Manual Hippocampal Subfield Segmentation Using High-Field MRI: Impact of Different Subfields in Hippocampal Volume Loss of Temporal Lobe Epilepsy Patients.

In patients with temporal lobe epilepsy (TLE), presurgical magnetic resonance imaging (MRI) often reveals hippocampal atrophy, while neuropathological assessment indicates the different types of hippocampal sclerosis (HS). Different HS types are not discriminated in MRI so far. We aimed to define the volume of each hippocampal subfield on MRI manually and to compare automatic and manual segmentations for the discrimination of HS types. The T2-weighted images from 14 formalin-fixed age-matched control hippocampi were obtained with 4.7T MRI to evaluate the volume of each subfield at the anatomical level of the hippocampal head, body, and tail. Formalin-fixed coronal sections at the level of the body of 14 control cases, as well as tissue samples from 24 TLE patients, were imaged with a similar high-resolution sequence at 3T. Presurgical three-dimensional (3D) T1-weighted images from TLE went through a FreeSurfer 6.0 hippocampal subfield automatic assessment. The manual delineation with the 4.7T MRI was identified using Luxol Fast Blue stained 10-µm-thin microscopy slides, collected at every millimeter. An additional section at the level of the body from controls and TLE cases was submitted to NeuN immunohistochemistry for neuronal density estimation. All TLE cases were classified according to the International League Against Epilepsy's (ILAE's) HS classification. Manual volumetry in controls revealed that the dentate gyrus (DG)+CA4 region, CA1, and subiculum accounted for almost 90% of the hippocampal volume. The manual 3T volumetry showed that all TLE patients with type 1 HS (TLE-HS1) had lower volumes for DG+CA4, CA2, and CA1, whereas those TLE patients with HS type 2 (TLE-HS2) had lower volumes only in CA1 (p ≤ 0.038). Neuronal cell densities always decreased in CA4, CA3, CA2, and CA1 of TLE-HS1 but only in CA1 of TLE-HS2 (p ≤ 0.003). In addition, TLE-HS2 had a higher volume (p = 0.016) and higher neuronal density (p < 0.001) than the TLE-HS1 in DG + CA4. Automatic segmentation failed to match the manual or histological findings and was unable to differentiate TLE-HS1 from TLE-HS2. Total hippocampal volume correlated with DG+CA4 and CA1 volumes and neuronal density. For the first time, we also identified subfield-specific pathology patterns in the manual evaluation of volumetric MRI scans, showing the importance of manual segmentation to assess subfield-specific pathology patterns.

Individual hippocampal subfield assessment indicates that matrix macromolecules and gliosis are key elements for the increased T2 relaxation time seen in temporal lobe epilepsy.

OBJECTIVE: Increased T2 relaxation time is often seen in temporal lobe epilepsy (TLE) with hippocampal sclerosis. Water content directly affects the effective T2 in a voxel. Our aim was to evaluate the relation between T2 values and two molecules associated with brain water homeostasis aquaporin 4 (AQP4) and chondroitin sulfate proteoglycan (CSPG), as well as cellular populations in the hippocampal region of patients with TLE. METHODS: Hippocampal T2 imaging and diffusion tensor imaging (DTI) were obtained from 42 drug-resistant patients with TLE and 20 healthy volunteers (radiologic controls, RCs). A similar protocol (ex vivo) was applied to hippocampal sections from the same TLE cases and 14 autopsy control hippocampi (histologic and radiologic controls, HRCs), and each hippocampal subfield was evaluated. Hippocampal sections from TLE cases and HRC controls were submitted to immunohistochemistry for neurons (neuron nuclei [NeuN]), reactive astrocytes (glial fibrillary acidic protein [GFAP]), activated microglia (human leukocyte antigen-D-related [HLA-DR]), polarized AQP4, and CSPG. RESULTS: Patients with TLE had higher in vivo and ex vivo hippocampal T2 relaxation time. Hippocampi from epilepsy cases had lower neuron density, higher gliosis, decreased AQP4 polarization, and increased CSPG immunoreactive area. In vivo relaxation correlated with astrogliosis in the subiculum and extracellular CSPG in the hilus. Ex vivo T2 relaxation time correlated with astrogliosis in the hilus, CA4, and subiculum, and with microgliosis in CA1. The difference between in vivo and ex vivo relaxation ratio correlated with mean diffusivity and with the immunopositive area for CSPG in the hilus. SIGNIFICANCE: Our data indicate that astrogliosis, microgliosis, and CSPG expression correlate with the increased T2 relaxation time seen in the hippocampi of patients with TLE.

