Abstract
Understanding seizure development requires an integrated knowledge of different scales of organization of epileptic networks. We developed a model of “epilepsy-in-a-dish” based on dissociated primary neuronal cells from neonatal rat hippocampus. We demonstrate how a single application of glutamate stimulated neurons to generate spontaneous synchronous spiking activity with further progression into spontaneous seizure-like events after a distinct latency period. By computational analysis, we compared the observed neuronal activity in vitro with intracranial electroencephalography (EEG) data recorded from epilepsy patients and identified strong similarities, including a related sequence of events with defined onset, progression, and termination. Next, a link between the neurophysiological changes with network composition and cellular structure down to molecular changes was established. Temporal development of epileptiform network activity correlated with increased neurite outgrowth and altered branching, increased ratio of glutamatergic over GABAergic synapses, and loss of calbindin-positive interneurons, as well as genome-wide alterations in DNA methylation. Differentially methylated genes were engaged in various cellular activities related to cellular structure, intracellular signaling, and regulation of gene expression. Our data provide evidence that a single short-term excess of glutamate is sufficient to induce a cascade of events covering different scales from molecule- to network-level, all of which jointly contribute to seizure development.
Highlights
We previously developed an in vitro model of epileptogenesis based on a self-organized network of interconnected neurons and a few glial cells [43]
Starting from dissociated primary neuronal cells from neonatal rat hippocampus, we showed that a single and transient (10 min) application of physiological levels of 10 μM glutamate stimulated neurons to generate spontaneous synchronous spiking activity progressing into spontaneous seizure-like events (SLE)
We performed a temporal series of live cell calcium imaging to functionally characterize our model and quantify the dynamics of the potential epileptogenic process
Summary
Epilepsy is not a single disease, but highly heterogeneous with diverse clinical syndromes, associated etiologies (i.e., structural, genetic, infectious, metabolic, immune, unknown), and many different mechanisms contributing to the epileptic phenotype and known frequent comorbidities. Hippocampal sclerosis (HS) is a frequent structural brain lesion identified in patients with drug-resistant focal epilepsy submitted to surgical treatment [1]. It is histopathologically characterized by segmental neuronal cell loss in the hippocampal formation [2]. Clinical disease presentation in patients with TLE often follows a characteristic pattern. A prevailing hypothesis to best anticipate this phenomenon is secondary epileptogenesis [4,5]
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