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Proteins exhibiting prion-like properties are implicated in tauopathies. The prion-like traits of tau influence disease progression and correlate with severity. Techniques to measure tau bioactivity such as RT-QuIC and biosensor cells lack spatial specificity. Therefore, we developed a histological probe aimed at detecting and localizing bioactive tau in situ. We first induced the recruitment of a tagged probe by bioactive Tau in human brain tissue slices using biosensor cell lysates containing a fluorescent probe. We then enhanced sensitivity and flexibility by designing a recombinant probe with a myc tag. The probe design aimed to replicate the recruitment process seen in prion-like mechanisms based on the cryo-EM structure of tau aggregates in Alzheimer disease (AD). Using this novel probe, we observed selective staining of misfolded tau in pre- and post-synaptic structures within neurofibrillary tangles and neurites, whether or not associated with neuritic plaques. The probe specifically targeted AD-associated bioactive tau and did not recognize bioactive tau from other neurodegenerative diseases. Electron microscopy and immunolabeling further confirmed the identification of fibrillar and non-fibrillar tau. Finally, we established a correlation between quantifying bioactive tau using this technique and gold standard biosensor cells. This technique presents a robust approach for detecting bioactive tau in AD tissues and has potential applications for deciphering mechanisms of tau propagation and degradation pathways., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Association of Neuropathologists, Inc. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Pathological tau fibrils in progressive supranuclear palsy, frontotemporal dementia, chronic traumatic encephalopathy, and Alzheimer's disease each have unique conformations, and post-translational modifications that correlate with unique disease characteristics. However, within Alzheimer's disease (AD), both fibrillar (sarkosyl insoluble (AD SARK tau)), and nonfibrillar (aqueous extractable high molecular weight (AD HMW tau)) preparations have been suggested to be seed-competent. We now explore if these preparations are similar or distinct in their in vivo seeding characteristics. Using an in vivo amplification and time-course paradigm we demonstrate that, for AD HMW and AD SARK tau species, the amplified material is biochemically similar to the original sample. The HMW and SARK materials also show different clearance, propagation kinetics, and propagation patterns. These data indicate the surprising co-occurrence of multiple distinct tau species within the same AD brain, supporting the idea that multiple tau conformers - both fibrillar and nonfibrillar- can impact phenotype in AD., (© 2024. The Author(s).)

The aim of this multicenter prospective survey called PIT-EASY was to assess the relevance of the European Pituitary Pathology Group (EPPG) diagnostic tools for pituitary neuroendocrine tumors (PitNETs) to improve the quality of their histological diagnosis. Each center performed at least 30 histological cases of PitNETs using the EPPG tools and assessed their value using a scorecard with 10 questions. For each center, the histological cases were carried out by pathologists with varying levels of expertise in pituitary pathology defined as junior, intermediate, and expert. Two hundred and ninety histological cases were collected from six French and Italian centers. The three EPPG tools were validated and regarded as helpful for a more accurate and time-efficient diagnosis. The usefulness of level 2 and level 3 of the "EPPG's multi-step approach for immunohistochemistry" including pituitary transcription factors (PIT1, TPIT, and SF1) and chromogranin, SSTRs, and P53 respectively was higher in "other non-functioning" (silent plurihormonal PIT1, silent corticotroph, and null cell): 88% vs 32%, p < 10-6 and 42% vs 14%, p = 0.002, respectively. The diagnostic algorithm proved more useful for junior pathologists (p = 0.0001) and those with intermediate experience. PIT-EASY survey confirmed the importance of a standardized approach to PitNETs for an accurate and reproducible diagnosis and served as validation of the EPPG proposal. The tool appeared to be of practical value to junior participants and staff with intermediate experience for safe routine diagnostic reporting., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Ewing sarcoma is an aggressive cancer with a defective response to DNA damage leading to an enhanced sensitivity to genotoxic agents. Mechanistically, Ewing sarcoma is driven by the fusion transcription factor EWS-FLI1, which reprograms the tumor cell epigenome. The nucleosome remodeling and deacetylase (NuRD) complex is an important regulator of chromatin function, controlling both gene expression and DNA damage repair, and has been associated with EWS-FLI1 activity. Here, a NuRD-focused CRISPR/Cas9 inactivation screen identified the helicase CHD4 as essential for Ewing sarcoma cell proliferation. CHD4 silencing induced tumor cell death by apoptosis and abolished colony formation. Although CHD4 and NuRD colocalized with EWS-FLI1 at enhancers and super-enhancers, CHD4 promoted Ewing sarcoma cell survival not by modulating EWS-FLI1 activity and its oncogenic gene expression program but by regulating chromatin structure. CHD4 depletion led to a global increase in DNA accessibility and induction of spontaneous DNA damage, resulting in an increased susceptibility to DNA-damaging agents. CHD4 loss delayed tumor growth in vivo, increased overall survival, and combination with PARP inhibition by olaparib treatment further suppressed tumor growth. Collectively, these findings highlight the NuRD subunit CHD4 as a therapeutic target in Ewing sarcoma that can potentiate the antitumor activity of genotoxic agents., Significance: CRISPR/Cas9 screening in Ewing sarcoma identifies a dependency on CHD4, which is crucial for the maintenance of chromatin architecture to suppress DNA damage and a promising therapeutic target for DNA damage repair-deficient malignancies., (©2023 American Association for Cancer Research.)

