual cells re-divided indefinitely into "stem-cell lines."
Scientists experimented with these pluripotent stem cells, attempting to find out whether they could coax them into becoming specialized cells of the body.
If researchers in the lab can transform stem cells into somatic (body) cells, surgeons might be able to implant them into patients suffering from medical conditions caused by defective or damaged cells. Scientists also theorize that they may even be able to use stem cells to grow entire replacement organs. This is the future promise of stem-cell research.
One study concluded that more than 100 million Americans suffer from diseases, disorders, and injuries that might someday be treated or cured by stem-cell transplantation. For example, patients with heart disease, diabetes, birth defects, and severe burns could benefit.
The greatest potential for stem-cell therapies involves injury or loss of nerve cells that, unlike other body cells, cannot regenerate (reproduce) themselves. Currently, such conditions as severe strokes, spinal-cord injuries, and Alzheimer’s disease are treatable but incurable.
Parkinson’s disease is another example of the nervous system gone awry. Cells in the brain that make dopamine, a chemical necessary to transmit signals between nerve cells, die and do not regenerate. Patients experience uncontrollable shaking, lose the ability to walk, and finally are bedridden and die. Researchers are hoping to use stem cells to grow healthy dopamine-producing cells to implant into the brains of Parkinson’s patients.
None of these uses for stem cells in treating or curing human medical conditions exists yet. Researchers must overcome significant barriers. The biggest problem is to learn how to prompt human stem cells to form nerve or other specialized somatic cells as they do naturally in the developing embryo. Apparently, chemicals, electric fields, and interactions with neighboring cells in the embryo are necessary to turn stem cells into particular body cells. Researchers cannot do this yet with human stem cells. They have, however, done this with stem cells from a few animals.
If scientists are able to coax human stem cells to grow into a variety of body cells, a patient’s immune system still may reject them, the same problem that sometimes occurs with organ transplants today. Another risk is that transplanted cells might turn into deadly cancers or move to unwanted areas of the body.
Sources of Stem Cells
The controversy over stem cells arises from how scientists get these special cells. Right now, most come from surplus embryos donated by parents undergoing in vitro fertilization.
Fertility clinics routinely discard unused embryos or freeze them for future use by the patients who provided them. But the process of freezing and thawing embryos or keeping them frozen for a long period may destroy them. A tiny number of frozen embryos have been adopted for use by other childless couples and when born are sometimes called "snowflake children."
When researchers receive embryos from a fertility lab, the embryos are only a few days old. But they are alive and growing. The researchers destroy the embryo as a unified organism when they physically remove the stem cells to grow them in the lab. The pluripotent embryonic stem cells can never become babies since the placenta layer of cells is no longer present.
There are sources for stem cells other than embryos. So far, however, scientists have concluded that only embryonic stem cells can form virtually all the different cells in the body. Umbilical-cord stem cells mostly produce blood cells. Only a few stem cells from the umbilical cord can form other types of somatic cells. Bone-marrow stem cells continuously produce blood cells. At least some stem cells in adults seem to be able to generate more than one somatic cell type. But these stem cells are relatively few in number and have a limited ability to divide in a lab culture.
Umbilical-cord and somatic stem cells are not pluripotent and do not grow as vigorously in the lab as those found in a blastocyst. The one advantage of umbilical and somatic stem cells is that they do not require the destruction of embryos to get them.
What About Cloning?
In 1996, scientists cloned a sheep they named "Dolly." Cloning basically means genetic copying. It involves a process scientists call somatic cell nuclear transfer.
To clone Dolly, researchers took the genetic material, or DNA, from the nucleus of a somatic cell of one female sheep. They then inserted it into a second female sheep’s egg cell whose DNA had been removed. After receiving a careful burst of electricity, the egg began to divide into an embryo as if a male sheep’s sperm had fertilized it.
The researchers implanted the tiny embryo into the uterus of a third sheep that gave birth to Dolly. Theoretically, Dolly was a living genetic copy of the first sheep in the cloning process.
Since the birth of Dolly, scientists have cloned other animals. No one, however, has succeeded in cloning a human being. Moreover, researchers have discovered a high degree of abnormalities in cloned animals. For example, Dolly had arthritis at an early age.
Researchers, including the scientist who cloned Dolly, are increasingly turning away from "reproductive cloning," trying to make genetic copies of entire animals. Instead, they are researching the potential of using the cloning process as another way to produce animal and human stem cells.
Scientists theorize that they may be able to take DNA from a somatic cell, say a skin cell, of a Parkinson’s patient, insert it into a hollowed-out donated human egg cell, and grow an embryo. Scientists would remove stem cells from this embryo and prompt them in the lab to form dopamine-producing cells. Surgeons then would implant these cells into the brain of the Parkinson’s patient to replace those that had been lost.
This method, called "therapeutic cloning," would have the likely advantage of using a patient’s own genetic material to produce cells that his or her immune system would not reject. But troubling moral issues remain. Should researchers pay women to undergo the procedure necessary to secure their egg cells? Also, the embryo resulting from therapeutic cloning still will be destroyed when the stem cells are removed.
The Moral Debate
Strong moral objections are raised to stem-cell research that destroys human embryos. The Roman Catholic Church, long a foe of abortion, probably has developed the most comprehensive moral argument against human embryonic stem-cell research:
- The fertilized egg is a "human subject" at the moment of conception. From that point on, the embryo is a human individual with a soul and is part of God’s plan.
- The newly formed human has "moral status" and rights, especially the right to life. Experimenting on human embryos is a crime against their dignity and right to life.
- Harming the embryos or stopping their development is a "gravely immoral act."
- Working for the "common good" such as helping others who are suffering cannot justify evil ways to do it. Purposely destroying an embryo to remove stem cells for research or treating others is inherently wrong.
