Hippocampal Sclerosis in the Oldest Old: A Finnish Population-Based Study

Limbic-predominant age-related TDP-43 encephalopathy (LATE-NC): Co-pathologies and genetic risk factors provide clues about pathogenesis

Limbic-predominant age-related TDP-43 encephalopathy neuropathologic change (LATE-NC) is detectable at autopsy in more than one-third of people beyond age 85 years and is robustly associated with dementia independent of other pathologies. Although LATE-NC has a large impact on public health, there remain uncertainties about the underlying biologic mechanisms. Here, we review the literature from human studies that may shed light on pathogenetic mechanisms. It is increasingly clear that certain combinations of pathologic changes tend to coexist in aging brains. Although "pure" LATE-NC is not rare, LATE-NC often coexists in the same brains with Alzheimer disease neuropathologic change, brain arteriolosclerosis, hippocampal sclerosis of aging, and/or age-related tau astrogliopathy (ARTAG). The patterns of pathologic comorbidities provide circumstantial evidence of mechanistic interactions ("synergies") between the pathologies, and also suggest common upstream influences. As to primary mediators of vulnerability to neuropathologic changes, genetics may play key roles. Genes associated with LATE-NC include TMEM106B, GRN, APOE, SORL1, ABCC9, and others. Although the anatomic distribution of TDP-43 pathology defines the condition, important cofactors for LATE-NC may include Tau pathology, endolysosomal pathways, and blood-brain barrier dysfunction. A review of the human phenomenology offers insights into disease-driving mechanisms, and may provide clues for diagnostic and therapeutic targets.

In severe ADNC, hippocampi with comorbid LATE-NC and hippocampal sclerosis have substantially more astrocytosis than those with LATE-NC or hippocampal sclerosis alone

Limbic-predominant age-related TDP-43 encephalopathy neuropathologic change (LATE-NC) and hippocampal sclerosis of aging (HS-A) pathologies are found together at autopsy in ∼20% of elderly demented persons. Although astrocytosis is known to occur in neurodegenerative diseases, it is currently unknown how the severity of astrocytosis is correlated with the common combinations of pathologies in aging brains. To address this knowledge gap, we analyzed a convenience sample of autopsied subjects from the University of Kentucky Alzheimer's Disease Research Center community-based autopsy cohort. The subjects were stratified into 5 groups (n = 51 total): pure ADNC, ADNC + LATE-NC, ADNC + HS-A, ADNC + LATE-NC + HS-A, and low-pathology controls. Following GFAP immunostaining and digital slide scanning with a ScanScope, we measured GFAP-immunoreactive astrocytosis. The severities of GFAP-immunoreactive astrocytosis in hippocampal subfield CA1 and subiculum were compared between groups. The group with ADNC + LATE-NC + HS-A had the most astrocytosis as operationalized by either any GFAP+ or strong GFAP+ immunoreactivity in both CA1 and subiculum. In comparison to that pathologic combination, ADNC + HS or ADNC + LATE-NC alone showed lower astrocytosis. Pure ADNC had only marginally increased astrocytosis in CA1 and subiculum, in comparison to low-pathology controls. We conclude that there appeared to be pathogenetic synergy such that ADNC + LATE-NC + HS-A cases had relatively high levels of astrocytosis in the hippocampal formation.

Characterization of hippocampal sclerosis of aging and its association with other neuropathologic changes and cognitive deficits in the oldest-old