Importance: Factors associated with synapse loss beyond amyloid-β plaques and neurofibrillary tangles may more closely correlate with the emergence of cognitive deficits in Alzheimer disease (AD) and be relevant for early therapeutic intervention., Objective: To investigate whether accumulation of tau oligomers in synapses is associated with excessive synapse elimination by microglia or astrocytes and with cognitive outcomes (dementia vs no dementia [hereinafter termed resilient]) of individuals with equal burdens of AD neuropathologic changes at autopsy., Design, Setting, and Participants: This cross-sectional postmortem study included 40 human brains from the Massachusetts Alzheimer Disease Research Center Brain Bank with Braak III to IV stages of tau pathology but divergent antemortem cognition (dementia vs resilient) and cognitively normal controls with negligible AD neuropathologic changes. The visual cortex, a region without tau tangle deposition at Braak III to IV stages, was assessed after expansion microscopy to analyze spatial relationships of synapses with microglia and astrocytes. Participants were matched for age, sex, and apolipoprotein E status. Evidence of Lewy bodies, TDP-43 aggregates, or other lesions different from AD neuropathology were exclusion criteria. Tissue was collected from July 1998 to November 2020, and analyses were conducted from February 1, 2022, through May 31, 2023., Main Outcomes and Measures: Amyloid-β plaques, tau neuropil thread burden, synapse density, tau oligomers in synapses, and internalization of tau oligomer-tagged synapses by microglia and astrocytes were quantitated. Analyses were performed using 1-way analysis of variance for parametric variables and the Kruskal-Wallis test for nonparametric variables; between-group differences were evaluated with Holm-Šídák tests., Results: Of 40 included participants (mean [SD] age at death, 88 [8] years; 21 [52%] male), 19 had early-stage dementia with Braak stages III to IV, 13 had resilient brains with similar Braak stages III to IV, and 8 had no dementia (Braak stages 0-II). Brains with dementia but not resilient brains had substantial loss of presynaptic (43%), postsynaptic (33%), and colocalized mature synaptic elements (38%) compared with controls and significantly higher percentages of mature synapses internalized by IBA1-positive microglia (mean [SD], 13.3% [3.9%] in dementia vs 2.6% [1.9%] in resilient vs 0.9% [0.5%] in control; P < .001) and by GFAP-positive astrocytes (mean [SD], 17.2% [10.9%] in dementia vs 3.7% [4.0%] in resilient vs 2.7% [1.8%] in control; P = .001). In brains with dementia but not in resilient brains, tau oligomers more often colocalized with synapses, and the proportions of tau oligomer-containing synapses inside microglia (mean [SD] for presynapses, mean [SD], 7.4% [1.8%] in dementia vs 5.1% [1.9%] resilient vs 3.7% [0.8%] control; P = .006; and for postsynapses 11.6% [3.6%] dementia vs 6.8% [1.3%] resilient vs 7.4% [2.5%] control; P = .001) and astrocytes (mean [SD] for presynapses, 7.0% [2.1%] dementia vs 4.3% [2.2%] resilient vs 4.0% [0.7%] control; P = .001; and for postsynapses, 7.9% [2.2%] dementia vs 5.3% [1.8%] resilient vs 3.0% [1.5%] control; P < .001) were significantly increased compared with controls. Those changes in brains with dementia occurred in the absence of tau tangle deposition in visual cortex., Conclusion and Relevance: The findings from this cross-sectional study suggest that microglia and astrocytes may excessively engulf synapses in brains of individuals with dementia and that the abnormal presence of tau oligomers in synapses may serve as signals for increased glial-mediated synapse elimination and early loss of brain function in AD.

