Embryonic neural progenitor cells: the effects of species, region, and culture conditions on long-term proliferation and neuronal differentiation.

One of the major obstacles to the use of neural stem/progenitor cells in neuronal replacement therapy is the limited ability of these cells to generate sufficient numbers of specific neuronal phenotypes either in the culture dish or after transplantation in animal models of neurodegenerative disease. It is not yet fully understood whether embryonic neural stem and progenitor cells show species-specific or regional identities, or if current culture paradigms select for a particular subset of stem cells/progenitors with similar proliferation and differentiation capacities. To investigate this issue, we isolated embryonic neural progenitors derived from the developing rat and mouse central nervous system for in vitro culture to assess the regional, species-specific, and temporal effects on both cell proliferation and generation of neurons. Neurosphere cultures were derived from E13-15 mouse or rat developing striatum (medial, lateral, or whole ganglionic eminence), ventral mesencephalon, and cortex. We compared basic fibroblast growth factor and epidermal growth factor for their influence on cell proliferation and neuronal differentiation under defined differentiation paradigms. Seeding density and conditioned media were also tested for their effects on maintenance of cell proliferation over protracted time periods. Results showed that embryonic neural stem/progenitor cells maintained defined patterns of proliferation and neuronal differentiation, with both declining with time in vitro. Proliferation rate was more dependent on species and region than the neurotrophins or conditions used for culture. These results suggest that the appropriate selection of embryonic neural stem cells and culture conditions may be crucial for the optimization of their neurogenic potential.