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Extracellular vesicles (EVs), including exosomes, microvesicles, and oncosomes, are nano-sized particles enclosed by a lipid bilayer. EVs are released by virtually all eukaryotic cells and have been shown to contribute to intercellular communication by transporting proteins, lipids, and nucleic acids. In the context of neurodegenerative diseases, EVs may carry toxic, misfolded forms of amyloidogenic proteins and facilitate their spread to recipient cells in the central nervous system (CNS). CNS-originating EVs can cross the blood–brain barrier into the bloodstream and may be found in other body fluids, including saliva, tears, and urine. EVs originating in the CNS represent an attractive source of biomarkers for neurodegenerative diseases, because they contain cell- and cell state-specific biological materials. In recent years, multiple papers have reported the use of this strategy for identification and quantitation of biomarkers for neurodegenerative diseases, including Parkinson's disease and atypical parkinsonian disorders. However, certain technical issues have yet to be standardized, such as the best surface markers for isolation of cell type-specific EVs and validating the cellular origin of the EVs. Here, we review recent research using CNS-originating EVs for biomarker studies, primarily in parkinsonian disorders, highlight technical challenges, and propose strategies for overcoming them. [ABSTRACT FROM AUTHOR]

In this article the author comments on the review papers published within the issue which show that mutation in human GRN gene was the cause of frontotemporal lobar dementia (FTLD). As stated, very little was known about the importance of progranulin, a protein that regulates cell division, survival and migration within the central nervous system. He opines that the prevailing hypothesis of global GRN haploinsufficiency is too simple to account for development of FTLD.

Multiple sclerosis is a complex and heterogeneous, most likely autoimmune, demyelinating disease of the central nervous system (CNS). Although a number of histological classification systems for CNS lesions have been used by different groups in recent years, no uniform classification exists. In this paper, we propose a simple and unifying classification of MS lesions incorporating many elements of earlier histological systems that aims to provide guidelines for neuropathologists and researchers studying MS lesions to allow for better comparison of different studies performed with MS tissue, and to aid in understanding the pathogenesis of the disease. Based on the presence/absence and distribution of macrophages/microglia (inflammatory activity) and the presence/absence of ongoing demyelination (demyelinating activity), we suggest differentiating between active, mixed active/inactive, and inactive lesions with or without ongoing demyelination. Active lesions are characterized by macrophages/microglia throughout the lesion area, whereas mixed active/inactive lesions have a hypocellular lesion center with macrophages/microglia limited to the lesion border. Inactive lesions are almost completely lacking macrophages/microglia. Active and mixed active/inactive lesions can be further subdivided into lesions with ongoing myelin destruction (demyelinating lesions) and lesions in which the destruction of myelin has ceased, but macrophages are still present (post-demyelinating lesions). This distinction is based on the presence or absence of myelin degradation products within the cytoplasm of macrophages/microglia. For this classification of MS lesions, identification of myelin with histological stains [such as luxol fast blue-PAS] or by immunohistochemistry using antibodies against myelin basic-protein (MBP) or proteolipid-protein (PLP), as well as, detection of macrophages/microglia by, e.g., anti-CD68 is sufficient. Active and demyelinating lesions may be further subdivided into the early and late demyelinating lesions. The former is defined by the presence in macrophages of major and small molecular weight myelin proteins, such as cyclic nucleotide diphosphoesterase (CNP), myelin oligodendrocyte glycoprotein (MOG), or myelin-associated protein (MAG), whereas macrophages in the latter demonstrate merely the presence of the major myelin proteins MBP or PLP. We discuss the histological features and staining techniques required to classify MS lesions, and, in addition, describe the histological hallmarks of cortical pathology and diffuse white matter changes, as well as of remyelination. [ABSTRACT FROM AUTHOR]

The purpose of this study was to develop a spinal cord injury model in the mouse. Various degrees of extradural compression were used to induce mild, moderate or severe compression injuries. Furthermore, a locomotor rating scale was developed by which the functional outcome of the spinal cord injury could be assessed. The introduction of such a model will be useful for further studies on the pathogenesis and treatment strategies of spinal cord injury. To assess hindlimb motor function, a 10-point scale was used. Initially, the animals were allowed to move freely in an open field and were rated 0–5, 0 being no movement and 5 being almost normal. Animals scoring a 5 were then assessed using steel bars with decreasing widths from 2 cm to 5 mm. For each bar successfully crossed over, they gained additional points. Before injury the hindlimb motor function score (MFS) in all the animals was 10. In mice with mild compression, MFS was decreased slightly on day 1 and recovered to 9 ± 0.6 on day 14. For mice with moderate compression, the MFS decreased to 4.6 ± 0.4 on day 1 after injury and gradually improved to 8.1 ± 0.6 on day 14. Severe injury resulted in paraplegia of the hindlimbs day 1 after injury with a score of 0.6 ± 0.2. By day 14 after injury, these animals gradually recovered to 3.9 ± 0.1, could bear the weight on the hindlimbs and walk with a severe deficit. There was a 3%, 9% and 19% decrease in the total cross-sectional area of the spinal cord 14 days after mild, moderate and severe injury, respectively. Microtubule-associated protein immunostaining revealed that the gray matter decreased to 61 ± 7% in moderately injured animals, while severe compression resulted in a complete loss of gray matter. White matter decreased to 86 ± 6% in moderately injured animals and 29 ±11% in severely injured animals. This study shows that the mouse can be used to achieve reproducible spinal cord compression injuries of various degrees of severity. The force of the impact correlates well with the neurological and light microscopic outcome. The motor function test presented in this paper and the computerized quantification of tissue damage can be used to evaluate the efficacy of different treatment strategies. [ABSTRACT FROM AUTHOR]

Parkinson's Disease (PD) is a neurodegenerative and progressive disorder characterised by intracytoplasmic inclusions called Lewy bodies (LB) and degeneration of dopaminergic neurons in the substantia nigra (SN). Aggregated α-synuclein (αSYN) is known to be the main component of the LB. It has also been reported to interact with several proteins and organelles. Galectin-3 (GAL3) is known to have a detrimental function in neurodegenerative diseases. It is a galactose-binding protein without known catalytic activity and is expressed mainly by activated microglial cells in the central nervous system (CNS). GAL3 has been previously found in the outer layer of the LB in post-mortem brains. However, the role of GAL3 in PD is yet to be elucidated. In post-mortem samples, we identified an association between GAL3 and LB in all the PD subjects studied. GAL3 was linked to less αSYN in the LB outer layer and other αSYN deposits, including pale bodies. GAL3 was also associated with disrupted lysosomes. In vitro studies demonstrate that exogenous recombinant Gal3 is internalised by neuronal cell lines and primary neurons where it interacts with endogenous αSyn fibrils. In addition, aggregation experiments show that Gal3 affects spatial propagation and the stability of pre-formed αSyn fibrils resulting in short, amorphous toxic strains. To further investigate these observations in vivo, we take advantage of WT and Gal3KO mice subjected to intranigral injection of adenovirus overexpressing human αSyn as a PD model. In line with our in vitro studies, under these conditions, genetic deletion of GAL3 leads to increased intracellular αSyn accumulation within dopaminergic neurons and remarkably preserved dopaminergic integrity and motor function. Overall, our data suggest a prominent role for GAL3 in the aggregation process of αSYN and LB formation, leading to the production of short species to the detriment of larger strains which triggers neuronal degeneration in a mouse model of PD. [ABSTRACT FROM AUTHOR]

Pediatric spinal low-grade glioma (LGG) and glioneuronal tumours are rare, accounting for less 2.8–5.2% of pediatric LGG. New tumour types frequently found in spinal location such as diffuse leptomeningeal glioneuronal tumours (DLGNT) have been added to the World Health Organization (WHO) classification of tumours of the central nervous system since 2016, but their distinction from others gliomas and particularly from pilocytic astrocytoma (PA) are poorly defined. Most large studies on this subject were published before the era of the molecular diagnosis and did not address the differential diagnosis between PAs and DLGNTs in this peculiar location. Our study retrospectively examined a cohort of 28 children with LGGs and glioneuronal intramedullary tumours using detailed radiological, clinico-pathological and molecular analysis. 25% of spinal PAs were reclassified as DLGNTs. PA and DLGNT are nearly indistinguishable in histopathology or neuroradiology. 83% of spinal DLGNTs presented first without leptomeningeal contrast enhancement. Unsupervised t-distributed stochastic neighbor embedding (t-SNE) analysis of DNA methylation profiles showed that spinal PAs formed a unique methylation cluster distinct from reference midline and posterior fossa PAs, whereas spinal DLGNTs clustered with reference DLGNT cohort. FGFR1 alterations were found in 36% of spinal tumours and were restricted to PAs. Spinal PAs affected significantly younger patients (median age 2 years old) than DLGNTs (median age 8.2 years old). Progression-free survival was similar among the two groups. In this location, histopathology and radiology are of limited interest, but molecular data (methyloma, 1p and FGFR1 status) represent important tools differentiating these two mitogen-activated protein kinase (MAPK) altered tumour types, PA and DLGNT. Thus, these molecular alterations should systematically be explored in this type of tumour in a spinal location. [ABSTRACT FROM AUTHOR]