Correction: Increased Metallothionein I/II Expression in Patients with Temporal Lobe Epilepsy.

[This corrects the article DOI: 10.1371/journal.pone.0044709.].

Decreased neuron loss and memory dysfunction in pilocarpine-treated rats pre-exposed to hypoxia.

Preconditioning can induce a cascade of cellular events leading to neuroprotection against subsequent brain insults. In this study, we investigated the chronic effects of hypoxic preconditioning on spontaneous recurrent seizures (SRS), neuronal death, and spatial memory performance in rats subjected to pilocarpine (Pilo)-induced status epilepticus (SE). Rats underwent a short hypoxic episode (7% O2+93% N2; 30min on two consecutive days) preceding a 4-h SE (HSE group). Control groups were rats submitted to SE only (SE), rats subjected to hypoxia only (H) or normoxia-saline (C). Animals were monitored for the occurrence of SRS, and spatial memory performance was evaluated in the radial-arm maze. Hippocampal sections were analyzed for cell death and mossy fiber sprouting at 1 or 60days after SE. Compared to SE group, HSE had increased SE latency, reduced number of rats with SRS, reduced mossy fiber sprouting at 60days, and reduced cell death in the hilus and the CA3 region 1 and 60days after SE. Additionally, HSE rats had better spatial memory performance than SE rats. Our findings indicated that short hypoxic preconditioning preceding SE promotes long-lasting protective effects on neuron survival and spatial memory.

Characterization of ICP Behavior in an Experimental Model of Hemorrhagic Stroke in Rats.

Intracranial pressure (ICP) monitoring is sometimes required in clinical pictures of stroke, as extensive intraparenchymal hematomas and intracranial bleeding may severely increase ICP, which can lead to irreversible conditions, such as dementia and cognitive derangement. ICP monitoring has been accepted as a procedure for the safe diagnosis of increased ICP, and for the treatment of intracranial hypertension in some diseases. In this work, we evaluated ICP behavior during the induction of an experimental model of autologous blood injection in rats, simulating a hemorrhagic stroke. Rats were subjected to stereotactic surgery for the implantation of a unilateral cannula into the left striatal region of the brain. Autologous blood was infused into the left striatal region with an automatic microinfusion pump. ICP monitoring was performed throughout the procedure of hemorrhagic stroke induction. Analyses consisted of short-time Fourier transform for ICP before and after stroke induction and the histological processing of the animals' brains. Short-time Fourier transform analysis demonstrated oscillations in the ICP frequency components throughout time after the microinjections compared with data before them. Histological analysis revealed neuropathological changes in the striatum in all microinjected animals.

Beta-tubulin expression In the hippocampus Of patients with mesial temporal lobe epilepsy / Expressão de beta-tubulina no hipocampo de pacientes com epilepsia do lobo temporal mesial / Expresión de beta-tubulina en el hipocampo de los pacientes con epilepsia del lóbulo temporal mesial

Introduction: The neuronal loss and abnormal mossy fibers sprouting are frequently observed in patients with mesial temporal lobe epilepsy (MTLE). Beta-tubulin, a cytoskeleton protein, is critical for the maintenance of the neuritic structure. Objective: Considering the axonal reorganization in patients with MTLE, our objective was to analyze the beta-tubulin expression in the hippocampus of these patients. Methods: We evaluated the hippocampus of 38 MTLE patients and seven control cases. Histological sections were submitted to neo-Timm histochemistry to evaluate the sprouting of mossy fiber, and to immunohis- tochemistry for neuronal density evaluation (NeuN) and beta-tubulin expression. Results: The MTLE group showed lower neuronal density than the control group in the granular layer (GL), hilus, CA4, CA3, CA1, and presubiculum. The MTLE group showed higher gray value on the neo-Timm staining when compared to the control group in GL, IML, and outer mo- lecular layer (OML), and sprouting of thicker mossy fibers in the IML. When compared to the control group, group MTLE showed higher beta-tubulin expression in GL and lower expression in CA3 region. The aberrant sprouting of mossy fibers correlated inversely with the beta-tubulin expression in several subs of the hippocampal formation. Conclusions: The differential expression of beta-tubulin in the regions CA3 and GL of the MTLE group, as well as its correlation with neuronal loss and the mossy fiber sprouting, suggests a possible role of this protein in the neuropathological changes that occur in the hippocampus in chronic cases of MTLE.

