Neurofibrillary tangle-predominant dementia: comparison with classical Alzheimer disease

Investigating the feasibility of 18F-flortaucipir PET imaging in the antemortem diagnosis of primary age-related tauopathy (PART): An observational imaging-pathological study

INTRODUCTION

Primary age-related tauopathy (PART) is characterized by neurofibrillary tangles and minimal β-amyloid deposition, diagnosed postmortem. This study investigates 18F-flortaucipir (FTP) PET imaging for antemortem PART diagnosis.

METHODS

We analyzed FTP PET scans from 50 autopsy-confirmed PART and 13 control subjects. Temporal lobe uptake was assessed both qualitatively and quantitatively. Demographic and clinicopathological characteristics and voxel-level uptake using SPM12 were compared between FTP-positive and FTP-negative cases. Intra-reader reproducibility was evaluated with Krippendorff's alpha.

RESULTS

Minimal/mild and moderate FTP uptake was seen in 32% of PART cases and 62% of controls, primarily in the left inferior temporal lobe. No demographic or clinicopathological differences were found between FTP-positive and FTP-negative cases. High intra-reader reproducibility (α = 0.83) was noted.

DISCUSSION

FTP PET imaging did not show a specific uptake pattern for PART diagnosis, indicating that in vivo PART identification using FTP PET is challenging. Similar uptake in controls suggests non-specific uptake in PART.

HIGHLIGHTS

18F-flortaucipir (FTP) PET scans were analyzed for diagnosing PART antemortem. 32% of PART cases had minimal/mild FTP uptake in the left inferior temporal lobe. Similar to PART FTP uptake was found in 62% of control subjects. No specific uptake pattern was found, challenging in vivo PART diagnosis.

Automated deep learning segmentation of neuritic plaques and neurofibrillary tangles in Alzheimer disease brain sections using a proprietary software

Neuropathological diagnosis of Alzheimer disease (AD) relies on semiquantitative analysis of phosphorylated tau-positive neurofibrillary tangles (NFTs) and neuritic plaques (NPs), without consideration of lesion heterogeneity in individual cases. We developed a deep learning workflow for automated annotation and segmentation of NPs and NFTs from AT8-immunostained whole slide images (WSIs) of AD brain sections. Fifteen WSIs of frontal cortex from 4 biobanks with varying tissue quality, staining intensity, and scanning formats were analyzed. We established an artificial intelligence (AI)-driven iterative procedure to improve the generation of expert-validated annotation datasets for NPs and NFTs thereby increasing annotation quality by >50%. This strategy yielded an expert-validated annotation database with 5013 NPs and 5143 NFTs. We next trained two U-Net convolutional neural networks for detection and segmentation of NPs or NFTs, achieving high accuracy and consistency (mean Dice similarity coefficient: NPs, 0.77; NFTs, 0.81). The workflow showed high generalization performance across different cases. This study serves as a proof-of-concept for the utilization of proprietary image analysis software (Visiopharm) in the automated deep learning segmentation of NPs and NFTs, demonstrating that AI can significantly improve the annotation quality of complex neuropathological features and enable the creation of highly precise models for identifying these markers in AD brain sections.

Prevalence and clinicopathological features of primary age-related tauopathy (PART): A large forensic autopsy study

INTRODUCTION

Primary age-related tauopathy (PART), often regarded as a minimally symptomatic pathology of old age, lacks comprehensive cohorts across various age groups.

METHODS

We examined PART prevalence and clinicopathologic features in 1589 forensic autopsy cases (≥40 years old, mean age ± SD 70.2 ± 14.2 years).

RESULTS

PART cases meeting criteria for argyrophilic grain diseases (AGD) were AGD+PART (n = 181). The remaining PART cases (n = 719, 45.2%) were classified as comorbid conditions (PART-C, n = 90) or no comorbid conditions (pure PART, n = 629). Compared to controls (n = 208), Alzheimer's disease (n = 133), and AGD+PART, PART prevalence peaked in the individuals in their 60s (65.5%) and declined in the 80s (21.5%). No significant clinical background differences were found (excluding controls). However, PART-C in patients inclusive of age 80 had a higher suicide rate than pure PART (p < 0.05), and AGD+PART showed more dementia (p < 0.01) and suicide (p < 0.05) than pure PART.

DISCUSSION

Our results advocate a reevaluation of the PART concept and its diagnostic criteria.

HIGHLIGHTS

We investigated 1589 forensic autopsy cases to investigate the features of primary age-related tauopathy (PART). PART peaked in people in their 60s in our study. Many PART cases over 80s had comorbid pathologies in addition to neurofibrillary tangles pathology. Argyrophilic grain disease and Lewy pathology significantly affected dementia and suicide rates in PART. Our results suggest that the diagnostic criteria of PART need to be reconsidered.

Neuropathological substrate of incident dementia in older patients with schizophrenia: A clinicopathological study

AIM

Clinical studies reported that patients with schizophrenia are at a higher risk of developing dementia than people without schizophrenia. However, early neuropathological studies have shown that the incidence of Alzheimer's disease (AD) in schizophrenia patients does not differ from that in controls. These inconsistent results may be attributable to the inclusion of non-AD dementia, but there have been few clinicopathological studies in older patients with schizophrenia based on the current neuropathological classification. This study aimed to investigate the neuropathological basis of incident dementia in older patients with schizophrenia.

METHODS

We systematically examined 32 brains of old patients with schizophrenia using standardized pathological methods. The severity of dementia-related neuropathologies was analyzed using standardized semiquantitative assessments. After excluding patients who fulfilled the neuropathological criteria, clinicopathological variables were compared between patients with and without incident dementia to identify potential differences.

RESULTS

Seven patients fulfilled the pathological criteria for AD (n = 3), argyrophilic grain disease (AGD) (n = 2), dementia with Lewy bodies (n = 1), and AGD/progressive supranuclear palsy (n = 1). Among 25 patients for whom a neuropathological diagnosis was not obtained, 10 had dementia, but the clinicopathological findings did not differ from the remaining 15 patients without dementia.

CONCLUSION

Two types of older schizophrenia patient present dementia: patients with co-existing neurodegenerative disease and patients who do not meet pathological criteria based on the current classification. To understand the neurobiological aspects of incident dementia in older patients with schizophrenia, further clinicopathological studies are needed that do not simply analyze incident dementia as a comorbidity of conventional dementia-related neuropathologies.

Early CA2 Tau Inclusions Do Not Distinguish an Age-Related Tauopathy from Early Alzheimer's Disease

Background

Neuropathologic studies of brains from autopsy series show tau inclusions (pretangles, neuropils threads, neurofibrillary tangles) are detectable more than a decade before amyloid-β (Aβ) deposition in Alzheimer's disease (AD) and develop in a characteristic manner that forms the basis for AD staging. An alternative position views pathological tau without Aβ deposition as a 'primary age-related tauopathy' (PART) rather than prodromal AD. Recently, an early focus of tau inclusions in the Ammon's horn second sector (CA2) with relative sparing of CA1 that occurs before tau inclusions develop in the entorhinal cortex (EC) was proposed as an additional feature of PART.

Objective

To test the 'definite PART' hypothesis.

Methods

We used AT8-immunohistochemistry in 100μm sections to examine the EC, transentorhinal cortex (TRE), and Ammon's horn in 325 brains with tau inclusions lacking Aβ deposits (average age at death 66.7 years for females, 66.4 years for males).

Results

100% of cases displayed tau inclusions in the TRE. In 89% of cases, the CA1 tau rating was greater than or equal to that in CA2. In 25%, CA2 was devoid of tau inclusions. Only 4% displayed a higher tau score in CA2 than in the TRE, EC, and CA1. The perforant path also displayed early tau changes. APOE genotyping was available for 199/325 individuals. Of these, 44% had an ɛ4 allele that placed them at greater risk for developing later NFT stages and, therefore, clinical AD.

Conclusions

Our new findings call into question the PART hypothesis and are consistent with the idea that our cases represent prodromal AD.

