Stem cell stroke treatment trial results 'show promise'

Behind the Headlines

Tuesday May 28 2013

It is hoped that stem cells could help repair damaged brain tissue

'Stroke patients see signs of recovery in stem cell trial,' BBC News reports. The news, which has saturated the media, is based on a press release from the University of Glasgow. This press release reports further positive early findings of the world's first clinical trial of the use of brain stem cells to treat stroke.

This research – known as the PISCES trial – is a phase I trial. Such trials typically involve giving a small number of people a new treatment to see if it is safe. They are not designed to test if the treatment is effective, so any results that suggest this should be treated with caution.

This study looked at the safety and tolerability of a stem cell therapy called ReN001 in the treatment of ischaemic stroke, where the blood supply to the brain is blocked by a blood clot.

The findings, which were reported in a press release, suggest that the nine people included in the study experienced no adverse effects and showed a modest improvement in stroke-related symptoms.

However, the full findings from the PISCES trial are yet to be published in a peer-reviewed journal. Until this happens, it is worth exercising a little healthy scepticism about the claims being made. This research is still at a very early stage, and, as the professor in charge of the trial points out, the improvement in symptoms could be down to the placebo effect.

It is likely that the encouraging results seen in this trial will lead to a phase II trial involving larger groups of stroke patients. This type of trial may give a better picture about whether ReN001 stem cell therapy is truly effective in the treatment of stroke.

Can we believe claims about stem cell treatments?

Stem cell research is still at a very early stage – we are only just beginning to see the first trials of stem cell treatments in humans. Many of the headlines about stem cell treatments gloss over the fact that we are still a long way from having proven, effective treatments ready for general use. Predictions about how soon these therapies are likely to be available are often wide of the mark.  


For more information, read the Behind the Headlines special report, Hope and hype: stem cells in the media.

What is a stroke?

A stroke is a serious medical condition that occurs when blood supply to the brain is disrupted, leading to a loss of, or reduction in, brain function. There are two types of stroke:

  • Ischaemic stroke accounts for about 80% of strokes. In ischaemic strokes, the blood supply to an area of the brain is cut off due to a blood clot.
  • Haemorrhagic stroke is where there is a leakage of blood in the brain due to a blood vessel bursting. This blood causes pressure on the brain, eventually leading to damage.

This new stem cell treatment development only relates to ischaemic stroke. With ischaemic stroke, the disruption of the blood supply to the brain can starve brain cells of oxygen, causing them to die. It is not uncommon to see large areas of damaged tissue on the brain scans of people who have had an ischaemic stroke.

Depending on the part of the brain affected, people who have had a stroke may experience difficulties with speech and language, orientation and movement, or memory. These problems can be permanent or temporary.

Any advances in the treatment of stroke are particularly important – about 150,000 people in the UK have a stroke each year, with potentially devastating consequences. The only current treatment for ischaemic stroke occurs in the acute phase of the condition (within several hours of the stroke), when anti-clotting agents are administered to dissolve the clot that has blocked the blood flow to the brain. Unfortunately, only a small proportion of patients get to hospital in time to be treated in this way.

There are no existing treatments for an ischaemic stroke beyond the initial acute phase. However, rehabilitation can alleviate the disabilities caused by a stroke.


What are stem cells?

Stem cells are the very early (precursor) cells that can develop into almost all other types of cell in the body, such as skin, muscle or blood cells. They are the building blocks of the body and are unique because they can renew themselves. They also have the ability to form different specialised cell types.

Broadly, there are two types of stem cell: embryonic stem cells, found in early embryos and in significant numbers in the foetus and cord blood at birth, and adult stem cells, which are found in small numbers in bone marrow and blood.

There is currently a great deal of medical research looking at the potential for harnessing the regenerating power of stem cells to repair damaged tissue and fight disease. This is based on the idea that stem cells could be used to produce appropriate cells to repair or replace damaged tissue.


What are the implications of this stem cell research?

The PISCES study is the world's first clinical trial of a neural stem cell therapy for stroke patients. The phase I trial was designed to look at whether the use of the experimental treatment (ReN001 therapy) was safe and tolerable. This type of safety trial precedes tests of effectiveness. As such, treatments in phase I trials are usually applied at low dosages and in small numbers of people.

In this trial, the stem cell therapy was initially tested at lower doses in three people. After this was found to be safe and tolerable, it was tested on a further six people at higher doses. The researcher leading the PISCES study, Professor Keith Muir of the University of Glasgow, said: "Data from the first nine patients treated has shown no cell-related or immunological adverse effects."

This early stage of testing has shown positive findings, but the effectiveness of the therapy, and further information on possible adverse effects, needs to be tested in larger phase II and phase III trials before any conclusions can be drawn about how well it works and how safe it is for treating people who have had an ischaemic stroke.


What could happen next?

The University of Glasgow press release reports that the phase I trial is drawing to a close and its results will be published in 2014. It also states that an application for a phase II trial is expected to be submitted to the UK regulators in July 2013.

If the application is approved, the trial is likely to start later this year. The proposals for this phase II trial mean that it will be carried out across several research centres, and will look at how well the stem cell treatment works for an initial group of 20 stroke patients.


Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.

Analysis by Bazian

Edited by NHS Choices


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Someone has a stroke every five minutes in the UK, and strokes are the third most common cause of death. The cause varies from person to person but it's important to know what your personal risk factors are.

Media last reviewed: 14/07/2015

Next review due: 14/07/2017

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