- Even making use of stem-cell lines that come from embryos destroyed in the past by other researchers is wrong. Such use still makes the current researcher complicit in the original immoral act.
Many Protestant Christian churches agree with the Catholic view of embryonic stem-cell research. Other world religions tend to differ over when the embryo acquires "moral status" as a human person with a soul.
Some ethical experts outside of religions also have serious doubts about continuing embryonic stem-cell research. They see danger in tampering with human life and argue it is not worth killing human embryos for research that may lead nowhere. They say it is better to limit research to umbilical and somatic stem cells.
Other ethical experts argue that it would be immoral not to continue with embryonic stem-cell research:
- Millions of people in the world may someday benefit from embryonic stem-cell research and treatments. Should the moral status of a group of 50–100 cells automatically outweigh that of a person suffering from Parkinson’s disease?
- The blastocyst is too "primitive" to be a person with full human rights. Even so, researchers should treat it with respect and use the stem cells only for good medical reasons.
- "Personhood" comes later in the development of the embryo and fetus when such things as feeling pain, brain activity, and taking on a human appearance become evident.
- It is not entirely true that researchers destroy an embryo when they remove its stem cells. The DNA in the stem cells lives on in the lab and hopefully later in the bodies of patients with severe diseases.
- Most stem cells for research now come from surplus fertility clinic embryos that are going to be discarded or will die naturally over time. Why not make use of them for the benefit of humanity?
Glossary of Stem-Cell Research Terms
blastocyst A hollow ball of cells or very early embryo that develops in the days after fertilization; it consists of stem cells and cells that will become the placenta.
cloning A method of producing theoretically genetic copies by transferring the DNA from a somatic cell of one individual into an egg cell without its DNA of another; the resulting embryo may be implanted into a mother’s womb for reproductive purposes or grown in a lab to harvest the stem cells for research.
in vitro fertilization Sperm are added to eggs in a fertility clinic lab, producing embryos for transfer into a mother’s womb; researchers remove stem cells from surplus in vitro embryos.
pluripotent The unique characteristic of embryonic stem cells that enables them to form all the specialized cells of the body.
somatic cells The specialized cells of the body such as those forming skin, nerve, and muscle, but not sperm and egg cells.
stem cells Mostly embryonic cells that can re-divide indefinitely and are pluripotent; umbilical and somatic stem cells are not pluripotent, but researchers are discovering that some may produce more than one type of somatic cell.
stem-cell line A group of stem cells that can re-divide indefinitely in a research lab; derived from an embryonic stem cell or some other stem-cell source like the umbilical cord.
Stem-Cell Research and U.S. Law
Given all the controversy over embryonic stem-cell research, few laws regulate it in the United States. As yet, even reproductive human-cloning research is not unlawful in the United States except in a few states.
On August 9, 200l, President George W. Bush announced a compromise for federal funding of embryonic stem-cell research. He issued an executive order that limited funding to research on about 70 embryonic stem-cell lines then in existence. The embryos that yielded the stem cells for these "presidential lines" had already been destroyed. Bush declared there would be no federal funding for stem-cell research that caused the "further destruction of human embryos."
Bush agreed that federal funding would continue for research on umbilical-cord, somatic, and animal stem cells. His executive order would not affect private companies, universities, or other institutions not relying on federal funds for their research.
Soon it became clear that only 20 or so of the 70 "presidential lines" were usable. Mutations affected some lines while others stopped growing. Some scientists argue that eventually all stem-cell lines grown in a lab will degrade and become useless for research unless replaced by new ones.
In 2006, Congress passed a bill allowing federal funding to cover new stem-cell lines created by donated surplus embryos from fertility clinics. President Bush, however, vetoed this bill in the presence of "snowflake children" born of embryos frozen at fertility clinics. "These boys and girls are not spare parts," Bush said. "They remind us what is lost when embryos are destroyed in the name of research."
Meanwhile, some states and private companies are funding embryonic stem-cell research without the federal restrictions. In 2004, California voters approved $3 billion in bonds to fund stem-cell research. In the 2006 election, Missouri voters amended their state constitution to allow stem-cell research. Outside the United States, governments and companies are also competing to achieve the promise of stem-cell cures.
For Discussion and Writing
1. What do you think is the strongest argument for each side of the stem-cell research controversy?
2. Why do researchers think embryonic stem cells are better than umbilical-cord and somatic stem cells?
3. Some believe that the United States should outlaw all cloning research. What is your view on this? Why?
For Further Reading
Gibbs, Nancy. "Stem Cells, the Hope and the Hype." Time. 7 Aug. 2006: 40-46.
Ruse, Michael and Pynes, Christopher A., eds. The Stem Cell Controversy, Debating the Issues, 2nd ed. Amherst, N.Y.: Prometheus Books, 2006.
A C T I V I T Y
A U.S. Policy on Embryonic Stem Cell Research
1. Form small groups to discuss U.S. policy options on embryonic stem-cell research.
2. After discussion, each group should choose one of the policy options and prepare a defense of it based on information from the article.
3. Each group should finally present its policy choice and defense to the rest of the class.
A. Prohibit federal funding of all embryonic stem-cell research while encouraging only research that does not destroy human embryos.
B. Permit federal funding of research only on embryonic stem-cell lines formed by surplus fertility clinic embryo stem cells that existed before August 9, 2001. These are the "presidential lines" that President Bush made eligible for federal funding on that date.
C. Permit federal funding of research on stem-cell lines created on an ongoing basis from surplus fertility clinic embryos.
D. Permit federal funding of research on stem-cell lines created on an ongoing basis from surplus fertility clinic embryos as well as from embryos created by cloning for research.