OS02.5.A Alzheimer-type neuropathological changes in glioblastoma-adjacent cortex

Background

Glioblastoma (GBM) is an aggressive type of brain cancer that is prevalent and fatal in the elderly. Age is not only the most common risk factor for brain cancer but also for neurodegenerative diseases, and previous studies have indicated an excess risk of co-occurrence of both diseases. Here, we aim to map Alzheimer (AD)-related pathology in GBM-adjacent cortex.

Material and Methods

To this end, we have screened a cohort of 99 individuals with 200 tissue samples comprising tumor and adjacent cortex, including longitudinal samples in 13 patients. The samples were provided by the Division of Neuropathology and Neurochemistry, Medical University of Vienna from 2002 to 2021. Age and tumor location were abstracted from clinical data where available. All samples were stained for A-beta, tau-AT8 and NeuN using immunohistochemistry. Whole slide scans were segmented and protein deposits were quantified with QuPath. Further statistical analyses were conducted with R. Tau pathology was recorded as neurofibrillary tangles, neuropil threads, and astroglial pathology. Likewise, amyloid pathology was assessed as plaques and/or cerebral amyloid angiopathy (CAA). For both proteins, deposits were grouped into: absent, mild, moderate, and severe.

Results

In the total cohort, median age was 67.5 ys (range 20-92 ys), the female-to-male ratio 0.68. Overall 44.4 % (n=44/99) showed any type of A-beta and/or taupathology, which was strongly correlated with age (R=0.26, p= 0.001). Among them, 38.6 % (n=17/44) had combined pathology, while 36.4 % (n=16/44) displayed pure amyloid-beta, and 25 % (n=11/44) only tau pathology. A-beta pathology comprised plaques in 74.4 % (n=29/39) and CAA in 28.2 % (n=11/29). Consistent with the spatiotemporal evolution of AD, neurofibrillary tangle load was highest in the temporal lobe (42.9 % n=21/49), while plaque load was most prevalent in the occipital lobe (62.5 % n=5/8). This pattern was accentuated in patients above age 65, while it deviated in those below age 65. Over time, the AD-type pathology increased in 38.4 % (n=5/13) and remained stable in 53.8 % (n=7/13) of recurrent tumors. Total cell densities in tumor-infiltrated cortex ranged from 474 to 7,540 cells/mm2, being similar across all lobes. Higher cell density correlated with decreased neuronal counts (R= -0.46, p<0.0001) and decreased AD-load (R= -0.25, p= 0.002).

Conclusion

Collectively, our results establish frequent co-occurrence of Alzheimer disease neuropathological changes in the GBM-adjacent cortex. They prompt further investigation of shared pathogenic mechanisms and seek to raise awareness for synergistic effects on cognitive decline.

Argyrophilic grain disease in individuals younger than 75 years: clinical variability in an under-recognized limbic tauopathy

BACKGROUND AND PURPOSE

Argyrophilic grain disease (AGD) is a limbic-predominant 4R-tauopathy. AGD is thought to be an age-related disorder and is frequently detected as a concomitant pathology with other neurodegenerative conditions. There is a paucity of data on the clinical phenotype of pure AGD. In elderly patients, however, AGD pathology frequently associates with cognitive decline, personality changes, urine incontinence and cachexia. In this study, clinicopathological findings were analysed in individuals younger than 75.

METHODS

Patients were identified retrospectively based on neuropathological examinations during 2006-2017 and selected when AGD was the primary and dominant pathological finding. Clinical data were obtained retrospectively through medical records.

RESULTS

In all, 55 patients (2% of all examinations performed during that period) with AGD were identified. In seven cases (13%) AGD was the primary neuropathological diagnosis without significant concomitant pathologies. Two patients were female, median age at the time of death was 64 years (range 51-74) and the median duration of disease was 3 months (range 0.5-36). The most frequent symptoms were progressive cognitive decline, urinary incontinence, seizures and psychiatric symptoms. Brain magnetic resonance imaging revealed mild temporal atrophy.

