Stem cells FAQs — Covers cell types, including embryonic stem cells, uses and ethical issues.
You've heard about stem cells in the news, and perhaps you've wondered if they might help you or a loved one with a serious disease. You may struggle with understanding what stem cells are, how they're being used to treat disease and injury, and why they're the subject of such vigorous debate.
Here, you can sort through the hype and the hope and get answers to frequently asked questions about stem cells.
What exactly are stem cells?
Stem cells are master cells of the body — cells from which all other cells with specialized functions are created. Under the right conditions in the body or a laboratory, stem cells divide to form more cells, called daughter cells. These daughter cells either become new stem cells (self-renewal) or become specialized cells (differentiation) with a more specific function, such as blood cells, brain cells, heart muscle or bone. Stem cells are unique — no other cell in the body has the ability to self-renew or to differentiate.
Where do these embryos come from?
The embryos being used in embryonic stem cell research come from eggs that were fertilized at in vitro fertilization clinics but never implanted in a woman's uterus because they were no longer wanted or needed. The excess embryos were frozen and later voluntarily donated for research purposes. The stem cells can live and grow in special solutions in test tubes or petri dishes in laboratories.
What is a stem cell line and why do researchers want to use them?
A stem cell line is a group of cells that all descend from a single original stem cell. Cells in a stem cell line keep dividing but don't differentiate into specialized cells. Ideally, they remain free of genetic defects and continue to create more stem cells. Clusters of cells can be taken from a stem cell line and frozen for storage or shared with other researchers. This way, researchers don't have to get stem cells from an embryo itself.
Why do researchers want to create more embryonic stem cell lines?
Researchers who receive federal funding to support their experiments — as most academic researchers do — are limited by law to working with about 20 stem cell lines. Those who want to experiment using other stem cell lines must find private funding for separate laboratory space and private funding must also be used to buy separate equipment for research.
The 20 or so stem cell lines approved for research date back to the late 1990s, and some researchers contend that they pose several problems:
- The limited number of stem cell lines limits the genetic diversity available, so cells may be useful only for certain diseases or people.
- The lines are old, so cells don't grow as well as new ones.
- The lines may have been contaminated by nonhuman cells in the growth cultures, compromising their safety.
- The DNA in some of the cells may subtly change over time, causing genetic flaws that could be passed along to daughter cells or to humans.
What is stem cell therapy and how does it work?
Stem cell therapy is the replacement of diseased, dysfunctional or injured cells with either adult or embryonic stem cells. It's somewhat similar to the organ transplant process but uses cells instead of organs. Stem cell therapy is sometimes called regenerative medicine.
Researchers grow stem cells in the lab. These stem cells are manipulated to make them specialize into specific types of cells, such as heart muscle cells, blood cells or nerve cells. This manipulation may involve changing the material in which the stem cells are grown or even injecting genes into the cells. The specialized cells are then implanted into a person. If the person has heart disease, the cells would be injected into the heart muscle. The normally functioning implanted heart cells, in theory, could replace the defective heart cells.
What are the potential problems with using embryonic stem cells in humans?
To be useful in people, researchers must be certain that embryonic stem cells will differentiate into the specific cell types desired. Researchers, for instance, don't want to transplant a stem cell into a person hoping it'll become a heart cell only to learn that it's become a bone cell, with potentially dangerous consequences. Researchers have found ways to direct stem cells to become specific types of cells, and research into this area continues.
Embryonic stem cells could also become tumor cells — something that's happened in animal experiments — or travel to a part of the body where they're not intended to go. They also might trigger an immune response in which the recipient's body attacks the stem cells as foreign invaders, or simply fail to function normally, with unknown consequences. Researchers have found ways to avoid these complications and continue studying ways to control stem cells.
Has therapeutic cloning in people been successful?
Researchers haven't been able to successfully perform therapeutic cloning of humans. In 2005, South Korean researchers reported creation of human embryonic stem cells this way, but their claims were ultimately not substantiated.
Last Updated: 11/24/2007
