Stem cells have three important properties including unlimited self-renewal, multipotent differentiation potential and ability to repopulate tissue upon transplantation. This opens the possibility of transplanting these cells in the heart to replace and repair the failing heart muscle and produce new blood vessels for restoring the lost function of heart in certain cardiac diseases.
Many different types of stem cells, such as myoblast, bone marrow stem cells, endothelial stem cells, mesenchymal stem cells, cardiac progenitor cells and fat-derived stem cells, are being explored as potential therapeutic sources for this purpose. These cells are delivered to the heart using various approaches that may include:
- Intracoronary injection: This is the most common approach used, and involves the injection of the stem cells directly into the arteries of the heart using a balloon like catheter. The main concern with this approach is the possibility of embolism and plugging of the small vessels by the injected cells that may reduce the blood flow to the heart. However, it has shown an excellent safety profile in the clinical studies.
- Intravenous injection: This is the least invasive, and involves injection of stem cells via a vein.
- Transepicardial injection: This is the most invasive route, but also the most dependable. It delivers cells directly to the infarcted or scarred myocardium during a planned open heart procedure. It can thus be used with routine bypass surgery to inject stem cells into the areas that cannot be grafted.
- Transendocardial injection: This delivery method involves injection of the stem cells through the inner wall of the heart using a catheter. It employs a sophisticated imaging and guidance system to ensure delivery to the correct areas. This is comparatively less invasive than the transepicardial injection.
Stem cells are also being used as a vehicle for gene therapy. They are genetically engineered to provide a stable local secretion of recombinant therapeutic proteins. Though results of initial clinical trials utilizing gene therapy and stem cell therapy are encouraging, more research studies are needed before this therapy is used as a frontline treatment for cardiac failure.
Baylor Heart Hospital