Severe cerebrovascular pathology of the first supercentenarian to be autopsied in the world

We report on a 116-year-old Japanese woman who was the first officially documented supercentenarian to be autopsied in the world. She lived a remarkably healthy life until suffering cerebral infarction at 109 years of age. She became Japan's oldest person at 113 years and died in 1995 from colon cancer at 116 years 175 days. Her medical records show the delayed onset of stroke, cancer, dementia, and heart disease and the importance of appropriate medical treatment and intensive dedicated care provided during the last stage of her life. She was the longest-lived person in Japan for 21 years from 1993 until 2014. The neuropathological findings of her autopsied brain were briefly reported in the Japanese literature in 1997. In this study, we reinvestigated her brain and spinal cord in more detail. Severe cerebrovascular lesions and cervical spondylotic myelopathy were found to be the main causes of her disability. Although the density of senile plaques was relatively high, the distribution of neurofibrillary tangles was limited. Ghost tangles and argyrophilic grains were mild. The mildness of tau pathological changes in her neurons, in other words the resistance of neurons to tau pathology, may be a factor responsible for her longevity.

Mixed pathology as a rule, not exception: Time to reconsider disease nosology

Parkinson's disease is a progressive neurodegenerative disorder that is associated with motor and nonmotor symptoms. Accumulation of misfolded α-synuclein is considered a key pathological feature during disease initiation and progression. While clearly deemed a synucleinopathy, the development of amyloid-β plaques, tau-containing neurofibrillary tangles, and even TDP-43 protein inclusions occur within the nigrostriatal system and in other brain regions. In addition, inflammatory responses, manifested by glial reactivity, T-cell infiltration, and increased expression of inflammatory cytokines, plus other toxic mediators derived from activated glial cells, are currently recognized as prominent drivers of Parkinson's disease pathology. However, copathologies have increasingly been recognized as the rule (>90%) and not the exception, with Parkinson's disease cases on average exhibiting three different copathologies. While microinfarcts, atherosclerosis, arteriolosclerosis, and cerebral amyloid angiopathy may have an impact on disease progression, α-synuclein, amyloid-β, and TDP-43 pathology do not seem to contribute to progression.

Possible association of limbic tau pathology with psychosis or behavioral disturbances: Studies of two autopsied psychiatric patients

Tauopathies, including Alzheimer's disease and primary age-related tauopathy (PART), present heterogeneous clinico-pathological phenotypes that include dementia, aphasia, motor neuron diseases, and psychiatric symptoms. PART is neuropathologically characterized by the presence of neurofibrillary tangles in limbic regions without significant Aβ deposition, but its clinical features have not yet been fully established. Here, we present two patients with distinct psychosis and behavioral symptoms. At autopsy, these patients showed tau pathologies that could not be classified as typical PART, although PART-like neurofibrillary tangles were present in limbic regions. Clinically, both patients were admitted to mental hospitals due to severe delusions or other neuropsychiatric/behavioral symptoms. The first case presented with hallucination, delusion, and apathy at age 70, and died of pancreatic cancer at age 75. He had neuronal cytoplasmic inclusions with selective accumulation of 3Rtau in the striatum and thorn-shaped astrocytes in the amygdala. The second case, who presented with abnormal behaviors such as wandering, agitation and disinhibition, exhibited limbic neurodegeneration with massive 4R tau-positive oligodendroglial inclusions in the medial temporal white matter. His age at onset was 73, and the duration of disease was 15 years. These findings support the notion that distinct limbic tau pathology with concomitant degeneration of the related neural circuits might induce specific psychosis and behavioral symptoms. This underlines the importance of neuropathological evaluation for both clinical education and practice in the fields of neuropathology and neuropsychiatry.

The Aging Patterns of Brain Structure, Function, and Energy Metabolism

The normal aging process brings changes in brain structure, function, and energy metabolism, which are presumed to contribute to the age-related decline in brain function and cognitive ability. This chapter aims to summarize the aging patterns of brain structure, function, and energy metabolism to distinguish them from the pathological changes associated with neurodegenerative diseases and explore protective factors in aging. We first described the normal atrophy pattern of cortical gray matter with age, which is negatively affected by some neurodegenerative diseases and is protected by a healthy lifestyle, such as physical exercise. Next, we summarized the main types of age-related white matter lesions, including white matter atrophy and hyperintensity. Age-related white matter changes mainly occurred in the frontal lobe, and white matter lesions in posterior regions may be an early sign of Alzheimer's disease. In addition, the relationship between brain activity and various cognitive functions during aging was discussed based on electroencephalography, magnetoencephalogram, and functional magnetic resonance imaging. An age-related reduction in occipital activity is coupled with increased frontal activity, which supports the posterior-anterior shift in aging (PASA) theory. Finally, we discussed the relationship between amyloid-β deposition and tau accumulation in the brain, as pathological manifestations of neurodegenerative disease and aging.

Towards an understanding of the pathological basis of senile depression and incident dementia: Implications for treatment

Senile depression (SD) is a heterogeneous syndrome. Several clinical profiles are more likely to appear in SD than in early-life depression, but it remains unclear whether the pathophysiology is different. The prevalence of dementia increases with aging, and the underlying pathophysiological processes in the preclinical phase begin even before cognitive deficits or neurological signs appear. SD may be either a risk factor for developing dementia or a prodromal stage of dementia. The inconsistent findings regarding the association between SD and incident dementia may be attributable to the neuropathological heterogeneity underlying SD. Most studies have focused on patients with the clinical diagnosis of Alzheimer disease (AD) as an outcome, but several clinicopathological studies suggest that primary age-related tauopathy and argyrophilic grain disease may account for a proportion of cases clinically misdiagnosed as AD in the elderly population. Furthermore, most AD cases have additional neuropathologic changes such as cerebrovascular disease and Lewy body disease. Here, we review the neuropathological findings linking SD to incident dementia, focusing on common age-related neuropathologies. In particular, the roles of disturbance of neural circuity, imbalance of monoaminergic systems, dysregulation of the hypothalamic-pituitary-adrenal axis, and elevated neuroinflammatory status are discussed. Finally, we review the current treatment of SD in the context of age-related neuropathological changes.

Single cell transcriptomic profiling of a neuron-astrocyte assembloid tauopathy model

The use of iPSC derived brain organoid models to study neurodegenerative disease has been hampered by a lack of systems that accurately and expeditiously recapitulate pathogenesis in the context of neuron-glial interactions. Here we report development of a system, termed AstTau, which propagates toxic human tau oligomers in iPSC derived neuron-astrocyte assembloids. The AstTau system develops much of the neuronal and astrocytic pathology observed in tauopathies including misfolded, phosphorylated, oligomeric, and fibrillar tau, strong neurodegeneration, and reactive astrogliosis. Single cell transcriptomic profiling combined with immunochemistry characterizes a model system that can more closely recapitulate late-stage changes in adult neurodegeneration. The transcriptomic studies demonstrate striking changes in neuroinflammatory and heat shock protein (HSP) chaperone systems in the disease process. Treatment with the HSP90 inhibitor PU-H71 is used to address the putative dysfunctional HSP chaperone system and produces a strong reduction of pathology and neurodegeneration, highlighting the potential of AstTau as a rapid and reproducible tool for drug discovery.

TDP-43 Pathology Exacerbates Cognitive Decline in Primary Age-Related Tauopathy

OBJECTIVE

Primary age-related tauopathy (PART) refers to tau neurofibrillary tangles restricted largely to the medial temporal lobe in the absence of significant beta-amyloid plaques. PART has been associated with cognitive impairment, but contributions from concomitant limbic age-related TDP-43 encephalopathy neuropathologic change (LATE-NC) are underappreciated.

METHODS

We compare prevalence of LATE-NC and vascular copathologies in age- and Braak-matched patients with PART (n = 45, Braak stage I-IV, Thal phase 0-2) or early stage Alzheimer disease neuropathologic change (ADNC; n = 51, Braak I-IV, Thal 3-5), and examine their influence on clinical and cognitive decline.

RESULTS

Concomitant LATE-NC and vascular pathology were equally common, and cognition was equally impaired, in PART (Mini-Mental State Examination [MMSE] = 24.8 ± 6.9) and ADNC (MMSE = 24.2 ± 6.0). Patients with LATE-NC were more impaired than those without LATE-NC on the MMSE (by 5.8 points, 95% confidence interval [CI] = 3.0-8.6), Mattis Dementia Rating Scale (DRS; 17.5 points, 95% CI = 7.1-27.9), Clinical Dementia Rating, sum of boxes scale (CDR-sob; 5.2 points, 95% CI = 2.1-8.2), memory composite (0.8 standard deviations [SD], 95% CI = 0.1-1.6), and language composite (1.1 SD, 95% CI = 0.2-2.0), and more likely to receive a dementia diagnosis (odds ratio = 4.8, 95% CI = 1.5-18.0). Those with vascular pathology performed worse than those without on the DRS (by 10.2 points, 95% CI = 0.1-20.3) and executive composite (1.3 SD, 95% CI = 0.3-2.3). Cognition declined similarly in PART and ADNC over the 5 years preceding death; however, LATE-NC was associated with more rapid decline on the MMSE (β = 1.9, 95% CI = 0.9-3.0), DRS (β = 7.8, 95% CI = 3.4-12.7), CDR-sob (β = 1.9, 95% CI = 0.4-3.7), language composite (β = 0.5 SD, 95% CI = 0.1-0.8), and vascular pathology with more rapid decline on the DRS (β = 5.2, 95% CI = 0.6-10.2).

