Neural stem cell (NSC) biology is a rapidly emerging field. Only recently discovered, NSCs may redefine the manner in which neurodegenerative disorders such as Parkinson's disease will be treated in the future. In addition to replacing fetal tissue as a source of transplantable material, NSCs may also be used to test new drugs, and be manipulated genetically to behave as drug delivery vehicles. Due to the anticipated future demand for NSCs, methods must be developed to scale-up their production in an efficient, quality-assured manner. This thesis examined the behaviour of these cells in suspension culture in order to develop protocols for the long-term expansion of NSCs in bioreactors.

A new medium was developed for the expansion of both murine and human NSCs, and was used to conduct all subsequent studies which included optimizing environmental conditions and examining production methods, A novel chemical technique was developed that proved to be superior to other methods of dissociating NSC aggregates. Hydrodynamic studies revealed that manipulation of bioreactor shear conditions could be used to control aggregate size, and resulted in the development of a correlation relating aggregate size to medium viscosity and power input. Feeding protocols were developed which were able to significantly extend the viable lifespan of a culture. Subculturing studies demonstrated that the development of a bioreactor system for the semicontinuous production of NSCs over extended periods of time is possible, but would require the periodic removal of large aggregates. However, long term studies revealed that NSC populations can undergo fundamental changes when maintained in culture for excessive periods, indicating that a strict quality-assurance regimen must be implemented to periodically monitor cell characteristics during extended culture. Finally, a transplantation study involving a rat model of Parkinson's disease found that implanted NSCs can survive at a graft site for at least 8 weeks, differentiate, and incorporate into the existing brain architecture without forming teratomas. This study demonstrated for the first time that NSCs grown in suspension bioreactors are a viable source of cells for transplantation.