SCIENCE & SOCIETY

The Promise and Perplexities
of Stem Cells:
Academies Weigh In on Hotly Debated Research Area of Regenerative Medicine

To individuals suffering from certain types of debilitating illnesses and to medical researchers seeking to help them, the potential of stem cell research seems limitless. Regenerative medicine offers the possibility of someday providing healthy, new red blood cells for patients with leukemia, neurons for those afflicted by stroke or Alzheimer's or Parkinson's, pancreatic cells for diabetics, and more.

No less profound, however, are the ethical and public-policy questions raised by using embryonic stem cells, primarily drawn from frozen human embryos left over from in vitro fertilization procedures. Another potential source of stem cells includes certain adult organs, but adult stem cells are difficult to isolate and not as versatile, which is why their embryonic counterparts are more attractive to researchers.

Although stem cell research is on the cutting edge of biological science today, it is still in its infancy. An enormous amount of basic research must first be done to achieve advances in medical treatments that could be widely available to patients. Publicly sponsored research -- on stem cells from both embryos and adults -- would provide the most efficient and responsible means to fulfill the promise of stem cells, according to a new report from the National Research Council and Institute of Medicine.

Without government funding of basic research on stem cells, progress toward medical therapies is likely to be hindered. Private industry may be reluctant to fund research that could take many years and with no guarantee of the results yielding profitable applications. Moreover, public sponsorship of basic research would help ensure that many more scientists with a broader spectrum of perspectives could pursue a variety of research questions and that their results would be made widely accessible through scientific publication -- two factors that can significantly speed progress. Public funding also offers greater opportunities for regulatory oversight and scrutiny.

President Bush announced in August that he would allow federal financial support of research that uses embryonic stem cells being cultured in laboratories around the world, but would prohibit funding for the development of new lines that involved creating and destroying additional embryos.

"We believe that new embryonic stem cell lines will need to be developed in the long run to replace existing lines that become compromised by age, and to address concerns about culture with animal cells and serum that could result in health risks for humans," said Bert Vogelstein, chair of the committee that wrote the report, professor of oncology and pathology at the Johns Hopkins University School of Medicine, Baltimore, and a Howard Hughes Medical Institute investigator.

Another problem relates to the possible rejection of transplanted stem cells by a patient's immune system. The committee called for the aggressive pursuit of research on immune rejection, including further study of somatic cell nuclear transfer, a technique that can overcome rejection problems. Sometimes referred to as therapeutic cloning, and ethically controversial, the practice involves removing the nucleus of an egg cell, inserting genetic material from the transplant recipient, and triggering cell division. Because there is no intention of ever implanting the resulting embryo to produce a child, the nuclear transfer technique should not be confused with reproductive cloning, the committee said.

In light of the numerous ethical concerns raised by stem cell research, the committee called for a national advisory board to be established at the National Institutes of Health -- similar to one that was set up to oversee genetic engineering research -- comprising outstanding scientists, ethicists, and others. The board would ensure that proposals for federally funded work were scientifically sound and met mandated codes of conduct.

Aware of the wide array of social, political, legal, and economic considerations involved in the issue, the committee's consensus report was informed in large part by a workshop held in June, where some two dozen experts spoke to an audience of hundreds of stem cell scientists from academia and industry, policy-makers, ethicists, and religious leaders.

"A complex and confusing reality is involved in this contentious issue," said Father Kevin FitzGerald, assistant professor of medicine at Loyola University Medical Center and one of several speakers who argued against the use of embryonic stem cells in research and of cells derived from those original lines. "What is the difference between a natural embryo and an 'engineered' entity? What is the moral status of human embryos? This is society's dilemma."

Stem cells are prized by medical science because, unlike any other cell in the body, some are able to renew themselves indefinitely, explained Irving Weissman, professor of cancer biology and cell and developmental biology at Stanford University. Because they are unspecialized, they serve as a kind of raw material that can give rise to specialized cells that constitute blood, the brain, specific tissues such as those that make up muscle and bone, and organs such as the heart and kidneys.

The biotech industry has already tapped into the potential of stem cells. "Living cells will be tomorrow's 'pharmaceuticals,'" said speaker Thomas Okarma, chief executive officer of Geron Corp., about a commercialization strategy for regenerative medicine. Holding exclusive license to certain stem cell discoveries made by researchers, Geron has made progress in growing a variety of specialized cells from stem cells. "We want to have frozen, packaged products [e.g., heart cells] to sell to hospitals for use in patients. This work offers high value for medicine and a huge potential impact on society," said Okarma.

But in spite of early progress in stem cell research, and reason for optimism, much remains to be understood. Researchers have yet to determine, for example, how a neuron "knows" that it isn't a liver cell. Or why a stem cell taken from an adult organ seems limited in its potential, compared with an embryonic stem cell. While some studies in lab animals have shown promising results, scientists' ability to use stem cells for restoring function in humans may be many years away, the report says.

With the complexity of the science presenting more questions than answers, the enthusiasm of certain researchers is tempered by the caution of others.

"This research should be pursued with great care," said Olle Lindvall, chair of the department of clinical neuroscience at Lund University, Sweden. "Before applying a new therapy widely, it must show effectiveness in the reversal of actual symptoms and be successful in restoring normal function." It must also be shown to be safe, he noted.

And so, the debate and the work on stem cells continue, with both the promise of medical breakthroughs and the perplexities inherent in such a complex enterprise.   -- Saira Moini & Bill Kearney

Stem Cells and the Future of Regenerative Medicine. Committee on the Biological and Biomedical Applications of Stem Cell Research; Board on Life Sciences, Division on Earth and Life Studies; and Board on Neuroscience and Behavioral Health, Institute of Medicine (2001, approx. 71 pp.; ISBN 0-309-07630-7; available from National Academy Press, tel. 1-800-624-6242; $17.95 plus $4.50 shipping for single copies).

The study was led by Bert Vogelstein, professor of oncology and pathology at the Johns Hopkins University School of Medicine, Baltimore, and a Howard Hughes Medical Institute investigator. The study was sponsored by the National Academies with additional funding from the Ellison Foundation.

From top: Bert Vogelstein, Johns Hopkins University School of Medicine

Patricia King, Georgetown University Law Center (left), Corey Goodman, University of California, Berkeley (center), and Paul Berg, Stanford University School of Medicine (right)

Father Kevin FitzGerald, Loyola University Medical Center

Barry Bloom, Harvard University (left), Irving Weissman, Stanford University School of Medicine (center), and Ernest Beutler, Scripps Research Institute (right)

Ihor Lemischka, Princeton University (left), and Markus Grompe, Oregon Health and Science University (right)

Patricia King, Georgetown University Law Center

Thomas Okarma, Geron Corp.

Photographs by Greg Hadley