Hippocampal sclerosis of aging (HS-A) is a common age-related neuropathological lesion characterized by neuronal loss and astrogliosis in subiculum and CA1 subfield of hippocampus. HS-A is associated with cognitive decline that mimics Alzheimer's disease. Pathological diagnosis of HS-A is traditionally binary based on presence/absence of the lesion. We compared this traditional measure against our novel quantitative measure for studying the relationship between HS-A and other neuropathologies and cognitive impairment. We included 409 participants from The 90+ study with neuropathological examination and longitudinal neuropsychological assessments. In those with HS-A, we examined digitized H&E and LFB stained hippocampal slides. The length of HS-A in each subfield of hippocampus and subiculum, each further divided into three subregions, was measured using Aperio eSlide Manager. For each subregion, the proportion affected by HS-A was calculated. Using regression models, both traditional/binary and quantitative measures were used to study the relationship between HS-A and other neuropathological changes and cognitive outcomes. HS-A was present in 48 (12%) of participants and was always focal, primarily affecting CA1 (73%), followed by subiculum (9%); overlapping pathology (subiculum and CA1) affected 18% of individuals. HS-A was more common in the left (82%) than the right (25%) hemisphere and was bilateral in 7% of participants. HS-A traditional/binary assessment was associated with limbic-predominant age-related TDP-43 encephalopathy (LATE-NC; OR = 3.45, p < 0.001) and aging-related tau astrogliopathy (ARTAG; OR = 2.72, p = 0.008). In contrast, our quantitative approach showed associations between the proportion of HS-A (CA1/subiculum/combined) and LATE-NC (p = 0.001) and arteriolosclerosis (p = 0.005). While traditional binary assessment of HS-A was associated with impaired memory (OR = 2.60, p = 0.007), calculations (OR = 2.16, p = 0.027), and orientation (OR = 3.56, p < 0.001), our quantitative approach revealed additional associations with impairments in language (OR = 1.33, p = 0.018) and visuospatial domains (OR = 1.37, p = 0.006). Our novel quantitative method revealed associations between HS-A and vascular pathologies and impairment in cognitive domains that were not detected using traditional/binary measures.

Performance of a condensed protocol to assess limbic-predominant age-related TDP-43 encephalopathy neuropathologic change

Limbic-predominant age-related TDP-43 encephalopathy neuropathologic change (LATE-NC) is a dementia-related proteinopathy common in the elderly population. LATE-NC stages 2 or 3 are consistently associated with cognitive impairment. A condensed protocol (CP) for the assessment of Alzheimer disease neuropathologic change and other disorders associated with cognitive impairment, recommended sampling of small brain portions from specific neuroanatomic regions that were consolidated, resulting in significant cost reduction. Formal evaluation of the CP for LATE-NC staging was not previously performed. Here, we determined the ability of the CP to identify LATE-NC stages 2 or 3. Forty brains donated to the University of Washington BioRepository and Integrated Neuropathology laboratory with known LATE-NC status were resampled. Slides containing brain regions required for LATE-NC staging were immunostained for phospho-TDP-43 and reviewed by 6 neuropathologists blinded to original LATE-NC diagnosis. Overall group performance distinguishing between LATE-NC stages 0-1 and 2-3 was 85% (confidence interval [CI]: 75%-92%). We also used the CP to evaluate LATE-NC in a hospital autopsy cohort, in which LATE-NC was more common in individuals with a history of cognitive impairment, older age, and/or comorbid hippocampal sclerosis. This study shows that the CP can effectively discriminate higher stages of LATE-NC from low or no LATE-NC and that it can be successfully applied in clinical practice using a single tissue block and immunostain.

LATE-NC staging in routine neuropathologic diagnosis: an update

An international consensus report in 2019 recommended a classification system for limbic-predominant age-related TDP-43 encephalopathy neuropathologic changes (LATE-NC). The suggested neuropathologic staging system and nomenclature have proven useful for autopsy practice and dementia research. However, some issues remain unresolved, such as cases with unusual features that do not fit with current diagnostic categories. The goal of this report is to update the neuropathologic criteria for the diagnosis and staging of LATE-NC, based primarily on published data. We provide practical suggestions about how to integrate available genetic information and comorbid pathologies [e.g., Alzheimer's disease neuropathologic changes (ADNC) and Lewy body disease]. We also describe recent research findings that have enabled more precise guidance on how to differentiate LATE-NC from other subtypes of TDP-43 pathology [e.g., frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS)], and how to render diagnoses in unusual situations in which TDP-43 pathology does not follow the staging scheme proposed in 2019. Specific recommendations are also made on when not to apply this diagnostic term based on current knowledge. Neuroanatomical regions of interest in LATE-NC are described in detail and the implications for TDP-43 immunohistochemical results are specified more precisely. We also highlight questions that remain unresolved and areas needing additional study. In summary, the current work lays out a number of recommendations to improve the precision of LATE-NC staging based on published reports and diagnostic experience.

