Neurotrophic factor delivery by encapsulated cell grafts

One of the objectives of neural transplantation for neurological disorders is to deliver neurotransmitters or neurotrophic factors into the host brain. Neurotrophic factor delivery is considered more ideal because neuronal circuit reconstruction of the host can be expected by this method. In order to deliver neurotrophic factors into the brain, three approaches have been studied: direct injection of neurotrophic factors by using osmotic pump, induction of genes of neurotrophic factors into the host brain (in vivo gene therapy), and grafting of encapsulated neurotrophic factor-secreting cells into the brain (ex vivo gene therapy). Due to the development of molecular biology techniques, many types of neurotrophic factor-secreting cells have been created and these cells can be used for the treatment of certain neurological disorders such as Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis (ALS), and cerebral ischemia. Encapsulated cell grafting procedure is very useful for using these cells because immunological reaction of the host brain and tumorigenesis of donor cells can be prevented by this procedure. In this review, neurotrophic factor-secreting cell grafting into the brain is summarized.