INTERPRETATION

LATE-NC, and to a lesser extent vascular copathology, exacerbate cognitive impairment and decline in PART and early stage ADNC. ANN NEUROL 2022;92:425-438.

Exploring discordant low amyloid beta and high neocortical tau positron emission tomography cases

Introduction

Neocortical 3R4R (3-repeat/4-repeat) tau aggregates are rarely observed in the absence of amyloid beta (Aβ). 18F-MK6240 binds specifically to the 3R4R form of tau that is characteristic of Alzheimer's disease (AD). We report four cases with negative Aβ, but positive tau positron emission tomography (PET) findings.

Methods

All Australian Imaging, Biomarkers and Lifestyle study of aging (AIBL) study participants with Aβ (18F-NAV4694) and tau (18F-MK6240) PET scans were included. Centiloid <25 defined negative Aβ PET (Aβ-). The presence of neocortical tau was defined quantitatively and visually.

Results

Aβ- PET was observed in 276 participants. Four of these participants (one cognitively unimpaired [CU], two mild cognitive impairment [MCI], one AD) had tau tracer retention in a pattern consistent with Braak tau stages V to VI. Fluid biomarkers supported a diagnosis of AD. In silico analysis of APP, PSEN1, PSEN2, and MAPT genes did not identify relevant functional mutations.

Discussion

Discordant cases were infrequent (1.4% of all Aβ- participants). In these cases, the Aβ PET ligand may not be detecting the Aβ that is present.

The relationship of early- and late-onset Alzheimer’s disease genes with COVID-19

Individuals with Alzheimer’s disease and other neurodegenerative diseases have been exposed to excess risk by the COVID-19 pandemic. COVID-19’s main manifestations include high body temperature, dry cough, and exhaustion. Nevertheless, some affected individuals may have an atypical presentation at diagnosis but suffer neurological signs and symptoms as the first disease manifestation. These findings collectively show the neurotropic nature of SARS-CoV-2 virus and its ability to involve the central nervous system. In addition, Alzheimer’s disease and COVID-19 has a number of common risk factors and comorbid conditions including age, sex, hypertension, diabetes, and the expression of APOE ε4. Until now, a plethora of studies have examined the COVID-19 disease but only a few studies has yet examined the relationship of COVID-19 and Alzheimer’s disease as risk factors of each other. This review emphasizes the recently published evidence on the role of the genes of early- or late-onset Alzheimer’s disease in the susceptibility of individuals currently suffering or recovered from COVID-19 to Alzheimer’s disease or in the susceptibility of individuals at risk of or with Alzheimer’s disease to COVID-19 or increased COVID-19 severity and mortality. Furthermore, the present review also draws attention to other uninvestigated early- and late-onset Alzheimer’s disease genes to elucidate the relationship between this multifactorial disease and COVID-19.

Genome-wide association study and functional validation implicates JADE1 in tauopathy

Primary age-related tauopathy (PART) is a neurodegenerative pathology with features distinct from but also overlapping with Alzheimer disease (AD). While both exhibit Alzheimer-type temporal lobe neurofibrillary degeneration alongside amnestic cognitive impairment, PART develops independently of amyloid-β (Aβ) plaques. The pathogenesis of PART is not known, but evidence suggests an association with genes that promote tau pathology and others that protect from Aβ toxicity. Here, we performed a genetic association study in an autopsy cohort of individuals with PART (n = 647) using Braak neurofibrillary tangle stage as a quantitative trait. We found some significant associations with candidate loci associated with AD (SLC24A4, MS4A6A, HS3ST1) and progressive supranuclear palsy (MAPT and EIF2AK3). Genome-wide association analysis revealed a novel significant association with a single nucleotide polymorphism on chromosome 4 (rs56405341) in a locus containing three genes, including JADE1 which was significantly upregulated in tangle-bearing neurons by single-soma RNA-seq. Immunohistochemical studies using antisera targeting JADE1 protein revealed localization within tau aggregates in autopsy brains with four microtubule-binding domain repeats (4R) isoforms and mixed 3R/4R, but not with 3R exclusively. Co-immunoprecipitation in post-mortem human PART brain tissue revealed a specific binding of JADE1 protein to four repeat tau lacking N-terminal inserts (0N4R). Finally, knockdown of the Drosophila JADE1 homolog rhinoceros (rno) enhanced tau-induced toxicity and apoptosis in vivo in a humanized 0N4R mutant tau knock-in model, as quantified by rough eye phenotype and terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) in the fly brain. Together, these findings indicate that PART has a genetic architecture that partially overlaps with AD and other tauopathies and suggests a novel role for JADE1 as a modifier of neurofibrillary degeneration.

Primary Age‐Related Tauopathy (PART) in a Finnish Population‐Based Study of the Oldest Old (Vantaa 85+)

Aims

Few studies have investigated primary age‐related tauopathy (PART) in a population‐based setting. Here, we assessed its prevalence, genetic background, comorbidities and features of cognitive decline in an unselected elderly population.

Methods

The population‐based Vantaa 85+ study includes all 601 inhabitants of Vantaa aged ≥ 85 years in 1991. Neuropathological assessment was possible in 301. Dementia (DSM IIIR criteria) and Mini‐Mental State Examination (MMSE) scores were assessed at the baseline of the study and follow‐ups. PART subjects were identified according to the criteria by Crary et al and were compared with subjects with mild and severe Alzheimer's disease (AD) neuropathological changes. The effects of other neuropathologies were taken into account using multivariate and sensitivity assays. Genetic analyses included APOE genotypes and 29 polymorphisms of the MAPT 3′ untranslated region (3′UTR region).

Results

The frequency of PART was 20% (n = 61/301, definite PART 5%). When PART subjects were compared with those with severe AD pathology, dementia was less common, its age at onset was higher and duration shorter. No such differences were seen when compared with those with milder AD pathology. However, both AD groups showed a steeper decline in MMSE scores in follow‐ups compared with PART. APOE ε4 frequency was lower, and APOE ε2 frequency higher in the PART group compared with each AD group. The detected nominally significant associations between PART and two MAPT 3′UTR polymorphisms and haplotypes did not survive Bonferroni correction.

Conclusions

PART is common among very elderly. PART subjects differ from individuals with AD‐type changes in the pattern of cognitive decline, associated genetic and neuropathological features.

The hybrid compounds as multi-target ligands for the treatment of Alzheimer's Disease: Considerations on Donepezil

The strategies to combat Alzheimer's Disease (AD) have been changing with respect to the failures of many drug candidates assessed in clinical studies, the complex pathophysiology of AD, and the limitations of the current drugs employed. So far, none of the targets, either validated or nonvalidated, have been shown to be purely causative in the generation and development of AD. Considering the progressive and the neurodegenerative characteristics of the disease, the main strategy has been based on the design of molecules capable of showing activity on more than one receptor, and it is defined as multi-target ligand design strategy. The hybrid molecule concept is an outcome of this approach. Donepezil, as one of the currently employed drugs for AD therapy, has also been utilized in hybrid drug design studies. This review has aimed to present the promising donepezil-like hybrid molecules introduced in the recent period. Particularly, multi-target ligands with additional activities concomitant to cholinesterase inhibition are preferred.

Visualization of neurofibrillary tangle maturity in Alzheimer's disease: A clinicopathologic perspective for biomarker research

Neurofibrillary tangles, one of the neuropathologic hallmarks of Alzheimer's disease, have a dynamic lifespan of maturity that associates with progressive neuronal dysfunction and cognitive deficits. As neurofibrillary tangles mature, the biology of the neuron undergoes extensive changes that may impact biomarker recognition and therapeutic targeting. Neurofibrillary tangle maturity encompasses three levels: pretangles, mature tangles, and ghost tangles. In this review, we detail distinct and overlapping characteristics observed in the human brain regarding morphologic changes the neuron undergoes, conversion from intracellular to extracellular space, tau immunostaining patterns, and tau isoform expression changes across the lifespan of the neurofibrillary tangle. Post-translational modifications of tau such as phosphorylation, ubiquitination, conformational events, and truncations are discussed to contextualize tau immunostaining patterns. We summarize accumulated and emerging knowledge of neurofibrillary tangle maturity, discuss the current tools used to interpret the dynamic nature in the postmortem brain, and consider implications for cognitive dysfunction and tau biomarkers.