Frequency of LATE neuropathologic change across the spectrum of Alzheimer's disease neuropathology: combined data from 13 community-based or population-based autopsy cohorts

Limbic-predominant age-related TDP-43 encephalopathy neuropathologic change (LATE-NC) and Alzheimer's disease neuropathologic change (ADNC) are each associated with substantial cognitive impairment in aging populations. However, the prevalence of LATE-NC across the full range of ADNC remains uncertain. To address this knowledge gap, neuropathologic, genetic, and clinical data were compiled from 13 high-quality community- and population-based longitudinal studies. Participants were recruited from United States (8 cohorts, including one focusing on Japanese-American men), United Kingdom (2 cohorts), Brazil, Austria, and Finland. The total number of participants included was 6196, and the average age of death was 88.1 years. Not all data were available on each individual and there were differences between the cohorts in study designs and the amount of missing data. Among those with known cognitive status before death (n = 5665), 43.0% were cognitively normal, 14.9% had MCI, and 42.4% had dementia-broadly consistent with epidemiologic data in this age group. Approximately 99% of participants (n = 6125) had available CERAD neuritic amyloid plaque score data. In this subsample, 39.4% had autopsy-confirmed LATE-NC of any stage. Among brains with "frequent" neuritic amyloid plaques, 54.9% had comorbid LATE-NC, whereas in brains with no detected neuritic amyloid plaques, 27.0% had LATE-NC. Data on LATE-NC stages were available for 3803 participants, of which 25% had LATE-NC stage > 1 (associated with cognitive impairment). In the subset of individuals with Thal Aβ phase = 0 (lacking detectable Aβ plaques), the brains with LATE-NC had relatively more severe primary age-related tauopathy (PART). A total of 3267 participants had available clinical data relevant to frontotemporal dementia (FTD), and none were given the clinical diagnosis of definite FTD nor the pathological diagnosis of frontotemporal lobar degeneration with TDP-43 inclusions (FTLD-TDP). In the 10 cohorts with detailed neurocognitive assessments proximal to death, cognition tended to be worse with LATE-NC across the full spectrum of ADNC severity. This study provided a credible estimate of the current prevalence of LATE-NC in advanced age. LATE-NC was seen in almost 40% of participants and often, but not always, coexisted with Alzheimer's disease neuropathology.

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.

TDP-43 Related Neuropathologies and Phosphorylation State: Associations with Age and Clinical Dementia in the Cambridge City over-75s Cohort

Pathologies associated with the Tar-DNA binding protein 43 KDa (TDP-43) are associated with neurodegenerative diseases and aging. Phosphorylation of cellular proteins is a well-accepted mechanism of biological control and can be associated with disease pathways. Phosphorylation state associated with TDP-43 associated pathology has not been investigated with respect to dementia status in a population representative sample. TDP-43 immunohistochemistry directed toward phosphorylated (TDP-43P) and unphosphorylated (TDP-43U) was assessed in sections of hippocampus and temporal cortex from 222 brains donated to the population representative Cambridge City over-75s Cohort. Relationships between dementia status and age at death for TDP-43 immunoreactive pathologies by phosphorylation state were investigated. TDP-43 pathologies are common in the oldest old in the population and often do not conform to MacKenzie classification. Increasing age is associated with glial (TDP-43P) and neuronal inclusions (TDP-43P and TDP-43U), neurites, and granulovacuolar degeneration (GVD). Dementia status is associated with GVD and glial (TDP-43 P) and neural inclusions (TDP-43 P and U). Dementia severity was associated with glial (TDP-43P) and neuronal inclusions (TDP-43U and TDP-43P), GVD, and neurites. The associations between dementia severity and both glial cytoplasmic inclusions and GVD were independent from other pathologies and TDP-43 neuronal cytoplasmic inclusions. TDP-43 pathology contributes to dementia status and progression in a variety of ways in different phosphorylation states involving both neurons and glia, independently from age and from classic Alzheimer-related pathologies. TDP-43 pathologies as cytoplasmic inclusions in neurons or glia or as GVD contribute independently to dementia.

Utility of MRI in the identification of hippocampal sclerosis of aging

INTRODUCTION

Hippocampal sclerosis of aging (HS) is a common pathology often misdiagnosed as Alzheimer's disease. We tested the hypothesis that participants with HS would have a magnetic resonance imaging (MRI)-detectable hippocampal pattern of atrophy distinct from participants without HS, both with and without Alzheimer's disease neuropathology (ADNP).

METHODS

Query of the National Alzheimer's Coordinating Center database identified 198 participants with MRI and autopsy. Hippocampal subfields were segmented with FreeSurfer v6. Analysis of covariance for subfield volumes compared HS+ participants to those without HS, both with ADNP (HS-/ADNP+) and without (HS-/ADNP-).

