A: Researchers are testing treatments that combine genes and stem cells – with the idea that the synergistic benefits of this combined therapy are better than those of either the gene or stem cell therapies alone.
Dr. Duncan Stewart of the Ottawa Health Research Institute (OHRI) developed the world’s first experimental gene plus cell therapy for pulmonary arterial hypertension, a devastating heart-lung disease affecting mainly young women, in which the vessels that carry blood from the heart to the lungs become damaged. The new treatment involves adding a gene that makes nitric oxide (which stimulates the growth and repair of blood vessels) into stemlike cells called endothelial progenitor cells, which circulate in the bloodstream. He then injects these souped-up cells into the lungs. "We're seeing improved lung function in these patients, and the safety looks excellent," says Stewart, a cardiologist and CEO of the OHRI.
Both gene therapy and stem cell treatments have been tested separately in heart attack patients, with only limited success. One reason for this, suggests Stewart, is that the stemlike cells circulating in the blood of patients with heart disease don’t produce enough nitric oxide.
Stewart is now set to launch a three-year clinical trial in which investigators will be injecting heart attack patients in Ottawa, Montreal and Toronto with stemlike cells that contain the nitric oxide gene. This strategy, he adds, holds tremendous promise in the field of cardiovasclar research. "Unlike drug treatments, it could potentially restore functional tissue in regions of the heart that otherwise would form only scar tissue."
Q: Some patients with a faulty aortic valve – the valve controlling blood flow from the heart to the rest of the body – are too sick for surgery. Are there other alternatives?
A: Yes. A good example is a procedure pioneered by Dr. John Webb of the Providence Heart and Lung Institute at St. Paul's Hospital in Vancouver. This minimally invasive technique, known as a percutaneous (through the skin) valve replacement, replaces the aortic valve in patients who aren't candidates for open-heart surgery. Without a valve replacement, most of these patients would die within three to five years.
In this new procedure, Webb inserts a replacement aortic valve (attached to a catheter) through an incision on the upper thigh and threads it along an artery into the heart. Unlike open-heart surgery, the procedure does not require cracking the ribs and breastbone, stopping the heart or putting the patient on a heart-lung machine.
Webb has performed this procedure on more than 150 patients, and trained doctors at hospitals in Canada (including Laval Hospital in Quebec City, McGill University Health Centre in Montreal, and the UHN's Toronto General Hospital) and the U.S. and Europe.
The results have been excellent. "The success rate is over 95 per cent," says Webb. "It’s very exciting to see patients who had no options have their valve disease cured in a matter of hours and leave hospital in a few days," whereas about 30 per cent of them would have died within a month after conventional open-heart surgery. Webb predicts that not only high-risk patients but also many others who need a new aortic valve may one day be candidates for this procedure.
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