Background: We have recently demonstrated a causal link between loss of gonadotropin-releasing hormone (GnRH), the master molecule regulating reproduction, and cognitive deficits during pathological aging, including Down syndrome and Alzheimer's disease. Olfactory and cognitive alterations, which persist in some COVID-19 patients, and long-term hypotestosteronaemia in SARS-CoV-2-infected men are also reminiscent of the consequences of deficient GnRH, suggesting that GnRH system neuroinvasion could underlie certain post-COVID symptoms and thus lead to accelerated or exacerbated cognitive decline., Methods: We explored the hormonal profile of COVID-19 patients and targets of SARS-CoV-2 infection in post-mortem patient brains and human fetal tissue., Findings: We found that persistent hypotestosteronaemia in some men could indeed be of hypothalamic origin, favouring post-COVID cognitive or neurological symptoms, and that changes in testosterone levels and body weight over time were inversely correlated. Infection of olfactory sensory neurons and multifunctional hypothalamic glia called tanycytes highlighted at least two viable neuroinvasion routes. Furthermore, GnRH neurons themselves were dying in all patient brains studied, dramatically reducing GnRH expression. Human fetal olfactory and vomeronasal epithelia, from which GnRH neurons arise, and fetal GnRH neurons also appeared susceptible to infection., Interpretation: Putative GnRH neuron and tanycyte dysfunction following SARS-CoV-2 neuroinvasion could be responsible for serious reproductive, metabolic, and mental health consequences in long-COVID and lead to an increased risk of neurodevelopmental and neurodegenerative pathologies over time in all age groups., Funding: European Research Council (ERC) grant agreements No 810331, No 725149, No 804236, the European Union Horizon 2020 research and innovation program No 847941, the Fondation pour la Recherche Médicale (FRM) and the Agence Nationale de la Recherche en Santé (ANRS) No ECTZ200878 Long Covid 2021 ANRS0167 SIGNAL, Agence Nationale de la recherche (ANR) grant agreements No ANR-19-CE16-0021-02, No ANR-11-LABEX-0009, No. ANR-10-LABEX-0046, No. ANR-16-IDEX-0004, Inserm Cross-Cutting Scientific Program HuDeCA, the CHU Lille Bonus H, the UK Medical Research Council (MRC) and National Institute of Health and care Research (NIHR)., Competing Interests: Declaration of interests The authors declare no competing interest., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: The prion-like propagation of tau in neurodegenerative disorders implies that misfolded pathological tau can recruit the normal protein and template its aggregation. Here, we report the methods for the development of sensitive biosensor cell lines for the detection of tau seeding activity., Results: We performed the rational design of novel tau probes based on the current structural knowledge of pathological tau aggregates in Alzheimer's disease. We generated Förster resonance energy transfer (FRET)-based biosensor stable cell lines and characterized their sensitivity, specificity, and overall ability to detect bioactive tau in human samples. As compared to the reference biosensor line, the optimized probe design resulted in an increased efficiency in the detection of tau seeding. The increased sensitivity allowed for the detection of lower amount of tau seeding competency in human brain samples, while preserving specificity for tau seeds found in Alzheimer's disease., Conclusions: This next generation of FRET-based biosensor cells is a novel tool to study tau seeding activity in Alzheimer's disease human samples, especially in samples with low levels of seeding activity, which may help studying early tau-related pathological events., (© 2023. Editorial Group and BioMed Central Ltd., part of Springer Nature.)

Insoluble fibrillar tau, the primary constituent of neurofibrillary tangles, has traditionally been thought to be the biologically active, toxic form of tau mediating neurodegeneration in Alzheimer's disease. More recent studies have implicated soluble oligomeric tau species, referred to as high molecular weight (HMW), due to their properties on size-exclusion chromatography, in tau propagation across neural systems. These two forms of tau have never been directly compared. We prepared sarkosyl-insoluble and HMW tau from the frontal cortex of Alzheimer patients and compared their properties using a variety of biophysical and bioactivity assays. Sarkosyl-insoluble fibrillar tau comprises abundant paired-helical filaments (PHF) as quantified by electron microscopy (EM) and is more resistant to proteinase K, compared to HMW tau, which is mostly in an oligomeric form. Sarkosyl-insoluble and HMW tau are nearly equivalent in potency in HEK cell bioactivity assay for seeding aggregates, and their injection reveals similar local uptake into hippocampal neurons in PS19 Tau transgenic mice. However, the HMW preparation appears to be far more potent in inducing a glial response including Clec7a-positive rod microglia in the absence of neurodegeneration or synapse loss and promotes more rapid propagation of misfolded tau to distal, anatomically connected regions, such as entorhinal and perirhinal cortices. These data suggest that soluble HMW tau has similar properties to fibrillar sarkosyl-insoluble tau with regard to tau seeding potential, but may be equal or even more bioactive with respect to propagation across neural systems and activation of glial responses, both relevant to tau-related Alzheimer phenotypes., (© 2023. The Author(s).)