As extremely sensitive immune cells, microglia act as versatile watchdogs of the central nervous system (CNS) that tightly control tissue homeostasis. Therefore, microglial activation is an early and easily detectable hallmark of virtually all neuropsychiatric, neuro-oncological, neurodevelopmental, neurodegenerative and neuroinflammatory diseases. The recent introduction of novel high-throughput technologies and several single-cell methodologies as well as advances in epigenetic analyses helped to identify new microglia expression profiles, enhancer-landscapes and local signaling cues that defined diverse previously unappreciated microglia states in the healthy and diseased CNS. Here, we give an overview on the recent developments in the field of microglia biology and provide a practical guide to analyze disease-associated microglia phenotypes in both the murine and human CNS, on several morphological and molecular levels. Finally, technical limitations, potential pitfalls and data misinterpretations are discussed as well. [ABSTRACT FROM AUTHOR]

Medulloblastoma, a common pediatric malignant central nervous system tumour, represent a small proportion of brain tumours in adults. Previously it has been shown that in adults, Sonic Hedgehog (SHH)-activated tumours predominate, with Wingless-type (WNT) and Group 4 being less common, but molecular risk stratification remains a challenge. We performed an integrated analysis consisting of genome-wide methylation profiling, copy number profiling, somatic nucleotide variants and correlation of clinical variables across a cohort of 191 adult medulloblastoma cases identified through the Medulloblastoma Advanced Genomics International Consortium. We identified 30 WNT, 112 SHH, 6 Group 3, and 41 Group 4 tumours. Patients with SHH tumours were significantly older at diagnosis compared to other subgroups (p < 0.0001). Five-year progression-free survival (PFS) for WNT, SHH, Group 3, and Group 4 tumours was 64.4 (48.0–86.5), 61.9% (51.6–74.2), 80.0% (95% CI 51.6–100.0), and 44.9% (95% CI 28.6–70.7), respectively (p = 0.06). None of the clinical variables (age, sex, metastatic status, extent of resection, chemotherapy, radiotherapy) were associated with subgroup-specific PFS. Survival among patients with SHH tumours was significantly worse for cases with chromosome 3p loss (HR 2.9, 95% CI 1.1–7.6; p = 0.02), chromosome 10q loss (HR 4.6, 95% CI 2.3–9.4; p < 0.0001), chromosome 17p loss (HR 2.3, 95% CI 1.1–4.8; p = 0.02), and PTCH1 mutations (HR 2.6, 95% CI 1.1–6.2; p = 0.04). The prognostic significance of 3p loss and 10q loss persisted in multivariable regression models. For Group 4 tumours, chromosome 8 loss was strongly associated with improved survival, which was validated in a non-overlapping cohort (combined cohort HR 0.2, 95% CI 0.1–0.7; p = 0.007). Unlike in pediatric medulloblastoma, whole chromosome 11 loss in Group 4 and chromosome 14q loss in SHH was not associated with improved survival, where MYCN, GLI2 and MYC amplification were rare. In sum, we report unique subgroup-specific cytogenetic features of adult medulloblastoma, which are distinct from those in younger patients, and correlate with survival disparities. Our findings suggest that clinical trials that incorporate new strategies tailored to high-risk adult medulloblastoma patients are urgently needed. [ABSTRACT FROM AUTHOR]

Large-scale molecular profiling studies in recent years have shown that central nervous system (CNS) tumors display a much greater heterogeneity in terms of molecularly distinct entities, cellular origins and genetic drivers than anticipated from histological assessment. DNA methylation profiling has emerged as a useful tool for robust tumor classification, providing new insights into these heterogeneous molecular classes. This is particularly true for rare CNS tumors with a broad morphological spectrum, which are not possible to assign as separate entities based on histological similarity alone. Here, we describe a molecularly distinct subset of predominantly pediatric CNS neoplasms (n = 60) that harbor PATZ1 fusions. The original histological diagnoses of these tumors covered a wide spectrum of tumor types and malignancy grades. While the single most common diagnosis was glioblastoma (GBM), clinical data of the PATZ1-fused tumors showed a better prognosis than typical GBM, despite frequent relapses. RNA sequencing revealed recurrent MN1:PATZ1 or EWSR1:PATZ1 fusions related to (often extensive) copy number variations on chromosome 22, where PATZ1 and the two fusion partners are located. These fusions have individually been reported in a number of glial/glioneuronal tumors, as well as extracranial sarcomas. We show here that they are more common than previously acknowledged, and together define a biologically distinct CNS tumor type with high expression of neural development markers such as PAX2, GATA2 and IGF2. Drug screening performed on the MN1:PATZ1 fusion-bearing KS-1 brain tumor cell line revealed preliminary candidates for further study. In summary, PATZ1 fusions define a molecular class of histologically polyphenotypic neuroepithelial tumors, which show an intermediate prognosis under current treatment regimens. [ABSTRACT FROM AUTHOR]

Ependymomas encompass a heterogeneous group of central nervous system (CNS) neoplasms that occur along the entire neuroaxis. In recent years, extensive (epi-)genomic profiling efforts have identified several molecular groups of ependymoma that are characterized by distinct molecular alterations and/or patterns. Based on unsupervised visualization of a large cohort of genome-wide DNA methylation data, we identified a highly distinct group of pediatric-type tumors (n = 40) forming a cluster separate from all established CNS tumor types, of which a high proportion were histopathologically diagnosed as ependymoma. RNA sequencing revealed recurrent fusions involving the pleomorphic adenoma gene-like 1 (PLAGL1) gene in 19 of 20 of the samples analyzed, with the most common fusion being EWSR1:PLAGL1 (n = 13). Five tumors showed a PLAGL1:FOXO1 fusion and one a PLAGL1:EP300 fusion. High transcript levels of PLAGL1 were noted in these tumors, with concurrent overexpression of the imprinted genes H19 and IGF2, which are regulated by PLAGL1. Histopathological review of cases with sufficient material (n = 16) demonstrated a broad morphological spectrum of tumors with predominant ependymoma-like features. Immunohistochemically, tumors were GFAP positive and OLIG2- and SOX10 negative. In 3/16 of the cases, a dot-like positivity for EMA was detected. All tumors in our series were located in the supratentorial compartment. Median age of the patients at the time of diagnosis was 6.2 years. Median progression-free survival was 35 months (for 11 patients with data available). In summary, our findings suggest the existence of a novel group of supratentorial neuroepithelial tumors that are characterized by recurrent PLAGL1 fusions and enriched for pediatric patients. [ABSTRACT FROM AUTHOR]

Sporadic Creutzfeldt-Jakob disease (sCJD) is the commonest human prion disease, occurring most likely as the consequence of spontaneous formation of abnormal prion protein in the central nervous system (CNS). Variant Creutzfeldt–Jakob disease (vCJD) is an acquired prion disease that was first identified in 1996. In marked contrast to vCJD, previous investigations in sCJD revealed either inconsistent levels or an absence of PrPSc in peripheral tissues. These findings contributed to the consensus that risks of transmitting sCJD as a consequence of non-CNS invasive clinical procedures were low. In this study, we systematically measured prion infectivity levels in CNS and peripheral tissues collected from vCJD and sCJD patients. Unexpectedly, prion infectivity was detected in a wide variety of peripheral tissues in sCJD cases. Although the sCJD infectivity levels varied unpredictably in the tissues sampled and between patients, these findings could impact on our perception of the possible transmission risks associated with sCJD. [ABSTRACT FROM AUTHOR]