Comparison of the decreases in regional cerebral blood flow in the posterior cingulate cortex, precuneus, and parietal lobe between suspected non-Alzheimer's disease pathophysiology and Alzheimer's disease

BACKGROUND

Suspected non-Alzheimer's disease pathophysiology (SNAP) shows Alzheimer's disease (AD)-like neurodegeneration; however, amyloid β, which is a biological marker in AD, remains within normal levels. Since the effectiveness of anti-dementia drugs for AD on SNAP is unknown, it is important to distinguish between patients with SNAP and AD. We aimed to compare decreases in regional cerebral blood flow (rCBF) of the posterior cingulate cortex (PCC), precuneus, and parietal lobe critical to AD between SNAP and AD groups using the easy Z-score imaging system in single-photon emission computed tomography (eZIS-SPECT).

METHODS

We retrospectively analysed eZIS-SPECT data of 13 SNAP and 24 AD patients. The three indicators (severity, extent, and ratio) that distinguished AD patients from healthy controls in previous studies were automatically calculated and were compared between the SNAP and AD groups. Receiver operating characteristic curve analysis and the area under the curve (AUC) were used to evaluate the diagnostic performance of the three indicators of eZIS in discriminating between the two groups.

RESULTS

The mean values of severity, extent, and ratio were significantly lower in the SNAP group than in the AD group (P = 0.024, P = 0.044, and P = 0.045, respectively). The AUC values for severity, extent, and ratio were 0.668, 0.683, and 0.692, respectively.

CONCLUSIONS

The present study suggests that SNAP shows milder reduction of rCBF in the PCC, precuneus, and parietal lobe as compared to AD. However, it may be difficult to distinguish between SNAP and AD with the degrees of decrease in rCBF in these regions.

Predictors of cognitive impairment in primary age-related tauopathy: an autopsy study

Primary age-related tauopathy (PART) is a form of Alzheimer-type neurofibrillary degeneration occurring in the absence of amyloid-beta (Aβ) plaques. While PART shares some features with Alzheimer disease (AD), such as progressive accumulation of neurofibrillary tangle pathology in the medial temporal lobe and other brain regions, it does not progress extensively to neocortical regions. Given this restricted pathoanatomical pattern and variable symptomatology, there is a need to reexamine and improve upon how PART is neuropathologically assessed and staged. We performed a retrospective autopsy study in a collection (n = 174) of post-mortem PART brains and used logistic regression to determine the extent to which a set of clinical and neuropathological features predict cognitive impairment. We compared Braak staging, which focuses on hierarchical neuroanatomical progression of AD tau and Aβ pathology, with quantitative assessments of neurofibrillary burden using computer-derived positive pixel counts on digitized whole slide images of sections stained immunohistochemically with antibodies targeting abnormal hyperphosphorylated tau (p-tau) in the entorhinal region and hippocampus. We also assessed other factors affecting cognition, including aging-related tau astrogliopathy (ARTAG) and atrophy. We found no association between Braak stage and cognitive impairment when controlling for age (p = 0.76). In contrast, p-tau burden was significantly correlated with cognitive impairment even when adjusting for age (p = 0.03). The strongest correlate of cognitive impairment was cerebrovascular disease, a well-known risk factor (p < 0.0001), but other features including ARTAG (p = 0.03) and hippocampal atrophy (p = 0.04) were also associated. In contrast, sex, APOE, psychiatric illness, education, argyrophilic grains, and incidental Lewy bodies were not. These findings support the hypothesis that comorbid pathologies contribute to cognitive impairment in subjects with PART. Quantitative approaches beyond Braak staging are critical for advancing our understanding of the extent to which age-related tauopathy changes impact cognitive function.

Green tea consumption is associated with annual changes in hippocampal volumes: A longitudinal study in community-dwelling middle-aged and older Japanese individuals

BACKGROUND

To investigate the association between green tea consumption and the annual rate of change of gray matter (GM), white matter (WM), and hippocampal volumes in community-dwelling middle-aged and older Japanese individuals.

METHODS

A prospective cohort study with two years of follow-up was conducted as part of the National Institute for Longevity Sciences-Longitudinal Study of Aging (NILS-LSA) project. A total of 1693 participants (862 men and 831 women, aged 40-89 years) were included. Green tea consumption (mL/day) data were collected with a 3-day dietary record. Volumes of GM, WM, and the hippocampus were estimated by T1-weighted brain magnetic resonance imaging and FreeSurfer software. The GM ratio, WM ratio, and hippocampal ratio (HR) were calculated as the percentages of total intracranial volume, respectively.

RESULTS

The mean (SD) annual rate of change of hippocampal volume [(HR at baseline - HR at follow-up)/HR at baseline/follow-up years×100%] was 0.499 (1.128) (%). In the multivariable-adjusted general linear model, green tea consumption was negatively associated only with the annual rate of change of hippocampal volume (%) [β (95% CI) for each 1 mL/day increase in green tea consumption = -20.2E-5 (-35.0E-5 to -5.3E-5); P-value = 0.008]. No associations were observed for the annual rate of change of GM or WM volumes. The results remained significant when the analysis was limited to those with stable green tea consumption and were especially evident among individuals aged 65 years and older and among women.

CONCLUSIONS

In this study, higher green tea consumption was associated with less annual hippocampal atrophy, and each additional 100 mL/day of green tea intake was related to a reduction of approximately 5% in annual hippocampal atrophy. This association was especially evident among older individuals and among women. Further study in different settings is needed to confirm this association.

Pathobiological Subtypes of Alzheimer Disease

Alzheimer disease (AD), the most common form of dementia, is a heterogenous disorder with various pathobiological subtypes. In addition to the 4 major subtypes based on the distribution of tau pathology and brain atrophy (typical, limbic predominant, hippocampal sparing, and minimal atrophy [MA]), several other clinical variants showing distinct regional patterns of tau burden have been identified: nonamnestic, corticobasal syndromal, primary progressive aphasia, posterior cortical atrophy, behavioral/dysexecutive, and mild dementia variants. Among the subtypes, differences were found in age at onset, sex distribution, cognitive status, disease duration, APOE genotype, and biomarker levels. The patterns of key network destructions parallel the tau and atrophy patterns of the AD subgroups essentially. Interruption of key networks, in particular the default-mode network that is responsible for cognitive decline, is consistent in hetero-genous AD groups. AD pathology is often associated with co-pathologies: cerebrovascular lesions, Lewy pathology, and TDP-43 proteinopathies. These mixed pathologies essentially influence the clinical picture of AD and may accel-erate disease progression. Unraveling the heterogeneity among the AD spectrum entities is important for opening a window to pathogenic mechanisms affecting the brain and enabling precision medicine approaches as a basis for developing preventive and ultimately successful disease-modifying therapies for AD.

Beta-Secretase 1 Underlies Reactive Astrocytes and Endothelial Disruption in Neurodegeneration

Dysfunction in the neurovascular unit (NVU) is a key component in the progressive deterioration of Alzheimer's disease (AD) and is critical in vascular dementia. Recent studies have shown that inflammation plays early and perhaps causal roles in the pathogenesis of AD related to NVU damage, possibly in part by overactivating the aspartic acid protease activity of β-site amyloid precursor protein-cleaving enzyme 1 (BACE1), which until now has almost solely been studied in the context of the β-amyloid cascade. In this study, we analyzed the relationship of BACE1 with astrocytes and blood vessels in human brains with sporadic and familial dementia [Autosomal dominant cerebral arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), sporadic Alzheimer's disease (SAD), and familial Alzheimer's disease (FAD)] and how BACE1 inhibition affects astrocytes and endothelial cells under conditions of glutamate toxicity. Our results show increased BACE1, PHF (Paired helical filaments)-tau and GFAP (Glial Fibrillary Acid Protein) immunoreactivity (IR) in the CA1 hippocampal regions of FAD and SAD brains. Furthermore, BACE1 immunoprecipitated with GFAP in tissue samples from all study cases, but their immunofluorescence close to (10 μm³) or overlapping blood vessels was only increased in FAD and SAD brains, and PHF-tau was present around the vessels mainly in FAD brains. Interestingly, the increased BACE1 levels were associated with reactive astrocytes, characterized by morphological changes and upregulation of GFAP under pathological and stressful conditions, and endothelial disruption by glutamate excitotoxicity, and these effects were reversed by BACE1 inhibition; further, BACE1-inhibited astrocytes protected endothelial cell integrity by preserving zonula occludens-1 (ZO-1) distribution and decreasing the expression of inflammatory markers. Taken together, these findings suggest that BACE1 dysregulation in astrocytes may have a role in the alterations in NVU integrity implicated in neurodegeneration.