RESULTS

HS+ participants (N = 27, 14%) showed atrophied cornu ammonis 1 (CA1; left P < .001, η_p ²  = 0.14; right P = .001, η_p ²  = 0.09) and subiculum (left P < .001, η_p ²  = 0.139; right P = .001, η_p ²  = 0.085) compared to HS-/ADNP+ (N = 100, 51%). Compared to HS-/ADNP- (N = 71, 36%), HS+ also had atrophy in subiculum (left P < .001, η_p ²  = 0.235; right P = .002, η_p ²  = 0.137) and CA1 (left P < .001, η_p ²  = 0.137; right P = .006, η_p ²  = 0.070).

DISCUSSION

Subiculum and CA1 atrophy from clinical MRI may be a promising in vivo biomarker for HS.

Limbic-predominant age-related TDP-43 encephalopathy, ADNC pathology, and cognitive decline in aging

OBJECTIVE

To examine the impact of 3 pathologic groups, pure limbic-predominant age-related transactive response DNA-binding protein 43 encephalopathy (LATE) neuropathologic changes (NC), pure Alzheimer disease neuropathologic change (ADNC), and mixed ADNC with LATE-NC, on late-life cognitive decline.

METHODS

Data came from 1,356 community-based older persons who completed detailed annual cognitive testing and systematic neuropathologic examination at autopsy to identify LATE-NC, ADNC, and other age-related pathologies. Persons were categorized into (0) a group without a pathologic diagnosis of LATE or ADNC (n = 378), (1) LATE-NC without ADNC (n = 91), (2) ADNC without LATE-NC (n = 535), and (3) mixed ADNC with LATE-NC (n = 352). We used mixed-effect models to examine the group associations with rate of decline in global cognition and 5 cognitive domains and then examined whether age modified associations.

RESULTS

Compared to those without LATE-NC or ADNC, those with pure LATE-NC had a faster decline in global cognition (p = 0.025) and episodic memory (p = 0.002); however, compared to persons with pure ADNC, those with pure LATE-NC showed a slower decline. Those with mixed ADNC with LATE-NC showed the fastest decline compared to those with either pathology alone. Persons ≥90 years of age with mixed ADNC with LATE-NC had slower cognitive decline compared to those ≤89 years of age.

CONCLUSION

Persons with pure LATE-NC follow a slower trajectory compared to those with pure ADNC. Those with mixed LATE/ADNC have a steeper decline than individuals with either pathology alone. In addition, age may modify the effect of pathology on cognitive decline. These findings have important implications for the development of biomarkers and prognosis for late-life cognitive decline.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that LATE-NC and Alzheimer disease pathologic changes are associated with different trajectories of late-life cognitive decline.

Concomitant LATE-NC in Alzheimer's disease is not associated with increased tau or amyloid-β pathological burden

AIMS

Limbic-predominant age-related TDP-43 encephalopathy neuropathological change (LATE-NC) is present in approximately 50% of Alzheimer's disease (AD) cases and is associated with accelerated cognitive decline. Studies indicate a potential synergistic relationship between LATE-NC and hyperphosphorylated tau. It is unknown if LATE-NC is an independent driver of cognitive impairment or exerts its influence through synergistic relationships with tau. This cliniconeuropathological study investigated the impact of LATE-NC on quantified measures of AD-associated pathology and its impact on clinical measures.

METHODS

A total of 61 AD cases underwent neuropathological assessment for LATE-NC and quantitative assessment [area covered by immunoreactivity (IR)] for early conformational tau (MC-1), late-stage hyperphosphorylated tau (AT8) and amyloid-β in the amygdala and five neocortical regions. Clinical measures included age of disease onset, final Mini-Mental State Examination (MMSE) score and rate of cognitive decline.

RESULTS

LATE-NC was present in 41 AD cases (AD/LATE-NC; 67.2%). No significant differences in MC-1-IR, AT8-IR or 4G8-IR were observed in any region between AD/LATE-NC and AD without LATE-NC, indicating no accelerated aggregation or hyperphosphorylation of tau proteins in the AD/LATE-NC cases. Final MMSE was significantly lower in AD/LATE-NC cases and was significantly associated with LATE-NC score even when controlled for the presence of both MC-1-IR and AT8-IR (P = 0.009).

CONCLUSION

The presence of LATE-NC in AD is not associated with an increase in the burden of early or late tau or Aβ pathology. LATE-NC is associated with a lower final MMSE score independent of tau pathology.