CONCLUSIONS

Argyrophilic grain disease is a rarely recognized limbic tauopathy in younger individuals. Widening the clinicopathological spectrum of tauopathies may allow identification of further patients who could benefit from tau-based therapeutic strategies.

New classification of tauopathies

Tauopathies are a group of neurodegenerative diseases characterized by pathological intracellular deposits of the protein tau. Isoform composition, morphology and anatomical distribution of cellular tau-immunoreactivities are defining distinct tauopathies as molecular pathological disease entities. The clinical spectrum of tauopathies includes syndromes with primary motor symptoms and with primary cognitive dysfunction. The traditional syndrome-based classification is currently being complemented by a molecular-pathological classification. While the syndrome-based classification is helpful to select symptomatic therapies, and to generate clinical working hypotheses about underlying etiologies, the molecular-pathological classification is most important for the development and application of molecularly tailored disease-modifying therapies.

Developmental Expression and Dysregulation of miR-146a and miR-155 in Down's Syndrome and Mouse Models of Down's Syndrome and Alzheimer's Disease

BACKGROUND

miR-146a and miR-155 are key regulators of the innate immune response. We hypothesized that an inflammation-mediated dysregulation of these miRNAs may occur in patients with Down syndrome (DS) and Alzheimer's disease (AD).

METHODS

The miRNA expression patterns were investigated by in situ hybridization in developing hippocampus from controls, patients with DS and in adults with AD pathology (DS and sporadic AD; sAD). Quantitative real-time PCR was employed to evaluate the miRNA levels in the hippocampus of sAD and in mouse models of DS and AD. Both miRNAs were expressed in prenatal human hippocampus. In DS we detected increased miR-146a expression in reactive astrocytes. Increased expression of miR-146a was found in the hippocampus of sAD and negatively correlated with its target IRAK-1. APP/PS1 mice showed a significant increase in the expression of both miRNAs at 11-13 months of age as compared to WT and mice at 3 months. A negative correlation between miR-146a levels and its target TRAF6 was observed in both Ts65Dn and APP/PS1 mice.

CONCLUSION

These findings suggest a possible involvement of miR-146a and miR-155 in brain development and neurodegeneration. In particular, we provide evidence of a dysregulation of these two immunomodulatory miRNAs in AD with a potential therapeutical implication, deserving further investigation.

Prevalence of transactive response DNA-binding protein 43 (TDP-43) proteinopathy in cognitively normal older adults: systematic review and meta-analysis

OBJECTIVE

To perform a systematic review and meta-analysis on the prevalence of transactive response DNA-binding protein 43 (TDP-43) proteinopathy in cognitively normal older adults.

METHODS

We systematically reviewed and performed a meta-analysis on the prevalence of TDP-43 proteinopathy in older adults with normal cognition, evaluated by the Mini-Mental State Examination or the Clinical Dementia Rating. We estimated the overall prevalence of TDP-43 using random-effect models, and stratified by age, sex, sample size, study quality, antibody used to assess TDP-43 aggregates, analysed brain regions, Braak stage, Consortium to Establish a Registry for Alzheimer's Disease score, hippocampal sclerosis and geographic location.

RESULTS

A total of 505 articles were identified in the systematic review, and 7 were included in the meta-analysis with 1196 cognitively normal older adults. We found an overall prevalence of TDP-43 proteinopathy of 24%. Prevalence of TDP-43 proteinopathy varied widely across geographic location (North America: 37%, Asia: 29%, Europe: 14%, and Latin America: 11%). Estimated prevalence of TDP-43 proteinopathy also varied according to study quality (quality score >7: 22% vs. quality score <7: 42%), antibody used to assess TDP-43 proteinopathy (native: 18% vs. hyperphosphorylated: 24%) and presence of hippocampal sclerosis (without 24% vs. with hippocampal sclerosis: 48%). Other stratified analyses by age, sex, analysed brain regions, sample size and severity of AD neuropathology showed similar pooled TDP-43 prevalence.