Introdução: A perda neuronal e o brotamento anormal de fibras musgosas são observados com frequência em pacientes com epilepsia do lobo temporal mesial (ELTM). A beta-tubulina, uma proteína do citoesqueleto, é essencial para a manutenção da estrutura neurítica. Objetivo: Considerando a reorganização axonal nos pacientes com ELTM, nosso objetivo foi analisar a expressão de beta-tubulina no hipo- campo desses pacientes. Métodos: Foram avaliados 38 hipocampos de pacientes com ELTM e sete casos controle. Cortes histológicos foram submetidos à histoquímica de neo-Timm para avaliação do neobrotamento de fibras musgosas e à imuno-histoquímica para avaliações da densidade neuronal (NeuN) e da expressão de beta-tubulina. Resultados: O grupo ELTM apresentou menor densidade neuronal do que o grupo controle na camada granular (CG), hilo, CA4, CA3, CA1 e no pró-subículo. O grupo ELTM apresentou maior valor de cinza na coloração neo-Timm com relação ao grupo controle na CG, CMI e camada molecular externa (CME) e neobrotamento mais espesso de fibras musgosas na CMI. O grupo ELTM apresentou maior expressão de beta-tubulina na CG e menor expressão na região de CA3, quando comparado ao grupo controle. O neobrotamento aberrante de fibras musgosas correlacionou-se inversamente com a expressão de beta-tubulina em diversos subcampos da formação hipocampal. Conclusões: A expressão diferencial da beta-tubulina nas regiões da CA3 e CG do grupo ELTM, assim como suas correlações com a perda neuronal e o neobrotamento de fibras musgosas sugerem uma possível participação dessa proteína nas alterações neuropatológicas que ocorrem no hipocampo nos casos crônicos de ELTM.

Introducción: La pérdida neuronal y la brotación anormal de fibras musgosas se observan con frecuencia en los pacientes con epilepsia del lóbulo temporal mesial (ELTM). La beta-tubulina, una proteína del citoesqueleto, es crítica para el mantenimiento de la estructura neurítica. Objetivo: Teniendo en cuenta la reorganización axonal en pacientes con ELTM, nuestro objetivo fue analizar la expresión de beta-tubulina en el hipocampo de estos pacientes. Métodos: Se evaluó el hipocampo de 38 pacientes con ELTM y siete casos de control. Cortes histológicos fueron sometidos a la histoquímica neo-Timm para evaluar la brotación de fibras musgosas, y a inmunohistoquímica para la evaluación de la densidad neuronal (NeuN) y la expresión de beta-tubulina. Resultados: El grupo ELTM mostró una menor densidad neuronal que el grupo control en la capa granular (CG), hilo, CA4, CA3, CA1 y pró-subículo. El grupo ELTM mostró mayor valor de gris en la tinción neo-Timm en comparación con el grupo control en CG, CMI y en la capa externa molecular (CME), y la brotación de fibras musgosas más gruesas en la CMI. El grupo ELTM mostró una mayor expresión de beta- tubulina en CG y expresión más baja en la región CA3, cuando se compara con el grupo control. La brotación aberrante de fibras musgosa está inversamente correlacionada con la expresión de beta-tubulina en varios subcampos de la formación del hipocampo. Conclusiones: La expresión diferencial de beta-tubulina en las regiones CA3 y CG del grupo ELTM, así como su correlación con la pérdida neuronal y el surgimiento de fibras musgosas, sugiere un posible papel de esta proteína en los cambios neuropatológicos que se producen en el hipocampo en los casos crónicos de ELTM.

