July 19, 2005 > Stem Cells: A Dream for a Cure
Stem Cells: A Dream for a Cure
by Praveena Raman
(This is the second of a series of articles addressing the biology and promise of stem cell research)
The power of the dream
The faith in things unseen
The courage to embrace your fear
No matter where you are
To reach for your own star
To realize the power of the dream
Roman Reed, 19-year-old son of Horner Junior High School teacher Don Reed, made 11 unassisted tackles, forced and recovered a fumble and made a diving interception on September 10, 1994 for his Chabot College football team. In the fourth quarter, at the end of a play, he lay with a broken neck under a pile of players. Paralyzed from the neck down, Roman was told there was no hope of ever walking, closing his fingers or fathering a child. Today, Roman has use of his triceps, is married and has two children. With the support of his wife, Terri, and his father who co-founded Californians for Cure, the Roman Reed Core Laboratory for Spinal Cord Injury awards grants for research in this area. Stem cell research is on the cutting edge of progress to help those with spinal cord injury regain mobility. Dr. Hans Keirstead and his colleagues at the Reeve-Irvine Research Center have shown that human embryonic stem cell therapy developed in their laboratory has restored mobility in rats with SCI 1
What are stem cells?
Stem cells are primitive cells that do not have special characteristics. They can undergo cell division and renew themselves for long periods. Under certain conditions they can be converted into cells with specialized functions like those that produce insulin in the pancreas. There are primarily two types of stem cells from animals and humans that are used in research: the embryonic stem cells and adult stem cells.
Embryonic Stem Cells: Embryonic stem cells are obtained from 5 to 6-day-old embryos developed from eggs that have been fertilized in vitro (which literally means "in glass" or in an artificial environment like a laboratory dish or test tube). The eggs divide into a hollow ball (blastocyst) of about 100 cells. The inside of the ball is lined with about 30 cells that are the embryonic stem cells. The remaining 70 cells on the outside form the placenta. The stem cells on their own cannot develop into a fetus 2.
In fertility clinics, usually many eggs are developed to the "hollow ball" stage and only two to three are implanted in the uterus. The rest are frozen as a backup and, if unused, discarded. These frozen embryos are often donated for research with the informed consent of the donors3. The embryonic stem cells on the inside of the blastocyst are removed and placed in a flat plastic laboratory dish, called a Petri dish, which contains a broth (culture medium) that releases nutrients for the growing cells.
The cells start proliferating and soon crowd the culture dish forming a colony. When this happens, the cells are gently taken from the original dish and placed in smaller amounts in fresh culture dishes. This is called subculture. After many months and numerous subculture processes, the original 30 cells yield millions of genetically normal and undifferentiated embryonic stem cells. These are called embryonic stem cell lines; individual cells can become any type the body may need.
Recently Dr. Keirstead and his colleagues at the Reeve-Irvine Research Center were successful in coaxing such human embryonic stem cells to differentiate and become early stage oligodendrocytes. These are the building blocks of myelin, insulation around the nerves in the body. This insulator is important for nerves to carry messages from the brain to the muscles. When this insulation is stripped away due to injury or disease, paralysis can occur. Injured rats, treated soon after injury with such stem cells, formed myelin around the damaged neurons (nerve cells) in the spinal cord and within a couple of months, were able to walk1.
"Embryonic stem cells have one major advantage over adult stem cells; they can be expanded almost indefinitely without developing into mature cells. This allows one to generate a bulk of tissue, which can then be differentiated to a cell type that is desired for treatments or research. Embryonic stem cells can be grown into cubic yards of tissue, which can then be qualified for clinical use, and portioned into treatments for thousands of patients" Dr. Keirstead told TCV by email.
Adult Stem Cells: Also known as somatic stem cells, undifferentiated cells are found among differentiated cells in a tissue or organ. These cells can renew themselves and change into specialized cells of a particular tissue or organ. Adult stem cells are present in living organisms for the maintenance and repair of the tissue. In adult stem cell therapy, a patient's own cells could be grown in culture, reintroduced into the patient's body, preventing rejection problems. This is an advantage over embryonic stem cells. However, only a few adult stem cells are available and they cannot be cultured easily.
"The technology to generate similar numbers [like embryonic stem cells] of cells from adult stem cells does not currently exist, although major advances are being made. I believe that this technological limitation will eventually be overcome. It is important to note, if this limitation is overcome, then all of the advances that we make from the study of embryonic stem cells will apply to the growth of adult stem cells. In any case, we are working with what we have available right now; it seems to be having a tremendous beneficial effect," said Dr. Keirstead (by email to TCV).
Stem Cell Use: Apart from their use in Spinal Cord Injuries, stem cells, due to their ability to renew and modify into different adult cell types, have the potential to treat a variety of diseases and conditions such as Parkinson's, Alzheimer's, cancer, stroke, burns, heart disease, Type 1 diabetes, osteoarthritis, rheumatoid arthritis, muscular dystrophies, liver diseases and autoimmune diseases such as lupus. Hematopoietic stem cells, present in the bone marrow and precursor to blood cells, are used to treat blood disorders like leukemia and lymphoma. They are also being investigated for use in multiple sclerosis. Stem cells also have the potential to test and screen new drugs4.
(End of Part II. Part III will discuss current stem cell research.)
Hans S. Keirstead, Gabriel Nistor, Giovanna Bernal, Minodora Totoiu, Frank Cloutier, Kelly Sharp, Oswald Steward. "Human Embryonic Stem Cell-Derived Oligodendrocyte Progenitor Cell Transplants Remyelinate and Restore Locomotion after Spinal Cord Injury", J. Neurosci., May 2005; 25: 4694 - 4705.
Oswald Steward. "Human Embryonic Stem Cells Come to the Center", Spinal Connections, Spring 2002; 4: 3. Reeve-Irvine research center Publication.
Stem Cell Basics. The Official National Institutes of Health Resource for Stem Cell Research. http://stemcells.nih.gov
Stem Cells: Scientific Progress and Future Research Directions http://stemcells.nih.gov/info/scireport/
Weiss, Rick "The Stem Cell Divide" National Geographic Magazine, July 2005, Pg.3-27.
Reeve- Irvine Research Center - www.reeve.uci.edu
California Institute for Regenerative Medicine - www.cirm.ca.gov
International Society for Stem Cell Research. www.isscr.org