Multiple lines of evidence have linked oxidative stress, tau pathology and neuronal cell cycle re-activation to Alzheimer's disease (AD). While a prevailing idea is that oxidative stress-induced neuronal cell cycle reactivation acts as an upstream trigger for pathological tau phosphorylation, others have identified tau as an inducer of cell cycle abnormalities in both mitotic and postmitotic conditions. In addition, nuclear hypophosphorylated tau has been identified as a key player in the DNA damage response to oxidative stress. Whether and to what extent these observations are causally linked remains unclear. Using immunofluorescence, fluorescence-activated nucleus sorting and single-nucleus sequencing, we report an oxidative stress-associated accumulation of nuclear hypophosphorylated tau in a subpopulation of cycling neurons confined in S phase in AD brains, near amyloid plaques. Tau downregulation in murine neurons revealed an essential role for tau to promote cell cycle progression to S phase and prevent apoptosis in response to oxidative stress. Our results suggest that tau holds oxidative stress-associated cycling neurons in S phase to escape cell death. Together, this study proposes a tau-dependent protective effect of neuronal cell cycle reactivation in AD brains and challenges the current view that the neuronal cell cycle is an early mediator of tau pathology., Competing Interests: Declaration of Competing Interests The authors declare that they have no competing interests., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Tauopathies are neurodegenerative disorders involving the accumulation of tau isoforms in cell subpopulations such as astrocytes. The origins of the 3R and 4R isoforms of tau that accumulate in astrocytes remain unclear. Extracellular vesicles (EVs) were isolated from primary neurons overexpressing 1N3R or 1N4R tau or from human brain extracts (progressive supranuclear palsy or Pick disease patients or controls) and characterized (electron microscopy, nanoparticle tracking analysis (NTA), proteomics). After the isolated EVs were added to primary astrocytes or human iPSC-derived astrocytes, tau transfer and mitochondrial system function were evaluated (ELISA, immunofluorescence, MitoTracker staining). We demonstrated that neurons in which 3R or 4R tau accumulated had the capacity to transfer tau to astrocytes and that EVs were essential for the propagation of both isoforms of tau. Treatment with tau-containing EVs disrupted the astrocytic mitochondrial system, altering mitochondrial morphology, dynamics, and redox state. Although similar levels of 3R and 4R tau were transferred, 3R tau-containing EVs were significantly more damaging to astrocytes than 4R tau-containing EVs. Moreover, EVs isolated from the brain fluid of patients with different tauopathies affected mitochondrial function in astrocytes derived from human iPSCs. Our data indicate that tau pathology spreads to surrounding astrocytes via EVs-mediated transfer and modifies their function.

Introduction: Few studies have attempted to evaluate the early efficacy of first-generation somatostatin analogues in somatotroph macroadenomas., Objective: To investigate the short-term efficacy of primary therapy with lanreotide 120 mg at 1 and 3 months on tumour shrinkage and ophthalmologic symptoms in newly diagnosed patients with acromegaly., Design and Patients: This single-centre retrospective study included 21 patients with de novo acromegaly resulting from pituitary macroadenoma, with optic chiasm compression (Grade ≤ 2) and/or cavernous sinus invasion, treated with a monthly injection of lanreotide 120 mg. Clinical, hormonal, ophthalmologic and magnetic resonance imaging scan evaluations were conducted after the first and the third months of treatment., Results: Tumour volume reduction was more pronounced at 1 month; mean volume change: -31.4 ± 19.5%, p < .0001 than between the first and third month of treatment; mean volume reduction: -20.6 ± 13.4%, p = .0009. The mean volume change between baseline and the third month was - 46.4 ± 21.6, (p < .0001). A significant volume reduction (≥25%) was observed in 61.9% of individuals (13/21) at the first month. Among 14 individuals with optic chiasm compression and visual field defects, visual field normalization or improvement were observed in seven cases (50%), stabilization in four cases (28.5%), and mild worsening in three cases (21.4%) at 1 month. The decrease in growth hormone and IGF-1 serum values was significant at 1 month., Conclusions: Primary treatment with lanreotide 120 mg in patients with somatotroph macroadenomas provides early significant tumour shrinkage with rapid improvement of visual symptoms at the end of the first month in 50% of patients., (© 2022 John Wiley & Sons Ltd.)

Introduction: This study evaluated the association between fetal heart rate variability (HRV) and the occurrence of hypoxic-ischemic encephalopathy in a fetal sheep model., Material and Methods: The experimental protocol created a hypoxic condition with repeated cord occlusions in three phases (A, B, C) to achieve acidosis to pH <7.00. Hemodynamic, gasometric and HRV parameters were analyzed during the protocol, and the fetal brain, brainstem and spinal cord were assessed histopathologically 48 h later. Associations between the various parameters and neural injury were compared between phases A, B and C using Spearman's rho test., Results: Acute anoxic-ischemic brain lesions in all regions was present in 7/9 fetuses, and specific neural injury was observed in 3/9 fetuses. The number of brainstem lesions correlated significantly and inversely with the HRV fetal stress index (r = -0.784; p = 0.021) in phase C and with HRV long-term variability (r = -0.677; p = 0.045) and short-term variability (r = -0.837; p = 0.005) in phase B. The number of neurological lesions did not correlate significantly with other markers of HRV., Conclusions: Neural injury caused by severe hypoxia was associated with HRV changes; in particular, brainstem damage was associated with changes in fetal-specific HRV markers., (© 2022 The Authors. Acta Obstetricia et Gynecologica Scandinavica published by John Wiley & Sons Ltd on behalf of Nordic Federation of Societies of Obstetrics and Gynecology (NFOG).)

