Embryonic stem cells have amazing qualities. Created only days after an egg and sperm have come together, these few cells become the many that form the human body. Two unique characteristics (their capacity to continuously grow and divide, and their ability to become any cell type) give them another vital power: to cure disease.
Scientists have been using a different stem cell for over 40 years. Adult stem cells, removed from the spine, are commonly used to rehabilitate an immune system that has been weakened from diseases like leukemia and lymphoma. But their limitations restrict their usefulness. These stem cells can only transform into a few cell types, and their stubborn growth rates prove troublesome with therapies that require many stem cells.
This changed in 1998 when Dr. James Thomson first collected and grew human embryonic stem cells (hESC). Its technique begins with an egg fertilized in a laboratory. Four to five days after fertilization, the stem cells are removed, and placed in a dish where they grow and divide. The original cells multiply to become millions. Testing ensures that the final cells are healthy and genetically normal. After 6 months these cells become pluripotent, which means that they are ready to become any type of cell in the human body. When enough cells are pluripotent, they are ready to go to work, and scientists induce them to become specialized.
Stem Cell-Based Therapy
This primary goal of human embryonic stem cell research is to repair the body from injury and disease. Dr. Thomas Okarma, of Geron, says that results from this research mark the beginning of what is potentially a new chapter in medical therapeutics – one that reaches beyond pills to a new level of healing: the restoration of organ and tissue function achieved by the injection of healthy replacement cells. Once implanted these cells will continue to grow and divide, becoming a source of renewable, healthy cells.
Diseases that could benefit from cell-based therapy include Parkinson’s disease, diabetes, heart disease, vision loss, hearing loss, arthritis and Alzheimer’s’ disease. Injuries with the potential for repair using a cell-based therapy include strokes and spinal cord injuries. With millions of Americans affected by these issues, the potential benefit to society is staggering.
Cell therapies are all based on a similar procedure. To cure a disease, for example heart disease, doctors would start by obtaining embryonic stem cells specialized for the heart muscle. These would be injected into the heart, where they help repair the damage and grow new, healthy heart cells. Because stem cells continuously regenerate, this therapy could potentially continue to work long term.
Another important use of hESC is to research how genes turn on and off while a normal cell is growing. This will help scientists understand more about cell mutation, which cause cancer and birth defects. The possibility of keeping a cell’s genetics healthy potentially means the ability to stop diseases like cancer before they form.
Stem cells could also be used to test medications, reducing the need for human trials on untested formulas. It could result in the availability of better drugs to treat diseases. This process is already being used for some cancer drugs, which are tested on cancer cell lines.
Many research projects are underway worldwide. In January 2009 the FDA granted clearance to Geron to begin human trials of hESC therapy. Their trial will focus on patients with spinal cord injuries, and will use cell-based therapy.
The possibilities for hESC are impressive. As a science still in its infancy, the true potential for hESC may still be unrealized.
Stem Cell Basics: What are embryonic stem cells? . In Stem Cell Information [World Wide Web site]. Bethesda, MD: National Institutes of Health, U.S. Department of Health and Human Services, 2009 [cited Monday, November 16, 2009] Available at http://stemcells.nih.gov/info/basics/basics3