Cross-species comparative hippocampal transcriptomics in Alzheimer's disease.

Alzheimer's disease (AD) is a multifactorial pathology, with most cases having a sporadic origin. Recently, knock-in (KI) mouse models, such as the novel humanized amyloid-ß (hAß)-KI, have been developed to better resemble sporadic human AD. METHODS: Here, we compared hippocampal publicly available transcriptomic profiles of transgenic (5xFAD and APP/PS1) and KI (hAß-KI) mouse models with early- (EOAD) and late- (LOAD) onset AD patients. RESULTS: The three mouse models presented more Gene Ontology biological processes terms and enriched signaling pathways in common with LOAD than with EOAD individuals. Experimental validation of consistently dysregulated genes revealed five altered in mice (SLC11A1, S100A6, CD14, CD33, and C1QB) and three in humans (S100A6, SLC11A1, and KCNK). Finally, we identified 17 transcription factors potentially acting as master regulators of AD. CONCLUSION: Our cross-species analyses revealed that the three mouse models presented a remarkable similarity to LOAD, with the hAß-KI being the more specific one.

Learning fast and fine-grained detection of amyloid neuropathologies from coarse-grained expert labels.

Precise, scalable, and quantitative evaluation of whole slide images is crucial in neuropathology. We release a deep learning model for rapid object detection and precise information on the identification, locality, and counts of cored plaques and cerebral amyloid angiopathy (CAA). We trained this object detector using a repurposed image-tile dataset without any human-drawn bounding boxes. We evaluated the detector on a new manually-annotated dataset of whole slide images (WSIs) from three institutions, four staining procedures, and four human experts. The detector matched the cohort of neuropathology experts, achieving 0.64 (model) vs. 0.64 (cohort) average precision (AP) for cored plaques and 0.75 vs. 0.51 AP for CAAs at a 0.5 IOU threshold. It provided count and locality predictions that approximately correlated with gold-standard human CERAD-like WSI scoring (p = 0.07 ± 0.10). The openly-available model can quickly score WSIs in minutes without a GPU on a standard workstation.

Enlarged perivascular spaces and plasma Aß42/Aß40 ratio in older adults without dementia.

Dilation of perivascular spaces (PVS) in the brain may indicate poor fluid drainage due to the accumulation of perivascular cell debris, waste, and proteins, including amyloid-beta (Aß). No prior study has assessed whether plasma Aß levels are related to PVS in older adults without dementia. Independently living older adults (N = 56, mean age = 68.2 years; Standard deviation (SD) = 6.5; 30.4% male) free of dementia or clinical stroke were recruited from the community and underwent brain MRI and venipuncture. PVS were qualitatively scored and dichotomized to low PVS burden (scores 0-1,) or high PVS burden (score>1). Plasma was assayed using a Quanterix Simoa Kit to quantify Aß42 and Aß40 levels. A significant difference was observed in plasma Aß42/Aß40 ratio between low and high PVS burden, controlling for age (F[1, 53] = 5.59, p = 0.022, η2 = 0.10), with lower Aß42/Aß40 ratio in the high PVS burden group. Dilation of PVS is associated with a lower plasma Aß42/Aß40 ratio, which may indicate higher cortical amyloid deposition. Future longitudinal studies examining PVS changes, and the pathogenesis of AD are warranted.

Modulating heart rate oscillation affects plasma amyloid beta and tau levels in younger and older adults.

Slow paced breathing via heart rate variability (HRV) biofeedback stimulates vagus-nerve pathways that counter noradrenergic stress and arousal pathways that can influence production and clearance of Alzheimer's disease (AD)-related proteins. Thus, we examined whether HRV biofeedback intervention affects plasma Αß40, Αß42, total tau (tTau), and phosphorylated tau-181 (pTau-181) levels. We randomized healthy adults (N = 108) to use slow-paced breathing with HRV biofeedback to increase heart rate oscillations (Osc+) or to use personalized strategies with HRV biofeedback to decrease heart rate oscillations (Osc-). They practiced 20-40 min daily. Four weeks of practicing the Osc+ and Osc- conditions produced large effect size differences in change in plasma Aß40 and Aß42 levels. The Osc+ condition decreased plasma Αß while the Osc- condition increased Αß. Decreases in Αß were associated with decreases in gene transcription indicators of ß-adrenergic signaling, linking effects to the noradrenergic system. There were also opposing effects of the Osc+ and Osc- interventions on tTau for younger adults and pTau-181 for older adults. These results provide novel data supporting a causal role of autonomic activity in modulating plasma AD-related biomarkers.Trial registration: NCT03458910 (ClinicalTrials.gov); first posted on 03/08/2018.

