Interactions between in vivo neuronal-glial markers, side of hippocampal sclerosis, and pharmacoresponse in temporal lobe epilepsy

Hippocampal sclerosis: A review on current research status and its mechanisms

Hippocampal sclerosis (HS) is a pathological condition characterized by significant loss of hippocampal neurons and gliosis. This condition represents the most common neuropathological change observed in patients with temporal lobe epilepsy (TLE) and is also found in aging individuals. TLE related to HS is the most prevalent type of drug-resistant epilepsy in adults, and its underlying mechanisms are not yet fully understood. Therefore, developing improved methods for predicting and treating drug-resistant patients with TLE-HS is crucial. Patients with TLE-HS often experience cognitive impairment and psychological comorbidities, significantly affecting their quality of life. Consequently, a thorough review of the current research status of TLE-HS is essential, focusing on its prediction, diagnosis, treatment, and underlying mechanisms. The hippocampus plays a pivotal role in memory and cognition. HS of aging (HS-Aging), a condition linked to dementia in the ultra-elderly, is marked by severe CA1 (cornu ammonis) neuronal loss and frequent transactive response DNA-binding protein of 43 kDa (TDP-43) proteinopathy, often misdiagnosed as Alzheimer's disease (AD). Nonetheless, clinical characteristics and patterns of hippocampal atrophy can help differentiate between the two disorders. This review aims to provide a comprehensive overview of the pathological features of HS, the relevant mechanisms underlying TLE-HS and HS-Aging, current imaging diagnostic techniques, including machine learning, and available treatment modalities. It also explores the prognosis and comorbidities related to these conditions. Future research directions include establishing animal models to clarify the poorly understood mechanisms underlying HS, particularly those related to emotional processing. Investigating post-HS behavioral and cognitive changes in these models will lay the foundation for further advancements in this field. This review is a cornerstone for future investigations and suggests additional research endeavors.

Integrated Proteomics and Protein Co-expression Network Analysis Identifies Novel Epileptogenic Mechanism in Mesial Temporal Lobe Epilepsy

Over 50 million people worldwide are affected by epilepsy, a common neurological disorder that has a high rate of drug resistance and diverse comorbidities such as progressive cognitive and behavioural disorders, and increased mortality from direct or indirect effects of seizures and therapies. Despite extensive research with animal models and human studies, limited insights have been gained into the mechanisms underlying seizures and epileptogenesis, which has not translated into significant reductions in drug resistance, morbidities, or mortality. To better understand the molecular signaling networks associated with seizures in MTLE patients, we analyzed the proteome of brain samples from MTLE and control cases using an integrated approach that combines mass spectrometry-based quantitative proteomics, differential expression analysis, and co-expression network analysis. Our analyses of 20 human brain tissues from MTLE patients and 20 controls showed the organization of the brain proteome into a network of 9 biologically meaningful modules of co-expressed proteins. Of these, 6 modules are positively or negatively correlated to MTLE phenotypes with hub proteins that are altered in MTLE patients. Our study is the first to employ an integrated approach of proteomics and protein co-expression network analysis to study patients with MTLE. Our findings reveal a molecular blueprint of altered protein networks in MTLE brain and highlight dysregulated pathways and processes including altered cargo transport, neurotransmitter release from synaptic vesicles, synaptic plasticity, proteostasis, RNA homeostasis, ion transport and transmembrane transport, cytoskeleton disorganization, metabolic and mitochondrial dysfunction, blood micro-particle function, extracellular matrix organization, immune response, neuroinflammation, and cell signaling. These insights into MTLE pathogenesis suggest potential new candidates for future diagnostic and therapeutic development.

TNF-α: A serological marker for evaluating the severity of hippocampal sclerosis in medial temporal lobe epilepsy?

OBJECTIVE

By analysing the difference in TNF-α levels in the peripheral blood of patients with medial temporal lobe epilepsy (mTLE) with or without hippocampal sclerosis and the correlation between TNF-α and N-acetylaspartate levels in the hippocampus, we explored the relationship between TNF-α and the degree of damage to hippocampal sclerosis neurons in medial temporal lobe epilepsy.