CONCLUSIONS

Different methodology to access TDP-43, and also differences in lifestyle and genetic factors across different populations could explain our results. Standardization of TDP-43 measurement, and future studies about the impact of genetic and lifestyle characteristics on the development of neurodegenerative diseases are needed.

Connexin-43 and aquaporin-4 are markers of ageing-related tau astrogliopathy (ARTAG)-related astroglial response

AIMS

Ageing-related tau astrogliopathy (ARTAG) appears in subependymal, subpial, perivascular, white matter (WM) and grey matter (GM) locations. Physical effects, blood-brain barrier dysfunction and blood- or vessel-related factors have been considered as aetiology. As connexin-43 (Cx43) and aquaporin-4 (AQP4) are related to these, we hypothesized that their immunoreactivity (IR) varies with ARTAG in a location-specific manner.

METHODS

We performed a morphometric immunohistochemical study measuring the densities of IR of Cx43, AQP4, AT8 (phospho-tau) and glial fibrillar acidic protein (GFAP). We analysed the amygdala and hippocampus in age-matched cases with (n = 19) and without (n = 20) ARTAG in each of the locations it aggregates.

RESULTS

We show a dramatic increase (>6-fold; P < 0.01) of Cx43 density of IR in ARTAG cases correlating strongly with AT8 density of IR, irrespective of the presence of neuronal tau pathology or reactive gliosis measured by GFAP density of IR, in the GM. In contrast, AQP4 density of IR was increased only in the WM and GM, and was associated with increased AT8 density of IR only in WM and perivascular areas.

DISCUSSION

Our study reveals distinctive astroglial responses in each of the locations associated with ARTAG. Our observations support the concept that factors related to brain-fluid interfaces and water-ion imbalances most likely play a role in the generation of ARTAG. As Cx43 is crucial for maintaining neuronal homeostasis, the ARTAG-dependent increase of Cx43 density of IR suggests that the development of ARTAG in the GM most likely indicates an early response to the degeneration of neurons.

Plasma and cerebrospinal fluid tau and neurofilament concentrations in rapidly progressive neurological syndromes: a neuropathology-based cohort

BACKGROUND AND PURPOSE

Cerebrospinal fluid (CSF) tau and neurofilament light chain (NF-L) proteins have proved to be reliable biomarkers for neuronal damage; however, there is a strong need for blood-based tests.

METHODS

The present study included 132 autopsy cases with rapidly progressive neurological syndromes, including Alzheimer disease (AD) (21), sporadic (65) and genetic (21) Creutzfeldt-Jakob disease (CJD), 25 cases with vascular, neoplastic and inflammatory alterations, and additionally 18 healthy control individuals. CSF tau and NF-L concentrations were measured by enzyme-linked immunosorbent assay. Plasma tau and NF-L concentrations were measured using ultra-sensitive single molecule array technology.

RESULTS

Plasma and CSF tau (R = 0.59, P < 0.001) and NF-L (R = 0.69, P < 0.001) levels correlated significantly (Spearman test). Plasma tau and NF-L levels were significantly higher in all disease groups compared to healthy controls (P < 0.001). Receiver operating characteristic curves were used and area under the curve values for comparisons with controls were 0.82 (AD), 0.94 (sporadic CJD), 0.92 (genetic CJD) and 0.83 (other neurological disorders) for plasma tau and 0.99, 0.99, 1.00 and 0.96 for plasma NF-L, respectively. Molecular subtyping of sporadic CJD showed a strong effect (linear logistic regression) on plasma tau (P < 0.001) but not NF-L levels (P = 0.19).

CONCLUSION

Plasma tau and NF-L concentrations are strongly increased in CJD and show similar diagnostic performance to the corresponding CSF measure. Molecular subtypes of sporadic CJD show different levels of plasma tau. Although not disease-specific, these findings support the use of plasma tau and NF-L as tools to identify, or to rule out, neurodegeneration.