Learning fast and fine-grained detection of amyloid neuropathologies from coarse-grained expert labels.

Precise, scalable, and quantitative evaluation of whole slide images is crucial in neuropathology. We release a deep learning model for rapid object detection and precise information on the identification, locality, and counts of cored plaques and cerebral amyloid angiopathies (CAAs). We trained this object detector using a repurposed image-tile dataset without any human-drawn bounding boxes. We evaluated the detector on a new manually-annotated dataset of whole slide images (WSIs) from three institutions, four staining procedures, and four human experts. The detector matched the cohort of neuropathology experts, achieving 0.64 (model) vs. 0.64 (cohort) average precision (AP) for cored plaques and 0.75 vs. 0.51 AP for CAAs at a 0.5 IOU threshold. It provided count and locality predictions that correlated with gold-standard CERAD-like WSI scoring (p=0.07± 0.10). The openly-available model can quickly score WSIs in minutes without a GPU on a standard workstation.

Blood pressure variability and plasma Alzheimer's disease biomarkers in older adults.

Blood pressure variability is an emerging risk factor for Alzheimer's disease in older adults, independent of average blood pressure levels. Growing evidence suggests increased blood pressure variability is linked to Alzheimer's disease pathophysiology indexed by cerebrospinal fluid and positron emission tomography markers, but relationships with plasma Alzheimer's disease markers have not been investigated. In this cross-sectional study of 54 community-dwelling older adults (aged 55-88, mean age 69.9 [8.2 SD]), elevated blood pressure variability over 5 min was associated with lower levels of plasma Aß1-42 (standardized ß = - 0.36 [95% CI - 0.61, - 0.12]; p = 0.005; adjusted R2 = 0.28) and Aß1-42: Aß1-40 ratio (ß = - 0.49 [95% CI - 0.71, - 0.22]; p < 0.001; adjusted R2 = 0.28), and higher levels of total tau (ß = 0.27 [95% CI 0.01, 0.54]; p = 0.04; adjusted R2 = 0.19) and Ptau181:Aß1-42 ratio (ß = 0.26 [95% CI 0.02, 0.51]; p = 0.04; adjusted R2 = 0.22). Findings suggest higher blood pressure variability is linked to plasma biomarkers of increased Alzheimer's disease pathophysiology.

Exploring the role of sex differences in Alzheimer's disease pathogenesis in Down syndrome.

Women are disproportionately affected by Alzheimer's disease (AD), yet little is known about sex-specific effects on the development of AD in the Down syndrome (DS) population. DS is caused by a full or partial triplication of chromosome 21, which harbors the amyloid precursor protein (APP) gene, among others. The majority of people with DS in their early- to mid-40s will accumulate sufficient amyloid-beta (Aß) in their brains along with neurofibrillary tangles (NFT) for a neuropathological diagnosis of AD, and the triplication of the APP gene is regarded as the main cause. Studies addressing sex differences with age and impact on dementia in people with DS are inconsistent. However, women with DS experience earlier age of onset of menopause, marked by a drop in estrogen, than women without DS. This review focuses on key sex differences observed with age and AD in people with DS and a discussion of possible underlying mechanisms that could be driving or protecting from AD development in DS. Understanding how biological sex influences the brain will lead to development of dedicated therapeutics and interventions to improve the quality of life for people with DS and AD.

Type-I-interferon signaling drives microglial dysfunction and senescence in human iPSC models of Down syndrome and Alzheimer's disease.

Microglia are critical in brain development and Alzheimer's disease (AD) etiology. Down syndrome (DS) is the most common genetic developmental disorder and risk factor for AD. Surprisingly, little information is available on the impact of trisomy of human chromosome 21 (Hsa21) on microglial functions during DS brain development and in AD in DS. Using induced pluripotent stem cell (iPSC)-based organoid and chimeric mouse models, we report that DS microglia exhibit an enhanced synaptic pruning function, which alters neuronal synaptic functions. In response to human brain tissue-derived pathological tau, DS microglia undergo cellular senescence and exhibit elevated type-I-interferon signaling. Mechanistically, knockdown of Hsa21-encoded type I interferon receptors, IFNARs, rescues the DS microglial phenotypes both during brain development and in response to pathological tau. Our findings provide in vivo evidence that human microglia respond to pathological tau by exhibiting dystrophic phenotypes. Targeting IFNARs may improve DS microglial functions and prevent senescence.

Cholesterol and matrisome pathways dysregulated in astrocytes and microglia.