Hippocampal sclerosis, TDP-43, and the duration of the symptoms of dementia of AD patients

OBJECTIVES

To examine the relationship between duration of the cognitive symptoms, from the earliest reported symptom to death, and hippocampal sclerosis (HS) and TAR-DNA binding protein of 43kDA (TDP-43) in Alzheimer's disease (AD) patients.

METHODS

The study was conducted in 359 cognitively impaired patients who met the pathological criteria for AD (NIA-Reagan intermediate or high). The mean age at onset was 69.5 ± 8.8 years (range 37-95) and the mean duration of the symptoms was 10.5 ± 4.2 years. The association between symptoms duration and HS and TDP-43 was examined with logistic regression analyses controlling for age at death, atherosclerosis in the Circle of Willis (CW), cerebral infarcts, gender, baseline Mini Mental State Examination scores, APOE-4 allele, and presence of Lewy bodies (LB).

RESULTS

HS was present in 18% (n = 64) and TDP-43 in 51.5% (n = 185) of the patients. HS and TDP-43 were more frequent in patients whose symptoms lasted more than 10 years. LBs were present in 72% of the patients with HS and in 64% of the patients with TDP-43. Age at onset was not associated with TDP-43 or HS. HS was associated with duration of symptoms and LB, TDP-43, and atherosclerosis in the CW. TDP-43 was associated with duration of symptoms, LB, and HS.

INTERPRETATION

HS and TDP-43 are present in early and late onset AD. However, their presence is mainly driven by the duration of symptoms and the presence of LB. This suggests that HS and TDP-43 are part of the later neuropathological changes in AD.

Putative risk alleles for LATE-NC with hippocampal sclerosis in population-representative autopsy cohorts

Limbic‐predominant age‐related TAR‐DNA‐binding protein‐43 (TDP‐43) encephalopathy with hippocampal sclerosis pathology (LATE‐NC + HS) is a neurodegenerative disorder characterized by severe hippocampal CA1 neuron loss and TDP‐43‐pathology, leading to cognitive dysfunction and dementia. Polymorphisms in GRN, TMEM106B and ABCC9 are proposed as LATE‐NC + HS risk factors in brain bank collections. To replicate these results in independent population‐representative cohorts, hippocampal sections from brains donated to three such studies (Cambridge City over 75‐Cohort [CC75C], Cognitive Function and Ageing Study [CFAS], and Vantaa 85+ Study) were stained with hematoxylin–eosin (n = 744) and anti‐pTDP‐43 (n = 713), and evaluated for LATE‐NC + HS and TDP‐43 pathology. Single nucleotide polymorphism genotypes in GRN rs5848, TMEM106B rs1990622 and ABCC9 rs704178 were determined. LATE‐NC + HS (n = 58) was significantly associated with the GRN rs5848 genotype (χ²(2) = 20.61, P < 0.001) and T‐allele (χ²(1) = 21.04, P < 0.001), and TMEM106B rs1990622 genotype (Fisher's exact test, P < 0.001) and A‐allele (χ²(1) = 25.75, P < 0.001). No differences in ABCC9 rs704178 genotype or allele frequency were found between LATE‐NC + HS and non‐LATE‐NC + HS neuropathology cases. Dentate gyrus TDP‐43 pathology associated with GRN and TMEM106B variations, but the association with TMEM106B nullified when LATE‐NC + HS cases were excluded. Our results indicate that GRN and TMEM106B are associated with severe loss of CA1 neurons in the aging brain, while ABCC9 was not confirmed as a genetic risk factor for LATE‐NC + HS. The association between TMEM106B and LATE‐NC + HS may be independent of dentate TDP‐43 pathology.

