A stem cell treatment for heart failure patients is safe and shows early signs of effectiveness, according to a study published Wednesday.

The study was conducted by Japanese researchers in 27 patients, who received transplants of stem cells taken from their own thigh muscles. There were no major complications, and most patients showed considerable improvement in their symptoms.

The study was published in the open-access Journal of the American Heart Association. Dr Yoshiki Sawa of Osaka University Graduate School of Medicine was the senior author. It can be found at j.mp/stemheart.

However, two San Diego cardiologists who do stem cell research on heart disease cautioned that similar clinical trials have shown promise over the years, only to fail at the end for various reasons. There is no approved stem cell therapy for heart failure.

So while the trial itself appears to be well-conducted, the researchers are very far from actually proving their treatment is effective, said Dr. Richard Schatz of Scripps Health and Dr. Eric Adler of UC San Diego School of Medicine.

For one thing, the trial was small, they said, and larger trials are where the most rigorous scientific evaluations are made.

These early trials have looked beneficial in the past, Adler said. When we do the larger trials, the results are more equivocal.

Adler said the signs of efficacy in this trial are modest. For example, the change in ejection fraction, a measurement of efficiency in pumping blood, rose from 27 percent to 30 percent in 15 of the 27 patients. Their heart failure was associated with a lack of blood flow, or ischemia. The remaining non-ischemic patients actually had a slight decline.

The entire field of stem cell and regenerative therapy for heart disease has been a disappointment to date, Schatz said.

Weve been at it for 20 years now, and we dont have a product or a positive (late-stage) trial, so that tells you pretty much everything you need to know, he said. Its not for lack of trying or billions of dollars invested. Its just very, very difficult.

The cardiac field has had more success with other technologies, such as cardiac stents. Schatz is the co-inventor of the first stent.

In the study, the researchers acknowledge that previous attempts had only been modestly effective. They devised a method of producing sheets of muscle stem cells and attaching them to the inner layer of the sac that encloses the heart, a layer that rests directly on the heart surface.

The stem cell sheets stimulate healing by producing chemicals that stimulate cardiac regeneration, the study said. The cells themselves dont survive in the long term, but by the time they die they have served their purpose.

Loss of function

Heart failure is a progressive disease in which the heart gradually loses its ability to pump blood. This can be triggered by a heart attack or any other cause that damages the heart muscle.

When damaged heart muscle is replaced with scar tissue, as often happens, the heart loses pumping capacity. It becomes overstressed, and its output of blood declines. This limits the patients ability to engage in intensive physical activity. In advanced cases, patients may become bedridden.

Existing treatments include drugs and LVAD units, which take over some of the hearts function to relieve stress. Some drugs may help the heart work more efficiently, but none have been shown to improve heart failure by actually regenerating lost heart muscle.

Stem cell therapy is tested in patients who havent responded well to other treatments. Trials have been and are being conducted in San Diego area hospitals.

Scripps Health has been testing a cardiac stem cell therapy from Los Angeles-based Capricor. The cells, taken from donor hearts, are injected into the coronary artery, where they are expected to settle in the heart and encourage regrowth.

UC San Diego is testing a heart failure therapy from Teva Pharmaceutical Industries. It consists of bone marrow derived mesenchymal precursor cells. These can give rise to several different cell types, including muscle cells.

And many other trials are going on throughout the country and internationally.

Adler and Schatz said theres reason for optimism in the long run, as technologies improve.

Just because the other trials have been negative doesnt mean this technique wont be beneficial, Adler said. Its just too early to tell.

That said, Schatz emphasized that the nature of the three-phase clinical trial process means that the show-stoppers for a treatment typically appear late.

Tighter standards needed

Clean trials trials where we all agree that this is the patient population we want to look at, are needed, he said.

For example, heart failure comes in two types, he said. Ischemic heart failure is caused by heart attacks and blocked arteries, which impede blood flow. Non-ischemic heart failure can be caused by damage from diseases, such as a virus.

Non-ischemics can be younger people, in their 20s and 30s, while the ischemic patients are older. Mixing those patient groups in a single trial is a mistake, he said.

Theyre different animals, Schatz said.

Another pitfall is failing to screen carefully enough to enroll only patients likely to benefit, Schatz said.

You can have a patient who has chest pain, and coronary disease just incidentally, he said.

His shoulder or chest pain is from a virus. So he goes into the trial and gets a placebo injection in his arm of cortisone, and his arm pain goes away. And because hes in that placebo group, hes counted as a success the pain went away. It has nothing to do with his heart. Thats an extreme example, but we actually saw that happen.

In a failed gene therapy trial for heart disease, some patients apparently had received the injection in the wrong location, missing the heart muscle, Schatz said.

You assume they got the gene, but they didnt, Schatz said. The study was negative, and thats why I think it was negative.

Such errors dont show up in Phase 1 trials, Adler and Schatz said, because theyre focused on evaluating safety. And these early trials dont have many patients, there arent enough to comfortably determine the therapy is really effective.

By the last stage of the trial, these sources of error have often been identified and trial standards have tightened up. And thats when the faulty assumptions made early appear as the trial ends in failure.

Despite those forbidding hurdles, Adler said research should continue.

This disease is killing a lot of people. Theres not going to be enough hearts to go around for transplant. Theres six million Americans with heart failure, and theres 2,000 heart transplants a year. So coming up with novel regenerative cell-based therapy is something were still excited about.

bradley.fikes@sduniontribune.com

(619) 293-1020

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Study: heart failure stem cell therapy safe, shows early signs of effectiveness - The San Diego Union-Tribune