The science and politics of stem cells

In late November of last year, scientists at Advanced Cell Technology, Inc. (ACT), in Massachusetts announced that they had created a human embryo through a procedure known as “somatic cell nuclear transfer” or, in popular parlance, cloning. The company’s president assured the public that the embryo was not created for reproductive purposes. Instead, he explained that his company’s achievement heralded the dawn of a new era of therapeutic cloning, a procedure that might eventually yield a “limitless source of immune-compatible cells for tissue engineering and transplantation medicine.”

Although some conservatives assailed ACT’s breakthrough as a step down the path toward human reproductive cloning, many scientists recognize that there is a profound utilitarian and ethical difference between reproductive and therapeutic cloning. The intent of therapeutic cloning is to create human embryos for the sole purpose of removing the stem cells, which would in turn be used for biomedical research that might someday lead to cures for a wide range of human diseases.

As much of the American public is now aware, embryonic stem cell research is a controversial scientific, cultural, and political subject. Enemies of stem cell research have tried to link it inextricably with human cloning, primarily to discredit it in the eyes of a scientifically misinformed citizenry. But what is it about stem cell research that makes it such a political hot button? When a vast majority of scientists argue that stem cells may hold the key to exciting new therapies capable of eradicating some of the most pernicious diseases and disorders plaguing humanity, one would think that support for stem cell research would easily gain broad political and financial support.

Yet, as the heated public debates over stem cells and human cloning reveal, the future of embryonic stem cell research in the United States is not altogether secure. Careful consideration of the nature of the dispute, including the crucial ethical and religious questions involved, might help to explain why.

Stem cell types
The opposition to embryonic stem cell research is linked directly to the very nature of the cells and the manner in which they are harvested. While there are 220 different types of cells in the human body, stem cells are unique precursor cells found in all animals. They divide and mature into many different tissue types (e.g., heart, muscle, or brain) and can constantly reproduce.

There are important distinctions between different types of stem cells. Totipotent stem cells are cells that can give rise to a fully functional organism as well as to every cell type of the body. Pluripotent stem cells may give rise to any tissue type, but not to an independent organism. Multipotent stem cells are more differentiated and less plastic. They can give rise to a limited number of tissues. A familiarity with these differences is essential not only to a more complete understanding of stem cells, but to a better appreciation of the ethical and religious controversy surrounding stem cell research.

The science of stem cells is more than 30 years old. Stem cells were discovered in mice in 1971, and certain limited stem cell therapies have been in use for years. For example, cancer patients receive bone marrow transplants in which stem cells that give rise to blood cells are administered to restore tissue destroyed by high-dose chemotherapy. Yet it was not until recently that scientists understood stem cells well enough to imagine the myriad possibilities for disease treatment. In 1998, researchers at Johns Hopkins University and the University of Wisconsin found a way to harvest stem cells from human embryos and grow them in the laboratory. By mid-2001, scientists had learned to develop stem cells into more than 110 types of human cells.

The stem cells that come from early-stage human embryos are termed human embryonic stem cells (ES cells), and they are believed to offer the most therapeutic potential because of their pluripotent character. The normal embryo contains about 100 ES cells that exist for one day and then begin to develop into more advanced cell types. Thus, the cells must be removed quickly from the embryo before further development occurs. Not surprisingly, this procedure kills the embryo. ES cells appear to replicate indefinitely, they are genetically normal, and once again (most importantly) they are pluripotent. Most scientists believe that research on these cells may yield treatments for diseases and disorders as disparate as Type I diabetes, Parkinson’s disease, hepatitis, muscular dystrophy, and various forms of cancer.

Although ES cells are the most heralded variety of stem cell, there are others. Embryonic germ cells (EG cells) are derived from human fetal tissue, and experiments suggest that they can form the three germ layers that make all the organs of the body.

Yet the potential uses for these cells are thought to be considerably more limited, primarily be cause the cells are much further along in development than ES cells (5–9 weeks, as opposed to approximately 5 days).

Although fetal tissue was the initial source of human stem cells, many scientists question the feasibility of the large-scale manufacture of products using EG cells. That is, in part, because these cells are harvested from aborted fetuses, a procedure that is legal but unpopular among some conservative religious and political groups.

The least politically controversial types of stem cells are termed adult stem cells. These stem cells are found in fully developed tissue, and their function is to repair and replace body tissue. Adult stem cells are multipotent, and the number of tissues they can regenerate is quite limited compared with the capabilities of ES and EG cells.

