A group of US researchers have found that injecting human stem cells derived from bone marrow into the brain after it has suffered a stroke can alleviate symptoms. The research was carried out at the Center for Gene Therapy, Tulane University, New Orleans, and reported in Proceedings of the National Academy of Sciences.
Strokes are characterised by reduced blood flow to the brain caused by a blockage or bleed, thereby starving the brain of blood. An immune response ensues, during which healthy tissue is attacked and nerve damage is caused. Stroke is the third most common cause of death in the UK, and also the leading cause of severe disability. Every year 150,000 people in the UK suffer from a stroke - mostly people over 65 - but it can affect people of all ages.
During the study, a stroke-like state was simulated in six mice by blocking their carotid arteries and therefore halting the flow of blood to the brain. The researchers then injected the mice with human mesenchymal stromal cells (bone marrow stem cells), and found that neuron damage was reduced by up to 60 per cent.
Instead of generating new cells as expected, the team revealed that the cells exerted the effect by changes in gene expression, resulting in production of biochemicals which reduced inflammation. After the blood flow was stopped, 586 genes were more active in untreated mice. In mice injected with stem cells, 10 per cent fewer of these genes were more active. This suggests that those genes are likely to be involved in the immune response. In addition, the motor responses of the treated mice were dramatically improved, shown by better performances in movement, cognitive and behavioural tests than untreated mice.
Professor Darwin Prockop, co-author of the study, said that it 'provides for the first time a molecular explanation of how adult stem/progenitor cells can ameliorate ischaemic (reduced blood flow) damage to the brain'. He also highlighted that 'the fascinating thing was the cells were talking to each other - human cells and mouse cells' and that 'the human cells specifically turned down immune and inflammatory responses'.
The team is currently building a facility of sufficient standard to produce stem cells for use in patients, and is planning further testing of the technique in animals for efficacy and toxicity. Following this, human clinical trials should begin in the hope that stem cells can be used to treat strokes in humans in the future.
