THURSDAY, Feb. 2, 2006 (HealthDay News) -- In theory, it seemed simple: Doctors would transplant stem cells into diseased hearts to create new, healthy tissue that could reverse heart failure.
But experts gathered in New York City recently for a major conference on stem-cell therapy agreed that such a "cure" is proving elusive.
While small studies show modest benefit from these cell-transplant therapies, major improvements in heart function haven't yet materialized.
"Nothing that I've seen at this meeting, with regard to cell therapy, show that it prolongs the life of heart-failure patients," said Dr. Eric Rose, chairman of the department of surgery and associate dean of translational research at Columbia University College of Physicians and Surgeons, in New York City. He also co-chaired a special symposium on the therapy during the conference.
Despite the lack of major breakthroughs, Rose stressed the field is still in its infancy -- barely five years old.
And he said the fact that many heart-failure patients in clinical trials have benefited from stem-cell treatments shows the strategy still has great promise.
"For some patients, cell therapy may improve their quality of life," he said. "Those are the kinds of early signals that you look for in a field that's this young."
Heart failure occurs when the heart cannot pump blood fast enough or efficiently enough to meet the body's needs. In many cases, heart failure involves some kind of residual damage to heart muscle, such as that occurring after a heart attack. Restoring function to dysfunctional cardiac tissue is the goal of stem cell research.
Leading researchers from centers around the world presented their findings at the conference symposium. Some used stem cells sourced from the patient's bone marrow, while others turned to cells cultured from cell lines in a laboratory. Others used cells found in the peripheral blood supply, a much less invasive method.
The researchers also presented a variety of cell-delivery methods, the most common being injecting the cells directly into dysfunctional areas of the heart, either through invasive surgery or less invasive catheterization procedures.
The real problem usually arises after the cells reach the targeted tissue, however.
Experts estimate that because this damaged tissue area is often inflamed or otherwise hostile to stem cells, up to 95 percent of the cells will perish before they can do a patient any good.
Much of the work presented at the meeting examined the role of cytokines, kinases and other cellular compounds in this process.
The bottom line? "We just don't know what the best, most plausible recipe is" for maximizing stem-cell therapy's potential, said Rose, who is also surgeon-in-chief at NewYork-Presbyterian/Columbia Hospital, in New York City.
Still, positive results from small clinical trials are keeping hope alive.
Dr. Gustav Steinhoff, of the University of Rostock, Germany, presented six-month results from his phase 2 trial comparing outcomes of 20 heart-failure patients who received bone marrow stem cells, delivered via traditional balloon angioplasty to the heart.
Compared to 20 patients who received traditional angioplasty without stem cells, the stem-cell recipients gained a modest improvement in left ventricular (LV) ejection fraction -- the amount of blood forced out of the heart's left ventricle. Ejection fraction rose from an average of 37 percent before the procedure to 47 percent six months later, Steinhoff said.
An even bigger improvement was seen in a second study of 10 heart-failure patients treated with peripheral blood stem cells, delivered laparoscopically via a catheter to the heart. All of the patients had tough-to-treat non-ischemic heart failure -- a progressive form of the disease that's unrelated to a previous heart attack.
According to lead researcher Dr. Amit Patel, of the University of Pittsburgh, three months after the procedure, LV ejection fraction rose from a patient average of 27 percent to 45 percent -- a significant increase.
This benefit has been maintained over the longer term, Patel added, with most patients able to cut back on at least some of their heart medicines.
However, Rose cautioned that this study -- conducted at a heart center in Thailand but involving U.S. patients -- was "very small, and had no control group."
He also noted that many of the patients were former heavy smokers who had given up the habit prior to undergoing treatment. "Everyone knows that quitting smoking is a formidable treatment for heart failure in itself," Rose said. "This study needs a lot more replication."
A major clinical trial will come, he said, as soon as experts arrive at a consensus on the right stem-cell therapy "recipe." And he noted that there's real momentum toward that goal.
"At the American Heart Association's annual meeting five years ago, there were just five presentations on cell therapies," he pointed out. "This year, 25 percent of all papers presented were on stem cells or regenerative therapies."
So how long till the promise of stem-cell therapy becomes a reality? Rose said he remains cautiously optimistic.
"It's likely to be less than 10 years before there will be some routine form of this being used at the bedside, at least for some narrow [therapeutic] indication," he said. "And I think there are going to be a lot of cell therapies used in 25 years."
To learn more about heart failure, head to the American Heart Association.