Zebrafish Models to Study New Pathways in Tauopathies

Tauopathies represent a vast family of neurodegenerative diseases, the most well-known of which is Alzheimer’s disease. The symptoms observed in patients include cognitive deficits and locomotor problems and can lead ultimately to dementia. The common point found in all these pathologies is the accumulation in neural and/or glial cells of abnormal forms of Tau protein, leading to its aggregation and neurofibrillary tangles. Zebrafish transgenic models have been generated with different overexpression strategies of human Tau protein. These transgenic lines have made it possible to highlight Tau interacting factors or factors which may limit the neurotoxicity induced by mutations and hyperphosphorylation of the Tau protein in neurons. Several studies have tested neuroprotective pharmacological approaches. On few-days-old larvae, modulation of various signaling or degradation pathways reversed the deleterious effects of Tau mutations, mainly hTauP301L and hTauA152T. Live imaging and live tracking techniques as well as behavioral follow-up enable the analysis of the wide range of Tau-related phenotypes from synaptic loss to cognitive functional consequences.

Asymmetry of Hippocampal Tau Pathology in Primary Age-Related Tauopathy and Alzheimer Disease

Primary age-related tauopathy (PART) is a neurodegenerative entity defined as neurofibrillary degeneration generally restricted to the medial temporal region (Braak stage I-IV) with complete or near absence of diffuse and neuritic plaques. Symptoms range in severity but are generally milder and later in onset than in Alzheimer disease (AD). Recently, an early predilection for neurofibrillary degeneration in the hippocampal CA2 subregion has been demonstrated in PART, whereas AD neuropathologic change (ADNC) typically displays relative sparing of CA2 until later stages. In this study, we utilized a semiquantitative scoring system to evaluate asymmetry of neurofibrillary degeneration between left and right hippocampi in 67 PART cases and 17 ADNC cases. 49% of PART cases demonstrated asymmetric findings in at least one hippocampal subregion, and 79% of the asymmetric cases displayed some degree of CA2 asymmetry. Additionally, 19% of cases revealed a difference in Braak score between the right and left hippocampi. There was a significant difference in CA2 neurofibrillary degeneration (p = 0.0006) and CA2/CA1 ratio (p < 0.0001) when comparing the contralateral sides, but neither right nor left was more consistently affected. These data show the importance of analyzing bilateral hippocampi in the diagnostic evaluation of PART and potentially of other neurodegenerative diseases.

A Practical Approach to Differentiate the Frontotemporal Tauopathy Subtypes

This study proposes a practical approach, using the minimum number of brain regions and stains, to consolidate previously published neuropathological criteria into one operationalized schema to differentiate subtypes of frontotemporal lobar degeneration with tau-immunopositive inclusions (FTLD-tau). This approach uses the superior frontal and precentral cortices and hippocampus stained for phosphorylated-tau, p62 and modified Bielschowsky silver, and the midbrain stained only for modified Bielschowsky silver. Accuracy of interrater reliability was determined by 10 raters in 24 FTLD-tau cases (Pick disease = 4, corticobasal degeneration = 9, progressive supranuclear palsy = 5, globular glial tauopathy = 6) including 4 with a mutation in MAPT collected with consent by Sydney Brain Bank. All brain regions and stains assessed proved informative for accurate pathological subtyping, and many neuropathological features were identified as common across the FTLD-tau subtypes. By identifying subtype-specific neuropathological features in the sections selected, 10 independent observers assigned the cases to a FTLD-tau subtype with almost perfect agreement between raters, emphasizing the requirement for the assessment of subtype-specific features for the accurate subtyping of FTLD-tau. This study consolidates current consensus diagnostic criteria for classifying FTLD-tau subtypes with an efficient, simple and accurate approach that can be implemented in future clinicopathological studies.

Clinical impact of 11C-Pittsburgh compound-B positron emission tomography in addition to magnetic resonance imaging and single-photon emission computed tomography on diagnosis of mild cognitive impairment to Alzheimer's disease

This study aimed to evaluated the clinical impact of adding [11C] Pittsburgh compound-B (11C-PiB) PET for clinical diagnosis of mild cognitive impairment (MCI) to Alzheimer's disease (AD) dementia.Twenty six (mean age 78.5 ± 5.18 years, 21 females) AD (n = 7), amnestic MCI (n = 12), non-amnestic MCI (n = 3), vascular dementia, progressive supranuclear palsy (PSP) with frontotemporal dementia (FTD), FTD (n = 1 each), and normal (n = 1) patients underwent 11C-PiB-PET, MRI, and SPECT scanning. 11C-PiB-PET was compared with MRI and SPECT for clinical impact.11C-PiB-PET showed positivity in 6, 9, and 0 of the AD, amnestic MCI, and non-amnestic MCI patients, respectively, and 0 of those with another disease. Parahippocampal atrophy at VSASD was observed in 5 AD patients, 6 amnestic and PiB-positive MCI patients, 1 amnestic and PiB-negative MCI patient, and 1 vascular dementia patient. Parietal lobe hypoperfusion in SPECT findings was observed in 6, 4, and 2 of those, respectively, as well as 1 each of non-amnestic MCI, vascular dementia, and normal cases. Sensitivity/specificity/accuracy for selecting PiB-positive patients among the 15 MCI patients for 11C-PiB-PET were 100% (9/9)/100% (6/6)/100% (15/15), for VSRAD were 66.7% (6/9)/83.3% (5/6)/73.3% (11/15), and for SPECT were 44.4% (4/9)/50.0% (3/6)/46.7% (7/15), while those were 88.9% (8/9)/33.3% (2/6)/66.7% (10/15)/for combined VSRAD and SPECT. 11C-PiB-PET accuracy was significantly higher than that of SPECT.11PiB-PET alone may be useful for selecting patients who will progress from MCI to AD in the future, although follow-up study is necessary to clarify the outcome of MCI patients.

Lipidomic Analysis of Postmortem Prefrontal Cortex Phospholipids Reveals Changes in Choline Plasmalogen Containing Docosahexaenoic Acid and Stearic Acid Between Cases With and Without Alzheimer's Disease

Alzheimer's disease (AD) is a progressive and incurable brain disorder that has been associated with structural changes in brain phospholipids (PLs), including diacyl species and ether-linked PLs known as plasmalogens. Most studies have characterized total changes in brain PL pools (e.g., choline plasmalogens), particularly in prefrontal cortex, but detailed and quantitative information on the molecular PL species impacted by the disease is limited. In this study, we used a comprehensive mass-spectrometry method to quantify diacyl and plasmalogen species, alkyl synthetic precursors of plasmalogens, and lysophospholipid degradation products of diacyl and plasmalogen PLs, in postmortem samples of prefrontal cortex from 21 AD patients and 20 age-matched controls. Total PLs were also quantified with gas-chromatography analysis of bound fatty acids following thin layer chromatography isolation. There was a significant 27% reduction in the concentration (nmol/g wet weight) of choline plasmalogen containing stearic acid (alkenyl group) and docosahexaenoic acid in AD compared to controls. Stearic acid concentration in total PLs was reduced by 26%. Our findings suggest specific changes in PLs containing stearic acid and docosahexaenoic acid in AD prefrontal cortex, highlighting structural and turnover PL pathways that could be targeted.

