Patients with heart failure could one day be treated with injections of their own stem cells, according to new US trials that provide the 'first convincing evidence' that such an approach might work. Previous studies have produced conflicting results, and some researchers have questioned whether stem cell therapies for failing hearts are ready for human trials. But the new findings, presented at the American Association for Thoracic Surgery meeting in Toronto last week, show that injections of bone marrow stem cells can increase the strength of damaged heart muscle.
There is some evidence that adult stem cells present in bone marrow can produce other body tissues, as well as different types of blood cells. But it is not known exactly how this happens - it could be that the cells are fusing with existing cells, rather than transforming into them. Several preliminary human trials suggest that blood stem cells from bone marrow can successfully repair heart attack damage, while others have highlighted potential problems with this approach.
In the latest trial, researchers based at the University of Pittsburgh School of Medicine studied 20 South American patients undergoing bypass surgery for heart failure. Half the participants received up to 30 injections of their own bone marrow stem cells (taken from the hip bones), directly into the heart. The team found that the hearts of the treated patients were subsequently able to pump more blood than those who just had the surgery. It is thought that the stem cell therapy worked by helping the damaged heart muscle to regrow, and also by triggering the formation of new blood vessels.
The treated patients had higher levels of a key protein involved in cell communication, called connexin 43, which is normally reduced in people with heart failure. Team member Amit Patel said: 'We do not know if this increase was due to the growth of new heart muscle cells resulting from the stem cell injections or whether the stem cells coaxed existing cells to come out of hibernation'. None of the patients have had any side effects, in contrast to those taking part in a South Korean trial reported earlier this year. The researchers now plan to carry out further trials, to replicate their findings and to optimise the treatment. Belinda Linden, of the British Heart Foundation, welcomed the study, but stressed that 'it must be remembered that this treatment is experimental'.