Wnt1 and BMP2: two factors recruiting multipotent neural crest progenitors isolated from adult bone marrow.

Recent studies have shown that neural crest-derived progenitor cells can be found in diverse mammalian tissues including tissues that were not previously shown to contain neural crest derivatives, such as bone marrow. The identification of those "new" neural crest-derived progenitor cells opens new strategies for developing autologous cell replacement therapies in regenerative medicine. However, their potential use is still a challenge as only few neural crest-derived progenitor cells were found in those new accessible locations. In this study, we developed a protocol, based on wnt1 and BMP2 effects, to enrich neural crest-derived cells from adult bone marrow. Those two factors are known to maintain and stimulate the proliferation of embryonic neural crest stem cells, however, their effects have never been characterized on neural crest cells isolated from adult tissues. Using multiple strategies from microarray to 2D-DIGE proteomic analyses, we characterized those recruited neural crest-derived cells, defining their identity and their differentiating abilities.

Neuregulin-1 modulates the differentiation of neural stem cells in vitro through an interaction with the Swi/Snf complex.

The neuregulin-1 (Nrg-1) gene is translated into several protein isoforms, which are either secreted or membrane-anchored. In vitro, neural stem cells (NSC) express mainly the cystein-rich-domain NRG (CRD-NRG) isoform, a membrane-anchored type III form. This isoform exhibits a cystein-rich-domain, which constitutes a second transmembrane domain and can be cleaved to release both a signaling EGF-containing domain (ECD) at the cell surface and an intracellular domain (ICD). The main goal of this paper was to determine the exact role of ECD and ICD in NSC survival and differentiation. Using an siRNA approach, we demonstrated that CRD-NRG inhibition was followed by a decrease in NSC proliferation and of neuronal or oligodendroglial differentiation. Overexpression of ICD but not ECD was followed by a decrease in NSC proliferation and an increase in neuronal and oligodendroglial differentiation. Moreover, we showed that ICD physically interacted in cultured NSC with BRM and BAF57, two members of the Swi/Snf remodeling complex, and that ICD stimulation of neuronal cell differentiation is dependent on the presence of BAF57.

Regulation of neural markers nestin and GFAP expression by cultivated bone marrow stromal cells.

Bone marrow stromal cells can differentiate into many types of mesenchymal cells, i.e. osteocyte, chondrocyte and adipocyte, but can also differentiate into non-mesenchymal cells, i.e. neural cells under appropriate in vivo experimental conditions (Kopen et al., 1999; Brazelton et al., 2000; Mezey et al., 2000). This neural phenotypic plasticity allows us to consider the utilization of mesenchymal stem cells as cellular material in regenerative medicine. In this study, we demonstrate that cultured adult rat stromal cells can express nestin, an intermediate filament protein predominantly expressed by neural stem cells. Two factors contribute to the regulation of nestin expression by rat stromal cells: serum in the culture medium inhibits nestin expression and a threshold number of passages must be reached below which nestin expression does not occur. Only nestin-positive rat stromal cells are able to form spheres when they are placed in the culture conditions used for neural stem cells. Likewise, only nestin-positive stromal cells are able to differentiate into GFAP (glial fibrillary acidic protein)-positive cells when they are co-cultivated with neural stem cells. We thus demonstrated that adult rat stromal cells in culture express nestin in absence of serum after passaging the cells at least ten times, and we suggest that nestin expression by these cells might be a prerequisite for the acquisition of the capacity to progress towards the neural lineage.