Stem cells: embryonic or adult? Stem cells: embryonic or adult? (October 26, 2005)

The difference isn't just age
Those thinking about the stem-cell issue undoubtedly have heard some advocates tout embryonic cells, while others push adult ones.

So what's the difference? Flexibility, for one thing, and ethical perspectives for another.

Embryonic stem cells are extracted from days-old embryos, a process that destroys the embryo. Proponents laud the stem cells' flexibility, called "pluripotency" -- the ability to turn into just about any cell or tissue type in the body. They also have the ability to replicate indefinitely, scientists report.

According to the National Institutes of Health, embryonic stem cells have to potential to be used as "replacement cells or tissues to treat a myriad diseases, conditions and disabilities including Parkinson's and Alzheimer's disease, spinal cord injury, stroke, burns, heart disease, diabetes, osteoarthritis and rheumatoid arthritis."

The field of human embryonic stem-cell research is young, however. Experiments have been conducted only for the past seven years, and no treatments have been formulated yet. Critics of embryonic stem-cell research charge that tumors frequently result from experiments in animals.

Adult stem cells are extracted from the body of a born person. They are "undifferentiated," meaning they haven't become a specialized type of cell. The role of the cells is to maintain and repair tissue as needed, according to the National Institutes of Health Web site.

Adult stem cells have been traditionally regarded as "multipotent," meaning they have the ability to become many types cells, but not all. However, biologists more recently have been rethinking that potential, as they've had success in turning them into a wider range of cells and tissues.

Critics note that adult stem cells are not plenteous in the body, however, and may not have the ability to replicate as well as embryonic stem cells.

Just how effective are adult stem cells? Over the past 40 years, they have given rise to therapies for cancers, auto-immune diseases, blood conditions, neural degenerative diseases -- including Parkinson's -- and more, according to the Web site, www.stemcellresearch.org. Clinical studies have also been conducted for patients with diabetes and advanced kidney cancer.

Adult stem cells do not raise the ethical questions that embryonic ones do, because extracting adult cells does not harm the person.

-- Jocelyn Dong

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