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Few topics in science and religion have been as hotly contested in recent years as stem cell research, largely because it involves the fate of, disposition of, and research on the human embryo. There are two basic types of stem cell research—that involving adult cells (AS cells) and that involving human embryonic cells (ESCs or hES cells); only the latter is a source of controversy. In both cases, research is still at the early stages regarding the programming and uses of these cells, and there is comparatively little data about the efficacy of AS and hES cells for human therapies. That is why most scientists agree that, in the United States, government funding should be widely available for research on both types of stem cells, an issue that has been contested in the U.S. Congress.

Stem cells are unspecialized and so are able to renew indefinitely; they also have the capacity to differentiate into specialized cells. In humans, these cells are found in some adult organs, in blood, and in bone marrow (Mezey et al. 2000; Bjornson et al.1999); in the inner cell mass of the human embryo at the blastocyst stage (five to six days after fertilization) (Thomson et al. 1998); on the gonadal ridge of aborted or miscarried fetuses (Shamblott et al. 1998); and in the placenta and umbilical cord (hematopoetic stem cells).

Because stem cells have the capacity to regenerate, particularly ESCs, they have ushered in the era of "regenerative medicine," signaling that, in theory, these cells can be used to regenerate human tissues and cells, and ultimately increase quality of life and the human life span. Embryonic stem cells are the progenitor cells for the human body and at their earliest stage (the blastocyst stage) they are completely undifferentiated and can give rise to any cell type in the human body (totipotent, pluripotent, and multipotent are all terms that have been used to describe this phenomenon). At this stage the cells have not yet received their "marching orders" for what they will become; therefore, scientists have been experimenting with controlling the programming of ESCs in culture in order to direct their ends (controlled differentiation) to specialized cells such as blood, skin, and nerve cells.

In order to extract these embryonic stem cells, scientists must collapse the trophectoderm that surrounds the blastocyst in order to get the stem cells from the inner cell mass (ICM) where they reside within the blastocyst or pre-embryo. Such a technique destroys the pre-embryo and renders it incapable of implantation in the uteran wall. This is the crux of the ethical problem for those who oppose embryonic stem cell research.

Studies in 2001 and 2002 indicate the potential for primate parthenotes to form embryonic stem cells and to develop a variety of differentiated cell types in culture (Cibelli et al. 2001; Holden 2002). Parthenotes are embryos that grow from unfertilized eggs (chemically tricked into fertilizing and retaining the full choromosomal complement) that are, so far as is known, incapable of becoming viable fetuses in primates and humans. Thus, scientists hope that this may prove to be an ethically uncontroversial way to obtain stem cells, allowing researchers to avoid therapeutic cloning as means to this end.

The ethical and religious issues surrounding stem cell research concern not so much the therapeutic ends of the research (cures for Parkinson's disease, juvenile diabetes, Alzheimer's disease, heart disease, and a host of other degenerative diseases); rather, the controversy surrounds the status of the human embryo and points to larger issues about what it means to be human and when life begins.

The Roman Catholic Church and conservative Protestant churches have made the strongest opposition to embryonic stem cell research of all religious traditions in the United States. The Catholic position is that life begins at conception; thus the human embryo is accorded the full rights and dignity of a human person from the very moment that the sperm penetrates the egg. Therefore, it is a grave sin to destroy any human embryo since the act constitutes destruction of life itself, a responsibility belonging only to God. Moreover, the Catholic Church has opposed the creation of human embryos for research purposes (therapeutic cloning, for example) for two reasons: To do so would be to treat human life as a mere means to an end, which is a violation of human dignity and the sanctity of life; and embryos ought only to be created in conjunction with the conjugal act of love within the context of marriage (natural law). (Donum Vitae 1987). It is important to note, however, that there are a variety of dissenting Catholic positions on this issue.

Conservative Protestant churches such as the Southern Baptist Convention and fundamentalist independent Christian churches have tended to join the Catholic protest against ESC research and have emphasized prioritizing AS research as an acceptable means to the end of regenerative therapies. The rationale for such opposition does not emphasize a natural law approach to ethics and emphasizes instead a biblical approach. An argument that the Christian tradition has a mandate to protect the weakest and most vulnerable members of society (the embryo in this case) is advanced by Lutheran theologian Gilbert Meilaender in his essay "Some Protestant Reflections" (2001).

On the other hand, mainline Protestant denominations (United Church of Christ, Episcopal, Presbyterian, Methodist) tend to be supportive of all stem cell research so long as the human embryo is treated with respect. In 2001, the General Convention of the Presbyterian Church voted to endorse embryonic stem cell research. Mainline Protestantism has focused on the great amount of good that can come of this research and on concerns of distributive justice to ensure that the poor will receive the benefits of stem cell research equally with the rich. Moreover, most mainline Protestants (and many Catholics) support using excess embryos for stem cell research. These embryos have been frozen in fertility clinics and would be thawed and discarded eventually if they were not put to what many believe is a good end—human healing. One Lutheran theologian who supports ESC research, in contrast to Meilaender's argument, is Ted Peters (Peters 2001).

Although there are three main branches of Judaism (Orthodox, Conservative, and Reform), and it is sometimes difficult to find agreement on bioethical issues, in this case most Jewish scholars are supportive of all stem cell research. This is due, primarily, to the fact that Judaism professes a strong mandate from God to heal and to reduce human suffering. Moreover, in Jewish law the embryo has no moral standing outside the womb; a developing embryo in laboratory culture is morally neutral until implantation. Therefore, the ends of all stem cell research appear to be morally coherent with Jewish ethics (Dorff).

Islam is also a diverse religious tradition. However, in general, Islam would be in favor of all forms of stem cell research since there appear to be no "recent rulings in Islamic bioethics regarding the moral status of the blastocyst from which the stem cells are isolated" (Sachedina). Islamic scholars have found that the Qur'han's focus is primarily on the developing fetus in the womb. Islam shares with Judaism a concern with human healing; thus, if ESCs hold real (not just speculative) potential for therapeutic healing, there would be no objection to proceeding with such research.

See also BIOTECHNOLOGY; CHRISTIANITY, ROMAN CATHOLIC, ISSUES IN SCIENCE AND RELIGION; CLONING; DNA; GENE PATENTING; GENE THERAPY; GENETIC ENGINEERING; GENETICS; JUDAISM; ISLAM

SUZANNE HOLLAND