Remyelination following CNS demyelination restores rapid signal propagation and protects axons; however, its efficiency declines with increasing age. Both intrinsic changes in the oligodendrocyte progenitor cell population and extrinsic factors in the lesion microenvironment of older subjects contribute to this decline. Microglia and monocyte-derived macrophages are critical for successful remyelination, releasing growth factors and clearing inhibitory myelin debris. Several studies have implicated delayed recruitment of macrophages/microglia into lesions as a key contributor to the decline in remyelination observed in older subjects. Here we show that the decreased expression of the scavenger receptor CD36 of aging mouse microglia and human microglia in culture underlies their reduced phagocytic activity. Overexpression of CD36 in cultured microglia rescues the deficit in phagocytosis of myelin debris. By screening for clinically approved agents that stimulate macrophages/microglia, we have found that niacin (vitamin B3) upregulates CD36 expression and enhances myelin phagocytosis by microglia in culture. This increase in myelin phagocytosis is mediated through the niacin receptor (hydroxycarboxylic acid receptor 2). Genetic fate mapping and multiphoton live imaging show that systemic treatment of 9–12-month-old demyelinated mice with therapeutically relevant doses of niacin promotes myelin debris clearance in lesions by both peripherally derived macrophages and microglia. This is accompanied by enhancement of oligodendrocyte progenitor cell numbers and by improved remyelination in the treated mice. Niacin represents a safe and translationally amenable regenerative therapy for chronic demyelinating diseases such as multiple sclerosis. [ABSTRACT FROM AUTHOR]

Neurofibromatosis 1 (NF1) is an autosomal dominant genetic disorder that presents with variable phenotypes as a result of mutations in the neurofibromatosis type 1 (NF1) gene and subsequently, abnormal function of the protein product, neurofibromin. Patients with NF1 are at increased risk for central nervous system (CNS) manifestations including structural, functional, and neoplastic disease. The mechanisms underlying the varied manifestations of NF1 are incompletely understood, but the loss of functional neurofibromin, resulting in sustained activation of the oncoprotein RAS, is responsible for tumorigenesis throughout the body, including the CNS. Much of our understanding of NF1-related CNS manifestations is from a combination of data from animal models and natural history studies of people with NF1 and CNS disease. Data from animal models suggest the importance of both Nf1 mutations and somatic genetic alterations, such as Tp53 loss, for development of neoplasms, as well as the role of the timing of the acquisition of such alterations on the variability of CNS manifestations. A variety of non-neoplastic structural (macrocephaly, hydrocephalus, aqueductal stenosis, and vasculopathy) and functional (epilepsy, impaired cognition, attention deficits, and autism spectrum disorder) abnormalities occur with variable frequency in individuals with NF1. In addition, there is increasing evidence that similar appearing CNS neoplasms in people with and without the NF1 syndrome are due to distinct oncogenic pathways. Gliomas in people with NF1 show alterations in the RAS/MAPK pathway, generally in the absence of BRAF alterations (common to sporadic pilocytic astrocytomas) or IDH or histone H3 mutations (common to diffuse gliomas subsets). A subset of low-grade astrocytomas in these patients remain difficult to classify using standard criteria, and occasionally demonstrate morphologic features resembling subependymal giant cell astrocytomas that afflict patients with tuberous sclerosis complex ("SEGA-like astrocytomas"). There is also emerging evidence that NF1-associated high-grade astrocytomas have frequent co-existing alterations such as ATRX mutations and an alternative lengthening of telomeres (ALT) phenotype responsible for unique biologic properties. Ongoing efforts are seeking to improve diagnostic accuracy for CNS neoplasms in the setting of NF1 versus sporadic tumors. In addition, MEK inhibitors, which act on the RAS/MAPK pathway, continue to be studied as rational targets for the treatment of NF1-associated tumors, including CNS tumors. [ABSTRACT FROM AUTHOR]

The conversion of endogenous alpha-synuclein (asyn) to pathological asyn-enriched aggregates is a hallmark of Parkinson's disease (PD). These inclusions can be detected in the central and enteric nervous system (ENS). Moreover, gastrointestinal symptoms can appear up to 20 years before the diagnosis of PD. The dual-hit hypothesis posits that pathological asyn aggregation starts in the ENS, and retrogradely spreads to the brain. In this study, we tested this hypothesis by directly injecting preformed asyn fibrils into the duodenum wall of wild-type rats and transgenic rats with excess levels of human asyn. We provide a meticulous characterization of the bacterial artificial chromosome (BAC) transgenic rat model with respect to initial propagation of pathological asyn along the parasympathetic and sympathetic pathways to the brainstem, by performing immunohistochemistry at early time points post-injection. Induced pathology was observed in all key structures along the sympathetic and parasympathetic pathways (ENS, autonomic ganglia, intermediolateral nucleus of the spinal cord (IML), heart, dorsal motor nucleus of the vagus, and locus coeruleus (LC)) and persisted for at least 4 months post-injection. In contrast, asyn propagation was not detected in wild-type rats, nor in vehicle-injected BAC rats. The presence of pathology in the IML, LC, and heart indicate trans-synaptic spread of the pathology. Additionally, the observed asyn inclusions in the stomach and heart may indicate secondary anterograde propagation after initial retrograde spreading. In summary, trans-synaptic propagation of asyn in the BAC rat model is fully compatible with the "body-first hypothesis" of PD etiopathogenesis. To our knowledge, this is the first animal model evidence of asyn propagation to the heart, and the first indication of bidirectional asyn propagation via the vagus nerve, i.e., duodenum-to-brainstem-to-stomach. The BAC rat model could be very valuable for detailed mechanistic studies of the dual-hit hypothesis, and for studies of disease modifying therapies targeting early pathology in the gastrointestinal tract. [ABSTRACT FROM AUTHOR]

Mutations in TDP-43 cause amyotrophic lateral sclerosis (ALS), a fatal paralytic disease characterized by degeneration and premature death of motor neurons. The contribution of mutant TDP-43-mediated damage within motor neurons was evaluated using mice expressing a conditional allele of an ALS-causing TDP-43 mutant (Q331K) whose broad expression throughout the central nervous system mimics endogenous TDP-43. TDP-43 mice develop age- and mutant-dependent motor deficits from degeneration and death of motor neurons. Cre-recombinase-mediated excision of the TDP-43 gene from motor neurons is shown to delay onset of motor symptoms and appearance of TDP-43-mediated aberrant nuclear morphology, and abrogate subsequent death of motor neurons. However, reduction of mutant TDP-43 selectively in motor neurons did not prevent age-dependent degeneration of axons and neuromuscular junction loss, nor did it attenuate astrogliosis or microgliosis. Thus, disease mechanism is non-cell autonomous with mutant TDP-43 expressed in motor neurons determining disease onset but progression defined by mutant acting within other cell types. [ABSTRACT FROM AUTHOR]

The 'integrated diagnosis' for infiltrating gliomas in the 2016 revised World Health Organization (WHO) classification of tumors of the central nervous system requires assessment of the tumor for IDH mutations and 1p/19q codeletion. Since TERT promoter mutations and ATRX alterations have been shown to be associated with prognosis, we analyzed whether these tumor markers provide additional prognostic information within each of the five WHO 2016 categories. We used data for 1206 patients from the UCSF Adult Glioma Study, the Mayo Clinic and The Cancer Genome Atlas (TCGA) with infiltrative glioma, grades II-IV for whom tumor status for IDH, 1p/19q codeletion, ATRX, and TERT had been determined. All cases were assigned to one of 5 groups following the WHO 2016 diagnostic criteria based on their morphologic features, and IDH and 1p/19q codeletion status. These groups are: (1) Oligodendroglioma, IDH-mutant and 1p/19q-codeleted; (2) Astrocytoma, IDH-mutant; (3) Glioblastoma, IDH-mutant; (4) Glioblastoma, IDH-wildtype; and (5) Astrocytoma, IDH-wildtype. Within each group, we used univariate and multivariate Cox proportional hazards models to assess associations of overall survival with patient age at diagnosis, grade, and ATRX alteration status and/or TERT promoter mutation status. Among Group 1 IDH-mutant 1p/19q-codeleted oligodendrogliomas, the TERT-WT group had significantly worse overall survival than the TERT-MUT group (HR: 2.72, 95% CI 1.05-7.04, p = 0.04). In both Group 2, IDH-mutant astrocytomas and Group 3, IDH-mutant glioblastomas, neither TERT mutations nor ATRX alterations were significantly associated with survival. Among Group 4, IDH-wildtype glioblastomas, ATRX alterations were associated with favorable outcomes (HR: 0.36, 95% CI 0.17-0.81, p = 0.01). Among Group 5, IDH-wildtype astrocytomas, the TERT-WT group had significantly better overall survival than the TERT-MUT group (HR: 0.48, 95% CI 0.27-0.87), p = 0.02). Thus, we present evidence that in certain WHO 2016 diagnostic groups, testing for TERT promoter mutations or ATRX alterations may provide additional useful prognostic information. [ABSTRACT FROM AUTHOR]