Limbic-predominant age-related TDP-43 encephalopathy (LATE): consensus working group report

We describe a recently recognized disease entity, limbic-predominant age-related TDP-43 encephalopathy (LATE). LATE neuropathological change (LATE-NC) is defined by a stereotypical TDP-43 proteinopathy in older adults, with or without coexisting hippocampal sclerosis pathology. LATE-NC is a common TDP-43 proteinopathy, associated with an amnestic dementia syndrome that mimicked Alzheimer's-type dementia in retrospective autopsy studies. LATE is distinguished from frontotemporal lobar degeneration with TDP-43 pathology based on its epidemiology (LATE generally affects older subjects), and relatively restricted neuroanatomical distribution of TDP-43 proteinopathy. In community-based autopsy cohorts, ∼25% of brains had sufficient burden of LATE-NC to be associated with discernible cognitive impairment. Many subjects with LATE-NC have comorbid brain pathologies, often including amyloid-β plaques and tauopathy. Given that the 'oldest-old' are at greatest risk for LATE-NC, and subjects of advanced age constitute a rapidly growing demographic group in many countries, LATE has an expanding but under-recognized impact on public health. For these reasons, a working group was convened to develop diagnostic criteria for LATE, aiming both to stimulate research and to promote awareness of this pathway to dementia. We report consensus-based recommendations including guidelines for diagnosis and staging of LATE-NC. For routine autopsy workup of LATE-NC, an anatomically-based preliminary staging scheme is proposed with TDP-43 immunohistochemistry on tissue from three brain areas, reflecting a hierarchical pattern of brain involvement: amygdala, hippocampus, and middle frontal gyrus. LATE-NC appears to affect the medial temporal lobe structures preferentially, but other areas also are impacted. Neuroimaging studies demonstrated that subjects with LATE-NC also had atrophy in the medial temporal lobes, frontal cortex, and other brain regions. Genetic studies have thus far indicated five genes with risk alleles for LATE-NC: GRN, TMEM106B, ABCC9, KCNMB2, and APOE. The discovery of these genetic risk variants indicate that LATE shares pathogenetic mechanisms with both frontotemporal lobar degeneration and Alzheimer's disease, but also suggests disease-specific underlying mechanisms. Large gaps remain in our understanding of LATE. For advances in prevention, diagnosis, and treatment, there is an urgent need for research focused on LATE, including in vitro and animal models. An obstacle to clinical progress is lack of diagnostic tools, such as biofluid or neuroimaging biomarkers, for ante-mortem detection of LATE. Development of a disease biomarker would augment observational studies seeking to further define the risk factors, natural history, and clinical features of LATE, as well as eventual subject recruitment for targeted therapies in clinical trials.

TDP-43 proteinopathy in aging: Associations with risk-associated gene variants and with brain parenchymal thyroid hormone levels

TDP-43 proteinopathy is very prevalent among the elderly (affecting at least 25% of individuals over 85 years of age) and is associated with substantial cognitive impairment. Risk factors implicated in age-related TDP-43 proteinopathy include commonly inherited gene variants, comorbid Alzheimer's disease pathology, and thyroid hormone dysfunction. To test parameters that are associated with aging-related TDP-43 pathology, we performed exploratory analyses of pathologic, genetic, and biochemical data derived from research volunteers in the University of Kentucky Alzheimer's Disease Center autopsy cohort (n = 136 subjects). Digital pathologic methods were used to discriminate and quantify both neuritic and intracytoplasmic TDP-43 pathology in the hippocampal formation. Overall, 46.4% of the cases were positive for TDP-43 intracellular inclusions, which is consistent with results in other prior community-based cohorts. The pathologies were correlated with hippocampal sclerosis of aging (HS-Aging) linked genotypes. We also assayed brain parenchymal thyroid hormone (triiodothyronine [T3] and thyroxine [T4]) levels. In cases with SLCO1A2/IAPP or ABCC9 risk associated genotypes, the T3/T4 ratio tended to be reduced (p = .051 using 2-tailed statistical test), and in cases with low T3/T4 ratios (bottom quintile), there was a higher likelihood of HS-Aging pathology (p = .025 using 2-tailed statistical test). This is intriguing because the SLCO1A2/IAPP and ABCC9 risk associated genotypes have been associated with altered expression of the astrocytic thyroid hormone receptor (protein product of the nearby gene SLCO1C1). These data indicate that dysregulation of thyroid hormone signaling may play a role in age-related TDP-43 proteinopathy.

Prediction models for dementia and neuropathology in the oldest old: the Vantaa 85+ cohort study

Background

We developed multifactorial models for predicting incident dementia and brain pathology in the oldest old using the Vantaa 85+ cohort.

Methods

We included participants without dementia at baseline and at least 2 years of follow-up (N = 245) for dementia prediction or with autopsy data (N = 163) for pathology. A supervised machine learning method was used for model development, considering sociodemographic, cognitive, clinical, vascular, and lifestyle factors, as well as APOE genotype. Neuropathological assessments included β-amyloid, neurofibrillary tangles and neuritic plaques, cerebral amyloid angiopathy (CAA), macro- and microscopic infarcts, α-synuclein pathology, hippocampal sclerosis, and TDP-43.

