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The discovery of stem cell populations in the adult central nervous system (CNS) that continually produce neurons and glial cells, and the hypothesis that they could contribute to neural plasticity/repair, has opened new and exciting areas of research in basic cell biology and regenerative medicine. The success of these studies relies on understanding the functional features and the normal fate of neural stem cells (NSCs) in vivo as well on the development of in vitro culture conditions enabling isolation, extensive propagation, and rigorous characterization of the "putative" NSCs. The neurosphere assay (NSA) has emerged as a valuable tool for isolating embryonic and adult CNS stem cells and for studying their biology. However, because this assay may select and expand a heterogeneous stem/progenitor cell population, rigorous clonal and serial subcloning analyses are required to detect and document stem cell activity and to unequivocally identify bona fide stem cells. We illustrate and discuss methods for the isolation, propagation, cryopreservation, and functional characterization of NSCs, focusing on the essential issue of their clonogenic capacity. [ABSTRACT FROM AUTHOR]

Neural stem cells (NSCs) have been identified in the mature central nervous system (CNS), and they reside in specific areas. Cultures of NSCs can be successfully established in vitro by exploiting the NeuroSphere assay. This methodology relies on the continuous exposure of neural cells to mitogens such as epidermal growth factor and fibroblast growth factor-2. Under these conditions, only NSCs and highly undifferentiated progenitors proliferate, whereas committed precursors and terminally differentiated cells are eliminated from the culture. The proper application of this method to the cells allows the establishment of long-term expanding stable NSC lines, starting from different neural tissues as the adult rodent CNS and human brain tumor specimens. [ABSTRACT FROM AUTHOR]

Human glioblastomas appear to be established and expanded by cancer stem cells, which are endowed with tumour-initiating and perpetuating ability. We report that bone morphogenetic proteins (BMPs), amongst which BMP4 elicits the strongest effect, activate their cognate receptors (BMPRs) and trigger the Smad but not the MAP38 kinase signalling cascade in cells isolated from human glioblastomas (GBMs). This is followed by a reduction in proliferation and increased expression of differentiated neural markers, without affecting cell viability. The concomitant reduction in the clonogenic ability, both in the size of the CD133+ side population and in the growth kinetics of GBM cells, indicates that BMP4 triggers a reduction in the in vitro cancer stem cell (CSC) pool. Accordingly, transient ex vivo exposure to BMP4 abolishes the capacity of transplanted GBM cells to establish intracerebral GBMs. Most important, in vivo delivery of BMP4 effectively blocks the tumour growth and associated mortality which occur in 100% of control mice in less than 12 weeks, following intracerebral grafting of human GBM cells. These findings show that the BMP-BMPR signalling system, which controls the activity of normal brain stem cells, may also act as a key inhibitory regulator of cancer-initiating, GBM stem-like cells and identifies BMP4 as a novel, non-cytotoxic therapeutic effector, which may be used to prevent growth and recurrence of GBMs in humans. [ABSTRACT FROM AUTHOR]

The mature mammalian central nervous system (CNS) has long been considered incapable of significant cell turnover. This view has changed over the last few decades. Recently, the existence of de novo neurogenesis in the adult brain and the presence of stem cells in the mammalian CNS have emerged. The adult brain of both rodents and primates has been shown to embody undifferentiated, mitotically active, precursor cells that are multipotent in nature, and can contribute new, differentiated, neurons and glia to specific regions of the mature brain, such as the olfactory bulb (1-5), the hippocampus (6-8), and the cortex (9-11). While the data clearly suggest the presence of stem cells in the adult CNS in vivo, testing the proliferation, self-renewal, and differentiation capacity of"putative" CNS stem cells relies on the development of methodologies that allow for their isolation and extensive propagation in vitro. [ABSTRACT FROM AUTHOR]