Multiple independent genomic profiling efforts have recently identified clinically and molecularly distinct subgroups of ependymoma arising from all three anatomic compartments of the central nervous system (supratentorial brain, posterior fossa, and spinal cord). These advances motivated a consensus meeting to discuss: (1) the utility of current histologic grading criteria, (2) the integration of molecular-based stratification schemes in future clinical trials for patients with ependymoma and (3) current therapy in the context of molecular subgroups. Discussion at the meeting generated a series of consensus statements and recommendations from the attendees, which comment on the prognostic evaluation and treatment decisions of patients with intracranial ependymoma (WHO Grade II/III) based on the knowledge of its molecular subgroups. The major consensus among attendees was reached that treatment decisions for ependymoma (outside of clinical trials) should not be based on grading (II vs III). Supratentorial and posterior fossa ependymomas are distinct diseases, although the impact on therapy is still evolving. Molecular subgrouping should be part of all clinical trials henceforth. [ABSTRACT FROM AUTHOR]

Diets high in fat (HFD) are known to cause an immune response in the periphery as well as the central nervous system. In peripheral adipose tissue, this immune response is primarily mediated by macrophages that are recruited to the tissue. Similarly, reactivity of microglia, the innate immune cells of the brain, has been shown to occur in the hypothalamus of mice fed a high-fat diet. To characterize the nature of the microglial response to diets high in fat in a temporal fashion, we studied the phenotypic spectrum of hypothalamic microglia of mice fed high-fat diet for 3 days and 8 weeks by assessing their tissue reaction and inflammatory signature. While we observed a significant increase in Iba1+ myeloid cells and a reaction of GFAP+ astrocytes in the hypothalamus after 8 weeks of HFD feeding, we found the hypothalamic myeloid cell reaction to be limited to endogenous microglia and not mediated by infiltrating myeloid cells. Moreover, obese humans were found to present with signs of hypothalamic gliosis and exacerbated microglia dystrophy, suggesting a targeted microglia response to diet in humans as well. Notably, the glial reaction occurring in the mouse hypothalamus was not accompanied by an increase in pro-inflammatory cytokines, but rather by an anti-inflammatory reaction. Gene expression analyses of isolated microglia not only confirmed this observation, but also revealed a downregulation of microglia genes important for sensing signals in the microenvironment. Finally, we demonstrate that long-term exposure of microglia to HFD in vivo does not impair the cell's ability to respond to additional stimuli, like lipopolysaccharide. Taken together, our findings support the notion that microglia react to diets high in fat in a region-specific manner in rodents as well as in humans; however, this response changes over time as it is not exclusively pro-inflammatory nor does exposure to HFD prime microglia in the hypothalamus. [ABSTRACT FROM AUTHOR]

Amyotrophic lateral sclerosis (ALS) is a devastating progressive neurodegenerative disease affecting primarily the upper and lower motor neurons. A common feature of all ALS cases is a well-characterized neuroinflammatory reaction within the central nervous system (CNS). However, much less is known about the role of the peripheral immune system and its interplay with CNS resident immune cells in motor neuron degeneration. Here, we characterized peripheral monocytes in both temporal and spatial dimensions of ALS pathogenesis. We found the circulating monocytes to be deregulated in ALS regarding subtype constitution, function and gene expression. Moreover, we show that CNS infiltration of peripheral monocytes correlates with improved motor neuron survival in a genetic ALS mouse model. Furthermore, application of human immunoglobulins or fusion proteins containing only the human Fc, but not the Fab antibody fragment, increased CNS invasion of peripheral monocytes and delayed the disease onset. Our results underline the importance of peripheral monocytes in ALS pathogenesis and are in agreement with a protective role of monocytes in the early phase of the disease. The possibility to boost this beneficial function of peripheral monocytes by application of human immunoglobulins should be evaluated in clinical trials. [ABSTRACT FROM AUTHOR]

The membrane-bound metalloprotease endothelin-converting enzyme-like 1 (ECEL1) has been newly identified as a causal gene of a specific type of distal arthrogryposis (DA). In contrast to most causal genes of DA, ECEL1 is predominantly expressed in neuronal cells, suggesting a unique neurogenic pathogenesis in a subset of DA patients with ECEL1 mutation. The present study analyzed developmental motor innervation and neuromuscular junction formation in limbs of the rodent homologue damage-induced neuronal endopeptidase (DINE)-deficient mouse. Whole-mount immunostaining was performed in DINE-deficient limbs expressing motoneuron-specific GFP to visualize motor innervation throughout the limb. Although DINE-deficient motor nerves displayed normal trajectory patterns from the spinal cord to skeletal muscles, they indicated impaired axonal arborization in skeletal muscles in the forelimbs and hindlimbs. Systematic examination of motor innervation in over 10 different hindlimb muscles provided evidence that DINE gene disruption leads to insufficient arborization of motor nerves after arriving at the skeletal muscle. Interestingly, the axonal arborization defect in foot muscles appeared more severe than in other hindlimb muscles, which was partially consistent with the proximal-distal phenotypic discordance observed in DA patients. Additionally, the number of innervated neuromuscular junction was significantly reduced in the severely affected DINE-deficient muscle. Furthermore, we generated a DINE knock-in (KI) mouse model with a pathogenic mutation, which was recently identified in DA patients. Axonal arborization defects were clearly detected in motor nerves of the DINE KI limb, which was identical to the DINE-deficient limb. Given that the encoded sequences, as well as ECEL1 and DINE expression profiles, are highly conserved between mouse and human, abnormal arborization of motor axons and subsequent failure of NMJ formation could be a primary cause of DA with ECEL1 mutation. [ABSTRACT FROM AUTHOR]

In the pathogenesis of central nervous system (CNS) demyelinating disorders, antigen-specific B cells are implicated to act as potent antigen-presenting cells (APC), eliciting waves of inflammatory CNS infiltration. Here, we provide the first evidence that CNS-reactive antibodies (Ab) are similarly capable of initiating an encephalitogenic immune response by targeting endogenous CNS antigen to otherwise inert myeloid APC. In a transgenic mouse model, constitutive production of Ab against myelin oligodendrocyte glycoprotein (MOG) was sufficient to promote spontaneous experimental autoimmune encephalomyelitis (EAE) in the absence of B cells, when mice endogenously contained MOG-recognizing T cells. Adoptive transfer studies corroborated that anti-MOG Ab triggered activation and expansion of peripheral MOG-specific T cells in an Fc-dependent manner, subsequently causing EAE. To evaluate the underlying mechanism, anti-MOG Ab were added to a co-culture of myeloid APC and MOG-specific T cells. At otherwise undetected concentrations, anti-MOG Ab enabled Fc-mediated APC recognition of intact MOG; internalized, processed and presented MOG activated naïve T cells to differentiate in an encephalitogenic manner. In a series of translational experiments, anti-MOG Ab from two patients with an acute flare of CNS inflammation likewise facilitated detection of human MOG. Jointly, these observations highlight Ab-mediated opsonization of endogenous CNS auto-antigen as a novel disease- and/or relapse-triggering mechanism in CNS demyelinating disorders. [ABSTRACT FROM AUTHOR]

The functional dynamics and cellular sources of oxidative stress are central to understanding MS pathogenesis but remain elusive, due to the lack of appropriate detection methods. Here we employ NAD(P)H fluorescence lifetime imaging to detect functional NADPH oxidases (NOX enzymes) in vivo to identify inflammatory monocytes, activated microglia, and astrocytes expressing NOX1 as major cellular sources of oxidative stress in the central nervous system of mice affected by experimental autoimmune encephalomyelitis (EAE). This directly affects neuronal function in vivo, indicated by sustained elevated neuronal calcium. The systemic involvement of oxidative stress is mirrored by overactivation of NOX enzymes in peripheral CD11b cells in later phases of both MS and EAE. This effect is antagonized by systemic intake of the NOX inhibitor and anti-oxidant epigallocatechin-3-gallate. Together, this persistent hyper-activation of oxidative enzymes suggests an 'oxidative stress memory' both in the periphery and CNS compartments, in chronic neuroinflammation. [ABSTRACT FROM AUTHOR]