METHODS

This is a prospective, population-based study. A total of 71 Patients with medial temporal lobe epilepsy diagnosed by clinical seizures, video-EEG, epileptic sequence MRI, and other imaging examinations were recruited from October 2020 to July 2022 in the Department of Neurology, Affiliated Hospital of Xuzhou Medical University. Twenty age-matched healthy subjects were selected as the control group. The patients were divided into two groups: the medial temporal epilepsy with hippocampal sclerosis group (positive group, mTLE-HS-P group) and the medial temporal epilepsy without hippocampal sclerosis group (negative group, mTLE-HS-N group). The levels of IL-1β, IL-5, IL-6, IL-8, IL-17, IFN-γ and TNF-α in the peripheral blood of the patients in the three groups were detected by multimicrosphere flow immunofluorescence assay. The level of N-acetylaspartate (NAA) in the hippocampus was measured by 1H-MRS. The differences in cytokine levels among the three groups were analysed, and the correlation between cytokine and NAA levels was analysed.

RESULTS

The level of TNF-α in the peripheral blood of the patients in the mTLE-HS-P group was significantly higher than that of the patients in the mTLE-HS-N and healthy control groups, and the level of TNF-α in the patients in the mTLE-HS-N group was significantly higher than that of the patients in the healthy control group. The NAA level in mTLE-HS-P group patients was significantly lower than that of mTLE-HS-N patients and healthy controls, but there was no significant difference between mTLE-HS-N patients and healthy controls (P > 0.05). Spearman correlation analysis showed that TNF-α level (rs = -0.437, P < 0.05) and the longest duration of a single seizure (rs = -0.398, P < 0.05) were negatively correlated with NAA level. Logistic regression analysis showed that there was no significant correlation between the longest duration of a single seizure and hippocampal sclerosis, but TNF-α level was closely related to hippocampal sclerosis in patients with mTLE (OR = 1.315, 95 % CI 1.084-1.595, P = 0.005).

CONCLUSION

The level of TNF-α in the peripheral blood of patients with medial temporal lobe epilepsy with hippocampal sclerosis was higher, and it was correlated with NAA and hippocampal sclerosis. The high expression of TNF-α may be of important value in the evaluation of hippocampal sclerosis patients.

Multi-omics Integration and Epilepsy: Towards a Better Understanding of Biological Mechanisms

The epilepsies are a group of complex neurological disorders characterised by recurrent seizures. Approximately 30% of patients fail to respond to anti-seizure medications, despite the recent introduction of many new drugs. The molecular processes underlying epilepsy development are not well understood and this knowledge gap impedes efforts to identify effective targets and develop novel therapies against epilepsy. Omics studies allow a comprehensive characterisation of a class of molecules. Omics-based biomarkers have led to clinically validated diagnostic and prognostic tests for personalised oncology, and more recently for non-cancer diseases. We believe that, in epilepsy, the full potential of multi-omics research is yet to be realised and we envisage that this review will serve as a guide to researchers planning to undertake omics-based mechanistic studies.

Mapping hippocampal glutamate in mesial temporal lobe epilepsy with glutamate weighted CEST (GluCEST) imaging

Temporal lobe epilepsy (TLE) is one of the most common subtypes of focal epilepsy, with mesial temporal sclerosis (MTS) being a common radiological and histopathological finding. Accurate identification of MTS during presurgical evaluation confers an increased chance of good surgical outcome. Here we propose the use of glutamate-weighted chemical exchange saturation transfer (GluCEST) magnetic resonance imaging (MRI) at 7 Tesla for mapping hippocampal glutamate distribution in epilepsy, allowing to differentiate lesional from non-lesional mesial TLE. We demonstrate that a directional asymmetry index, which quantifies the relative difference between GluCEST contrast in hippocampi ipsilateral and contralateral to the seizure onset zone, can differentiate between sclerotic and non-sclerotic hippocampi, even in instances where traditional presurgical MRI assessments did not provide evidence of sclerosis. Overall, our results suggest that hippocampal glutamate mapping through GluCEST imaging is a valuable addition to the presurgical epilepsy evaluation toolbox.