17q21.31 duplication causes prominent tau-related dementia with increased MAPT expression

To assess the role of rare copy number variations in Alzheimer's disease (AD), we conducted a case-control study using whole-exome sequencing data from 522 early-onset cases and 584 controls. The most recurrent rearrangement was a 17q21.31 microduplication, overlapping the CRHR1, MAPT, STH and KANSL1 genes that was found in four cases, including one de novo rearrangement, and was absent in controls. The increased MAPT gene dosage led to a 1.6-1.9-fold expression of the MAPT messenger RNA. Clinical signs, neuroimaging and cerebrospinal fluid biomarker profiles were consistent with an AD diagnosis in MAPT duplication carriers. However, amyloid positon emission tomography (PET) imaging, performed in three patients, was negative. Analysis of an additional case with neuropathological examination confirmed that the MAPT duplication causes a complex tauopathy, including prominent neurofibrillary tangle pathology in the medial temporal lobe without amyloid-β deposits. 17q21.31 duplication is the genetic basis of a novel entity marked by prominent tauopathy, leading to early-onset dementia with an AD clinical phenotype. This entity could account for a proportion of probable AD cases with negative amyloid PET imaging recently identified in large clinical series.

The physiological phosphorylation of tau is critically changed in fetal brains of individuals with Down syndrome

AIMS

Down syndrome (DS) is a common cause of mental retardation accompanied by cognitive impairment. Comprehensive studies suggested a link between development and ageing, as nearly all individuals with DS develop Alzheimer disease (AD)-like pathology. However, there is still a paucity of data on tau in early DS to support this notion.

METHODS

Using morphometric immunohistochemistry we compared tau phosphorylation in normal brains and in brains of individuals with DS from early development until early postnatal life.

RESULTS

We observed in DS a critical loss of physiological phosphorylation of tau. Rhombencephalic structures showed prominent differences between controls and DS using antibodies AT8 (Ser-202/Thr-205) and AT180 (Thr-231). In contrast, in the subiculum only a small portion of controls deviated from DS using antibodies AT100 (Thr-212/Ser-214) and AT270 (Thr-181). With exception of the subiculum, phosphorylation-independent tau did not differ between groups, as confirmed by immunostaining for the HT-7 antibody (epitope between 159 and 163 of the human tau) as well.

DISCUSSION

Our observations suggest functional tau disturbance in DS brains during development, rather than axonal loss. This supports the role of tau as a further important player in the pathophysiology of cognitive impairment in DS and related AD.

Invited review: Neuropathology of tauopathies: principles and practice

Tauopathies are clinically, morphologically and biochemically heterogeneous neurodegenerative diseases characterized by the deposition of abnormal tau protein in the brain. The neuropathological phenotypes are distinguished based on the involvement of different anatomical areas, cell types and presence of distinct isoforms of tau in the pathological deposits. The nomenclature of primary tauopathies overlaps with the modern classification of frontotemporal lobar degeneration. Neuropathological phenotypes comprise Pick's disease, progressive supranuclear palsy, corticobasal degeneration, argyrophilic grain disease, primary age-related tauopathy, formerly called also as neurofibrillary tangle-only dementia, and a recently characterized entity called globular glial tauopathy. Mutations in the gene encoding the microtubule-associated protein tau are associated with frontotemporal dementia and parkinsonism linked to chromosome 17. In addition, further neurodegenerative conditions with diverse aetiologies may be associated with tau pathologies. Thus, the spectrum of tau pathologies and tauopathy entities expands beyond the traditionally discussed disease forms. Detailed multidisciplinary studies are still required to understand their significance.