Temporal lobe epilepsy patients with severe hippocampal neuron loss but normal hippocampal volume: Extracellular matrix molecules are important for the maintenance of hippocampal volume.

OBJECTIVE: Hippocampal sclerosis is a common finding in patients with temporal lobe epilepsy (TLE), and magnetic resonance imaging (MRI) studies associate the reduction of hippocampal volume with the neuron loss seen on histologic evaluation. Astrogliosis and increased levels of chondroitin sulfate, a major component of brain extracellular matrix, are also seen in hippocampal sclerosis. Our aim was to evaluate the association between hippocampal volume and chondroitin sulfate, as well as neuronal and astroglial populations in the hippocampus of patients with TLE. METHODS: Patients with drug-resistant TLE were subdivided, according to hippocampal volume measured by MRI, into two groups: hippocampal atrophy (HA) or normal volume (NV) cases. Hippocampi from TLE patients and age-matched controls were submitted to immunohistochemistry to evaluate neuronal population, astroglial population, and chondroitin sulfate expression with antibodies against neuron nuclei protein (NeuN), glial fibrillary acidic protein (GFAP), and chondroitin sulfate (CS-56) antigens, respectively. RESULTS: Both TLE groups were clinically similar. NV cases had higher hippocampal volume, both ipsilateral and contralateral, when compared to HA. Compared to controls, NV and HA patients had reduced neuron density, and increased GFAP and CS-56 immunopositive area. There was no statistical difference between NV and HA groups in neuron density or immunopositive areas for GFAP and CS-56. Hippocampal volume correlated positively with neuron density in CA1 and prosubiculum, and with immunopositive areas for CS-56 in CA1, and negatively with immunopositive area for GFAP in CA1. Multiple linear regression analysis indicated that both neuron density and CS-56 immunopositive area in CA1 were statistically significant predictors of hippocampal volume. SIGNIFICANCE: Our findings indicate that neuron density and chondroitin sulfate immunopositive area in the CA1 subfield are crucial for the hippocampal volume, and that chondroitin sulfate is important for the maintenance of a normal hippocampal volume in some cases with severe neuron loss.

Mesial temporal lobe epilepsy with psychiatric comorbidities: a place for differential neuroinflammatory interplay.

BACKGROUND: Despite the strong association between epilepsy and psychiatric comorbidities, few biological substrates are currently described. We have previously reported neuropathological alterations in mesial temporal lobe epilepsy (MTLE) patients with major depression and psychosis that suggest a morphological and neurochemical basis for psychopathological symptoms. Neuroinflammatory-related structures and molecules might be part of the altered neurochemical milieu underlying the association between epilepsy and psychiatric comorbidities, and such features have not been previously investigated in humans. METHODS: MTLE hippocampi of subjects without psychiatric history (MTLEW), MTLE + major depression (MTLE + D), and MTLE + interictal psychosis (MTLE + P) derived from epilepsy surgery and control necropsies were investigated for reactive astrocytes (glial fibrillary acidic protein (GFAP)), activated microglia (human leukocyte antigen, MHC class II (HLA-DR)), glial metallothionein-I/II (MT-I/II), and aquaporin 4 (AQP4) immunohistochemistry. RESULTS: We found an increased GFAP immunoreactive area in the molecular layers, granule cell layer, and cornus ammonis region 2 (CA2) and cornus ammonis region 1 (CA1) of MTLEW and MTLE + P, respectively, compared to MTLE + D. HLA-DR immunoreactive area was higher in cornus ammonis region 3 (CA3) of MTLE + P, compared to MTLE + D and MTLEW, and in the hilus, when compared to MTLEW. MTLEW cases showed increased MT-I/II area in the granule cell layer and CA1, compared to MTLE + P, and in the parasubiculum, when compared to MTLE + D and MTLE + P. Differences between MTLE and control, such as astrogliosis, microgliosis, increased MT-I/II, and decreased perivascular AQP4 in the epileptogenic hippocampus, were in agreement to what is currently described in the literature. CONCLUSIONS: Neuroinflammatory-related molecules in MTLE hippocampus show a distinct pattern of expression when patients present with a comorbid psychiatric diagnosis, similar to what is found in the pure forms of schizophrenia and major depression. Future studies focusing on inflammatory characteristics of MTLE with psychiatric comorbidities might help in the design of better therapeutic strategies.

