Notch is Not Involved in Physioxia-Mediated Stem Cell Maintenance in Midbrain Neural Stem Cells

Int J Stem Cells. 2023 Aug 30;16(3):293-303. doi: 10.15283/ijsc22168. Epub 2023 Apr 30.


Background and objectives: The physiological oxygen tension in fetal brains (∼3%, physioxia) is beneficial for the maintenance of neural stem cells (NSCs). Sensitivity to oxygen varies between NSCs from different fetal brain regions, with midbrain NSCs showing selective susceptibility. Data on Hif-1α/Notch regulatory interactions as well as our observations that Hif-1α and oxygen affect midbrain NSCs survival and proliferation prompted our investigations on involvement of Notch signalling in physioxia-dependent midbrain NSCs performance.

Methods and results: Here we found that physioxia (3% O2) compared to normoxia (21% O2) increased proliferation, maintained stemness by suppression of spontaneous differentiation and supported cell cycle progression. Microarray and qRT-PCR analyses identified significant changes of Notch related genes in midbrain NSCs after long-term (13 days), but not after short-term physioxia (48 hours). Consistently, inhibition of Notch signalling with DAPT increased, but its stimulation with Dll4 decreased spontaneous differentiation into neurons solely under normoxic but not under physioxic conditions.

Conclusions: Notch signalling does not influence the fate decision of midbrain NSCs cultured in vitro in physioxia, where other factors like Hif-1α might be involved. Our findings on how physioxia effects in midbrain NSCs are transduced by alternative signalling might, at least in part, explain their selective susceptibility to oxygen.

Keywords: Cell cycle; Hif-1α; Hypoxia; Neural stem cells; Notch; Physioxia; Stem cell maintenance.

Grants and funding

Acknowledgments We would like to thank Sylvia Kanzler and Cornelia Mai for their excellent technical assistance. The work was supported in part by the DFG through the Collaborative Research Center 655 (SFB655) ‘Cells into tissues: stem cell and progenitor commitment and interactions during tissue formation’ (SFB 655, project A23) to A.S. and the Bundesministerium für Bildung und Forschung (BMBF) through the NBL-3 program (to A.S.).