The treatment is believed to be the first in the world to test the ability of a patient’s own stem cells, genetically engineered to have extra-strong healing powers, to repair damaged tissue caused by a heart attack.
Starting in February, as many as 100 patients in Ottawa, Toronto and Montreal will be enrolled in the study led by researchers at the Ottawa Hospital Research Institute.
The trial marks a pivotal step in the uncertain science of growing new heart cells.
If the treatment works and is eventually approved for clinical use, it would not replace existing therapies such as drugs to break up blood clots and angioplasty to widen coronary arteries
Research has shown that the human heart has a limited capacity to generate new heart-muscle cells, half of which are replaced over the course of a person’s lifetime. But the heart’s capacity to repair itself does not accelerate in response to a heart attack. Instead, the damaged cells are replaced by scar tissue, which does not contract, impairing the heart’s ability to pump blood efficiently.
“You get into this spiral where, over time, the heart gets bigger and bigger and weaker and weaker,” said Dr. Duncan Stewart, the trial’s lead investigator and chief executive of the research institute.
As a result, a significant number of the 54,000 Canadians who survive heart attacks every year go on to develop congestive heart failure, which lowers their quality of life and increases their risk of death.
The promise of stem cells is based on the idea that the best way to repair the body is with its own cells and signalling molecules.
To date, more than 2,000 heart-attack survivors, mostly in Europe, have received experimental injections of stem cells, often ones taken from their own bone marrow. However, the overall degree of improvement in the patients’ heart function has been disappointingly modest. That has led some researchers to think the stem-cell system itself might age and lose its effectiveness in older people.
To solve this problem, Stewart’s team has come up with a way to turn back the biological clock of aging stem cells by genetically reprogramming them to have stronger healing properties. The theory is that these younger, more potent stem cells could grow enough new blood vessels to improve, if not fully restore, the heart’s ability to pump blood.
In fact, previous studies have suggested that stem-cell therapy can still improve a patient’s quality of life even if the overall improvement to heart function is incremental.
“There’s less development of heart failure, less hospital readmission, less bypass (surgery) and better survival,” said Stewart. “The data suggest you don’t need to fully normalize. You just need to stabilize to such a degree that you’re unlikely to go down that slippery slope.”
For his study, Stewart plans to use stem cells harvested from a patient’s blood instead of those from the bone marrow. He is also looking to compare the effectiveness of the genetically enhanced stem-cell treatment with regular stem cells and a placebo.
The trial would be done under rigorous conditions, meaning all patients would be randomly assigned one of the three treatments, with neither they nor the researchers knowing which one was given. After six months, the patients’ heart function would be measured using MRI scans.