B cells are implicated in the etiology of multiple sclerosis (MS). Intrathecal IgG synthesis, cerebrospinal fluid (CSF) oligoclonal bands and lesional IgG deposition suggest a role for antibody-mediated pathology. We examined the binding of IgG1 monoclonal recombinant antibodies (rAbs) derived from MS patient CSF expanded B cell clones to central nervous system (CNS) tissue. MS rAbs displaying CNS binding to mouse and human CNS tissue were further tested for their ability to induce complement-mediated tissue injury in ex vivo spinal cord explant cultures. The staining of CNS tissue, primary human astrocytes and human neurons revealed a measurable bias in MS rAb binding to antigens preferentially expressed on astrocytes and neurons. MS rAbs that recognize myelin-enriched antigens were rarely detected. Both myelin-specific and some astrocyte/neuronal-specific MS rAbs caused significant myelin loss and astrocyte activation when applied to spinal cord explant cultures in the presence of complement. Overall, the intrathecal B cell response in multiple sclerosis binds to both glial and neuronal targets and produces demyelination in spinal cord explant cultures implicating intrathecal IgG in MS pathogenesis. [ABSTRACT FROM AUTHOR]

We examined the phosphorylated 43-kDa TAR DNA-binding protein (pTDP-43) inclusions as well as neuronal loss in full-length spinal cords and five selected regions of the central nervous system from 36 patients with amyotrophic lateral sclerosis (ALS) and 10 age-matched normal controls. The most severe neuronal loss and pTDP-43 lesions were seen in lamina IX motor nuclei columns 4, 6, and 8 of lower cervical segments and in columns 9-11 of lumbosacral segments. Severity of pTDP-43 pathology and neuronal loss correlated closely with gray and white matter oligodendroglial involvement and was linked to onset of disease, with severe involvement of columns 4, 6, and 8 of upper extremity onset cases and severe involvement of columns of 9, 10, and 11 in cases with lower extremity onset. Severe TDP-43 lesions and neuronal loss were observed in stage 4 cases and sometimes included Onuf's nucleus. Notably, three cases displayed pTDP-43 aggregates in the midbrain oculomotor nucleus, which we had not seen previously even in cases with advanced (i.e., stage 4) pathology. pTDP-43 aggregates were observed in neurons of Clarke's column in 30.6 % of cases but rarely in the intermediolateral nucleus (IML). Gray matter oligodendroglial pTDP-43 inclusions were present in areas devoid of neuronal pTDP-43 aggregates and neuronal loss. Taken together, our findings indicate that (1) the dorsolateral motor nuclei columns of the cervical and lumbosacral anterior horn may be the earliest foci of pTDP-43 pathology in the spinal cord, (2) gray matter oligodendroglial involvement is an early event in the ALS disease process that possibly heralds subsequent involvement of neurons by pTDP-43 pathology, and (3) in some very advanced cases, there is oculomotor nucleus involvement, which may constitute an additional neuropathological stage (designated here as stage 5) of pTDP-43 pathology in ALS.

Parkinson's disease primarily affects the central nervous system, but autopsy and small patient studies have revealed autonomic nervous system pathology in most cases. We looked for α-synuclein pathology in routinely acquired biopsies from patients and matched controls. Immunocytochemistry was performed and assessed blind to the clinical diagnoses. One hundred and seventeen gastrointestinal tissue samples from 62 patients, and 161 samples from 161 controls, were examined. Twelve biopsies from seven patients showed accumulation of α-synuclein within mucosal and submucosal nerve fibres, and ganglia, which was more extensive with an antibody to phosphorylated, than with an antibody to non-phosphorylated, α-synuclein. These included gastric, duodenal and colonic biopsies, and were taken up to 8 years prior to the onset of motor symptoms. All patients with positive biopsies had early autonomic symptoms and all controls were negative. This large scale study demonstrates that accumulation of α-synuclein in the gastrointestinal tract is a highly specific finding that could be used to confirm a clinical diagnosis of Parkinson's disease. We have shown that α-synuclein accumulation occurs prior to the onset of motor symptoms in the upper, as well as the lower gastrointestinal tract, remains present in serial biopsies until the onset of motor symptoms and is predominantly composed of phosphorylated α-synuclein. Accumulation of α-synuclein in the bowel therefore offers an accessible biomarker which allows further study of the early stages of the disease and could be of value in the assessment of disease modifying treatments. [ABSTRACT FROM AUTHOR]

The etiopathogenesis of neither the sporadic form of Alzheimer disease (AD) nor of amyotrophic lateral sclerosis (ALS) is well understood. The activity of protein phosphatase-2A (PP2A), which regulates the phosphorylation of tau and neurofilaments, is negatively regulated by the myeloid leukemia-associated protein SET, also known as inhibitor-2 of PP2A, I. In AD brain, PP2A activity is compromised, probably because I is overexpressed and is selectively cleaved at asparagine 175 into an N-terminal fragment, I, and a C-terminal fragment, I, and both fragments inhibit PP2A. Here, we analyzed the spinal cords from ALS and control cases for I cleavage and PP2A activity. As observed in AD brain, we found a selective increase in the cleavage of I into I and I and inhibition of the activity and not the expression of PP2A in the spinal cords of ALS cases. To test the hypothesis that both AD and ALS could be triggered by I, a cleavage product of I, we transduced by intracerebroventricular injections newborn rats with adeno-associated virus serotype 1 (AAV1) containing human I. AAV1-I produced reference memory impairment and tau pathology, and intraneuronal accumulation of Aβ by 5-8 months, and motor deficit and hyperphosphorylation and proliferation of neurofilaments, tau and TDP-43 pathologies, degeneration and loss of motor neurons and axons in the spinal cord by 10-14 months in rats. These findings suggest a previously undiscovered etiopathogenic relationship between sporadic forms of AD and ALS that is linked to I and the potential of I-based therapeutics for these diseases. [ABSTRACT FROM AUTHOR]

Immune surveillance of the central nervous system (CNS) by T cells is important to keep CNS-trophic viruses in a latent state, yet our knowledge of the characteristics of CNS-populating T cells is incomplete. We performed a comprehensive, multi-color flow-cytometric analysis of isolated T cells from paired corpus callosum (CC) and peripheral blood (PB) samples of 20 brain donors. Compared to PB, CC T cells, which were mostly located in the perivascular space and sporadically in the parenchyma, were enriched for cells expressing CD8. Both CD4 and CD8 T cells in the CC had a late-differentiated phenotype, as indicated by lack of expression of CD27 and CD28. The CC contained high numbers of T cells expressing chemokine receptor CX3CR1 and CXCR3 that allow for homing to inflamed endothelium and tissue, but hardly cells expressing the lymph node-homing receptor CCR7. Despite the late-differentiated phenotype, CC T cells had high expression of the IL-7 receptor α-chain CD127 and did not contain the neurotoxic cytolytic enzymes perforin, granzyme A, and granzyme B. We postulate that CNS T cells make up a population of tissue-adapted differentiated cells, which use CX3CR1 and CXCR3 to home into the perivascular space, use IL-7 for maintenance, and lack immediate cytolytic activity, thereby preventing immunopathology in response to low or non-specific stimuli. The presence of these cells in this tightly regulated environment likely enables a fast response to local threats. Our results will enable future detailed exploration of T-cell subsets in the brain involved in neurological diseases. [ABSTRACT FROM AUTHOR]

Multiple sclerosis is considered a disease of complex autoimmune etiology, yet there remains a lack of consensus as to specific immune effector mechanisms. Recent analyses of experimental autoimmune encephalomyelitis, the common mouse model of multiple sclerosis, have investigated the relative contribution of Th1 and Th17 CD4 T cell subsets to initial autoimmune central nervous system (CNS) damage. However, inherent in these studies are biases influenced by the adjuvant and toxin needed to break self-tolerance. We investigated spontaneous CNS disease in a clinically relevant, humanized, T cell receptor transgenic mouse model. Mice develop spontaneous, ascending paralysis, allowing unbiased characterization of T cell immunity in an HLA-DR15-restricted T cell repertoire. Analysis of naturally progressing disease shows that IFNγ cells dominate disease initiation with IL-17 cells apparent in affected tissue only once disease is established. Tregs accumulate in the CNS but are ultimately ineffective at halting disease progression. However, ablation of Tregs causes profound acceleration of disease, with uncontrolled infiltration of lymphocytes into the CNS. This synchronous, severe disease allows characterization of the responses that are deregulated in exacerbated disease: the correlation is with increased CNS CD4 and CD8 IFNγ responses. Recovery of the ablated Treg population halts ongoing disease progression and Tregs extracted from the central nervous system at peak disease are functionally competent to regulate myelin specific T cell responses. Thus, in a clinically relevant mouse model of MS, initial disease is IFNγ driven and the enhanced central nervous system responses unleashed through Treg ablation comprise IFNγ cytokine production by CD4 and CD8 cells, but not IL-17 responses. [ABSTRACT FROM AUTHOR]

