by Richard A. Schatz, MD, Scripps Health
Before cells in the body become heart cells, blood cells or skin cells, they start out in the bone marrow as undifferentiated stem cells. Unlike other cells, only these immature stem cells have the ability to divide and become another highly specialized cell or tissue such as bone, blood, or heart.
This unique ability of stem cells has been the source of intense research for many decades. Researchers have experimented with different cell types designed to grow new blood vessels in patients whose own blood vessels are critically blocked or repair damage to the heart wall from prior heart attacks. At Scripps, for example, we are currently planning several clinical trials to study the effectiveness of stem cells in treating people with these types of cardiac conditions.
How are the cells for stem cell research and therapy obtained? There are two main sources: embryonic stem cells and adult stem cells. Scripps’ clinical trials for heart disease will use only adult stem cells, which are found in several adult tissues, such as bone marrow and adipose or fat tissue. Stem cells taken from a patient’s own body are known as autologous stem cells; those donated by someone else are called allogeneic stem cells.
Stem cells have amazing potential for a diverse range of heart conditions. One of our clinical trials already underway will study the role of stem cells in treating refractory angina. Angina develops when plaque builds up in the arteries of the heart, slowing the flow of blood and depriving the heart of adequate oxygen-rich blood. Angina often feels like pressure, pain or tightness in the chest, and may be accompanied by shortness of breath, fatigue, nausea and dizziness. In people whose angina is stable, the symptoms often resolve with standard treatment. Refractory angina, however, does not respond to treatment and can be debilitating. Patients have relentless chest pain, weakness and sometimes difficulty breathing. By injecting millions of specialized stem cells into the heart through a minimally invasive catheter procedure, we hope that these patients will generate new blood vessels and essentially perform their own “bypass surgery” within four to six months following the procedure, ideally reducing or eliminating their chest pain.
Another clinical trial underway will study patients who have had a severe recent heart attack and, despite having received a stent, have a heart muscle that remains damaged and weak. In this trial, we will be studying whether injections of stem cells obtained from the patient’s own bone marrow a few days after the heart attack will help the heart heal more quickly by reversing the damage from the heart attack and making the heart pump better.
In future trials, we plan to study whether stem cell therapy can help patients with severe congestive heart failure whose hearts are not pumping well for any reason. By injecting either autologous or allogeneic stem cells into the heart muscle, we will determine whether the therapy can help the heart pump more strongly. Because all of the trials are randomized, neither the participants nor the doctors will know until the trial is completed whether participants received stem cells or placebos.
While much more research is needed before we can even begin to tap into the potential of stem cell therapy, these amazing cells hold great promise for medicine in the years to come.