Early Selective Vulnerability of the CA2 Hippocampal Subfield in Primary Age-Related Tauopathy

Primary age-related tauopathy (PART) is a neurodegenerative entity defined as Alzheimer-type neurofibrillary degeneration primarily affecting the medial temporal lobe with minimal to absent amyloid-β (Aβ) plaque deposition. The extent to which PART can be differentiated pathoanatomically from Alzheimer disease (AD) is unclear. Here, we examined the regional distribution of tau pathology in a large cohort of postmortem brains (n = 914). We found an early vulnerability of the CA2 subregion of the hippocampus to neurofibrillary degeneration in PART, and semiquantitative assessment of neurofibrillary degeneration in CA2 was significantly greater than in CA1 in PART. In contrast, subjects harboring intermediate-to-high AD neuropathologic change (ADNC) displayed relative sparing of CA2 until later stages of their disease course. In addition, the CA2/CA1 ratio of neurofibrillary degeneration in PART was significantly higher than in subjects with intermediate-to-high ADNC burden. Furthermore, the distribution of tau pathology in PART diverges from the Braak NFT staging system and Braak stage does not correlate with cognitive function in PART as it does in individuals with intermediate-to-high ADNC. These findings highlight the need for a better understanding of the contribution of PART to cognitive impairment and how neurofibrillary degeneration interacts with Aβ pathology in AD and PART.

Influence of APOE genotype in primary age-related tauopathy

The term “Primary age-related tauopathy” (PART) was coined in 2014 to describe the common neuropathological observation of neurofibrillary tangles without associated beta-amyloid (Aβ) pathology. It is possible for PART pathology to be present in both cognitively normal and cognitively impaired individuals. Genetically, Apolipoprotein E (APOE) ε4 has been shown to occur less commonly in PART than in Alzheimer’s disease (AD). Here, we investigate the relationships between PART, AD and those pathologically normal for age, with an emphasis on APOE and cognition, using 152 selected participants from The University of Manchester Longitudinal Study of Cognition in Normal Healthy Old Age and the Manchester arm of the Brains for Dementia Research cohort. APOE genotype differed between PART and AD with APOE ε2 more common in the former and APOE ε4 more common in the latter. Individuals with definite PART were less likely to be cognitively impaired than those with AD and those with pathology considered pathologically normal for age. We postulate that the lack of Aβ in definite PART cases may be due either to an increased frequency of APOE ε2 or decreased frequency of APOE ε4 as their resulting protein isoforms have differing binding properties in relation to Aβ. Similarly, an increased frequency of APOE ε2 or decreased frequency of APOE ε4 may lead to decreased levels of cognitive impairment, which raises questions regarding the impact of Aβ pathology on overall cognition in elderly subjects. We suggest that it may be possible to use the increased frequency of APOE ε2 in definite PART to assist neuropathological diagnosis.

Neuropathological assessment of the Alzheimer spectrum

Alzheimer disease (AD), the most common form of dementia globally, classically defined a clinicopathological entity, is a heterogenous disorder with various pathobiological subtypes, currently referred to as Alzheimer continuum. Its morphological hallmarks are extracellular parenchymal β-amyloid (amyloid plaques) and intraneuronal (tau aggregates forming neurofibrillary tangles) lesions accompanied by synaptic loss and vascular amyloid deposits, that are essential for the pathological diagnosis of AD. In addition to "classical" AD, several subtypes with characteristic regional patterns of tau pathology have been described that show distinct clinical features, differences in age, sex distribution, biomarker levels, and patterns of key network destructions responsible for cognitive decline. AD is a mixed proteinopathy (amyloid and tau), frequently associated with other age-related co-pathologies, such as cerebrovascular lesions, Lewy and TDP-43 pathologies, hippocampal sclerosis, or argyrophilic grain disease. These and other co-pathologies essentially influence the clinical picture of AD and may accelerate disease progression. The purpose of this review is to provide a critical overview of AD pathology, its defining pathological substrates, and the heterogeneity among the Alzheimer spectrum entities that may provide a broader diagnostic coverage of this devastating disorder as a basis for implementing precision medicine approaches and for ultimate development of successful disease-modifying drugs for AD.

Primary Age-Related Tauopathy (PART): Addressing the Spectrum of Neuronal Tauopathic Changes in the Aging Brain

PURPOSE OF REVIEW

Primary age-related tauopathy (PART) was recently proposed as a pathologic diagnosis for brains that harbor neurofibrillary tangles (Braak stage ≤ 4) with little, if any, amyloid burden. We sought to review the clinicopathologic findings related to PART.

RECENT FINDINGS

Most adult human brains show at least focal tauopathic changes, and the majority of individuals with PART do not progress to dementia. Older age and cognitive impairment correlate with increased Braak stage, and multivariate analyses suggest that the rate of cognitive decline is less than matched patients with Alzheimer disease (AD). It remains unclear whether PART is a distinct tauopathic entity separate from AD or rather represents an earlier histologic stage of AD. Cognitive decline in PART is usually milder than AD and correlates with tauopathic burden. Biomarker and ligand-based radiologic studies will be important to define PART antemortem and prospectively follow its natural history.

Aging and Alzheimer's disease pathology

The number of people with dementia worldwide is predicted to increase to 131.5 million by 2050. When studying dementia, understanding the basis of the neuropathological background is very important. Taking Alzheimer's disease (AD) neuropathology as an example, we know that the accumulation of abnormal structures such as senile plaques and neurofibrillary tangles is a hallmark. Macroscopic atrophy affects the entorhinal area and hippocampus, amygdala, and associative regions of the neocortex. Braak advocates the spread of tau deposits from the entorhinal to associative regions of the neocortex as the disease progresses. If the AD has only tau pathology, the degree and distribution of tau deposition may be associated with clinical symptoms. However, AD is also accompanied by amyloid-β deposition and even atrophy. Although it is possible to make a neuropathological diagnosis of AD from the spread of amyloid and tau depositions, neuropathological abnormal protein accumulation cannot explain all clinical symptoms of AD. There is an ambiguity between clinical symptoms and neuropathological findings. It is important to understand neuropathological findings while understanding that this ambiguity exists. So, for the reader's help, first we briefly explain the changes in the brain with age, and then describe AD as a typical disease of dementia; finally we will describe the diseases that mimic AD for neurologists who are not experts in neuropathology.

Magnetic resonance imaging brain atrophy assessment in primary age-related tauopathy (PART)

Alzheimer disease (AD) is a neurodegenerative disorder characterized pathologically by the accumulation of amyloid-beta (Aβ) plaques and tau neurofibrillary tangles (NFTs). Recently, primary age-related tauopathy (PART) has been described as a new anatomopathological disorder where NFTs are the main feature in the absence of neuritic plaques. However, since PART has mainly been studied in post-mortem patient brains, not much is known about the clinical or neuroimaging characteristics of PART. Here, we studied the clinical brain imaging characteristics of PART focusing on neuroanatomical vulnerability by applying a previously validated multiregion visual atrophy scale. We analysed 26 cases with confirmed PART with paired clinical magnetic resonance imaging (MRI) acquisitions. In this selected cohort we found that upon correcting for the effect of age, there is increased atrophy in the medial temporal region with increasing Braak staging (r = 0.3937, p = 0.0466). Upon controlling for Braak staging effect, predominantly two regions, anterior temporal (r = 0.3638, p = 0.0677) and medial temporal (r = 0.3836, p = 0.053), show a trend for increased atrophy with increasing age. Moreover, anterior temporal lobe atrophy was associated with decreased semantic memory/language (r = - 0.5823, p = 0.0056; and r = - 0.6371, p = 0.0019, respectively), as was medial temporal lobe atrophy (r = - 0.4445, p = 0.0435). Overall, these findings support that PART is associated with medial temporal lobe atrophy and predominantly affects semantic memory/language. These findings highlight that other factors associated with aging and beyond NFTs could be involved in PART pathophysiology.

Cellular and regional vulnerability in frontotemporal tauopathies

The frontotemporal tauopathies all deposit abnormal tau protein aggregates, but often of only certain isoforms and in distinguishing pathologies of five main types (neuronal Pick bodies, neurofibrillary tangles, astrocytic plaques, tufted astrocytes, globular glial inclusions and argyrophilic grains). In those with isoform specific tau aggregates glial pathologies are substantial, even though there is limited evidence that these cells normally produce tau protein. This review will assess the differentiating features and clinicopathological correlations of the frontotemporal tauopathies, the genetic predisposition for these different pathologies, their neuroanatomical selectivity, current observations on how they spread through the brain, and any potential contributing cellular and molecular changes. The findings show that diverse clinical phenotypes relate most to the brain region degenerating rather than the type of pathology involved, that different regions on the MAPT gene and novel risk genes are associated with specific tau pathologies, that the 4-repeat glial tauopathies do not follow individual patterns of spreading as identified for neuronal pathologies, and that genetic and pathological data indicate that neuroinflammatory mechanisms are involved. Each pathological frontotemporal tauopathy subtype with their distinct pathological features differ substantially in the cell type affected, morphology, biochemical and anatomical distribution of inclusions, a fundamental concept central to future success in understanding the disease mechanisms required for developing therapeutic interventions. Tau directed therapies targeting genetic mechanisms, tau aggregation and pathological spread are being trialled, although biomarkers that differentiate these diseases are required. Suggested areas of future research to address the regional and cellular vulnerabilities in frontotemporal tauopathies are discussed.

