BioProject

The culture of neural stem cells (NSCs) as floating neurospheres has become widely used as an experimental model to analyse the properties of NSCs. More...

The culture of neural stem cells (NSCs) as floating neurospheres has become widely used as an experimental model to analyse the properties of NSCs. Although the neurosphere model has existed for two decades, there is still no standard protocol to grow NSCs in this way. Thus, we have analysed the consequences of the frequency of growth factor (FGF-2 and EGF) addition to embryonic and adult olfactory bulb stem cells (eOBSCs and aOBSCs) cultures, specifically in terms of proliferation, cell cycle progression, death and differentiation, as well as on global changes in gene expression and signaling pathways. We found that addition of FGF-2 and EGF every two or four days rather than daily significantly reduces the volume of the neurospheres and the total number of cells, changes that were more evident in aOBSC than in eOBSC cultures. The reduction in neurosphere size was mainly due to an increase in cell death and occurs without major changes in the cell cycle parameters tested. Moreover, partial deprivation of FGF-2 and EGF produces a mild increase in aOBSC differentiation during the proliferative phase. Remarkably, these effects were accompanied by a significant upregulation in the expression of genes involved in cell death regulation (Cryab), lipid catabolic processes (Pla2g7), cell adhesion (Dscaml1), cell differentiation (Dscaml1, Gpr17, S100b) and signal transduction (Gpr17, Ndrg2), among others. These findings support that continuous supply of FGF-2 and EGF is critical to maintain the viability/survival of NSCs in culture and reveals novel molecular hallmarks of NSC maintenance/survival and expansion in response to these growth factors. Total RNA was extracted from aOBSC cultures using the Trizol reagent (Invitrogen) and purified with Qiagen RNeasy Mini Kit separation columns (Qiagen). The RNA was sent to the Genomic Unit of CNB (Centro Nacional de Biotecnologia, Madrid, Spain). RNA integrity was corroborated by using Bioanalyzer. Then, cDNA was synthesized and hybridized to Affymetrix GeneChip Mouse Genome 430 2.0 arrays (Affymetrix, Santa Clara, CA, http://www.affymetrix.com) which contain a total of 45101 transcripts to assess and compare the overall gene expression profiles. Overall design: 9 samples were analyzed. Ctr: Control mouse adult olfatory bulb stem cells (aOBSC) cultured with daily added Fgf2 and Egf, 3 biological rep C2: Mouse adult olfatory bulb stem cells (aOBSC) cultured with Fgf2 and Egf added every two days, 3 biological rep C4: Mouse adult olfatory bulb stem cells (aOBSC) cultured with Fgf2 and Egf added every four days, 3 biological rep Less...