Until recently, most of the news about stem cells focused on those derived from human embryos. These so-called "undifferentiated" cells have been heralded for their potential to treat or even cure-diseases ranging from Alzheimer's and Parkinson's to diabetes and spinal cord injuries.
Embryonic stem cells are capable of producing heart cells, blood cells, brain cells or any one of the more than 200 other types of specialized cells in the body. Although research related to embryonic cells is promising, it still is preliminary and has been performed only on laboratory animals. Human embryonic stem cell clinical trials will not begin for at least one year-and embryonic stem cells remain controversial, because some people believe that it is unethical to use the cells for medical purposes.
Now: Researchers are discovering new uses for adult stem cells, which have long been used in transplants (from the patient's own bone marrow or blood...or from the bone marrow of someone who is a genetic match) to treat leukemia, lymphoma and, more recently, as an adjunct therapy for advanced malignancies of the prostate, kidney and bladder.
Researchers at the University of California at Davis have for the first time identified adult bladder stem cells which might be used in the future to regenerate replacement bladder tissue in people whose bladders are too small or don't function properly, such as adults with spinal cord injuries or bladder cancer. These findings were reported in the May 2008 online issue of the American Journal of Physiology-Renal.
Other exciting research: Elsewhere, hundreds of recent clinical trials in the US and around the world show that adult stem cells found in specific tissues and organs, such as the heart, muscles and bones-or "harvested" from the patient's blood or bone marrow-can treat a variety of medical conditions, including congestive heart failure, rheumatoid arthritis and multiple sclerosis.
At the UC Davis Stem Cell Center, we often refer to adult stem cells as the "paramedics of the body" because they move very quickly to areas of tissue damage and secrete substances that repair tissue and improve blood flow.
Future research at our center will study the use of adult stem cells for, among other problems, repairing heart tissue after a heart attack...and restoring restricted blood flow in peripheral artery disease (PAD), a blockage in the arteries, occurring mainly in the legs.
Some current research in these areas…
A review article in an issue of the Journal of the American Medical Association cited more than 30 studies that have been conducted using adult stem cells in people who have had heart attacks or who suffer from cardiovascular disorders.
How they work: Adult stem cells from the bone marrow or blood may generate compounds, including proteins, that stop cell death and promote the body's own capacity to regenerate blood vessels.
Results have included fewer deaths from heart disease...an 18% improvement in the strength of the heartbeat, on average...less severe angina (chest pain)...fewer arrhythmias (abnormal heart rhythms)...slower rates of new arterial blockage...and better daily functioning.
Peripheral Artery Disease
About 10 million Americans suffer from peripheral artery disease. When the disease advances to the point where pain in the lower legs is nearly constant, and leg wounds and ulcers won't heal, the condition is called critical limb ischemia (CLI). CLI affects 1.4 million Americans. Every year, 100,000 people with CLI lose a toe, foot or an entire leg to amputation.
Latest development: In January 2008, researchers at Northwestern University Feinberg School of Medicine began studying 75 people with CLI for whom all standard therapies, including the use of a balloon-tipped catheter to open blocked arteries, had been unsuccessful.
Half the CLI patients were given a drug that stimulated the release of CD34+ cells (a type of adult stem cell from their bone marrow. The cells were then collected via an intravenous line, and a sophisticated machine "purified" that mixture to increase the concentration of CD34+ cells. The patients were injected intravenously with the cells. Researchers hope the cells will accumulate in-and help repair—the damaged arteries as well as attract other adult stem cells to the area.
Other promising research…
In the 1990s, doctors began to use stem cell transplants to treat autoimmune diseases, in which the white blood cells of the body's immune system attack a particular organ or type of tissue-for example, the joints in rheumatoid arthritis...the coverings (sheaths) of nerves in multiple sclerosis...and the pancreas in type 1 diabetes. The transplants were performed to generate new white blood cells that would not attack the body.
Recent clinical studies have used adult stem cells to repair tissue damaged by…
- Crohn's disease. Two-thirds of the 21 patients treated had complete remission of this form of inflammatory bowel disease.
- Lupus. Nearly two-thirds of the 26 patients treated were "event-free" for five years from the symptoms of this autoimmune disease. Lupus can attack the skin, joints, heart, lungs, blood, kidneys and brain.
- Multiple sclerosis. Of 21 patients, none had progression of this neurological disease over two years, and 62% were improved.