Background: Enhancing the blood clearance process is a promising therapeutic strategy for intracerebral hemorrhage (ICH). We aimed to investigate the kinetic of this process after ICH in human brain tissue through the monocyte-macrophage scavenger receptor (CD163)/HO-1 (hemoxygenase-1) pathway., Methods: We led a cross-sectional post-mortem study including 22 consecutive ICH cases (2005-2019) from the Lille Neurobank. Cases were grouped according to the time of death: ≤72 hours, 4 to 7 days, 8 to 15 days, 16 to 90 days, and >90 days after ICH onset. Paraffin-embedded tissue was extracted from 4 strategic areas, including hematoma core and peri-hematomal area to perform histological investigations. Additionally, we extracted RNA from the peri-hematomal area of 6 cases to perform transcriptomic analysis., Results: We included 19 ICH cases (median age: 79 [71-89] years; median delay ICH-death: 13 [5-41] days). The peri-hematomal area concentrated most of reactive microglia, CD163/HO-1 and iron deposits as compared with other brain areas. We found a surge in the blood clearance process from day 8 to day 15 after ICH onset. Transcriptomic analysis showed that HO-1 was the most upregulated gene (2.81±0.39, adjusted P =1.11×10 -10 ) and CD163 the sixth (1.49±0.29, adjusted P =1.68×10 - 5 ). We also identified several upregulated genes that exert a beneficial role in terminating inflammation and enhancing tissue repair., Conclusions: We provide histological and transcriptomic-based evidence in humans for the key role of peri-hematomal area in endogenous blood clearance process through the CD163/HO-1 pathway, especially from day 8 after ICH and favored by an anti-inflammatory environment. Our findings contribute to identify innovative therapeutic strategies for ICH.

Tauopathies are neurodegenerative diseases characterized by tau inclusions in brain cells. Seed-competent tau species have been suggested to spread from cell to cell in a stereotypical manner, indicating that this may involve a prion-like mechanism. Although the intercellular mechanisms of transfer are unclear, extracellular vesicles (EVs) could be potential shuttles. We assessed this in humans by preparing vesicles from fluids (brain-derived enriched EVs [BD-EVs]). These latter were isolated from different brain regions in various tauopathies, and their seeding potential was assessed in vitro and in vivo. We observed considerable heterogeneity among tauopathies and brain regions. The most striking evidence was coming mainly from Alzheimer's disease where the BD-EVs clearly contain pathological species that can induce tau lesions in vivo. The results support the hypothesis that BD-EVs participate in the prion-like propagation of tau pathology among tauopathies, and there may be implications for diagnostic and therapeutic strategies., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Aims: We searched for recurrent pathological features and molecular alterations in a retrospective series of 72 low-grade epilepsy-associated neuroepithelial tumours (LEATs) with a prominent oligodendroglioma-like component, in order to classify them according to the 2021 World Health Organization (WHO) classification of central nervous system (CNS) tumours., Methods: Centralised pathological examination was performed as well as targeted molecular analysis of v-Raf murine sarcoma viral oncogene homologue B (BRAF) and fibroblast growth factor receptor 1 (FGFR1) by multiplexed digital polymerase chain reaction (mdPCR). DNA methylation profiling was performed in cases with sufficient DNA. In cases with no genetic alteration by mdPCR and sufficient material, RNA sequencing was done., Results: We first reclassified our cohort into three groups: ganglioglioma (GG, n = 14), dysembryoplastic neuroepithelial tumours (DNTs, n = 19) and glioneuronal tumours/paediatric-type low-grade glioma (LGG) not otherwise specified (GNT/PLGG NOS, n = 39). mdPCR found an alteration in 38/72 cases. Subsequent RNA sequencing revealed a fusion transcript involving BRAF, FGFR1/2/3 or neurotrophic tyrosine kinase receptor type 2 [NTRK2] in 9/25 cases. DNA methylation profiling found 12/46 cases with a calibrated score ≥0.9. Unsupervised hierarchical clustering revealed two clusters: Cluster 1 was enriched with cases classified as DNT at histology, belonging to the LGG-DNT methylation class (MC), with haematopoietic progenitor cell antigen (CD34) negativity and FGRF1 alterations; Cluster 2 was enriched with cases classified at histology as GG, belonging to the LGG-GG MC MC, with BRAF V600E mutation and CD34 positivity. The tumours reclassified as GNT/PLGG NOS were equally distributed across both clusters. Interestingly, all polymorphous low-grade neuroepithelial tumour of the young belonged to Cluster 2, whereas diffuse LGG mitogen-activated protein kinase (MAPK) pathway-altered were equally distributed among the two clusters. This led us to build an algorithm to classify LEATs with a prominent oligodendroglioma-like component., Conclusions: Integrated histomolecular diagnosis of LEATs with a prominent oligodendroglioma-like component remains challenging. Because these tumours can be split into two major clusters of biological significance, the clinicopathological relevance of the four types recognised by the WHO CNS5 within this spectrum of tumours is questionable., (© 2021 British Neuropathological Society.)

