Eight heart attack patients given injections of stem cells harvested from their own hearts all show improvement in their heart function two years after treatment. The patients, who were enlisted in an early clinical trial, received only one injection of the cells and no adverse effects were reported.
The results were announced at an American Heart Association conference. An accompanying statement from the university hospitals involved in the study proclaimed that 'for a phase I clinical trial, these results are the holy grail'.
Lead author of the trial, Professor Roberto Bolli, of the University of Louisville, USA, called the results 'exciting; the effect of these cells has continued for up to two years, and has gotten stronger. There was also a major reduction in heart scarring'.
In the study, cardiac stem cells were taken from patients who had suffered heart attacks and were undergoing heart bypass surgery. These cells were kept in vitro and encouraged to proliferate before being injected in large numbers into the damaged heart tissue of the original patients.
Four months after treatment patients' hearts were pumping seven percent more blood with every beat than before. Eight of these patients also had a longer follow-up and two years after the injection, an average increase of 12.9 percent was observed. No improvement was noted for the 13 control patients from whom stem cells were extracted but did not receive the injections.
The treatment also considerably reduced scar tissue. Nine patients had heart scans and new heart tissue had replaced the tissue destroyed by the heart attack in every case.
The researchers say the scan for one patient showed no evidence of his previous two heart attacks. 'What is striking is that we are seeing what appears to be a long-lasting improvement in function', commented Professor Piero Anversa of Brigham and Women's Hospital, Boston, USA, who co-presented the study with Professor Bolli.
The trial will be continued for a further two years to expand upon the current results and Professor Bolli says the findings also 'warrant larger, phase II studies. If [these] continue to confirm our findings, we potentially have a cure for heart failure because we will have something that conceivably, for the first time, actually regenerates dead heart tissue'.
The use of cardiac stem cells to treat heart failure patients is a relatively novel approach. Use of bone marrow-derived stem cells is slightly better established but a study presented at the conference using this approach was less encouraging. The trial, led Dr Jay Traverse from the Minneapolis Heart Institute Foundation in the USA, found no evidence that, six months after an intervention, heart function had improved in patients who had had bone marrow stem cell treatment after a heart attack.
Dr Traverse said that the trial nonetheless demonstrated that 'stem cell therapy is safe, and [had] set a baseline in terms of quantity of stem cells, type of stem cells, and severity of heart attack'.