High-grade gliomas are the most common primary brain tumors. Their malignancy is promoted by the complex crosstalk between different cell types in the central nervous system. Microglia/brain macrophages infiltrate high-grade gliomas and contribute to their progression. To identify factors that mediate the attraction of microglia/macrophages to malignant brain tumors, we established a glioma cell encapsulation model that was applied in vivo. Mouse GL261 glioma cell line and human high-grade glioma cells were seeded into hollow fibers (HF) that allow the passage of soluble molecules but not cells. The glioma cell containing HF were implanted into one brain hemisphere and simultaneously HF with non-transformed fibroblasts (controls) were introduced into the contralateral hemisphere. Implanted mouse and human glioma- but not fibroblast-containing HF attracted microglia and up-regulated immunoreactivity for GFAP, which is a marker of astrogliosis. In this study, we identified GDNF as an important factor for microglial attraction: (1) GL261 and human glioma cells secret GDNF, (2) reduced GDNF production by siRNA in GL261 in mouse glioma cells diminished attraction of microglia, (3) over-expression of GDNF in fibroblasts promoted microglia attraction in our HF assay. In vitro migration assays also showed that GDNF is a strong chemoattractant for microglia. While GDNF release from human or mouse glioma had a profound effect on microglial attraction, the glioma-induced astrogliosis was not affected. Finally, we could show that injection of GL261 mouse glioma cells with GDNF knockdown by shRNA into mouse brains resulted in reduced tumor expansion and improved survival as compared to injection of control cells. [ABSTRACT FROM AUTHOR]

Autosomal-dominant Alzheimer disease (ADAD) is a genetic disorder caused by mutations in Amyloid Precursor Protein ( APP) or Presenilin ( PSEN) genes. Studies from families with ADAD have been critical to support the amyloid cascade hypothesis of Alzheimer disease (AD), the basis for the current development of amyloid-based disease-modifying therapies in sporadic AD (SAD). However, whether the pathological changes in APP processing in the CNS in ADAD are similar to those observed in SAD remains unclear. In this study, we measured β-site APP-cleaving enzyme (BACE) protein levels and activity, APP and APP C-terminal fragments in brain samples from subjects with ADAD carrying APP or PSEN1 mutations ( n = 18), patients with SAD ( n = 27) and age-matched controls ( n = 22). We also measured sAPP β and BACE protein levels, as well as BACE activity, in CSF from individuals carrying PSEN1 mutations (10 mutation carriers and 7 non-carrier controls), patients with SAD ( n = 32) and age-matched controls ( n = 11). We found that in the brain, the pattern in ADAD was characterized by an increase in APP β-C-terminal fragment ( β-CTF) levels despite no changes in BACE protein levels or activity. In contrast, the pattern in SAD in the brain was mainly characterized by an increase in BACE levels and activity, with less APP β-CTF accumulation than ADAD. In the CSF, no differences were found between groups in BACE activity or expression or sAPP β levels. Taken together, these data suggest that the physiopathological events underlying the chronic A β production/clearance imbalance in SAD and ADAD are different. These differences should be considered in the design of intervention trials in AD. [ABSTRACT FROM AUTHOR]

Multiple sclerosis (MS) is characterized by episodes of inflammatory demyelination with progressive failure of remyelination. Prior studies using murine models of MS indicate that remyelination within the adult central nervous system (CNS) requires the expression and activity of TNFR2 and CXCR4 by oligodendrocyte progenitor cells (OPCs), promoting their proliferation and differentiation into mature oligodendrocytes. Here, we extend these studies by examining the role of TNFR2 in the expression of the CXCR4 ligand, CXCL12, within the corpus callosum (CC) during cuprizone (CPZ) intoxication and by demonstrating that lentiviral-mediated gene delivery of CXCL12 to the demyelinated CC improves OPC proliferation and myelin expression during remyelination. Activated astrocytes and microglia express both TNFR1 and TNFR2 within the demyelinated CC. However, CPZ intoxicated TNFR2−/− mice exhibit loss of up-regulation of CXCL12 in astrocytes with concomitant decreases in numbers of CXCR4+ NG2+ OPCs within the CC. While CXCR4 antagonism does not affect OPC migration from subventricular zones into the CC, it decreases their proliferation and differentiation within the CC. Stereotactic delivery of lentivirus expressing CXCL12 protein into the CC of acutely demyelinated TNFR2−/− mice increases OPC proliferation and expression of myelin. In contrast, chronically demyelinated wild-type mice, which exhibit significant loss of astrocytes and OPCs, are unable to be rescued via CXCL12 lentivirus alone but instead required engraftment of CXCL12-expressing astrocytes for increased myelin expression. Our results show that TNFR2 activation induces CXCL12 expression in the demyelinated CC via autocrine signaling specifically within astrocytes, which promotes OPC proliferation and differentiation. In addition, gene delivery of critical pro-myelinating proteins might be a feasible approach for the treatment of remyelination failure in MS. [ABSTRACT FROM AUTHOR]

In this autopsy-based study, α-synuclein immunohistochemistry and lipofuscin pigment-Nissl architectonics in serial sections of 100 μm thickness were used to investigate the spinal cords and brains of 46 individuals: 28 patients with clinically and neuropathologically confirmed Parkinson's disease, 6 cases with incidental Lewy body disease, and 12 age-matched controls. α-Synuclein inclusions (particulate aggregations, Lewy neurites/bodies) in the spinal cord were present between neuropathological stages 2-6 in all cases whose brains were staged for Parkinson's disease-related synucleinopathy. The only individuals who did not have Lewy pathology in the spinal cord were a single stage 1 case (incidental Lewy body disease) and all controls. Because the Parkinson's disease-related lesions were observable in the spinal cord only after Lewy pathology was seen in the brain, it could be concluded that, within the central nervous system, sporadic Parkinson's disease does not begin in the spinal cord. In addition: (1) α-Synuclein-immunoreactive axons clearly predominated over Lewy bodies throughout the spinal cord and were visible in medial and anterior portions of the anterolateral funiculus. Their terminal axons formed dense α-synuclein-immunoreactive networks in the gray matter and were most conspicuous in the lateral portions of layers 1, 7, and in the cellular islands of layer 9. (2) Notably, this axonopathy increased remarkably in density from cervicothoracic segments to lumbosacral segments of the cord. (3) Topographically, it is likely that the spinal cord α-synuclein immunoreactive axonal networks represent descending projections from the supraspinal level setting nuclei (locus coeruleus, lower raphe nuclei, magnocellular portions of the reticular formation). (4) Following the appearance of the spinal cord axonal networks, select types of projection neurons in the spinal cord gray matter displayed α-synuclein-immunoreactive inclusions: chiefly, nociceptive neurons of the dorsal horn in layer 1, sympathetic and parasympathetic preganglionic neurons in layer 7, the cellular pools of α-motoneurons in layer 9, and the smaller motoneurons in Onuf's nucleus in layer 9 (ventral horn). The spinal cord lesions may contribute to clinical symptoms (e.g., pain, constipation, poor balance, lower urinary tract complaints, and sexual dysfunction) that occur during the premotor and motor phases of sporadic Parkinson's disease. [ABSTRACT FROM AUTHOR]

Human infections with highly pathogenic avian influenza (HPAI) H5N1 have been associated with central nervous system involvement. The purpose of this study was to examine the route of invasion of wild-type HPAI H5N1 virus into the central nervous system (CNS) using a ferret model of infection. Sixteen ferrets were exposed by the intranasal route to 10 TCID of A/Vietnam/1203/04, a Clade 1 strain originally isolated from a fatal human case. The ferrets were euthanased for histological and virological analysis at intervals after challenge at 1, 3, 5, 6 and 7 days post-inoculation (dpi). From 5 dpi encephalitis was seen in all examined ferrets. The detection of antigen in the olfactory epithelium, the olfactory bulb, and related nuclei, in that temporal sequence, supported the contention that this is a major infection route for this virus strain. The detection of antigen in the epithelial cells in the Eustachian tube on 1 dpi, followed by the cochlea and vestibulocochlear nerve on 5 dpi is consistent with a second anterograde route of invasion, namely the vestibulocochlear pathway. There was also antigen in the lining of the ventricles and central canal indicating spread via the cerebrospinal fluid. However, evidence for haematogenous dissemination in the form of antigen in the brain parenchyma surrounding blood vessels was not found. This study provides support to the contention that wild-type HPAI H5N1 virus strains may enter the CNS via cranial nerve pathways and that the ferret is an appropriate model to study preventive and therapeutic procedures involving neural infection with these viruses by this route. [ABSTRACT FROM AUTHOR]

