The patients were enrolled in a pilot study designed to test whether that therapy is safe.
'The improvements we saw in these patients are very encouraging, but it's too early to draw definitive conclusions about the effectiveness of the therapy', said Dr Soma Banerjee, a consultant at Imperial College Healthcare NHS Trust and one of the lead authors.
'We need to do more tests to work out the best dose and timescale for treatment before starting larger trials', Dr Banerjee added. At this stage, it cannot be excluded that the improvements in the treated patients occurred due to natural recovery after stroke.
Ischaemic stroke, affecting patients in this pilot study, occurs when blood supply to a certain part of the brain becomes limited due to the narrowing of blood vessels or a blood clot. It can take the form of either a total or partial anterior circulation stroke (TACS or PACS). TACS is the more severe variation; only four percent of patients experiencing TACS are expected to still be alive and independent six months after the stroke.
Of the treated patients, four suffered a TACS, resulting in loss of speech and paralysis of one side of the body. Among these, three were able to walk and look after themselves independently six months later. In addition, brain scans of all five patients showed that the size of brain damage decreased by an average of 28 percent over the six-month period. Importantly, no side effects from the stem cell therapy were observed and there were no signs of changes to the structure of blood vessels.
The stem cells, known as CD34+ cells, were collected from patients' bone marrow. They were then injected into an artery supplying the affected part of the brain, so that they could reach the site of the stroke. In previous studies on animals, these cells have been shown to release chemicals that promote growth of brain tissue and blood vessels.
The long-term goal of this research is to develop a drug mimicking the chemicals released by the CD34+ cells. 'Our aim is to develop a drug, based on the factors [chemicals] secreted by stem cells, that could be stored in the hospital pharmacy so that it is administered to the patient immediately following the diagnosis of stroke in the emergency room', said Professor Nagy Habib from Imperial College London.
This study was the first to specifically use CD34+ stem cells, and to administer them so early after the stroke. The findings were published in Stem Cells Translational Medicine.