Researchers at Northwestern University, Chicago, USA, have reported that the injection of stem cells into heart tissue can significantly improve the symptoms of people with severe angina. They found that exercise tolerance was increased and the number of pain episodes was halved compared to those not given the injections.
The new multi-centre study, published in the journal Circulation Research, investigated the safety and clinical benefit of using a patient's own CD34+ stem cells as a treatment. CD34+ stem cells circulate in the blood and have previously been shown to be able to create new blood vessels and improve function in diseased heart tissue.
Angina affects around 250,000 people in the UK and can make even very light exercise difficult. The chest pains, usually associated with heart disease, occur when there is not enough oxygen in the blood. Normal therapeutic measures include lifestyle changes, medication and surgery, but for some patients these treatments fail, leaving limited options.
Researchers took 167 patients with 'refraction' angina, which is unresponsive to treatment, and separated them into three groups. All patients were given a growth stimulation drug to increase the numbers of circulating stem cells, before these cells were extracted and purified. Each group then received either a low dose stem cell infusion, a high dose or a placebo injection.
After six months, patients in the low dose group showed a significantly reduced number of painful angina episodes during an average week - around six, compared to 11 in those given the placebo. The amount of exercise tolerated in patients also significantly increased in the low-dose group, at 139 seconds compared to 69 seconds in the control group. A similar improvement was seen in the high-dose group, but the team found no real advantage in receiving the high dose over the low dose.
Dr Douglas Losordo, the lead author of the study, said: 'While we need to validate these results in phase 3 studies before definitive conclusions can be drawn, we believe this is an important milestone in considering whether the body's own stem cells may one day be used to treat chronic cardiovascular conditions'.
He continued: 'One exciting potential of this procedure is that it will offer these folks an opportunity to get part of their lives back', adding that it could make the difference between being able to walk slowly and being able to ride a bike.
However, owing to the lack of research into the long term benefits of the treatment, and poorly understood underlying mechanisms, Professor Jeremy Pearson from the British Heart Foundation remained cautious: 'Until these uncertainties are resolved, it remains unclear how successful this treatment will prove to be'.