Stroke is caused by a blockage of the blood supply to a region of the brain. When such a blockage happens, the brain cells in that area are deprived of oxygen (a situation called ischaemia) and nutrients, and eventually die. Depending on the area of the brain that is affected, several functions may be impaired, such as walking, talking and cognitive ability.

Stem cells are not currently used for treatment of stroke. Cells from foetal brain, bone marrow, umbilical cord blood, and embryonic tumours have yielded some improvements when transplanted into animal models of stroke. In a clinical trial 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.

An alternative 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.

Relevant links:
Stroke Alliance for Europe - listing of European patient organizations
The Stroke Association
The Stroke Trials Directory of the Internet Stroke Center
The National Institute of Neurological Disorders and Stroke