Spontaneous activity alteration in in vitro models of neuronal pathologies

To understand pathologies and develop treatment for central nervous system (CNS) pathologies, several experimental steps are required. The first approach is almost always in vitro. This is because in vitro studies offer a simple and reproducible platform to model diseases at a scaled down, non-systemic level. Among in vitro tools for electrophysiology, microelectrode arrays (MEAs) have been developed to study the electrical activity of networks of neurons. This thesis explores the potential of MEAs for building ex vivo disease models and presents four comprehensive studies that utilize MEAs to investigate various neuropathological conditions. The first work presents a model of FOXG1 syndrome, a complex condition caused by distinct structural mutations of the gene FOXG1. MEAs were employed to record neuronal activity, revealing a clear and consistent difference between two different mutations. This study exemplifies how MEAs can provide functional insights into complex genetic disorders, in parallel to more traditional morphologic analysis of neurons. The second work delves into the role of exosomes in the pathogenesis of glioma-related seizures. MEAs recorded the electrical activity of cortical rat cultures incubated with exosomes from different patients, shedding light on the different effects of each on network synchrony and thus suggesting the need for precision medicine approaches. In the third work, the effects of SARS-CoV-2 infection on the electrophysiology of cortical rat cultures are examined. MEAs helped reveal disruptions in synaptic activity and provided evidence of the involvement of the cGAS-STING pro-inflammatory pathway, highlighting that the pathway to neuronal damage of SARS-CoV-2 involves the expression and production of cytokines and chemokines. The fourth work focuses on the role of the cellular Prion Protein in synapses, using primary cortical cultures from knockout mouse strains for the Prion protein itself. MEAs were used to investigate population dynamics and revealed alterations in the excitatory-inhibitory balance, which was confirmed with immunohistochemical analysis. Each of the four studies harnessed the unique capabilities of MEAs: recording from a large number of cells, facilitating mesoscale analysis of neuronal networks, and offering robust and generalizable results. MEAs were used both to study the alteration of wild type cortical cultures with the addition of a pathogenic factor and to study cultures obtained from recombinant animals. Moreover, MEAs allowed for longitudinal studies at different timepoints with no disruption of the cultured cells. This thesis shows that MEAs are powerful tools for building in vitro models of CNS pathologies. They offer flexibility, reliability, and the ability to complement ongoing research, bridging the gap between large-scale in vivo research and single-cell electrophysiology. MEAs have the potential to advance our understanding of CNS diseases and contribute to the development of targeted treatments, making them invaluable in the field of neuropathology.