Stem Cells FAQ: 9 Questions & Answers

Confused about stem cells and stem cell research? Here are answers to frequently asked questions about stem cells.

Q: What are stem cells?

A: Stem cells are unspecialized cells that can become other types of cells.

Q: What's the difference between adult stem cells and stem cells taken from an embryo?

A: Embryonic stem cells are stem cells in an embryo. They can develop into a wide range of cell types.

Scientists have found that a few stem cells persist even after birth; those are adult stem cells. Most adult stem cells can form a limited number of cell types.

Q: What's the controversy about?

A: There's no controversy about adult stem cells. But when it comes to embryonic stem cells, some people argue that an embryo is a living human being and destroying an embryo for any reason is morally unacceptable. Other people say that embryonic stem cells have the potential to cure many diseases, and that the embryos used would have been discarded by fertility clinics anyway.

Q. Why not just study adult stem cells?

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 three 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.  
• Adult stem cells are rare among the body's billions of cells, so they're hard to find.
• Adult stem cells take a long time to grow. 

Q: Where do scientists get the embryos they use?

A: From in vitro fertilization (IVF) clinics.

Many women who have difficulty having a baby use IVF. Doctors collect eggs from the mother and sperm from the father, and put them together in the laboratory. The doctors implant one or more of the resulting embryos in the mother. Other embryos are frozen and stored, in case the first embryo implanted doesn't take. But all of those frozen embryos may not be used.

According to federal policy, embryonic stem cells used for research can only come from embryos created for reproductive purposes that are no longer needed and the donors must consent and not profit financially from the donation.

Q. Could there be alternatives to studying embryonic stem cells?

Maybe. In 2007, scientists in the U.S. and Japan reported successfully reprogramming human skin cells to act like embryonic stem cells.

There is a catch. To reprogram the skin cells, the researchers had to use retroviruses as vectors to carry new genes into the cell nucleus. Once there, the retroviruses become part of the cell's genetic code. These retroviruses could cause deadly mutations or cancers in patients treated with the newly created stem cells.