Results

Prediction model performance was evaluated using AUC for 10 × 10-fold cross-validation. Overall AUCs were 0.73 for dementia, 0.64–0.68 for Alzheimer’s disease (AD)- or amyloid-related pathologies, 0.72 for macroinfarcts, and 0.61 for microinfarcts. Predictors for dementia were different from those in previous reports of younger populations; for example, age, sex, and vascular and lifestyle factors were not predictive. Predictors for dementia versus pathology were also different, because cognition and education predicted dementia but not AD- or amyloid-related pathologies. APOE genotype was most consistently present across all models. APOE alleles had a different impact: ε4 did not predict dementia, but it did predict all AD- or amyloid-related pathologies; ε2 predicted dementia, but it was protective against amyloid and neuropathological AD; and ε3ε3 was protective against dementia, neurofibrillary tangles, and CAA. Very few other factors were predictive of pathology.

Conclusions

Differences between predictors for dementia in younger old versus oldest old populations, as well as for dementia versus pathology, should be considered more carefully in future studies.

Electronic supplementary material

The online version of this article (10.1186/s13195-018-0450-3) contains supplementary material, which is available to authorized users.

Dichotomous scoring of TDP-43 proteinopathy from specific brain regions in 27 academic research centers: associations with Alzheimer's disease and cerebrovascular disease pathologies

TAR-DNA binding protein 43 (TDP-43) proteinopathy is a common brain pathology in elderly persons, but much remains to be learned about this high-morbidity condition. Published stage-based systems for operationalizing disease severity rely on the involvement (presence/absence) of pathology in specific anatomic regions. To examine the comorbidities associated with TDP-43 pathology in aged individuals, we studied data from the National Alzheimer's Coordinating Center (NACC) Neuropathology Data Set. Data were analyzed from 929 included subjects with available TDP-43 pathology information, sourced from 27 different American Alzheimer's Disease Centers (ADCs). Cases with relatively unusual diseases including autopsy-proven frontotemporal lobar degeneration (FTLD-TDP or FTLD-tau) were excluded from the study. Our data provide new information about pathologic features that are and are not associated with TDP-43 pathologies in different brain areas-spinal cord, amygdala, hippocampus, entorhinal cortex/inferior temporal cortex, and frontal neocortex. Different research centers used cite-specific methods including different TDP-43 antibodies. TDP-43 pathology in at least one brain region was common (31.4%) but the pathology was rarely observed in spinal cord (1.8%) and also unusual in frontal cortex (5.3%). As expected, TDP-43 pathology was positively associated with comorbid hippocampal sclerosis pathology and with severe AD pathology. TDP-43 pathology was also associated with comorbid moderate-to-severe brain arteriolosclerosis. The association between TDP-43 pathology and brain arteriolosclerosis appears relatively specific since there was no detected association between TDP-43 pathology and microinfarcts, lacunar infarcts, large infarcts, cerebral amyloid angiopathy (CAA), or circle of Willis atherosclerosis. Together, these observations provide support for the hypothesis that many aged brains are affected by a TDP-43 proteinopathy that is more likely to be seen in brains with AD pathology, arteriolosclerosis pathology, or both.

Autopsied centenarian case of Alzheimer's disease combined with hippocampal sclerosis, TDP-43, and α-synuclein pathologies

A Japanese woman showed slowly progressive memory disturbance starting at the age of 84 years, and disorientation gradually appeared. Head computed tomography revealed severe hippocampal atrophy, whereas the atrophy of the frontal lobe was considerably mild for her age. Behavioral and psychological symptoms of dementia were relatively inconspicuous during the disease course. Apolipoprotein E gene analysis showed ε3/ε4 heterozygosity. She died at the age of 100 years and she was clinically diagnosed as having Alzheimer's disease (AD). Autopsy revealed numerous neurofibrillary tangles, particularly in the hippocampal region, and extensively distributed senile plaques in the brain. Although the findings were compatible with the pathological criteria for AD, combined pathologies of hippocampal sclerosis, trans-activation response DNA-binding protein 43 kDa, and α-synuclein were also revealed. We believe that the clinicopathological findings of the present case are of significance for the diagnosis of elderly dementia and pathogenesis of AD.