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- Stem cells: What they are and what they do
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Stem cells: What they are and what they do
What are stem cell lines 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 growing 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. That way, researchers don't have to get stem cells from an embryo itself.
What is stem cell therapy (regenerative medicine) and how does it work?
Stem cell therapy, also known as regenerative medicine, is the replacement of diseased, dysfunctional or injured cells with stem cells or their derivatives. It's somewhat similar to the organ transplant process but uses cells instead of organs.
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 could then be implanted into a person. For example, if the person had heart disease, the cells could be injected into the heart muscle. The healthy, transplanted heart cells could then contribute to repairing defective heart muscle. In fact, researchers have already shown that adult bone marrow cells guided to become heart-like cells can repair heart tissue in mice, and much more research is ongoing.
Have stem cells already been used to treat diseases?
Yes, stem cell transplants, also known as bone marrow transplants, have been performed in the United States since the late 1960s. These transplants use adult stem cells.
Adult stem cells are being tested in other applications, including a number of degenerative diseases, such as heart failure. Stem cells from umbilical cord blood have been successfully used in clinical trials to treat cancer and blood-related diseases.
The Food and Drug Administration has approved an initial safety study using an embryonic stem cell therapy for the treatment of serious spinal cord injuries.
What are the potential problems with using embryonic stem cells in humans?
To be useful in people, researchers must be certain that 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 has advanced significantly.
Embryonic stem cells could also grow irregularly — something that's been reported 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 are working on ways to avoid these possible complications.
What is therapeutic cloning and what benefits might it offer?
Therapeutic cloning is a technique to create versatile stem cells independent of fertilized eggs. In this technique, the nucleus, which contains the genetic material, is removed from an unfertilized egg. The nucleus is also removed from a somatic cell of a donor. This donor nucleus is then injected into the egg, replacing the nucleus that was removed, a process called nuclear transfer. The egg is allowed to divide and soon forms a blastocyst. This creates a line of stem cells that is genetically identical to the donor's — in essence, a clone. This technique is also called somatic cell nuclear transfer.
Some researchers believe that stem cells derived from therapeutic cloning may offer benefits over those from fertilized eggs because they're less likely to be rejected once transplanted back into the donor, and they may allow researchers to see exactly how a disease develops.
Has therapeutic cloning in people been successful?
No. Researchers haven't been able to successfully perform therapeutic cloning with humans, despite success in a number of other species.
What does the future hold for stem cell therapy?
Researchers say the field has promise. Stem cell transplants using adult stem cells continue to be refined and improved. And researchers are discovering that adult stem cells may be somewhat more versatile than originally thought, which means they may be able to treat a wider variety of diseases. Studies using embryonic stem cells or embryonic-like stem cells to regenerate tissue and organs in people are just getting started. Researchers are enthusiastic about the potential for regenerative medicine treatments.
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- Stem cell information — Frequently asked questions (FAQs). National Institutes of Health. http://stemcells.nih.gov/info/faqs.asp. Accessed Aug. 8, 2010.
- Stem cell basics. National Institutes of Health. http://stemcells.nih.gov/staticresources/info/basics/SCprimer2009.pdf Accessed Aug. 8, 2010.
- FAQ. International Society for Stem Cell Research. http://www.isscr.org/public/faq.htm. Accessed Aug. 8, 2010.
- Geron to proceed with first human clinical trial of embryonic stem cell-based therapy. Geron. http://www.geron.com/media/pressview.aspx?id=1229. Accessed Aug. 9, 2010.
- Tabar V, et al. Therapeutic cloning in individual parkinsonian mice. Nature Medicine. 2008;14:379.
- Nelson TJ, et al. Stem cell platforms for regenerative medicine. Clinical and Translational Science. 2009;2:222.
- Behfar A, et al. Guided cardiopoiesis enhances therapeutic benefit of bone marrow human mesenchymal stem cells in chronic myocardial infarction. Journal of the American College of Cardiology. 2010;56:721.
- Nelson TJ, et al. Repair of acute myocardial infarction by human stemness factors induced pluripotent stem cells. Circulation 2009;120:408.
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