Nevertheless, research on adult stem cells is more advanced than inquiry into the other two types. Mesenchymal stem cells (MSCs) are adult cells that maintain bone, muscle, fat, and a few other tissue types. FDA-approved clinical trials, in which scientists are attempting to use MSCs for bone and cartilage replacement, are already under way.

Still, most scientists recognize that adult stem cell therapies cannot replace therapies that may be obtained from ES cells. Many cells of medical interest cannot yet be obtained from adult-derived cell types. And production of large numbers of adult stem cells is much more difficult than is the case for ES cells. Although the use of adult stem cells is less contentious than that of ES cells, it is not expected that they alone will provide answers to the most important questions in biomedical research.

“Political science”
On August 9, 2001, President George W. Bush announced his decision on the federal funding of embryonic stem cell research, and he pleased neither scientists nor the stalwart opponents of research. At issue was whether the U.S. government would fund research that involved stem cells that were acquired by the destruction of human embryos. Since 1996, the federal government has disallowed financial support for the destruction of embryos. This ban would not necessarily prevent funds from going to scientists who worked with stem cells, however, if researchers did not extract the cells themselves. Thus, federally funded scientists who wished to work with ES cells had to acquire the cells from private laboratories, where the destruction of embryos and the ES cell extraction had already taken place.

The government was preparing to issue its first embryonic stem cell research grants when George Bush took office. The Bush administration initially banned stem cell research funding until a definitive policy was developed. During the eight months from Bush’s inauguration until the announcement of his decision, the public debate grew loudest. The scientific community endorsed federal funding for ES cell research, as did many disease advocacy organizations (e.g., the Juvenile Diabetes Research Foundation International and the ALS [amyotrophic lateral sclerosis] Association).

The opponents of stem cell research were almost exclusively religious institutions and religiously inspired organizations, which argued that ES cell research was immoral because it involved the destruction of human embryos. The central issue that separated those who opposed funding from those who supported it was the status of the early-stage human embryo. The opponents of ES cell research believe that the embryo should enjoy the status of a human person from conception onward, and that to destroy an embryo for stem cells, even a five-day-old embryo, is to murder a human being.

Thus, the debate over the morality of the ES cell extraction process centers around the contentious definition of when human personhood begins. The opponents of ES cell research derive their understandings of human personhood from the religious traditions to which they belong. Yet not all religions proffer identical teachings about human development. Indeed, differences within traditions were exposed in the heated debate. The most prominent opponents of ES cell research are Roman Catholics and conservative evangelical Christians.

While there are profound differences between evangelicals and Catholics, both religious traditions generally believe that human personhood begins at conception. More accurately, the leadership of Catholic and evangelical institutions argue that personhood begins at conception. Public opinion polls conducted in the spring and summer of 2001 indicate that most American adults, including Catholics and evangelicals, support ES cell research, a finding which suggests that many ordinary believers disagree with their church leadership. For example, a Caravan OCR International survey found Catholics supporting ES cell research by more than 3 to 1, and fundamentalist Protestants supporting it by almost 2.5 to 1.

Nonetheless, conservative Protestants and Catholics were in the forefront of the movement to convince President Bush to ban federal funding of ES cell research. They argued that ES cell research was morally unacceptable and that, in the words of Georgetown University professor Edmund Pellegrino, “upon conception, the biological and ontological individuality of a human being is established” and the “fetus and the embryo have the same moral claim to the protection of their lives.” A spokesperson for the Family Research Council, a conservative political organization strongly influenced by evangelical Christianity, argued that ES cell research relies on the “killing of embryonic human beings.” Both arguments rest on the belief that an early-stage embryo is not merely human life (as scientists readily grant), but a human person.

Varieties of belief
Not all Christians adhere to the same definitions of human personhood, however. Testifying before the National Bioethics Advisory Commission, Protestant theologian Ronald Cole-Turner quoted from the 1997 General Synod of his denomination, the United Church of Christ. “General Synods have not . . . regarded the pre-embryo as the equivalent of a person,” stated the Church’s Committee on Genetics. Cole-Turner argued that human stem cell research should “go forward with federal funds,” and he asserted that his Church is even “open to the possibility that somatic cell nuclear transfer be used to create embryos for research.” This Christian pro-funding argument is similar to those offered by many Jewish leaders, who find no biblical opposition to their support of ES cell research. For instance, Rabbi Moshe David Tendler of Yeshiva University (New York) stated, “The Jewish tradition does not grant moral status to an embryo before 40 days of gestation,” because “the proposition that humanhood begins at zygote formation, even in vitro, is without basis in biblical moral theology.”