Laquinimod (LAQ) is a new oral immunomodulatory compound that reduces relapse rate, brain atrophy and disability progression in multiple sclerosis (MS). LAQ has well-documented effects on inflammation in the periphery, but little is known about its direct activity within the central nervous system (CNS). To elucidate the impact of LAQ on CNS-intrinsic inflammation, we investigated the effects of LAQ on cuprizone-induced demyelination in mice in vivo and on primary CNS cells in vitro. Demyelination, inflammation, axonal damage and glial pathology were evaluated in LAQ-treated wild type and Rag-1-deficient mice after cuprizone challenge. Using primary cells we tested for effects of LAQ on oligodendroglial survival as well as on cytokine secretion and NF-κB activation in astrocytes and microglia. LAQ prevented cuprizone-induced demyelination, microglial activation, axonal transections, reactive gliosis and oligodendroglial apoptoses in wild type and Rag-1-deficient mice. LAQ significantly decreased pro-inflammatory factors in stimulated astrocytes, but not in microglia. Oligodendroglial survival was not affected by LAQ in vitro. Astrocytic, but not microglial, NF-κB activation was markedly reduced by LAQ as evidenced by NF-κB reporter assay. LAQ also significantly decreased astrocytic NF-κB activation in cuprizone-treated mice. Our data indicate that LAQ prevents cuprizone-induced demyelination by attenuating astrocytic NF-κB activation. These effects are CNS-intrinsic and not mediated by peripheral immune cells. Therefore, LAQ downregulation of the astrocytic pro-inflammatory response may be an important mechanism underlying its protective effects on myelin, oligodendrocytes and axons. Modulation of astrocyte activation may be an attractive therapeutic target to prevent tissue damage in MS. [ABSTRACT FROM AUTHOR]

Oligodendrocyte gap junctions (GJs) are vital for central nervous system myelination, but their involvement in multiple sclerosis (MS) pathology remains unknown. The aim of this study was to examine alterations of oligodendrocyte and related astrocyte GJs in MS lesions and normal-appearing white matter (NAWM). Post-mortem brain samples from 9 MS and 11 age-matched non-MS control patients were studied. Tissue sections that included both chronic active and inactive lesions were characterized neuropathologically with Luxol Fast Blue staining and immunostaining for myelin oligodendrocyte glycoprotein (MOG) and the microglial marker Iba1. We analyzed the expression of Cx32 and Cx47 in oligodendrocytes and of Cx43, the major astrocytic partner in oligodendrocyte-astrocyte (O/A) GJs by quantitative immunoblot and real-time PCR. Formation of GJ plaques was quantified by immunohistochemistry. Compared to control brains, both Cx32 and Cx47 GJ plaques and protein levels were reduced in and around MS lesions, while Cx43 was increased as part of astrogliosis. In the NAWM, Cx32 was significantly reduced along myelinated fibers whereas Cx47 showed increased expression mainly in oligodendrocyte precursor cells (OPCs). However, OPCs showed only limited connectivity to astrocytes. Cx43 showed modestly increased levels in MS NAWM compared to controls, while GJ plaque counts were unchanged. Our findings indicate that oligodendrocyte GJs are affected not only in chronic MS lesions but also in NAWM, where disruption of Cx32 GJs in myelinated fibers may impair myelin structure and function. Moreover, limited O/A GJ connectivity of recruited OPCs in the setting of persistent inflammation and astrogliosis may prevent differentiation and remyelination. [ABSTRACT FROM AUTHOR]

The most common cause of amyotrophic lateral sclerosis (ALS) is mutations in superoxide dismutase-1 (SOD1). Since there is evidence for the involvement of non-neuronal cells in ALS, we searched for signs of SOD1 abnormalities focusing on glia. Spinal cords from nine ALS patients carrying SOD1 mutations, 51 patients with sporadic or familial ALS who lacked such mutations, and 46 controls were examined by immunohistochemistry. A set of anti-peptide antibodies with specificity for misfolded SOD1 species was used. Misfolded SOD1 in the form of granular aggregates was regularly detected in the nuclei of ventral horn astrocytes, microglia, and oligodendrocytes in ALS patients carrying or lacking SOD1 mutations. There was negligible staining in neurodegenerative and non-neurological controls. Misfolded SOD1 appeared occasionally also in nuclei of motoneurons of ALS patients. The results suggest that misfolded SOD1 present in glial and motoneuron nuclei may generally be involved in ALS pathogenesis. [ABSTRACT FROM AUTHOR]

Polyglutamine (polyQ) diseases are associated with a CAG/polyQ expansion mutation in unrelated proteins. Upon elongation of the glutamine tract, disease proteins aggregate within cells, mainly in the central nervous system (CNS) and this aggregation process is associated with neurotoxicity. However, it remains unclear to what extent and how this aggregation causes neuronal dysfunction in the CNS. Aiming at preventing neuronal dysfunction, it will be crucial to determine the links between aggregation and cellular dysfunction, understand the folding pathway of polyQ proteins and discover the relative neurotoxicity of polyQ protein species formed along the aggregation pathway. Here, we review what is known about conformations of polyQ peptides and proteins in their monomeric state from experimental and modelling data, how conformational changes of polyQ proteins relate to their oligomerisation and morphology of aggregates and which cellular function are impaired by oligomers, in vitro and in vivo. We also summarise the key modulatory cellular mechanisms and co-factors, which could affect the folding pathway and kinetics of polyQ aggregation. Although many studies have investigated the relationship between polyQ aggregation and toxicity, these have mainly focussed on investigating changes in the formation of the classical hallmark of polyQ diseases, i.e. microscopically visible inclusion bodies. However, recent studies in which oligomeric species have been considered start to shed light on the identity of neurotoxic oligomeric species. Initial evidence suggests that conformational changes induced by polyQ expansions and their surrounding sequence lead to the formation of particular oligomeric intermediates that may differentially affect neurotoxicity. [ABSTRACT FROM AUTHOR]

In the last few decades, there is an increasing emergence and re-emergence of viruses, such as West Nile virus, Enterovirus 71 and henipaviruses that cause epidemic viral encephalitis and other central nervous system (CNS) manifestations. The mortality and morbidity associated with these outbreaks are significant and frequently severe. While aspects of epidemiology, basic virology, etc., may be known, the pathology and pathogenesis are often less so, partly due to a lack of interest among pathologists or because many of these infections are considered “third world” diseases. In the study of epidemic viral encephalitis, the pathologist’s role in unravelling the pathology and pathogenesis is critical. The novel henipavirus infection is a good example. The newly created genus Henipavirus within the family Paramyxoviridae consists of two viruses, viz., Hendra virus and Nipah virus. These two viruses emerged in Australia and Asia, respectively, to cause severe encephalitides in humans and animals. Studies show that the pathological features of the acute encephalitis caused by henipaviruses are similar and a unique dual pathogenetic mechanism of vasculitis-induced microinfarction and parenchymal cell infection in the CNS (mainly neurons) and other organs causes severe tissue damage. Both viruses can cause relapsing encephalitis months and years after the acute infection due to a true recurrent infection as evidenced by the presence of virus in infected cells. Future emerging viral encephalitides will no doubt continue to pose considerable challenges to the neuropathologist, and as the West Nile virus outbreak demonstrates, even economically advanced nations are not spared. [ABSTRACT FROM AUTHOR]

The mammalian brain and spinal cord contain heterogeneous populations of cycling, immature cells. These include cells with stem cell-like properties as well as progenitors in various stages of early glial differentiation. This latter population is distributed widely throughout gray and white matter and numerically represents an extremely large cell pool. In this review, we discuss the possibility that the glial progenitors that populate the adult CNS are one source of gliomas. Indeed, the marker phenotypes, morphologies, and migratory properties of cells in gliomas strongly resemble glial progenitors in many ways. We review briefly some salient features of normal glial development and then examine the similarities and differences between normal progenitors and cells in gliomas, focusing on the phenotypic plasticity of glial progenitors and the responses to growth factors in promoting proliferation and migration of normal and glioma cells, and discussing known mutational changes in gliomas in the context of how these might affect the proliferative and migratory behaviors of progenitors. Finally, we will discuss the “cancer stem cell” hypothesis in light of the possibility that glial progenitors can generate gliomas. [ABSTRACT FROM AUTHOR]

