Using minimally invasive robotic surgery equipment, researchers injected the stem cells into the damaged hearts. The cells were "labeled" with iron particles so that researchers would be able to see if they engrafted in the pig hearts.
The cells were successfully transplanted in six of seven cases. Subsequent MRI studies showed that the cells took hold in the heart and function improved.
The team used a combination of skeletal myoblasts, or cells that give rise to muscle, and bone-marrow derived cells. Both cell types have been shown to improve the development of new blood vessels and to improve function of injured heart muscle. Both are in human clinical trials as well.
The research is published in the current issue of the Journal of Thoracic and Cardiovascular Surgery.
Once more animal studies are completed, the technique could be applied in human clinical trials.
"In people with heart failure, open surgery can be risky; finding a minimally invasive technique to deliver cell therapy to the damaged cardiac tissue would reduce the risk to patients," said Doris A. Taylor, Ph.D., professor of Physiology, holder of the Medtronic Bakken Chair in Cardiovascular Repair, and co-leader of the study.
The minimally invasive approach would offer several benefits for people in heart failure, Taylor said. It is less dangerous to the patient. It can be done while the heart is still beating, and requires less time under anesthesia. It also offers surgeons a magnified view of the heart and allows them to target the cell infusion more precisely.
Harald Ott, M.D., co-leader of this study, now a surgery resident at Massachusetts General Hospital in Boston, pointed out, "Currently these types of cell therapies, in which stem cells are injected into damaged hearts, are only available to people who are enrolled in clinical research trials."
Skeletal and bone marrow cells that are injected into damaged heart tissue have been shown to improve function in the left ventricle, the chamber of the heart that pumps blood into the aorta, the main artery through which oxygen-rich blood flows from the heart to the body.
Taylor said more research needs to be done to determine which types of cells are most beneficial to infuse into damaged hearts, as well as if the minimally invasive technique can deliver similar results as traditional open surgery. "But that is what keeps us busy," she added," finding the best treatment for patients with heart disease."