Metabotropic glutamate receptor 5 in Down's syndrome hippocampus during development: increased expression in astrocytes

Metabotropic glutamate receptor 5 (mGluR5) is highly expressed throughout the forebrain and hippocampus. Several lines of evidence support the role of this receptor in brain development and developmental disorders, as well as in neurodegenerative disorders like Alzheimer's disease (AD). In the present study, the expression pattern of mGluR5 was investigated by immunocytochemistry in the developing hippocampus from patients with Down's syndrome (DS) and in adults with DS and AD. mGluR5 was expressed in developing human hippocampus from the earliest stages tested (9 gestational weeks), with strong expression in the ventricular/subventricular zones. We observed a consistent similar temporal and spatial neuronal pattern of expression in DS hippocampus. However, in DS we detected increased prenatal mGluR5 expression in white matter astrocytes, which persisted postnatally. In addition, in adult DS patients with widespread ADassociated neurodegeneration (DS-AD) increased mGluR5 expression was detected in astrocytes around amyloid plaque. In vitro data confirm the existence of a modulatory crosstalk between amyloid-β and mGluR5 in human astrocytes. These findings demonstrate a developmental regulation of mGluR5 in human hippocampus and suggest a role for this receptor in astrocytes during early development in DS hippocampus, as well as a potential contribution to the pathogenesis of ADassociated pathology.

Bilateral Dentate Gyrus Structural Alterations in a Cat Associated With Hippocampal Sclerosis and Intraventricular Meningioma

A 13-year-old cat had a history of seizures for 3 years that resembled temporal lobe epilepsy. Histologic examination of the brain revealed bilateral hippocampal alterations, including hypergyration and broadening of the dentate gyrus associated with hippocampal sclerosis and an intraventricular meningioma near the hippocampal region. The findings in the dentate gyrus were interpreted as a congenital malformation; however, it could not be ruled out that the alterations were induced by the seizures. Similar changes of the dentate gyrus have not been previously described in cats.

Linking pathways in the developing and aging brain with neurodegeneration

The molecular and cellular mechanisms, which coordinate the critical stages of brain development to reach a normal structural organization with appropriate networks, are progressively being elucidated. Experimental and clinical studies provide evidence of the occurrence of developmental alterations induced by genetic or environmental factors leading to the formation of aberrant networks associated with learning disabilities. Moreover, evidence is accumulating that suggests that also late-onset neurological disorders, even Alzheimer's disease, might be considered disorders of aberrant neural development with pathological changes that are set up at early stages of development before the appearance of the symptoms. Thus, evaluating proteins and pathways that are important in age-related neurodegeneration in the developing brain together with the characterization of mechanisms important during brain development with relevance to brain aging are of crucial importance. In the present review we focus on (1) aspects of neurogenesis with relevance to aging; (2) neurodegenerative disease (NDD)-associated proteins/pathways in the developing brain; and (3) further pathways of the developing or neurodegenerating brains that show commonalities. Elucidation of complex pathogenetic routes characterizing the earliest stage of the detrimental processes that result in pathological aging represents an essential first step toward a therapeutic intervention which is able to reverse these pathological processes and prevent the onset of the disease. Based on the shared features between pathways, we conclude that prevention of NDDs of the elderly might begin during the fetal and childhood life by providing the mothers and their children a healthy environment for the fetal and childhood development.

Health professions and risk of sporadic Creutzfeldt-Jakob disease, 1965 to 2010

In 2009, a pathologist with sporadic Creutzfeldt-Jakob Disease (sCJD) was reported to the Spanish registry. This case prompted a request for information on health-related occupation in sCJD cases from countries participating in the European Creutzfeldt Jakob Disease Surveillance network (EuroCJD). Responses from registries in 21 countries revealed that of 8,321 registered cases, 65 physicians or dentists, two of whom were pathologists, and another 137 healthcare workers had been identified with sCJD. Five countries reported 15 physicians and 68 other health professionals among 2,968 controls or non-cases, suggesting no relative excess of sCJD among healthcare professionals. A literature review revealed: (i) 12 case or small case-series reports of 66 health professionals with sCJD, and (ii) five analytical studies on health-related occupation and sCJD, where statistically significant findings were solely observed for persons working at physicians' offices (odds ratio: 4.6 (95 CI: 1.2-17.6)). We conclude that a wide spectrum of medical specialities and health professions are represented in sCJD cases and that the data analysed do not support any overall increased occupational risk for health professionals. Nevertheless, there may be a specific risk in some professions associated with direct contact with high human-infectivity tissue.