Extracellular Vesicles (EVs) are released by a wide diversity of cells. They contain proteins, RNAs and lipids that will be exchanged between these cells. They represent therefore a major form of intercellular communication in both physiological and pathological conditions. This is particularly relevant in the nervous system where neurons and glial cells form a very dense network where billions of connections are made. In this review, the different roles played by the EVs in a healthy brain to maintain cerebral homeostasis during development, synaptic transmission or axonal myelination will be discussed. In addition, the pathological aspects of EVs presence will also be addressed. In recent years, the EVs have emerged as major players in the spread of neurodegenerative diseases, in neuroinflammation and in tumor development, although they may also be beneficial in some conditions., (© 2021 médecine/sciences – Inserm.)

Introduction: The relationship between meningioma and progestins has not been elucidated. Meningioma regression after acetate cyproterone (CA) withdrawal has been reported. Our purpose was to evaluate the meningioma evolution after withdrawal of progestins in patients who underwent long-term exposure to CA, nomegestrol acetate (NA), chlormadinone acetate (ChlA)., Methods: Our study retrospectively included 69 patients with intracranial meningioma and exposed to one of these 3 progestins between December 2006 and March 2019. In each patient, clinico-radiological (MRI) follow-up was performed every 6 months after diagnosis and treatment withdrawal recommendation. Statistical analyses were applied to compare tumor location and respect of prescription rules between the 3 groups., Results: The mean hormonal exposure was 16 years in CA group (n = 46), 16 years in NA group (n = 12) and 9.7 years in ChlA group (n = 11). A higher rate of "out of label" use was observed in the CA group (p = 0.003). Multiple meningiomas were demonstrated in more than 60% of cases in each group. Anterior skull base location was noted in 60.5% of cases in CA group, 25% of cases in NA group and 36.7% of cases in ChlA group (p = 0.05). Incomplete tumor regression was recorded in 11 cases of CA group and in 2 cases of ChlA group., Conclusion: In CA group, our results suggest a strong relationship between this treatment and development of intracranial meningioma. In presence of voluminous asymptomatic meningioma, treatment can be delayed due to the potential regression after withdrawal. On the contrary in NA and ChlA groups, further studies are needed., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Aims: Because of their prothrombotic and neuroinflammatory effects, neutrophils and neutrophil extracellular traps (NETs) represent interesting therapeutic targets for spontaneous intracerebral haemorrhage (sICH). We investigated the presence, spatial and temporal distribution of NETs in a human sICH post-mortem study., Methods: From 2005 to 2019, all sICH patients who came to autopsy within the first month after stroke were included and grouped according to the timing of death: 72 h, 4-7 days, 8-15 days and >15 days after ICH onset. Paraffin-embedded tissue was extracted from four strategic areas: haematoma, peri-haematomal area, ipsilateral surrounding brain tissue and a control contralateral area. Myeloperoxidase and histone H3 citrulline were immunolabelled to detect neutrophils and NETs respectively., Results: Neutrophils were present in the brains of the 14 cases (4 men, median age: 78 years) and NETs were found in 7/14 cases. Both neutrophils and NETs were detected within the haematoma but also in the surrounding tissue. The appearance of neutrophils and NETs was time-dependent, following a two-wave pattern: during the first 72 h and between 8 and 15 days after ICH onset. Qualitative examination showed that neutrophils and NETs were mainly located around dense fibrin fibres within the haematoma., Conclusions: These observations provide evidence for NETs infiltration in the brain of patients who die from sICH. NETs might interact with early haemostasis within the haematoma core, and with the surrounding neuroinflammatory response. These findings open research perspectives for NETs in the treatment of sICH injuries., (© 2021 British Neuropathological Society.)