Primary Age-Related Tauopathy: An Elderly Brain Pathology Frequently Encountered during Autopsy

Due to the progressive aging of Korean society and the introduction of brain banks to the Korean medical system, the possibility that pathologists will have access to healthy elderly brains has increased. The histopathological analysis of an elderly brain from a subject with relatively well-preserved cognition is quite different from that of a brain from a demented subject. Additionally, the histology of elderly brains differs from that of young brains. This brief review discusses primary age-related tauopathy; this term was coined to describe elderly brains with Alzheimer’s diseasetype neurofibrillary tangles mainly confined to medial temporal structures, and no β-amyloid pathology.

Heritability in frontotemporal tauopathies

Introduction

Exploring the degree of heritability in a large cohort of frontotemporal lobar degeneration with tau-immunopositive inclusions (FTLD-tau) and determining if different FTLD-tau subtypes are associated with stronger heritability will provide important insight into disease pathogenesis.

Methods

Using modified Goldman pedigree classifications, heritability was examined in pathologically proven FTLD-tau cases with dementia at any time (n = 124) from the Sydney-Cambridge collection.

Results

Thirteen percent of the FTLD-tau cohort have a suggested autosomal dominant pattern of inheritance, 25% have some family history, and 62% apparently sporadic. MAPT mutations were found in 9% of cases. Globular glial tauopathy was associated with the strongest heritability with 40% having a suggested autosomal dominant pattern of inheritance followed by corticobasal degeneration (19%), Pick's disease (8%), and progressive supranuclear palsy (6%).

Discussion

Similar to clinical frontotemporal dementia syndromes, heritability varies between pathological subtypes. Further identification of a genetic link in cases with strong heritability await discovery.

Tauopathy: A common mechanism for neurodegeneration and brain aging

Tau, a microtubule-associated protein promotes assembly and stability of microtubules which is related to axoplasmic flow and critical neuronal activities upon physiological conditions. Under neurodegenerative condition such as in Alzheimer's Disease (AD), tau-microtubule binding dynamics and equilibrium are severely affected due to its aberrant post-translational modifications including acetylation and hyperphosphorylation. This event results in its conformational changes to form neurofibrillary tangles (NFT) after aggregation in the cytosol. The formation of NFT is more strongly correlated with cognitive decline than the distribution of senile plaque, which is formed by polymorphous beta-amyloid (Aβ) protein deposits, another pathological hallmark of AD. In neurodegenerative conditions, other than AD, the disease manifestation is correlated with mutations of the MAPT gene. In Primary age-related tauopathy (PART), which is commonly observed in the brains of aged individuals, tau deposition is directly correlated with cognitive deficits even in the absence of Aβ deposition. Thus, tauopathy has been considered as an essential hallmark in neurodegeneration and normal brain aging. In this review, we highlighted the recent progress about the tauopathies in the light of its posttranslational modifications and its implication in AD and the aged brain.

Ten Years of Tau-Targeted Immunotherapy: The Path Walked and the Roads Ahead

Neurofibrillary pathology comprised of pathological tau protein is closely tied to a range of neurodegenerative disorders, the most common of which is Alzheimer's disease. While they are individually rarer, a range of other disorders, the tauopathies (including Pick's disease, progressive supranuclear palsy, corticobasal degeneration, primary progressive aphasia, and ∼50% of behavioral variant frontotemporal dementia cases) display pronounced underlying tau pathology. In all cases, the distribution and amount of tau pathology closely correlates with the severity and phenotype of cognitive impairment, and with the pattern and degree of brain atrophy. Successfully counteracting tau pathology is likely to halt or slow the progression of these debilitating disorders. This makes tau a target of prime importance, yet an elusive one. The diversity of the tau proteome and post-translational modifications, as well as pathophysiology of tau are reviewed. Beginning 2013, a range of tau-targeted immunotherapies have entered clinical development; these therapies, and their common themes and differences are reviewed. The manuscript provides an extensive discussion on epitope selection for immunotherapies against tau pathology, on immunological mechanisms involved in their action, and challenges such as immune senescence, vaccine design, or evolution of epitopes. Furthermore, we provide methodological recommendations for the characterization of active vaccines and antibodies, animal models, and the target itself - the diseased tau proteome.

Smaller Hippocampal Volume and Degraded Peripheral Hearing Among Japanese Community Dwellers

A growing body of literature has demonstrated that dementia and hearing loss are interrelated. Recent interest in dementia research has expanded to brain imaging analyses with auditory function. The aim of this study was to investigate the link between hearing ability, which was assessed using pure-tone audiometry, and the volume of brain regions, specifically the hippocampus, entorhinal cortex, Heschl's gyrus, and total gray matter, using Freesurfer software and T1-weighted brain magnetic resonance imaging. The data for 2082 samples (age range = 40-89 years) were extracted from a population-based cohort of community dwellers. Hearing-impaired individuals showed significantly smaller hippocampal volumes compared with their non-hearing-impaired counterparts for all auditory frequency ranges. In addition, a correlational analysis showed a significant dose-response relationship for hearing ability and hippocampal volume after adjusting for potential confounding factors so that the more degraded the peripheral hearing was, the smaller the hippocampal volume was. This association was consistent through the auditory frequency range. The volume of the entorhinal cortex, right Heschl's gyrus and total gray matter did not correlate with hearing level at any frequency. The volume of the left Heschl's gyrus showed a significant relationship with the hearing levels for some auditory frequencies. The current results suggested that the presence of hearing loss after middle age could be a modifier of hippocampal atrophy.

Cognitive composite score association with Alzheimer's disease plaque and tangle pathology

BACKGROUND

Cognitive composite scores are used as the primary outcome measures for Alzheimer's disease (AD) prevention trials; however, the extent to which these composite measures correlate with AD pathology has not been fully investigated. Since many on-going AD prevention studies are testing therapies that target either amyloid or tau, we sought to establish an association between a cognitive composite score and the underlying pathology of AD.

METHODS

Data from 192 older deceased and autopsied persons from the Rush Religious Order Study were used in this study. All participants were classified at their initial evaluations with a clinical diagnosis of no cognitive impairment (NCI). Of these individuals, 105 remained NCI at the time of their death while the remaining 87 progressed to mild cognitive impairment (MCI) or AD. A cognitive composite score composed of eight cognitive tests was used as the outcome measure. Individuals were classified into groups based on Consortium to Establish a Registry for Alzheimer's Disease (CERAD) neuropathological diagnosis and Braak stage.

RESULTS

The rate of annualized composite score decline was significantly greater for the high CERAD (p < 0.001, d = 0.56) and Braak (p < 0.001, d = 0.55) groups compared with the low CERAD and Braak groups, respectively. Mixed-model repeated measure (MMRM) analyses revealed a significantly greater difference in composite score change from baseline for the high CERAD group relative to the low CERAD group after 5 years (Δ = -2.74, 95% confidence interval (CI) -5.01 to -0.47; p = 0.02). A similar analysis between low and high Braak stage groups found no significant difference in change from baseline (Δ = -0.69, 95% CI -3.03 to 1.66; p = 0.56).

CONCLUSIONS

These data provide evidence that decreased cognitive composite scores were significantly associated with increased AD pathology and provide support for the use of cognitive composite scores in AD prevention trials.