Health professions and risk of sporadic Creutzfeldt–Jakob disease, 1965 to 2010

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How a neuropsychiatric brain bank should be run: a consensus paper of Brainnet Europe II

The development of new molecular and neurobiological methods, computer-assisted quantification techniques and neurobiological investigation methods which can be applied to the human brain, all have evoked an increased demand for post-mortem tissue in research. Psychiatric disorders are considered to be of neurobiological origin. Thus far, however, the etiology and pathophysiology of schizophrenia, depression and dementias are not well understood at the cellular and molecular level. The following will outline the consensus of the working group for neuropsychiatric brain banking organized in the Brainnet Europe II, on ethical guidelines for brain banking, clinical diagnostic criteria, the minimal clinical data set of retrospectively analyzed cases as well as neuropathological standard investigations to perform stageing for neurodegenerative disorders in brain tissue. We will list regions of interest for assessments in psychiatric disorder, propose a dissection scheme and describe preservation and storage conditions of tissue. These guidelines may be of value for future implementations of additional neuropsychiatric brain banks world-wide.

Serotonergic nuclei of the raphe are not affected in human ageing

Sleep disorders increase with ageing. The serotonergic system has been linked with sleep regulation. In fatal familial insomnia, a prion disease with insomnia as one major clinical feature, we recently observed a disturbance in the serotonergic system as likely substrate of typical symptoms. Using immunohistochemistry for the serotonin synthesizing enzyme, tryptophan hydroxylase, we investigated the serotonergic median raphe nuclei (dorsal raphe nucleus, superior central nucleus, and raphe obscurus nucleus) in brains of an older (n = 12; age range 62-84 years) and a younger group (n = 10; age range 5-29 years). We found no significant difference between age groups in the percentage of neurons able to synthesize serotonin. Other changes might relate to sleep disturbances in the elderly.

Clinicopathological phenotype of codon 129 valine homozygote sporadic Creutzfeldt-Jakob disease

The naturally occurring polymorphism at codon 129 of the human prion protein gene (PRNP) influences susceptibility to sporadic Creutzfeldt-Jakob Disease (CJD); the majority of the patients are methionine homozygotes at this locus, while valine homozygotes represent only 10% of cases. The aim was to study the clinical and neuropathological phenotype of sporadic CJD in valine homozygotes, to estimate the reliability of current clinical diagnostic criteria, and to identify any consistent and distinct features. Twelve cases of sporadic CJD with a codon 129 valine homozygote genotype were identified at the National CJD Surveillance Unit in Edinburgh. In addition to a retrospective clinical analysis, tissue blocks were stained by conventional techniques and by immunocytochemistry for prion protein. Frozen brain tissue was available from five cases for Western blot analysis of PrPRES, which in all cases showed a type 2 mobility. The cases included four males and eight females, average age 63.6 years, with a mean duration of illness of 6 months. Eleven patients presented with ataxia, and none had the characteristic EEG changes found in sporadic CJD. The neuropathological phenotype comprised spongiform change and prion protein immunopositivity most marked in the subcortical grey matter and cerebellum, prion protein positive plaque-like deposits in all regions, laminar deposition of prion protein in the cerebral cortex, and hippocampal involvement (which is seldom reported in sporadic CJD). In conclusion, these cases exhibited a fairly uniform phenotype, which is relatively distinct from sporadic CJD in methionine homozygotes, and thus diagnosis may be difficult using existing clinical criteria.