Preoperative and postoperative memory in epilepsy patients with 'gliosis only' versus hippocampal sclerosis: a matched case-control study

BACKGROUND

Gliosis only (GO) and hippocampal sclerosis (HS) are distinct histopathological entities in mesial temporal lobe epilepsy. This study explores whether this distinction also exists on a functional level when evaluating pre- and postoperative memory.

METHODS

Using a retrospective matched case-control study design, we analysed verbal and visual memory performance in 49 patients with GO and 49 patients with HS before and one year after elective surgery.

RESULTS

Clinical differences were evident with a later age at seizure onset (18±12 vs 12±9 years) and fewer postoperative seizure-free patients in the GO group (63% vs 82%). Preoperatively, group and individual-level data demonstrated that memory impairments were less frequent, less severe and relatively non-specific in patients with GO compared with HS. Postoperatively, verbal memory declined in both groups, particularly after left-sided resections, with more significant losses in patients with GO. Factoring in floor effects, GO was also associated with more significant visual memory loss, particularly after left resections.

CONCLUSIONS

Compared with HS, GO is characterised by (1) a later onset of epilepsy, (2) less pronounced and more non-specific memory impairments before surgery, (3) a less successful surgical outcome and (4) a more significant memory decline after surgery. Overall, our results regarding cognition provide further evidence that GO and HS are distinct clinical entities. Functional integrity of the hippocampus appears higher in GO, as indicated by a better preoperative memory performance and worse memory outcome after surgery. The different risk-benefit ratios should be considered during presurgical patient counselling.

Superficial and deep white matter diffusion abnormalities in focal epilepsies

OBJECTIVE

This study was undertaken to evaluate superficial-white matter (WM) and deep-WM magnetic resonance imaging diffusion tensor imaging (DTI) metrics and identify distinctive patterns of microstructural abnormalities in focal epilepsies of diverse etiology, localization, and response to antiseizure medication (ASM).

METHODS

We examined DTI data for 113 healthy controls and 113 patients with focal epilepsies: 51 patients with temporal lobe epilepsy (TLE) and hippocampal sclerosis (HS) refractory to ASM, 27 with pharmacoresponsive TLE-HS, 15 with temporal lobe focal cortical dysplasia (FCD), and 20 with frontal lobe FCD. To assess WM microstructure, we used a multicontrast multiatlas parcellation of DTI. We evaluated fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD), and assessed within-group differences ipsilateral and contralateral to the epileptogenic lesion, as well as between-group differences, in regions of interest (ROIs).

RESULTS

The TLE-HS groups presented more widespread superficial- and deep-WM diffusion abnormalities than both FCD groups. Concerning superficial WM, TLE-HS groups showed multilobar ipsilateral and contralateral abnormalities, with less extensive distribution in pharmacoresponsive patients. Both the refractory TLE-HS and pharmacoresponsive TLE-HS groups also presented pronounced changes in ipsilateral frontotemporal ROIs (decreased FA and increased MD, RD, and AD). Conversely, FCD patients showed diffusion changes almost exclusively adjacent to epileptogenic areas.

SIGNIFICANCE

Our findings add further evidence of widespread abnormalities in WM diffusion metrics in patients with TLE-HS compared to other focal epilepsies. Notably, superficial-WM microstructural damage in patients with FCD is more restricted around the epileptogenic lesion, whereas TLE-HS groups showed diffuse WM damage with ipsilateral frontotemporal predominance. These findings suggest the potential of superficial-WM analysis for better understanding the biological mechanisms of focal epilepsies, and identifying dysfunctional networks and their relationship with the clinical-pathological phenotype. In addition, lobar superficial-WM abnormalities may aid in the diagnosis of subtle FCDs.