The Muslim sacred text, the Koran, also suggests that moral personhood is a process and is not granted at the embryonic stage. Islamic scholar Abdulaziz Sachedina testified before the Bioethics Commission that most Sunni and Shiite jurists would “have little problem” endorsing ethically regulated research on ES cells, because the “fetus is accorded the status of a legal person only at the later stages of its development.”

These examples merely hint at the diversity of religious perspectives on ES cell research, but they should suggest that the opponents of such research do not speak for all religious people. Still, the conservative religious perspective had more influence on the Bush administration’s decision, primarily because of the prominent role of religious conservatives in the Republican Party.

The president and his staff recognized the scientific importance of his decision. In his statement announcing the approval of limited funding for ES cell research, Bush acknowledged that most scientists “believe that research on embryonic stem cells offers the most promise because these cells have the potential to develop in all of the tissues of the body.” At the same time, the president’s remarks betrayed the influence of conservative critics of ES cell research. He raised the specter of human cloning, suggesting that ES cell research was the “leading edge of a series of moral hazards,” and in doing so he failed to make the crucial distinction between therapeutic and reproductive cloning. This echoes the rhetorical moves made by opponents of ES cell research, who set up the straw man of reproductive cloning in order to discredit stem cell research. Nevertheless, the president did allow federal funds to support ES cell research, but only research performed on stem cells grown from lines that existed prior to August 9, 2001. In other words, federally supported researchers could not work with stem cells harvested anytime in the future, and no new embryos would be killed to extract ES cells.

Although this appeared to be an attempt at compromise, no one was entirely pleased. Many conservatives believed, as did the leader of the American Life League, that President Bush “can no longer consider himself pro-life.” Supporters of ES cell research responded more with skepticism than scorn. The Bush administration claimed that there were 64 existing lines of stem cells that were eligible for use in federally funded research. It has recently been learned, however, that the approved ES cell lines may be unusable, as they were grown in direct contact with mouse cells and might have acquired viruses that would preclude their use in clinical trials on humans.

More “political science”
In early September 2001, the Secretary of Health and Human Services admitted that most of the approved stem cell lines are not fully established and ready for research; but the Bush administration insists that this is not a serious problem. Many scientists disagree. Some, like cell biologist Roger Pedersen of the University of California, San Francisco, are leaving the United States to work in Britain and in other nations where there are no legal barriers to ES cell research. Others may join private biotechnology companies unaffected by the decision on federal funding.

While the Bush administration may have hoped that the August decision was the last word on ES cell research, the debate is unlikely to end anytime soon. The development of human embryo cloning for therapeutic use may prompt Congress to revisit the subject in the near future, and both supporters and opponents of ES cells are mobilizing for action. Regardless of what legal and legislative decisions are made, ES cell research will continue somewhere in the world. Whether it flourishes in the United States is still to be determined.

Suggested reading

• American Association for the Advancement of Science. Policy Brief: Stem Cell Research (November 2001); www.aaas.org/spp/cstc/issues/stemcells.htm.
• Bush, G. W. Remarks by the President on Stem Cell Research (Aug 9, 2001); http://whitehouse.gov/news/releases/2001/08/20010809-2.html.
• Frustrated Stem Cell Pioneer Quits United States for Britain. Nature, July 19, 2001, p 262.
• National Bioethics Advisory Commission. Ethical Issues in Human Stem Cell Research (June 2000); www.bioethics.gov.
• National Institutes of Health. National Institutes of Health Guidelines for Research Using Human Pluripotent Stem Cells; www.nih.gov/.
• Nuffield Council on Bioethics. Stem Cell Therapy: The Ethical Issues (April 2000); www.nuffieldfoundation.org/bioethics.
• Religious Tolerance.org. Human Stem Cells; www.religioustolerance.org/res_stem1.htm.
• Stolberg, S. G. U.S. Concedes Some Cell Lines Are Not Ready. The New York Times, Sept 6, 2001.
• Wade, N. Clearer Guidelines Help Britain To Advance Stem Cell Work. The New York Times, Aug 14, 2001.

Richard A. Pizzi is a freelance writer with an M.A. in history, currently working on a Ph.D. at Indiana University. Send your comments or questions regarding this article to mdd@acs.org or the Editorial Office by fax at 202-776-8166 or by post at 1155 16th Street, NW; Washington, DC 20036.