Hydrogen Peroxide Effect on Neural Stem Cells : Identification of transcription factors involved in oligodendrogenesis

Abstract: Demyelinating disorders affect many people around the globe and are characterized by loss of myelin sheaths and oligodendrocyte death, ultimately compromising neuronal signal transmission across the Central Nervous System (CNS). Adult Neural Stem Cells (NSC) are multipotent stem cells with the ability to differentiate into the three types of CNS cells: oligodendrocytes, neurons and astrocytes. Hydrogen peroxide (H2O2) is an inflammatory mediator, often present in demyelinating events, commonly associated with oxidative stress and cell death. However, H2O2 also plays a major role as an intracellular signaling molecule. It has been seen that NSC exposed to H2O2 revealed an increase in proliferation and oligodendrogenesis. In this project, we tried to understand how oligodendrogenesis is modulated at a transcriptional level by H2O2. We have identified the genes Hes1, Foxo1, Nrf2 and Prdx6 as being downregulated in the presence of H2O2 when compared to the non-exposed controls. In order to understand if the differential gene expression is involved in the H2O2-induced oligodendrogenesis, we silenced the genes through siRNA transfection (mimicking the downregulation observed after H2O2 exposure) and analyzed the effects on the transcriptome of NSCs and the impact on cell proliferation and differentiation. Our findings indicate that Foxo1 silencing induced the greatest increase in cell proliferation and that Nrf2 silencing revealed the greatest impact on oligodendrogenesis. While not very significant, Foxo1 silencing seems to induce oligodendrogenesis, and Prdx6 silencing seems to inhibit it. The results obtained give important hints on the role that these genes play in NSCs differentiation and fate determination when exposed to oxidative stress and might allow a better understanding of this complex system.