New advances in pharmacoresistant epilepsy towards precise management-from prognosis to treatments

Epilepsy, one of the most severe neurological diseases, is characterized by abrupt recurrent seizures. Despite great progress in the development of antiseizure drugs (ASDs) based on diverse molecular targets, more than one third of epilepsy patients still show resistance to ASDs, a condition termed pharmacoresistant epilepsy. The management of pharmacoresistant epilepsy involves serious challenges. In the past decade, promising advances have been made in the use of interdisciplinary techniques involving biophysics, bioinformatics, biomaterials and biochemistry, which allow more precise prognosis and development of drug target for pharmacoresistant epilepsy. Notably, novel experimental tools such as viral vector gene delivery, optogenetics and chemogenetics have provided a framework for promising approaches to the precise treatment of pharmacoresistant epilepsy. In this review, historical achievements especially recent advances of the past decade in the prognosis and treatment of pharmacoresistant epilepsy from both clinical and laboratory settings are presented and summarized. We propose that the further development of novel experimental tools at cellular or molecular levels with both temporal and spatial precision are necessary to make improve the management and drug development for pharmacoresistant epilepsy in the clinical arena.

Multi-omic strategies applied to the study of pharmacoresistance in mesial temporal lobe epilepsy

Mesial temporal lobe epilepsy (MTLE) is the most common type of focal epilepsy in adults, and hippocampal sclerosis (HS) is a frequent histopathological feature in patients with MTLE. Pharmacoresistance is present in at least one-third of patients with MTLE with HS (MTLE+HS). Several hypotheses have been proposed to explain the mechanisms of pharmacoresistance in epilepsy, including the effect of genetic and molecular factors. In recent years, the increased knowledge generated by high-throughput omic technologies has significantly improved the power of molecular genetic studies to discover new mechanisms leading to disease and response to treatment. In this review, we present and discuss the contribution of different omic modalities to understand the basic mechanisms determining pharmacoresistance in patients with MTLE+HS. We provide an overview and a critical discussion of the findings, limitations, new approaches, and future directions of these studies to improve the understanding of pharmacoresistance in MTLE+HS. However, it is important to point out that, as with other complex traits, pharmacoresistance to anti-seizure medications is likely a multifactorial condition in which gene-gene and gene-environment interactions play an important role. Thus, studies using multidimensional approaches are more likely to unravel these intricate biological processes.

Hippocampal CA3 transcriptional modules associated with granule cell alterations and cognitive impairment in refractory mesial temporal lobe epilepsy patients

In about a third of the patients with epilepsy the seizures are not drug-controlled. The current limitation of the antiepileptic drug therapy derives from an insufficient understanding of epilepsy pathophysiology. In order to overcome this situation, it is necessary to consider epilepsy as a disturbed network of interactions, instead of just looking for changes in single molecular components. Here, we studied CA3 transcriptional signatures and dentate gyrus histopathologic alterations in hippocampal explants surgically obtained from 57 RMTLE patients submitted to corticoamygdalohippocampectomy. By adopting a systems biology approach, integrating clinical, histopathological, and transcriptomic data (weighted gene co-expression network analysis), we were able to identify transcriptional modules highly correlated with age of disease onset, cognitive dysfunctions, and granule cell alterations. The enrichment analysis of transcriptional modules and the functional characterization of the highly connected genes in each trait-correlated module allowed us to unveil the modules’ main biological functions, paving the way for further investigations on their roles in RMTLE pathophysiology. Moreover, we found 15 genes with high gene significance values which have the potential to become novel biomarkers and/or therapeutic targets in RMTLE.

Female mice lacking ERβ display excitatory/inhibitory synaptic imbalance to drive the pathogenesis of temporal lobe epilepsy

