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Stem Cells FAQ

Your Stem Cell Questions Answered
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Q: What are embryonic stem cells?

A: Early in development, a fertilized egg becomes an embryo. The embryo is made up of stem cells that divide over and over again, until these stem cells develop into the cells and tissues that become a fetus.

During in-vitro fertilization, eggs taken from a woman's body are fertilized with sperm cells. If not implanted in a woman's womb, these embryos are discarded.

Researchers have learned to take embryonic stem cells from unused in-vitro fertilizations and, in laboratory culture, to get them to make more embryonic stem cells. Embryonic stem cells are not taken from fertilized eggs or embryos that have been in a woman's womb.

While embryonic stem cells can become any kind of cell in the body, it's unlikely they would be used directly as treatments. Because they have the ability to divide over and over again, they can become rapidly growing tumors. And because they are in such an early stage of development, they take a long time to become functional adult cells.

However, researchers are learning to coax embryonic stem cells to become more mature stem cells. One clinical trial, for example, matures embryonic stem cells into nerve stem cells. These nerve stem cells are being explored as a treatment for Lou Gehrig's disease.

Q: Why not just study adult stem cells?

A: Adult stem cells have some advantages. When they come from your own body, your immune system will probably not try to reject them. And adult stem cells aren't controversial.

But there are several main disadvantages to using adult stem cells:

  • Adult stem cells aren't able to form all types of cells, so their use may be limited.
  • They are relatively rare among the body's billions of cells, so they're hard to find.
  • They take a long time to grow.
  • Adult stem cells donated by one person may be rejected by another person's immune system.
  • Adult stem cells can't reveal to researchers the secrets of early human development.

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