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April 21, 2005

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After the debate, U.S. Sen. Sam Brownback (R-Kansas) spoke on the subject. 'Humans possess a unique value,' he said. 'They are an end in themselves. They can't be used as a means to an end.' (Staff photos Peter DiCampo/Harvard News Office)

Stem cell research debate continues

Can we cure disease with emryonic stem cells? And should we?

By Ken Gewertz
Harvard News Office

Stem cell research is a complicated subject, not only scientifically but ethically as well. This past Friday (April 15) a debate at Harvard Law School promised to shed light on both aspects of this urgent issue, but probably ended up raising as many questions as it answered.

The event, "Law and Ethics in a Brave New World: What Should Government Do About Cloning & Stem Cell Research?" was sponsored by the Society for Law, Life and Religion, a pro-life student organization at Harvard Law School. It featured a debate between Kevin Eggan, a researcher in the Department of Molecular and Cellular Biology and a junior fellow in the Harvard Society of Fellows, and David Prentice, a senior fellow at the Family Research Council. Following the debate, U.S. Sen. Sam Brownback (R-Kansas) delivered a talk on the subject.

Eggan, who spoke first, provided some useful clarification about the difference between adult and embryonic stem cells and the research and clinical possibilities of each.

Harvard researcher Kevin Eggan (left) makes a point as his adversary David Prentice waits to respond.

All stem cells, he said, possess two important properties - the ability to make identical copies of themselves and the ability to divide into other specialized types of cells. But while adult stem cells - those found in bone marrow, for example - have a limited ability to differentiate, embryonic stem cells can give rise to virtually any type of cell in the body.

"Adult stem cell research is important and must go forward," Eggan said. But embryonic stem cell research, while at an earlier stage of development, shows a potential for scientific and clinical breakthroughs that adult stem cell research lacks.

Embryonic stem cells can be grown indefinitely in culture, while adult stem cells cannot. Because of this ability, scientists can use them as models to study a variety of different genetically transmitted diseases such as Parkinson's, Alzheimer's, or diabetes, and to screen drugs that might cure those illnesses.

In the future, it might also be possible to create stem cell lines that would carry the genes of a patient so that replacement cells could be transplanted that would not challenge the patient's immune system. For example, stem cells could be coaxed into differentiating into dopamine-producing neurons to replace similar neurons destroyed by Parkinson's disease.

Scientists obtain embryonic stem cells at the blastocyst stage of embryonic development, about 96 hours after fertilization, Eggan explained. The embryos, which are grown in vitro, cease to develop and are destroyed after the cells are removed.

"This is not a fetus," he said. "It is not a pregnancy. It is grown in a culture, not in a mother's uterus."

Still, he said, we must answer the question of whether destroying human embryos is morally defensible.

"I believe the moral obligation we have to treat diseases and relieve suffering outweighs our obligation to the embryo," Eggan said.

Later, during the Q &A period, he elaborated on this idea: "I would tend toward the view that the blastocyst does not manifest many of the properties that we associate with humanity."

Eggan disagreed with the argument that cloning human embryos for research purposes will lead down a slippery slope to reproductive cloning and "designer babies," because at no time in the process of working with embryonic stem cells are embryos implanted in a woman's uterus.

Prentice said that, like Eggan, he believed that "we have a moral obligation to treat diseases, but we must also have respect for human life and dignity." Destroying human embryos, even 4-day-old blastocysts produced in the laboratory, goes against that principle.

But Prentice spent more time questioning Eggan's claims for the greater potential of embryonic stem cell research over adult stem cell research than he did elaborating on the ethical argument.

"Embryonic stem cells have great theoretical potential, but there have been problems in the laboratory. The cells are finicky, they're difficult to grow, it's difficult to get a pure culture, and there is a potential for tumor formation," he said.

He questioned whether there was any real difference between therapeutic cloning and reproductive cloning, as Eggan had argued. "Each involves the creation of a cloned human embryo, a genetic identical twin."

On the other hand, he said that there have been promising developments in the use of adult stem cells in clinical applications, including tissue repair for stroke, spinal cord injuries, and heart damage. Prentice said that there have been 58 medical conditions in which the therapeutic benefit of adult stem cell treatment has been established, while no clinical benefits have been achieved so far as a result of embryonic stem cell research.

"We need to debate this issue, but without emotion. We need to decide in which direction to move. I believe that if we're concerned with patients, adult stem cell research shows the greatest promise."

In his response, Eggan disagreed.

"I would be the first to admit that embryonic stem cell research is not ready to go to the clinic yet. It's not safe. Do I believe it can be made safe? Yes. We need new embryonic stem cell lines so that research can go forward."

Eggan also made the point that while research has been done on adult stem cells since early in the 20th century, human embryonic stem cells were first isolated only in 1998.

While the two debaters concentrated on the scientific aspects of the stem cell question, Brownback in his presentation waded resolutely into ethical waters.

"Humans possess a unique value," he said. "They are an end in themselves. They can't be used as a means to an end."

Nor did Brownback express any equivocation about whether a 4-day-old embryo qualifies as human.

"Life begins at the beginning. A young human embryo is a unique human being. It's not a dog, it's not a mouse."

Brownback said he believed it is appropriate for government to see that research is ethical and to provide boundaries to make sure that human life is protected. He reiterated Prentice's statement that, given its far greater record of clinical success, adult stem cell research should be given preferential treatment by federal funding agencies.

"We must protect the powerless," Brownback said. "When we harm human dignity, we harm all humans."

Copyright 2007 by the President and Fellows of Harvard College