Epilepsy is a highly prevalent and drug-refractory neurological disorder characterized by spontaneous recurrent seizures. Estrogen is identified to be proconvulsant and lowers the seizure threshold of female epilepsy. Estrogen receptor β (ERβ) has been proposed to mediate neuroprotection in epilepsy, although the underlying mechanism remains unknown. Rationale: In this study, we investigated the role of ERβ in the epileptogenesis of female temporal lobe epilepsy (TLE). Methods: Immunohistochemistry, immunofluorescence, western blots, Golgi staining, 1H MRS and whole-cell patch-clamp were used to evaluate ERβ expression, pathological changes, and synaptic excitation /inhibition (E/I) balance in female TLE patients and ovariectomized (OVX) chronic epileptic mice. Electroencephalogram (EEG) recordings were recorded to evaluate the epileptic susceptibility in OVX WT and ERβ-/- mice. And high-throughput RNA-sequence was performed to identify differential expression genes (DEGs) which can elucidate the potential mechanism of ERβ regulating the seizure susceptibility. Results: ERβ expression was decreased in the brains of female TLE patients and OVX chronic epileptic mice. ERβ deletion enhanced seizure susceptibility and exacerbated the imbalance of synaptic E/I in hippocampal CA1 area of OVX epileptic mice. In line with these observations, RNA-sequence data further identified glutamine ligase (GLUL) as the target of ERβ involved in regulating synaptic E/I in CA1. Furthermore, ERβ agonist WAY-200070 markedly suppressed epileptic phenotypes and normalized GLUL expression in CA1 region of kainic acid (KA) induced OVX chronic epileptic model. Conclusions: Our data provide novel insight into the pathogenesis of female TLE, and indicate ERβ provides a new therapeutic strategy for female TLE patients.

Fiber ball white matter modeling in focal epilepsy

Multicompartment diffusion magnetic resonance imaging (MRI) approaches are increasingly being applied to estimate intra‐axonal and extra‐axonal diffusion characteristics in the human brain. Fiber ball imaging (FBI) and its extension fiber ball white matter modeling (FBWM) are such recently described multicompartment approaches. However, these particular approaches have yet to be applied in clinical cohorts. The modeling of several diffusion parameters with interpretable biological meaning may offer the development of new, noninvasive biomarkers of pharmacoresistance in epilepsy. In the present study, we used FBI and FBWM to evaluate intra‐axonal and extra‐axonal diffusion properties of white matter tracts in patients with longstanding focal epilepsy. FBI/FBWM diffusion parameters were calculated along the length of 50 white matter tract bundles and statistically compared between patients with refractory epilepsy, nonrefractory epilepsy and controls. We report that patients with chronic epilepsy had a widespread distribution of extra‐axonal diffusivity relative to controls, particularly in circumscribed regions along white matter tracts projecting to cerebral cortex from thalamic, striatal, brainstem, and peduncular regions. Patients with refractory epilepsy had significantly greater markers of extra‐axonal diffusivity compared to those with nonrefractory epilepsy. The extra‐axonal diffusivity alterations in patients with epilepsy observed in the present study could be markers of neuroinflammatory processes or a reflection of reduced axonal density, both of which have been histologically demonstrated in focal epilepsy. FBI is a clinically feasible MRI approach that provides the basis for more interpretive conclusions about the microstructural environment of the brain and may represent a unique biomarker of pharmacoresistance in epilepsy.

A Narrative Review of Circular RNAs in Brain Development and Diseases of Preterm Infants

Circular RNAs (circRNAs) generated by back-splicing are the vital class of non-coding RNAs (ncRNAs). Circular RNAs are highly abundant and stable in eukaryotes, and many of them are evolutionarily conserved. They are blessed with higher expression in mammalian brains and could take part in the regulation of physiological and pathophysiological processes. In addition, premature birth is important in neurodevelopmental diseases. Brain damage in preterm infants may represent the main cause of long-term neurodevelopmental disorders in surviving babies. Until recently, more and more researches have been evidenced that circRNAs are involved in the pathogenesis of encephalopathy of premature. We aim at explaining neuroinflammation promoting the brain damage. In this review, we summarize the current findings of circRNAs properties, expression, and functions, as well as their significances in the neurodevelopmental impairments, white matter damage (WMD) and hypoxic-ischemic encephalopathy (HIE). So we think that circRNAs have a direct impact on neurodevelopment and brain injury, and will be a powerful tool in the repair of the injured immature brain. Even though their exact roles and mechanisms of gene regulation remain elusive, circRNAs have potential applications as diagnostic biomarkers for brain damage and the target for neuroprotective intervention.