Collections of human postmortem brains gathered in brain banks have underpinned many significant developments in the understanding of central nervous system (CNS) disorders and continue to support current research. Unfortunately, the worldwide decline in postmortem examinations has had an adverse effect on research tissue procurement, particularly from control cases (non-diseased brains). Recruitment to brain donor programmes partially addresses this problem and has been successful for dementing and neurodegenerative conditions. However, the collection of brains from control subjects, particularly from younger individuals, and from CNS disorders of sudden onset, remains a problem. Brain banks need to adopt additional strategies to circumvent such shortages. The establishment of brain bank networks allows data on, and access to, control cases and unusual CNS disorders to be shared, providing a larger resource for potential users. For the brain banks themselves, inclusion in a network fosters the sharing of protocols and development of best practice and quality control. One aspect of this collective experience concerns brain bank management, excellence in which is a prerequisite not only for gaining the trust of potential donors and of society in general, but also for ensuring equitable distribution to researchers of high quality tissue samples. This review addresses the legal, ethical and governance issues, tissue quality, and health and safety aspects of brain bank management and data management in a network, as well as the needs of users, brain bank staffing, donor programs, funding issues and public relations. Recent developments in research methodology present new opportunities for researchers who use brain tissue samples, but will require brain banks to adopt more complex protocols for tissue collection, preparation and storage, with inevitable cost implications for the future. [ABSTRACT FROM AUTHOR]

The ultrastructural features of SOD1-positive aggregates were determined to clarify whether these aggregates are associated with the pathogenesis of SOD1 mutant mice. We examined the spinal cord of transgenic mice expressing a G93A mutant human SOD1 gene with fewer copies (gene copy 10). At the early presymptomatic stage (age 24 weeks), SOD1- and ubiquitin-positive granular, linear, or round deposits were found occasionally in the neuropil of the anterior horns. Ultrastructurally, small filamentous aggregates were observed occasionally in the neuronal processes including the axons in the anterior horns. At the late presymptomatic stage (28 weeks), SOD1- and ubiquitin-positive deposits and Lewy body-like inclusions (LIs) were frequently demonstrated in the neuronal processes including cord-like swollen axons and in some remaining anterior horn neurons. Ultrastructurally, larger filamentous aggregates were frequent, predominating in the neuronal processes of the anterior horns including the proximal axons, but were rare in the somata and dendrites. The aggregates usually consisted of interwoven intermediate filaments (about 10-15 nm in diameter) and frequently contained electron-dense cores in the center resembling LIs. Occasionally the aggregates consisted mainly of granular, amorphous, or vesicular substance, showing fewer filamentous structures. At the symptomatic stages (32 and 35 weeks), LIs were frequently demonstrated within the neuronal processes in the anterior horns, particularly in the cord-like swollen axons. Many more prominent SOD1- and ubiquitin-positive deposits were observed over the whole white matter columns and in the gray matter of the anterior and posterior horns than at the previous stage. Ultrastructurally, aggregates frequently contained electron-dense cores, and were frequently observed in cord-like swollen axons consisting of accumulated neurofilaments. A high level of human SOD1-and ubiquitin-immunogold labeling was present in small to large aggregates even at the presymptomatic stages, and the aggregates increased in size and frequency with time. Compactly packed filaments and electron-dense cores of aggregates showed SOD1-and ubiquitin-immunogold labeling more prominently than in loosely packed filaments. These findings suggest that the accumulation of SOD1-positive aggregates in the neuronal processes, predominantly in the axons, constitutes an important determinant of neurotoxicity and the pathogenesis of this animal model, probably causing impairment of axonal transport by the sequestration of mutant SOD1 protein within aggregates, or in part by physically blocking the axonal transport. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine mitochondrial changes in the spinal cord of transgenic mice of a relatively low transgenic copy number (gene copy 10) expressing a G93A mutant human Cu/Zn superoxide dismutase (SOD1) that were generated in our own laboratories by electron and immunoelectron microscopy from presymptomatic to symptomatic stages. Age-matched non-transgenic mice served as controls at each stage. Ultrastructurally, at the early presymptomatic stage, many mitochondria in large myelinated axons exhibited swelling with an increased number of cristae, and bore small vacuoles in the matrix, cristae or both, in the anterior root exit zone, anterior root, and in the neuropils of the ventral portion of the anterior horn. At the late presymptomatic stage, vacuoles of various sizes (including large ones) were observed in the same regions as in the previous stage. The intermembrane space of mitochondria was also vacuolated. In mitochondria with advanced vacuolation, the vacuolar space was filled with a granular or amorphous substance. At the symptomatic stage, mitochondrial vacuolation seen in the late presymptomatic stage persisted, although to a lesser extent. These vacuolated mitochondria were predominantly seen in the axons, but not in the somata of normal-looking neurons or dendrites at any stage, which differs from that described in other reports. Non-transgenic littermates occasionally exhibited vacuolar changes in the axons of anterior horns. However, they were smaller both in size and number than those in transgenic mice. By immunoelectron microscopy using an immunogold labeling method, at the presymptomatic and symptomatic stages both SOD1 and ubiquitin determinants were localized in vacuolated mitochondria, particularly in the granular or amorphous substance of large vacuoles, but were not detected in most normal-appearing mitochondria. The SOD1-immunoreactive mitochondria were exclusively observed in the axons, and not in proximal dendrites or somata. These findings suggest that the toxicity of mutant SOD1 directly affects mitochondria in the axons and increases with the disease progression. Thus, the mutant SOD1 toxicity might disrupt axonal transport of substrates needed for neuronal viability, leading to motor neuron degeneration. The localization of both ubiquitin and SOD1 in vacuolated mitochondria indicates that protein degradation by ubiquitin-proteasomal system may be also disrupted by several pathomechanisms, such as decreased processing of ubiquitinated proteins due to impairment of mitochondrial function or of proteasomal function, both of which are caused by mutant SOD1. Moreover, giant mitochondrial vacuoles occupying almost the entire axonal caliber could be another contributing factor in motor neuron degeneration, in that they could physically block axonal transport. [ABSTRACT FROM AUTHOR]

Attempts at classification of fronto-temporal dementias have not yet been completely successful. We report ten cases of sporadic fronto-temporal dementia (FTD) with ubiquitin-positive neuronal inclusions in cortex or in motor neurons in brain stem or spinal cord, which may contribute to the classification of FTD. Marked variation in clinical presentation as well as in pathological findings was the rule in all cases. Dementia was a prominent feature. Only one case had clinical features suggestive of motor neuron disease. Three of four younger onset cases displayed an especially severe atrophy of the temporal lobes, the basal ganglia and the substantia nigra. This contrasted with the other seven cases in which the fronto-temporal atrophy and changes in basal ganglia and substantia nigra were variable and sometimes mild. In addition to the presence of ubiquitin-reactive, but tau-and silver impregnation-negative neuronal inclusions, all cases demonstrated tau 2-positive glial inclusions, similar to those recently reported in three motor neuron disease cases with dementia. The glial inclusions were not visible with antibody to tau 1. Reaction with antibody to alpha-synuclein was invariably negative. If the combination of ubiquitin-positive neuronal and tau 2-positive glial inclusions is found to be consistently present in FTD of motor neuron type, this feature will provide a firmer basis for this diagnosis than previously available. [ABSTRACT FROM AUTHOR]

Oxidative stress plays an important role in the pathogenesis of amyotrophic lateral sclerosis (ALS). In the present study, we investigated the expression of two major human enzymes that prevent errors caused by 8-oxoguanine (8-oxoG), a mitochondrial form of 8-oxoG DNA glycosylase (hOGG1) and oxidized purine nucleoside triphosphatase (hMTH1). We also investigated the relationship between their expression and the 8-oxoG accumulation observed in the large motor neurons of the lumbar spinal cord in seven cases of adult onset sporadic ALS, four cases of subarachnoid hemorrhage (SAH) and four control cases. 8-oxoG immunoreactivity increased in most large motor neurons in both the ALS and SAH cases. However, the large motor neurons in the control cases often lacked hOGG1 immunoreactivity, although some neurons expressed hOGG1 in either homogeneous or fine granular patterns. In SAH cases, most large motor neurons showed a fine granular pattern proportional to the increased 8-oxoG immunoreactivity. However, only half of the remaining motor neurons in ALS expressed hOGG1 in the fine granular pattern, and the rest did not show any immunoreactivity. In addition, small aggregates of hMTH1 in the nuclei of the anterior horn cells were present in several ALS cases. Our results indicate that the oxidative damage accumulates in the mitochondria of motor neurons in ALS, and that hOGG1 does not repair the damage efficiently, which may lead to a loss of motor neurons in ALS. [ABSTRACT FROM AUTHOR]