Retiring the term FTDP-17 as MAPT mutations are genetic forms of sporadic frontotemporal tauopathies

See Josephs (doi:10.1093/brain/awx367) for a scientific commentary on this article.In many neurodegenerative disorders, familial forms have provided important insights into the pathogenesis of their corresponding sporadic forms. The first mutations associated with frontotemporal lobar degeneration (FTLD) were found in the microtubule-associated protein tau (MAPT) gene on chromosome 17 in families with frontotemporal degeneration and parkinsonism (FTDP-17). However, it was soon discovered that 50% of these families had a nearby mutation in progranulin. Regardless, the original FTDP-17 nomenclature has been retained for patients with MAPT mutations, with such patients currently classified independently from the different sporadic forms of FTLD with tau-immunoreactive inclusions (FTLD-tau). The separate classification of familial FTLD with MAPT mutations implies that familial forms cannot inform on the pathogenesis of the different sporadic forms of FTLD-tau. To test this assumption, this study pathologically assessed all FTLD-tau cases with a known MAPT mutation held by the Sydney and Cambridge Brain Banks, and compared them to four cases of four subtypes of sporadic FTLD-tau, in addition to published case reports. Ten FTLD-tau cases with a MAPT mutation (K257T, S305S, P301L, IVS10+16, R406W) were screened for the core differentiating neuropathological features used to diagnose the different sporadic FTLD-tau subtypes to determine whether the categorical separation of MAPT mutations from sporadic FTLD-tau is valid. Compared with sporadic cases, FTLD-tau cases with MAPT mutations had similar mean disease duration but were younger at age of symptom onset (55 ± 4 years versus 70 ± 6 years). Interestingly, FTLD-tau cases with MAPT mutations had similar patterns and severity of neuropathological features to sporadic FTLD-tau subtypes and could be classified into: Pick's disease (K257T), corticobasal degeneration (S305S, IVS10‰+‰16, R406W), progressive supranuclear palsy (S305S) or globular glial tauopathy (P301L, IVS10‰+‰16). The finding that the S305S mutation could be classified into two tauopathies suggests additional modifying factors. Assessment of our cases and previous reports suggests that distinct MAPT mutations result in particular FTLD-tau subtypes, supporting the concept that they are likely to inform on the varied cellular mechanisms involved in distinctive forms of sporadic FTLD-tau. As such, FTLD-tau cases with MAPT mutations should be considered familial forms of FTLD-tau subtypes rather than a separate FTDP-17 category, and continued research on the effects of different mutations more focused on modelling their impact to produce the very different sporadic FTLD-tau pathologies in animal and cellular models.

Tauopathies

Tauopathies are neurodegenerative disorders characterized by the deposition of abnormal tau protein in the brain. The spectrum of tau pathologies expands beyond the traditionally discussed disease forms like Pick disease, progressive supranuclear palsy, corticobasal degeneration, and argyrophilic grain disease. Emerging entities and pathologies include globular glial tauopathies, primary age-related tauopathy, which includes neurofibrillary tangle dementia, chronic traumatic encephalopathy (CTE), and aging-related tau astrogliopathy. Clinical symptoms include frontotemporal dementia, corticobasal syndrome, Richardson syndrome, parkinsonism, pure akinesia with gait freezing and, rarely, motor neuron symptoms or cerebellar ataxia. Some disorders show specific neuroimaging features, while examination of the cerebrospinal fluid awaits markers for in vivo stratification of cases. The possibility of cell-to-cell propagation is a novel aspect of the pathogenesis of tauopathies, which is partly reflected by the hierarchic involvement of anatomic regions. This concept might have relevance for the development of therapies. For cost-effective screening for tau pathologies in neuropathologic practice, examination of the hippocampus, amygdala, and basal ganglia is recommended. Uncommon morphologies or unusually extensive forms of tau pathologies should raise the suspicion of a genetic background. Ongoing multidisciplinary studies are needed to understand the whole spectrum and significance of tau pathologies.

Brainstem tau pathology in Alzheimer's disease is characterized by increase of three repeat tau and independent of amyloid β

INTRODUCTION

Alzheimer-type neuropil threads (NTs) and neurofibrillary tangles (NFTs) are comprised of either 4 repeat (4R)-tau, 3 repeat (3R)-tau, or a mixture of both. In the hippocampus, the number of NFTs, and the proportion of 3R tau progressively increases. If this preferential accumulation of 3R tau also occurs in the brainstem, it may be fundamentally related to progression of Alzheimer pathology.

METHODS

Midbrain and pontine sections of brainstems from 23 cases (Braak-NFT stages I/II: 8, III/IV: 8, and V/VI: 7) were double immunofluorolabeled for 4R and 3R tau. High-resolution (0.645 μm/pixel), in-focus snapshots were tiled to cover entire brain sections using a virtual slide system. Each lesion was classified by size (NT < 200 μm² < NFT) and staining profile (3R/4R). In addition, the localization and quantity of amyloid β (Aβ) deposits were examined in adjacent sections for comparison with tau.

RESULTS

The data sets obtained from approximately 286 gigabytes of image files consisted of 847,763 NTs and 7859 NFTs. The proportion of 3R tau-positive NTs and NFTs in the midbrain, and 3R tau-positive NTs in the pons gradually increased with advancing NFT stages, while the proportion of 3R tau-positive NFTs in the pons was already elevated at early stages. Aβ deposits were absent at NFT stages I/II, and when present at later stages, their regional distribution was different from that of tau. These observations suggest that a progressive increase in the proportion of 3R tau occurs independently of Aβ deposits.

CONCLUSIONS

This is the first quantitative analysis of NFTs and NTs in the human brainstem. We demonstrate that the proportion of 3R tau in the brainstem neurofibrillary changes increases with disease progression. Because this phenomenon is shared between the brainstem and the hippocampus, this increase may be fundamental to the pathogenesis of Alzheimer disease.

Cognitive decline associated with pathological burden in primary age-related tauopathy

INTRODUCTION

Primary age-related tauopathy (PART) is a neuropathological diagnosis characterized by tau neurofibrillary tangles (NFTs) in the absence of amyloid plaque pathology. Although most individuals over 50 years of age have evidence of NFTs, the clinical and cognitive consequences of PART are not known.

METHODS

We evaluated 226 neuropathologically confirmed PART cases from the National Alzheimer's Coordinating Center database who participated in a total of 846 longitudinal neuropsychological assessments from the Alzheimer's Disease Center program's Uniform Data Set. Mixed-effects statistical models tested whether cognitive decline was associated with Braak stage NFT burden.

RESULTS

Higher stages of NFT burden in PART, with no evidence or minimal evidence of amyloid pathology, were associated with more rapid decline on tasks involving episodic and semantic memory along with tests of processing speed and attention.

DISCUSSION

We conclude that PART has cognitive consequences that should be considered in the context of emerging tau-targeted therapies in age-associated neurodegenerative diseases.

An Autopsy Proven Child Onset Chronic Traumatic Encephalopathy

Here we present an autopsy case of chronic traumatic encephalopathy (CTE) in a 36-year-old man. He had a history of febrile seizures at the age of four and was severely demented at age 10 when he was admitted to a mental hospital. He had suffered repetitive self-harm, such as frequent banging of the head on the wall in his hospital record, but he had no clear history between the ages of four and ten. Autopsy revealed global cerebral atrophy, including the basal ganglia, thalamus, hippocampus, amygdala, mammilary bodies and lateral geniculate bodies. This case showed typical pathological features of CTE. Phosphorylated tau (p-tau)-positive neurofibrillary tangles (NFTs) and neuropil threads (NT) we are widely distributed in the brain, especially in the depth of the cerebral sulci. NFT and NT were also found in the basal ganglia, thalamus, amygdala and brainstem. Scanty β-amyloid deposits were found in the motor and sensory cortices, but α-synuclein was completely negative in the brain. This example showed that CTE can occur in young ages and that even children can experience CTE dementia.

Suspected non-Alzheimer's pathology - Is it non-Alzheimer's or non-amyloid?

Neurodegeneration, the progressive loss of neurons, is a major process involved in dementia and age-related cognitive impairment. It can be detected clinically using currently available biomarker tests. Suspected Non-Alzheimer Pathology (SNAP) is a biomarker-based concept that encompasses a group of individuals with neurodegeneration, but no evidence of amyloid deposition (thereby distinguishing it from Alzheimer's disease (AD)). These individuals may often have a clinical diagnosis of AD, but their clinical features, genetic susceptibility and progression can differ significantly, carrying crucial implications for precise diagnostics, clinical management, and efficacy of clinical drug trials. SNAP has caused wide interest in the dementia research community, because it is still unclear whether it represents distinct pathology separate from AD, or whether in some individuals, it could represent the earliest stage of AD. This debate has raised pertinent questions about the pathways to AD, the need for biomarkers, and the sensitivity of current biomarker tests. In this review, we discuss the biomarker and imaging trials that first recognized SNAP. We describe the pathological correlates of SNAP and comment on the different causes of neurodegeneration. Finally, we discuss the debate around the concept of SNAP, and further unanswered questions that are emerging.