Adult stem cell therapy – an option for the brain?

Many different cell sources have been investigated for cell replacement therapy in Parkinsons's disease, and some cells have been already tested in animal models and/or clinical trials. So far, results with embryonic ventral mesencephalic neurons have yielded the most marked effects. However, only about 300–400 patients have been transplanted worldwide, mainly due to a shortage of donor tissue. Therefore, alternative cell sources for neurotransplantation in PD are currently being explored, among them genetically modified cell lines, progenitor cells, embryonic and adult stem cells. The ideal cell for transplantation in PD disease can be expanded indefinitely and constitutes an unlimited pool of cells capable of differentiating into neurones that extend axons, form synapses and release dopamine in a regulated fashion. Stem cells could constitute such a new source of donor tissue: These cells are undifferentiated, have a high proliferative potential, generate a wide variety of differentiated progeny, possess the capacity for self-renewal and retain the multi-lineage potential over time. However, problems, such as phenotype instability and tumour formation have to be overcome. Stem cells have also been found in a variety of tissues in adults, such as certain brain regions, bone marrow, liver, skin and intestine. Compared to embryonic-derived stem cells, adult stem cells are more easily accessible; they can be obtained after donor consent and would allow for autologous transplantation without immunosuppression. The presentation illustrates the current advances in the field of adult-derived stem cells and illustrates different types of adult stem cells that are investigated for brain repair, the hopes connected with them and whether they can hold their promise.