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Doris Taylor

A leader in the use of stem cells to repair heart damage, Doris Taylor co-led a team that used stem cells and minimally invasive surgery to improve heart function in pigs.

Mending broken hearts with stem cells

A University team improves the function of damaged pig hearts using stem cells and minimally invasive surgery

By Deane Morrison

August 4, 2006

Using stem cells and robotic surgical techniques, a team of University researchers has improved the function of pig hearts damaged in a way similar to what happens when a person has a heart attack. The technique may someday help people whose hearts are too fragile for conventional surgery while improving the overall efficiency with which cardiac muscle is repaired. The researchers used minimally invasive robotic surgical equipment to inject the stem cells into precisely targeted areas of the heart. The cells had been labeled with inert iron nanoparticles so that the researchers could tell whether they had engrafted in the heart or not. In six out of seven cases, the cells successfully established themselves in the pig hearts and heart function improved. Subsequent MRI (magnetic resonance imaging) images confirmed that the cells had integrated themselves into heart tissue. The work is published in the current issue of the Journal of Thoracic and Cardiovascular Surgery. The injected cells were myoblasts, which normally give rise to skeletal muscle cells, and mononuclear cells from bone marrow, which help new blood vessels form to keep the newcomer cells well nourished.

Besides being less risky for patients with heart damage, the technique can be performed while the heart continues beating and requires less time under anesthesia.

"What is new here is two things," says team co-leader Doris Taylor, a professor of physiology and medicine and holder of the Medtronic Bakken Chair in Cardiovascular Repair. "First, this is a precise way to get these cells to patients who might not otherwise be able to have the procedure because open chest surgery [where the chest is cut open] is too dangerous. These are likely older people or people with end-stage heart failure. "Second, the cells can be delivered in any patient in regions of the injured heart where a catheter cannot be used because the wall of the heart is too thin. Because you cannot see when you use a catheter, typically you can't use it in regions where the wall is thin due to a chance of perforation of the wall." Both cell types are in clinical trials at the moment. About 200 patients suffering from ischemic heart disease-caused by lack of oxygen to heart muscle due to constriction of coronary vessels-have been treated with skeletal muscle cells in clinical studies, and some are doing "remarkably better," Taylor says. But, she adds, as yet no randomized clinical trial has been completed. "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," says the other study co-leader, Harald Ott, M.D., who is now a surgical resident at Massachusetts General Hospital, in a news release. But once more studies with pigs or other experimental animals have been completed, the new technique could be applied in clinical trials. Besides being less risky for patients with heart damage, the technique can be performed while the heart continues beating and requires less time under anesthesia. Also, surgeons get a magnified view of the heart that allows them to target the cell infusion more precisely. Skeletal and bone marrow cells that have been injected into damaged heart tissue have been shown to improve function in the left ventricle-the heart's workhorse chamber, which pumps blood to most of the body. Taylor says that the muscle cells her team induced to grow in the heart can indeed contract, but the exact nature of the cells has yet to be determined. The skeletal muscle we use to flex our biceps is different from heart muscle in appearance and other properties, and it appears, says Taylor, that the myoblast-derived muscle is "more like heart muscle but not heart muscle per se. We don't know the final answer yet." More research must be done to determine what types of cells will work best in damaged hearts and whether the minimally invasive technique can deliver similar results for patients as traditional surgery. "But that is what keeps us busy," says Taylor, "finding the best treatment for patients with heart disease." Read about Taylor and the groundbreaking work that made her a sought-after member of the University faculty.