Selective specification of CNS stem cells into oligodendroglial or neuronal cell lineage: cell culture and transplant studies.

Neural stem cells (NSCs) were isolated from embryonic day 16 Sprague-Dawley rats and cultured in a novel serum-free stem cell medium that selected for the growth of NSCs and against the growth of GFAP(+) cells (astrocytes). NSCs maintained in culture for extended periods of time retained immunoreactivity for both nestin and PSA-NCAM, two markers characteristic of the stem cell phenotype. Moreover, using an oligodendrocyte (OL) specification medium, NSCs differentiated into OL as evidenced by their morphology and expression of multiple oligodendrocyte/myelin-specific markers. In addition, NSCs are capable of acquiring a neuronal phenotype as evidenced by expressing neuronal markers, such as neurofilament (NF) and NeuN when cultured in a defined medium for neurons indicating that these cells are also a good source of neuroblasts, which could be used to replace neuronal populations in the brain. We also showed successful propagation and differentiation of NSCs into OL after cryostorage, allowing for the later use of stored NSCs. The long-term goal of culturing NSCs and committed oligodendrocyte progenitors (OLP) is to obtain homogeneous populations for transplantation with the goal of remyelinating the myelin-deficient CNS. Our preliminary experiments carried out on normal and myelin deficient rats demonstrate that these cells survive and migrate extensively in both types of hosts. NSCs grafted as such, as well as cells derived from NSCs exposed to selective specification before grafting, are able to differentiate within the host brain. As expected, NSCs are capable of giving rise to astrocytes in a medium favoring this phenotype. (C) 2002 Wiley-Liss, Inc.