Transcriptional Characterization of Glioma Neural Stem Cells Diva ...

2.2 Neural Stem Cells Introduction
Figure 2.5: The neurosphere assay used to study neural precursor cells in culture.
Cells are first isolated from embryonic or adult brain, then cultured in serum-free
conditions in the presence of EGF and FGF2 to generate floating colonies. The
primary neurospheres can then be dissociated and re-plated in EGF and FGF2 to
generate secondary neurospheres that can then be made to differentiate in the three
primary lineages of the CNS by subtracting the growth factors in adherent conditions.
Adapted from Dirks et al 2008 [122].
and neurons, that, upon removal of EGF, differentiate into the three main
lineages of the CNS with a strong preference towards astrocytes [107]. This
heterogeneity likely provides a niche that sustains 3-4% of stem cells, raising
the question as to whether it is the multipotent cells or the more differenti-
ated ones within the mixed cellular environment, that give rise to the three
lineages [107,400]. In vivo, the external signals such as secreted factors and
cell-cell interactions mediated by integral membrane proteins and the extracel-
lular matrix, control stem cell fate collectively, defining the stem cell "niche",
which has a powerful effect in maintaining the balance between quiescence,
self-renewal and cell fate commitment [165]. In vitro, the neurosphere prob-
ably provides the right mixture of cellular environments that resembles the
complex niche, sustaining NS cells in the mammalian brain. Therefore, the
neurosphere discovery is invaluable in that it demonstrates the potential in
the developing and adult CNS of rodents and primates, to give rise to stem
cells [107].
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