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Stem Cell Research Prompts Hope, Debate

Kate Traynor

Stem-cell therapy—the replacement of missing or diseased cells with new ones derived from precursor cells—holds the promise of a cure for many human diseases including diabetes mellitus and Parkinson's disease.

Although stem-cell therapy is in its infancy, patients already benefit from this treatment. Cancer patients whose leukocytes succumb to chemotherapy may undergo stem-cell therapy, using blood-derived stem cells to generate new leukocytes.

Future uses for stem-cell therapy include the production of new pancreatic cells for diabetic patients, neural cells for people with Alzheimer’s or Parkinson’s disease, even skin cells for burn victims. Also conceivable is the use of stem cells to generate entire organs for use in transplantation.

Stem-cell therapy is only one of several promising areas of medical research in the 21st century. The recent unveiling of nearly complete maps of the human genome opens the door to many advances in medical therapy. For information on the mapping of the human genome, read the special issues published this week by Nature and Science. Also, the Feb. 7 issue of the Journal of the American Medical Association offers an assortment of articles on opportunities for medical research.

But the therapy's reliance on human embryos or aborted fetuses as the source of many stem cells may slow the rate of advancements in the field. 

Some embryonic stem cells are termed "totipotent," because they have the potential to differentiate into every type of cell in the human body. Totipotent embryonic stem cells can become "pluripotent" stem cells that produce a large but incomplete range of cell types. "Multipotent" stem cells, which arise further down the developmental path, produce a more limited number of cell types.

Embryonic stem cells are believed to have a greater potential for differentiation than any other stem-cell type. Because of this, clinical breakthroughs in stem-cell therapy are more likely to result from research on embryonic cells than other stem cells. Recent animal research, though, has uncovered more potential for differerentiation by multipotent and pluripotent stem cells than was previously suspected.

An important recent finding is that stem cells exist in organs, such as brain and muscle, that were once thought not to contain the cells. Researchers have been able to make stem cells from the brain grow and differentiate into mature nerve cells. Likewise, stem cells from muscle have grown and differentiated into mature muscle cells.

The 1997 birth of Dolly the sheep, an animal cloned from an adult mammary gland cell, proved that differentiated adult cells can transform into totipotent cells. Dolly’s birth was followed by the successful cloning of mice, cows—even a short-lived rare wild ox—from adult cells.

Not surprisingly, this influx of scientific progress has made an impression on both policymakers and the general public.

Last August, the National Institutes of Health released guidelines for performing research on pluripotent stem cells obtained from embryos. The government-funded research agency had anticipated funding such studies.

President Bush, who described the opportunities for adult stem-cell research as "exciting," said Jan. 3 that he does not support the use of federal money to do research on "aborted fetuses." It is not known what attempts the Bush administration will make to regulate or restrict federally funded stem-cell research.

The Juvenile Diabetes Foundation International commissioned a survey last month to assess the American public’s views on federally funded stem-cell research. Sixty-five percent of the 1,004 respondents favored stem-cell research involving "excess human embryos developed through in vitro fertilization and fetal tissue that has been donated to research." A quarter of the respondents opposed federal funding of the research.

Scientific advances and related debate on the issue of stem-cell research are likely to continue. For additional information, visit the Web sites described below.

Recommended Readings on Stem Cells

A report (PDF) released in 1999 by the American Association for the Advancement of Science and the Institute for Civil Society provides recommendations for stem-cell research policy.

Martha Stoddard, writing for the Nebraska Lincoln Journal Star, has put together an informative, nontechnical series about the science and politics of stem-cell research.

A Congressional Research Service report provides a good review of political factors that have influenced stem-cell research.

The National Institutes of Health stem-cell information page lists resources including the Institutes' guidelines for research on pluripotent stem cells.