Growth factors regulate the survival and fate of cells derived from human neurospheres

Cells isolated from the embryonic, neonatal, acid adult rodent central nerv ous system divide in response to epidermal growth factor (EGF) and fibrobla st growth factor 2 (FGF-2), while retaining the ability to differentiate in to neurons and glia(1,2). These cultures can be grown in aggregates termed neurospheres, which contain a heterogeneous mix of both multipotent stem ce lls and more restricted progenitor populations(3,4). Neurospheres can also be generated from the embryonic human brain(5-7) and in some cases have bee n expanded for extended periods of time in culture(8-10). However, the mech anisms controlling the number of neurons generated from human neurospheres are poorly understood. Here we show that maintaining cell-cell contact duri ng the differentiation stage, in combination with growth factor administrat ion, can increase the number of neurons generated under serum-free conditio ns from 8% to > 60%. Neurotrophic factors 3 and 4 (NT3, NT4) and platelet-d erived growth factor (PDGF) were the most potent, and acted by increasing n euronal survival rather than inducing neuronal phenotype. Following differe ntiation, the neurons could survive dissociation and either replating or tr ansplantation into the adult rat brain. This experimental system provides a practically limitless supply of enriched, non-genetically transformed neur ons. These should be useful for both neuroactive drug screening in vitro an d possibly cell therapy for neurodegenerative diseases.