Eurostemcell

Stroke is caused by a blockage of the blood supply to a region of the brain (ischaemic stroke) or when a blood vessel in the brain bursts, spilling blood into the spaces surrounding brain cells (haemorrhagic stroke). Brain cells die when they no longer receive oxygen and nutrients from the blood or there is sudden bleeding into or around the brain.  Depending on the area of the brain that is affected,several functions may be impaired, including walking, talking and cognitive ability.
Stem cells are not currently used for treatment of stroke. Cells from fetal brain, bone marrow, umbilical cord blood, and embryonic tumours have yielded some improvements when transplanted into animal models of stroke. In a clinical triali in which patients received implants of nerve cells generated from a human embryonic tumour, some of the patients showed short-term improvements. In most of these cases, the transplanted cells acted by releasing substances that enhanced the survival of existing cells.

One of the favoured approaches to long-term, effective stem cell therapy for stroke is to transplant neural (brain) stem cells into patients. Ideally, these cells, generated from either embryonic or fetal brain stem cells, would then specialize into the cells that have died in the affected area of the brain. In several studies using animal models the new cells were able to move to the affected area, replace the dead cells, survive, connect to existing healthy cells and re-establish the damaged circuits of the brain. 

In January 2009, UK company ReNeuron announced it had UK regulatory approval to start a Phase I clinical study of its neural stem cell treatment, which is designed to regenerate portions of the brain impaired by ischaemic stroke. The trial will test the safety of this treatment, which involves the injection of cells from derived from human fetal tissue directly into patients' brains. It is due to start mid-2009 in Glasgow with four groups of three patients over the next two years.

Another approach to stem cell therapy for stroke could be to stimulate the stem cells naturally present in the brains of stroke patients, so that they could generate replacements for the dead cells. Scientists are testing several substances for their effect on stimulating the existing stem cells.