Stem cell therapy for diseases in the nervous system - A potential for regeneration of inner ear

Recent advances in stem cells research and its application to medicine are reviewed. Stem cells are composed of embryonic stem cells (ES cells) and somatic stem cells, in which neural stem cells, hematopoietic stem cells, mesenchymal stem cells, and other forms have already been identified. Stem cells have a possibility of regenerating damaged organs, which were difficult to transplant, and may be able to serve as a source of donor organ to be used for transplantation. In nervous systems, ES cells, neural stem cells and mesenchymal stem cells are investigated to regenerate damaged central and peripheral neurons. ES cells and neural stem cells are reported to form synapses with host neurons when they are transplanted into the brain or spinal cords. Mesenchymal stem cells are reported to differentiate into neurons in vivo and are expected as a source of cells used for stem cell therapy in the future. The possibility of stem cell transplantation for the treatment of inner ear hearing loss is also discussed.