Stroke – Stem Cells Can Reduce Brain Damage

Rescuing a patient from a stroke and restoring cognitive functions are two significant medical challenges today. Blockage of a brain artery, usually by a clot or atherosclerotic plaque, results in reduction in oxygen supply to brain cells. If the supply of oxygen is interrupted for a long time, brain cells die resulting in severe loss of motor and cognitive functions. Therapeutic approaches to prevent the formation of plaques or blood clots are not a hundred percent successful in preventing a stroke. Recent research has focused on aiding regeneration of brain cells after an ischemic stroke and stem cells have been used with reasonable success.

Experiments conducted on rats show that intravenous injection of stem cells derived from adipose tissues as well as mesenchymal stem cells derived from bone marrow supported the recovery of brain cells after a stroke. In these experiments, rats were subjected to a stroke by blocking their middle cerebral artery permanently. Stem cells from bone marrow as well as fat cells were injected 30 minutes after induction and the health of the animals was assessed at 24 hours and 14 days after stroke. In the recovery period, animals injected with stem cells showed increased levels of vascular endothelial growth factor and synaptophysin. The injected stem cells did not migrate to the site of the lesion but presumably acted as a source of neurotrophic growth factors.

In another study, stem cells from the dental pulp of human deciduous teeth (milk teeth) were grafted in the brains of mice one day after induction of a stroke. In some animals, the culture medium in which these cells were grown was used instead of the cells. Mice treated with human dental pulp stem cells and conditioned medium from these cells showed better recovery and neurological outcome than untreated mice. Grafted stem cells as well as the conditioned medium inhibited death of neurons in the recovery period and prevented cell destruction resulting from inflammation. In these experiments, the actual integration of human dental pulp stem cells into the brain tissue occurred at very low frequency.

Both studies present important insights in the process of regeneration of brain cells followed hypoxic and ischemic stroke. Stem cells secrete a number of growth factors which help to promote generation of new neurons post a stroke. The results presented by Yamagata and colleagues where just the culture medium from dental pulp stem cells was effective in restoring brain tissue and neurological functions indicate that a suitable “growth factor cocktail” can be derived from cultures of stem cells to treat stroke. Since intravenous injection of stem cells also helps recovery from stroke, it is easy to deliver such a therapeutic intervention. A xenograft of human dental pulp stem cells was successful in helping mice recover from a stroke. It would be interesting to know whether stem cells from other animal systems have a similar beneficial effect on human neurons as well.

References

Gutierrez-Fernandez M, Rodriguez-Frutos B, Ramos-Cejudo J, Vallejo-Cremades MT, Fuentes B, Cerdan S, & Diez-Tejedor E (2013). Effects of intravenous administration of allogenic bone marrow- and adipose tissue-derived mesenchymal stem cells on functional recovery and brain repair markers in experimental ischemic stroke. Stem cell research & therapy, 4 (1) PMID: 23356495

Yamagata M, Yamamoto A, Kako E, Kaneko N, Matsubara K, Sakai K, Sawamoto K, & Ueda M (2013). Human dental pulp-derived stem cells protect against hypoxic-ischemic brain injury in neonatal mice. Stroke; a journal of cerebral circulation, 44 (2), 551-4 PMID: 23238858

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