Context.—: Distinguishing the different types of amyloid is clinically important because treatments and outcomes are different. Mass spectrometry is the new gold standard for amyloid typing, but it is costly and not widely available. Therefore, immunolabeling remains the first step in identifying the most common types of amyloidosis. In amyloid subtyping, direct immunofluorescence works well when applied to frozen sections, but immunohistochemistry on formalin-fixed, paraffin-embedded material often yields poor results, particularly for light chain amyloidosis. Recently, paraffin immunofluorescence has been described as a valuable salvage technique in renal pathology when frozen sections are not available but it has not been evaluated for extra-renal diseases., Objectives.—: To evaluate the use of paraffin immunofluorescence for light-chain detection in extra-renal amyloidosis and other light-chain-associated diseases., Design.—: First, we compared the staining intensity of both light chains between paraffin immunofluorescence and immunohistochemistry on a retrospective cohort of 28 cases of amyloidosis that have been previously typed. Then, we studied the role of paraffin immunofluorescence as an addition to our classical immunohistochemistry panel for amyloidosis typing., Results.—: In the retrospective cohort, we found that paraffin immunofluorescence outperformed immunohistochemistry for light-chain detection. Then, in the prospective part of the study, we showed that the proportion of correctly classified cases increased from 50% to 71.9% with the adjunction of second-intention paraffin immunofluorescence to the immunohistochemistry procedure., Conclusions.—: We therefore view paraffin immunofluorescence as a significant addition to the routine workflow for detection of light-chain-related diseases., Competing Interests: The authors have no relevant financial interest in the products or companies described in this article., (© 2021 College of American Pathologists.)

BCOR is an epigenetic regulator altered by various mechanisms including BCOR -internal tandem duplication ( BCOR -ITD) in a wide range of cancers. Six different BCOR -ITD in the 3'-part of the coding sequence of exon 15 have been reported ranging from 89 to 114 bp in length. BCOR -ITD is a common genetic alteration found in clear cell sarcoma of the kidney and primitive myxoid mesenchymal tumor of infancy (PMMTI) and it characterizes a new type of central nervous system tumor: "CNS tumor with BCOR -ITD". It can also be detected in undifferentiated round cell sarcoma (URCS) and in high-grade endometrial stromal sarcoma (HGESS). Therefore, it is of utmost importance to search for this genetic alteration in these cancers with the most frequent technique being RNA-sequencing. Here, we developed a new droplet PCR assay (dPCR) to detect the six sequences characterizing BCOR -ITD. To achieve this goal, we used a single colored probe to detect both the duplicated region and the normal sequence that acts as a reference. We first generated seven synthetic DNA sequences: ITD0 (the normal sequence) and ITD1 to ITD6 (the duplicated sequences described in the literature) and then we set up the optima dPCR conditions. We validated our assay on 19 samples from a representative panel of human tumors (9 HGNET-BCOR, 5 URCS, 3 HGESS, and 2 PMMTI) in which BCOR -ITD status was known using at least one other method including RNA sequencing, RT-PCR or DNA-methylation profiling for CNS tumors. Our results showed that our technique was 100% sensitive and specific. DPCR detected BCOR -ITD in 13/19 of the cases; in the remaining 6 cases additional RNA-sequencing revealed BCOR gene fusions. To conclude, in the era of histomolecular classification of human tumors, our modified dPCR assay is of particular interest to detect BCOR -ITD since it is a robust and less expensive test that can be applied to a broad spectrum of cancers that share this alteration., Competing Interests: FF is Scientific Director of ID-Solutions, Grabels, France. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Barets, Appay, Heinisch, Battistella, Bouvier, Chotard, Le Loarer, Macagno, Perbet, Pissaloux, Rousseau, Tauziède-Espariat, Varlet, Vasiljevic, Colin, Fina and Figarella-Branger.)

Alzheimer's disease (AD) is characterized by the accumulation of the tau protein in neurons, neurodegeneration and memory loss. However, the role of non-neuronal cells in this chain of events remains unclear. In the present study, we found accumulation of tau in hilar astrocytes of the dentate gyrus of individuals with AD. In mice, the overexpression of 3R tau specifically in hilar astrocytes of the dentate gyrus altered mitochondrial dynamics and function. In turn, these changes led to a reduction of adult neurogenesis, parvalbumin-expressing neurons, inhibitory synapses and hilar gamma oscillations, which were accompanied by impaired spatial memory performances. Together, these results indicate that the loss of tau homeostasis in hilar astrocytes of the dentate gyrus is sufficient to induce AD-like symptoms, through the impairment of the neuronal network. These results are important for our understanding of disease mechanisms and underline the crucial role of astrocytes in hippocampal function.

Leukocyte cell-derived chemotaxin 2-associated amyloidosis (ALECT2) is a recently described of amyloidosis described in the United States in 2007. It is a systemic disease that is predominantly associated with some ethnics groups. ALECT2 is usually diagnosed on a kidney biopsy performed in the context of slowly progressive chronic renal disease but can also be found incidentally on a liver sample. We report the case of a Syrian patient who benefited from a partial hepatectomy for the treatment of multiple metastasis of a colorectal adenocarcinoma. Microscopic analysis of the surgical specimen revealed numerous amyloid deposits that did not match any of the usual forms of liver amyloidosis after immunohistochemistry typing. Some morphologic features of the deposits were highly suggestive of ALECT2. Complementary immunohistochemical study and mass spectrometry confirmed the diagnosis., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

