| Abstract |
In the first part of this doctoral thesis, we focused on BNN20 which is a C17-spiroepoxy
derivative of the neurosteroid DHEA and has been shown to have strong neuroprotective
properties. The aim of this study was to investigate the effect of BNN20 on glial populations
by using in vitro and in vivo approaches, taking advantage of the well-established
lysophosphatidylcholine-induced focal demyelination mouse model. Our in vivo studies, using
this model and performed in male mice, showed that treatment with BNN20 leads to decreased
myelin loss and increased number of mature oligodendrocytes. BNN20 reduces astrocytic
accumulation during demyelination phase leading to a faster remyelination process, while it
does not affect oligodendrocyte precursor cell recruitment or microglia/macrophage
accumulation. In addition, our in vitro studies showed that BNN20 acts directly to
oligodendrocytes by enhancing their maturation and increasing the number of mature
myelinating oligodendrocytes, even after treatment with lysophosphatidylcholine. This
beneficial effect of BNN20 is mediated, primarily, through the neurotrophin receptor TrkA.
Lastly, BNN20 reduces microglia activation and their transition to their pro-inflammatory state
upon LPS stimulation in vitro. According to the data presented in this work, we propose that
BNN20 could serve as an important molecule to develop BBB-permeable synthetic agonists of
neurotrophin receptors that could reduce inflammation and increase the number of functional
oligodendrocytes by promoting their differentiation/maturation. In the second part of this doctoral thesis, we used the data of the Allen gene expression atlas in
combination with Tabula Muris, which is a compendium of single cell transcriptome data
collected from mice, enabling direct and controlled comparison of gene expression among cell
types to provide further insights into the physiology of TAG-1/Contactin-2 and its interactions,
by presenting the expression of the corresponding gene across the adult mouse brain under
baseline conditions and to investigate any spatial genomic correlations between TAG-
1/Contactin-2 and its interacting proteins and markers of mature and immature
oligodendrocytes, based on preexisting experimental, bibliographical or computational
evidence. The across-brain correlation analysis on the gene expression intensities showed a
positive spatial correlation of TAG-1/Contactin-2 with the gene expression of Plp1, Myrf,
Mbp, Mog, Cldn11, Bace1, Kcna1, Kcna2, App and Nfasc, and a negative spatial correlation
with the gene expression of Cspg4, Pdgfra, L1cam, Ncam1, Ncam2 and Ptprz1. Spatially
correlated genes are mainly expressed by mature oligodendrocytes (like Cntn2), while spatially
anticorrelated genes are mainly expressed by oligodendrocyte precursor cells. According to the
data presented in this work, we suggest that even though Contactin-2 expression during
development correlates with high plasticity events such as neuritogenesis, in adulthood it
correlates with pathways characterized by low plasticity.
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The effect of neurosteroids in the central nervous system and impact on demyelination
