Neurological disorders and neural regeneration, with special reference to Parkinson's disease and cerebral ischemia

For many years, it was recognized that brain and spinal cord tissues could not be regenerated once they were damaged. Recently, this concept has been challenged and many basic and clinical studies regarding neural regeneration and transplantation have been reported. In this review, we will summarize the clinical studies using cell transplantation for the treatment of Parkinson's disease and cerebral ischemia. Then, we will report the recent advancement of basic studies using cell lines and neural stem cells as donor tissue. Cell line grafting can be done by encapsulating desired cell line in semipermeable polymer hollow fibers, and neurotransmitter and neurotrophic factors can be delivered into the brain. Neural stem cells, especially those of adult origin, have the advantage that autologous cell transplantation can be done. The biological features of various types of stem cells have been widely investigated and will be applied to the treatment of neurological disorders through cell transplantation.