Pediatric diffuse midline gliomas are devastating diseases. Among them, diffuse midline gliomas H3K27M-mutant are associated with worse prognosis. However, recent studies have highlighted significant differences in clinical behavior and biological alterations within this specific subgroup. In this context, simple markers are needed to refine the prognosis of diffuse midline gliomas H3K27M-mutant and guide the clinical management of patients. The aims of this study were (i) to describe the molecular, immunohistochemical and, especially, chromosomal features of a cohort of diffuse midline gliomas and (ii) to focus on H3K27M-mutant tumors to identify new prognostic markers. Patients were retrospectively selected from 2001 to 2017. Tumor samples were analyzed by immunohistochemistry (including H3K27me3, EGFR, c-MET and p53), next-generation sequencing and comparative genomic hybridization array. Forty-nine patients were included in the study. The median age at diagnosis was 9 years, and the median overall survival (OS) was 9.4 months. H3F3A or HIST1H3B mutations were identified in 80% of the samples. Within the H3K27M-mutant tumors, PDGFRA amplification, loss of 17p and a complex chromosomal profile were significantly associated with worse survival. Three prognostic markers were identified in diffuse midline gliomas H3K27M-mutant: PDGFRA amplification, loss of 17p and a complex chromosomal profile. These markers are easy to detect in daily practice and should be considered to refine the prognosis of this entity., (© 2019 International Society of Neuropathology.)

Purpose BRAF V600E is a potentially highly targetable mutation detected in a subset of pediatric low-grade gliomas (PLGGs). Its biologic and clinical effect within this diverse group of tumors remains unknown. Patients and Methods A combined clinical and genetic institutional study of patients with PLGGs with long-term follow-up was performed (N = 510). Clinical and treatment data of patients with BRAF V600E mutated PLGG (n = 99) were compared with a large international independent cohort of patients with BRAF V600E mutated-PLGG (n = 180). Results BRAF V600E mutation was detected in 69 of 405 patients (17%) with PLGG across a broad spectrum of histologies and sites, including midline locations, which are not often routinely biopsied in clinical practice. Patients with BRAF V600E PLGG exhibited poor outcomes after chemotherapy and radiation therapies that resulted in a 10-year progression-free survival of 27% (95% CI, 12.1% to 41.9%) and 60.2% (95% CI, 53.3% to 67.1%) for BRAF V600E and wild-type PLGG, respectively ( P < .001). Additional multivariable clinical and molecular stratification revealed that the extent of resection and CDKN2A deletion contributed independently to poor outcome in BRAF V600E PLGG. A similar independent role for CDKN2A and resection on outcome were observed in the independent cohort. Quantitative imaging analysis revealed progressive disease and a lack of response to conventional chemotherapy in most patients with BRAF V600E PLGG. Conclusion BRAF V600E PLGG constitutes a distinct entity with poor prognosis when treated with current adjuvant therapy.

Background: Primary leptomeningeal melanomatosis (PLM) is a rare and aggressive form of nonmetastatic invasion of leptomeninges by malignant melanocytic cells. Clinical presentation includes nonspecific meningism with various forms of cerebrospinal fluid circulation or absorption disorders leading to hydrocephalus., Case Description: A 5-year-old child with PLM without neurocutaneous melanosis presented with cystic enlargement of the brainstem surrounding cisterns and hydrocephalus requiring occipitoaxial decompression and endoscopic cystostomy. Initial cerebrospinal fluid cytology screening and frontal meningeal and brain biopsy specimens showed negative results. The diagnosis of unpigmented (amelanotic) malignant melanocytic cells was made after a biopsy specimen of the bulbar leptomeninges was obtained. Despite continuous management of hydrocephalus and chemotherapy, the disease progressed, and the patient died 11 months after diagnosis., Conclusions: To the best of our knowledge, this is the first report of an amelanotic form of PLM without association of neurocutaneous melanosis in a child. This case report illustrates the difficulty of diagnosis in the absence of cutaneous lesions and lack of melanin., (Copyright © 2016 Elsevier Inc. All rights reserved.)

After detection of small cell lung cancer in a 67-year-old patient who had donated a kidney 7 months earlier, the graft recipient underwent FDG-PET/CT to determine the presence/absence of tumor cell transmission. It showed abnormal increased uptake of the renal graft, associated with hypermetabolic lymph nodes and hepatic, pulmonary and bone lesions. Emergency graft resection was performed 5 days after PET/CT, permitting immunosuppressive therapy withdrawal. Pathologic examination of the kidney showed parenchymal infiltration by tumor cells compatible with small cell lung cancer. Thereafter, pathologists proved that the recipient's and donor's tumor cells matched using microsatellite markers. FDG-PET/CT was performed in the follow-up and showed progression in the donor despite chemotherapy and radiotherapy. He died a few months later. However, FDG-PET/CT showed a complete metabolic response after only 3 courses of chemotherapy in the recipient.