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Stem Cells

Stem cells are unspecialized cells that are capable of turning into other specific, specialized cells of the body. They come from two main sources: adults and embryos. Human embryonic stem cells (often abbreviated hESC) are harvested from embryos, typically from fertilized eggs left over after in vitro fertilization procedures. An hESC is able to turn into any other type of cell and will grow easily in laboratory conditions. Adult stem cells, which have been used for years to treat lymphoma and leukemia, are relatively difficult to grow in laboratories and have a limited ability to change into different types of cells, although there is some very preliminary evidence that adult stem cells may be more flexible than was previously thought.


Stem cells have become a topic of political debate because harvesting embryonic stem cells requires the destruction of the embryo, and many people believe that killing an embryo is morally wrong. Scientists study stem cells to learn how they become specialized cells in the human body and to modify them for use in transplantation or the treatment of diseases. A few scientists say that research should be limited to adult stem cells, but most stem cell researchers believe that adult stem cells show less promise for curing some diseases than do embryonic stem cells. Researchers say the study of stem cells could possibly lead to treatments for various ailments, including Parkinson’s disease, diabetes and heart disease.


Some scientists have suggested that it might be possible to produce hESCs through cloning. To date, no one has succeeded in cloning humans. Human cloning is illegal in the United States.