Stem cells are undifferentiated cells, called progenitors, which can reproduce endlessly and create a variety of specialized cells. These are used by the body to heal or replace damaged or dead tissue. A heart stem cell is a progenitor cell which has the ability to become heart tissue.
Early research in heart stem cell therapy relied upon embryonic stem cells, and was largely unsuccessful. It is very difficult to match embryonic stem cells for physical compatibility, so rejection was a continual concern. Most research is now done using adult stem cells taken from the patient’s own body, which eliminates this risk.
A discovery occurred in the summer of 2009 which posed a significant breakthrough in heart stem cell research. A team of scientists from the Harvard Stem Cell Institute have discovered the master heart stem cell which develops into three types of heart tissue. These tissues include cardiomycocytes, which are the heart muscle cells that contract and force the blood out of the ventricle, or main pumping chamber of the heart; smooth muscle cells which form the walls of blood vessels; and vascular endothelial cells that form the inner lining of new blood vessels.
The second stage of this study involves harvesting myoblasts, or immature muscle stem cells, from the patient's thigh, processing them in the lab, and then injecting them into the heart muscle. The study patients all have serious heart damage or disease which is untreatable by other methods. One potential danger from this procedure is the possibility of arrhythmia, or irregular heartbeat, but if this treatment is successful, it may become a preferred procedure for patients with severe heart damage.
Clinical trials in Switzerland and Germany have been conducted using stem cells from the patient's bone marrow. A heart stem cell infusion was administered after the first heart attack for members of the study group. Patients in a control study did not receive the heart stem cell treatment. After two years, none of the patients who received the treatment had suffered a second heart attack, which was not true of the control group. The clinics involved only used adult stem cells because the procedure did not involve the controversial destruction of an embryo, and did not carry any risk for rejection.
Heart stem cell research not only offers potential treatment of damaged heart tissue, but also an improved method for the development and testing of heart medications. Pharmaceutical companies currently rely on animal stem cells in the early stages of testing and development, which cannot accurately mimic all of the potential benefits or adverse reactions that can occur when the drugs move into human testing. The use of human stem cells can help reduce the cost of drug development by eliminating the extensive amount of money spent on drugs which must be abandoned because of dangers or a lack of effectiveness which is frequently not discovered until the last stages of testing. Costs would also be reduced due to the shortened time frames made possible by using heart stem cell created tissues from the beginning of the development process.