Stem cells: How we could restore the brain function after ischemic damage

Ischemic stroke is caused by occlusion of a cerebral artery, which gives rise to focal ischemia with irreversible injury in a core region and partially reversible damage in the surrounding penumbra zone. Stroke leads to neural death and consequently neurological impairments. Therapeutic intervention of stroke comprises thrombolysis and thrombectomy by chemical or surgical means, respectively. If done in time, these treatments may improve stroke outcome. However, many stroke patients cannot get sufficient degree of such treatment due to incompatibility or delay with admission to the clinic and suffer chronic neurological impairments. This has raised the need to develop effective treatments to improve poststroke recovery. Induced brain plasticity and cell replacement using neural stem cells are two promising strategies for therapy for stroke. This review will discuss the potential of such therapy as well as the factors that need to be taken into account for successful development of new therapy. Neural stem cells are multipotent with the capacity to self-renew and generate mature cells of the nervous system. They can be obtained from embryonic, fetal, or adult central nervous system, as well as through genetic reprogramming of somatic cells. Neural stem cell transplantation has proved to be effective in rodent studies. However, to translate these results into the clinical application, the variety of intrinsic and external factors must be carefully evaluated. This includes accurate stroke outcome predictions, choice of neural stem cell sources and evaluation of the risk of malignant transformation, selection of cell implantation paradigms and criteria for suitable patients.