Epigenetic and bioelectronic tools to study neural stem cells in health and disease

Abstract

Brain development is a highly controlled, complex, and dynamic process. The mechanisms of its control need to accommodate the constantly changing contexts which, overtime, support the emergence of new neural structures and functions. Epigenetic mechanisms, among others, underlie the various stages of neurodevelopment, while epigenetic dysregulation has been associated with neurodevelopmental disorders and cancer. The overall aim of this thesis was to employ epigenetic and bioelectronic tools, to study neural stem cells in health and disease, specifically in the context of brain cancer or as part of the therapeutic regimen in brain tumor treatment. This was achieved through four studies:

In Paper I, we studied the global and specific effects of lithium on the gene expression and DNA methylation patterns of irradiated human neural stem and progenitor cells (hNSPCs). Here, we present that lithium, when administered after irradiation, induces changes in DNA methylation and gene expression in hNSPCs, potentially pointing to a shift from gliogenesis towards neurogenesis. Lithium and irradiation resulted in upregulation of the genes glutamate decarboxylase 2 (GAD2), gremlin1 (GREM1), ten eleven translocation methylcytosine dioxygenase 3 (TET3), and growth arrest and DNA damage inducible alpha (GADD45A), among others. These, taken together, point to lithium having a role in the epigenetic control of DNA methylation, in the context of irradiation, through TET3 and GADD45A, as well as promoting neurogenesis through GAD2 and also blocking gliogenesis through gremlin1-associated bone morphogenetic protein (BMP) signaling blockade.

In Paper II, we studied whether irradiation and lithium promoted the growth of human high-grade glioma (hHGG) cells in 3D cultures. Two cell lines were used, SF8628 (histone 3 lysine 27, H3K27, mutant) and SF188 (histone 3 variant H3.3 wild type), which were 3D printed and treated with irradiation and lithium. Treatment with lithium did not point to any severe risk regarding cancer cell growth in hHGG cells.

In Paper III, we investigated the use of a library of luminescent conjugated oligothiophenes (LCOs) as molecular probes for real-time NSPCs and glioblastoma-derived stem-like cell detection. In this study, we discovered that one probe, penta-hydrogen thiophene methylimidazole (p-HTMI), specifically stained live embryonic rodent brain- and human glioma-derived progenitors within 10 min of administration to the culture medium in vitro. For this reason, p-HTMI was named GlioStem. In Paper IV, we showed that GlioStem can be used to detect glioma stem cells, directly in glioblastoma tissue. The GlioStem-positive cells in glioblastoma biopsies were found to exhibit similar transcriptomic identity to oligodendrocyte progenitors and pro-neural stem cell subpopulations.

Overall, the findings of the papers comprising this PhD thesis hold great promise to improve patient health and outcomes.