RESUMO
Neural stem cells (NSC) self-renew and generate specialized cell types. There are reports indicating that Notch and Leukemia Inhibitory Factor (LIF) signaling are involved in cell determination of NSC, either preventing differentiation or promoting astrocytic fate. In this work, we aimed to compare the astrocytogenic effect of activated Notch with that induced by LIF. To this end, rat cerebral cortex neural progenitors/NSC were transduced with retroviral vectors in order to express green fluorescent protein (GFP), or a fusion protein of GFP with the active Notch1 intracellular domain (NICD). In parallel, other cultures were treated with increasing concentrations of LIF. We confirmed, in proliferating NSC, that LIF activated intracellular effectors by measuring STAT3 phosphorylation and Socs3 transcription. In NICD-expressing cells, Hes5 mRNA was induced, an effect not present in GFP-transduced NSC. We quantified the proportion of cells expressing Nestin in the presence of Fibroblast Growth Factor-2 (FGF-2) with LIF or NICD treatments. LIF significantly increased the proportion of cells co-expresssing Nestin and Glial Fibrillary Acidic Protein (GFAP), an effect absent in cells with activated Notch. After FGF2 withdrawal to promote differentiation, Nestin was markedly down-regulated, and neuronal and glial markers appeared in control cultures. LIF treatment caused a significant increase in the proportion of GFAP-positive cells, but cells expressing NICD showed a significantly higher percentage of astrocytes than control and LIF-treated cultures. These experiments show that cells stimulated with NICD differentiate more readily to astrocytes than LIF-treated NSC.