Increased metallothionein I/II expression in patients with temporal lobe epilepsy.

In the central nervous system, zinc is released along with glutamate during neurotransmission and, in excess, can promote neuronal death. Experimental studies have shown that metallothioneins I/II (MT-I/II), which chelate free zinc, can affect seizures and reduce neuronal death after status epilepticus. Our aim was to evaluate the expression of MT-I/II in the hippocampus of patients with temporal lobe epilepsy (TLE). Hippocampi from patients with pharmacoresistant mesial temporal lobe epilepsy (MTLE) and patients with TLE associated with tumor or dysplasia (TLE-TD) were evaluated for expression of MT-I/II, for the vesicular zinc levels, and for neuronal, astroglial, and microglial populations. Compared to control cases, MTLE group displayed widespread increase in MT-I/II expression, astrogliosis, microgliosis and reduced neuronal population. In TLE-TD, the same changes were observed, except that were mainly confined to fascia dentata. Increased vesicular zinc was observed only in the inner molecular layer of MTLE patients, when compared to control cases. Correlation and linear regression analyses indicated an association between increased MT-I/II and increased astrogliosis in TLE. MT-I/II levels did not correlate with any clinical variables, but MTLE patients with secondary generalized seizures (SGS) had less MT-I/II than MTLE patients without SGS. In conclusion, MT-I/II expression was increased in hippocampi from TLE patients and our data suggest that it is associated with astrogliosis and may be associated with different seizure spread patterns.

Different levels of MT-I/II between patients with MTLE with or without seizure generalization: does hippocampal MT-I/II affects seizure spread, or does seizure spread promotes differential expression of MT-I/II? / Níveis diferentes de MT-I/II entre pacientes com MTLE com ou sem crise generalizada: os níveis hipocampais de MT-I/II afetam o alastramento das crises, ou o alastramento das crises promove expressão diferencial de MT-I/II?

In the central nervous system, zinc is released along with glutamate during neurotransmission and, in excess, can promote neuronal death. Experimental studies have shown that metallothioneins I/II (MT-I/II), which chelate free zinc, can affect seizures and reduce neuronal death after status epilepticus. Our aim was to evaluate the expression of MT-I/II in the hippocampus of patients with temporal lobe epilepsy (TLE). Hippocampi from patients with pharmacoresistant mesial temporal lobe epilepsy (MTLE) were evaluated for expression of MT-I/II and for neuronal, astroglial, and microglial populations. Compared to control cases, MTLE group displayed widespread increase in MT-I/II expression, astrogliosis and reduced neuronal population. MT-I/II levels did not correlate with any clinical variables, but patients with secondary generalized seizures (SGS) had less MT-I/II than patients without SGS. In conclusion, MT-I/II expression was increased in hippocampi from MTLE patients and our data suggest that it may be associated with different seizure spread patterns.

No sistema nervoso central, o zinco é liberado juntamente com o glutamato durante a neurotransmissão e, quando liberado em excesso, pode promover morte neuronal. Estudos indicam que as metalotioneínas I/II (MT-I/II), proteínas quelantes de zinco livre, podem afetar parâmetros relacionados às crises e reduzir a morte neuronal subsequente a um status epilepticus. Nosso objetivo foi avaliar a expressão de MT-I/II no hipocampo de pacientes com epilepsia do lobo temporal (ELT). Hipocampos de pacientes com ELT mesial (ELTM) resistente ao tratamento farmacológico foram avaliados para a expressão de MT-I/II e para as populações neuronal e astroglial. Quando comparadas com o grupo controle, pacientes com ELTM apresentaram aumento na expressão de MT-I/II, astrogliose e redução na densidade neuronal. Não foram observadas correlações entre os níveis de MT-I/II e as características clínicas dos pacientes, mas pacientes com crises secundariamente generalizadas apresentaram um aumento menor nos níveis de MT-I/II que os pacientes sem estas crises. Em resumo, um aumento na expressão de MT-I/II é observado em pacientes com ELTM e nossos dados sugerem que o aumento pode estar associado a diferentes padrões de crises epilépticas.