Opening a New Path for Cardiac Stem Cells
Date: July 1, 2009
By the time Bill Beatty made it to the Emergency Department in Howard County, he was already several hours into a major heart attack. His physicians performed a series of emergency treatments that included an intra-aortic balloon pump, but the 57-year-old engineer’s blood pressure remained dangerously low. The cardiologist called for a helicopter to transfer him to Johns Hopkins.
It was fortuitous timing: Beatty was an ideal candidate for a clinical trial and soon received an infusion of stem cells derived from his own heart tissue, making him the second patient in the world to undergo the procedure.
Of all the attempts to harness the promise of stem cell therapy, few have garnered more hope than the bid to repair damaged hearts. Previous trials with other stem cells have shown conflicting results. But this new trial, conducted jointly with cardiologist Eduardo Marbán at Cedars-Sinai Medical Center in Los Angeles, is the first time stem cells come from the patient’s own heart.
Cardiologist Jeffrey Brinker, a member of the Hopkins team, thinks the new protocol could be a game-changer. That’s based partly on recent animal studies in which scientists at both institutions isolated stem cells from the injured animals’ hearts and infused them back into the hearts of those same animals. The stem cells formed new heart muscle and blood vessel cells. In fact, says Brinker, the new cells have a predetermined cardiac fate. “Even in the culture dish,” he says, “they’re a beating mass of cells.”
What’s more, says Hopkins lead investigator Gary Gerstenblith, the animals in these studies showed “a significant decrease in relative infarct size,” which shrank by about 25 percent. Based on those and earlier findings, investigators were cleared by the FDA and Hopkins’ Institutional Review Board to move forward with a human trial.
In Beatty’s case, Hopkins heart failure chief Stuart Russell extracted a small sample of heart tissue and shipped it to Cedars Sinai, where stem cells were isolated, cultured and expanded to large numbers. Hopkins cardiologist Peter Johnston says cardiac tissue is robust in its ability to generate stem cells, typically yielding several million transplantable cells within two months.
When ready, the cells were returned to Baltimore and infused back into Beatty through a balloon catheter placed in his damaged artery, ensuring target specific delivery. Then the watching and waiting began. For the Hopkins team, Beatty’s infarct size will be tracked by imaging chief Joao Lima and his associates using MRI scans.
Now back home and still struggling with episodes of compromised stamina and shortness of breath, Beatty says his Hopkins cardiologists were “fairly cautious” in their prognosis, but he’ll be happy for any improvement.
Nurse coordinator Elayne Breton says Beatty is scheduled for follow-up visits at six months and 12 months, when they hope to find an improvement in his heart’s function. But at least one member of the Hopkins team was willing to acknowledge a certain optimism. “The excitement here,” says Brinker, “is huge.”
The trial is expected to be completed within one to two years.