The impact of apolipoprotein E ε4 (APOE4), the strongest genetic risk factor for Alzheimer's disease (AD), on human brain cellular function remains unclear. Here, we investigated the effects of APOE4 on brain cell types derived from population and isogenic human induced pluripotent stem cells, post-mortem brain, and APOE targeted replacement mice. Population and isogenic models demonstrate that APOE4 local haplotype, rather than a single risk allele, contributes to risk. Global transcriptomic analyses reveal human-specific, APOE4-driven lipid metabolic dysregulation in astrocytes and microglia. APOE4 enhances de novo cholesterol synthesis despite elevated intracellular cholesterol due to lysosomal cholesterol sequestration in astrocytes. Further, matrisome dysregulation is associated with upregulated chemotaxis, glial activation, and lipid biosynthesis in astrocytes co-cultured with neurons, which recapitulates altered astrocyte matrisome signaling in human brain. Thus, APOE4 initiates glia-specific cell and non-cell autonomous dysregulation that may contribute to increased AD risk.

Absence of microglia promotes diverse pathologies and early lethality in Alzheimer's disease mice.

Microglia are strongly implicated in the development and progression of Alzheimer's disease (AD), yet their impact on pathology and lifespan remains unclear. Here we utilize a CSF1R hypomorphic mouse to generate a model of AD that genetically lacks microglia. The resulting microglial-deficient mice exhibit a profound shift from parenchymal amyloid plaques to cerebral amyloid angiopathy (CAA), which is accompanied by numerous transcriptional changes, greatly increased brain calcification and hemorrhages, and premature lethality. Remarkably, a single injection of wild-type microglia into adult mice repopulates the microglial niche and prevents each of these pathological changes. Taken together, these results indicate the protective functions of microglia in reducing CAA, blood-brain barrier dysfunction, and brain calcification. To further understand the clinical implications of these findings, human AD tissue and iPSC-microglia were examined, providing evidence that microglia phagocytose calcium crystals, and this process is impaired by loss of the AD risk gene, TREM2.

Beyond amyloid: Immune, cerebrovascular, and metabolic contributions to Alzheimer disease in people with Down syndrome.

People with Down syndrome (DS) have increased risk of Alzheimer disease (AD), presumably conferred through genetic predispositions arising from trisomy 21. These predispositions necessarily include triplication of the amyloid precursor protein (APP), but also other Ch21 genes that confer risk directly or through interactions with genes on other chromosomes. We discuss evidence that multiple genes on chromosome 21 are associated with metabolic dysfunction in DS. The resulting dysregulated pathways involve the immune system, leading to chronic inflammation; the cerebrovascular system, leading to disruption of the blood brain barrier (BBB); and cellular energy metabolism, promoting increased oxidative stress. In combination, these disruptions may produce a precarious biological milieu that, in the presence of accumulating amyloid, drives the pathophysiological cascade of AD in people with DS. Critically, mechanistic drivers of this dysfunction may be targetable in future clinical trials of pharmaceutical and/or lifestyle interventions.

SPG302 Reverses Synaptic and Cognitive Deficits Without Altering Amyloid or Tau Pathology in a Transgenic Model of Alzheimer's Disease.

Alzheimer's disease (AD) is conceptualized as a synaptic failure disorder in which loss of glutamatergic synapses is a major driver of cognitive decline. Thus, novel therapeutic strategies aimed at regenerating synapses may represent a promising approach to mitigate cognitive deficits in AD patients. At present, no disease-modifying drugs exist for AD, and approved therapies are palliative at best, lacking in the ability to reverse the synaptic failure. Here, we tested the efficacy of a novel synaptogenic small molecule, SPG302 - a 3rd-generation benzothiazole derivative that increases the density of axospinous glutamatergic synapses - in 3xTg-AD mice. Daily dosing of 3xTg-AD mice with SPG302 at 3 and 30 mg/kg (i.p.) for 4 weeks restored hippocampal synaptic density and improved cognitive function in hippocampal-dependent tasks. Mushroom and stubby spine profiles were increased by SPG302, and associated with enhanced expression of key postsynaptic proteins - including postsynaptic density protein 95 (PSD95), drebrin, and amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) - and increased colocalization of PSD95 with synaptophysin. Notably, SPG302 proved efficacious in this model without modifying Aß and tau pathology. Thus, our study provides preclinical support for the idea that compounds capable of restoring synaptic density offer a viable strategy to reverse cognitive decline in AD.

Aging in Down Syndrome: Latest Clinical Advances and Prospects.

Down syndrome (DS), or trisomy 21, is the most common genetic cause of intellectual disability [...].

Aging with Down Syndrome-Where Are We Now and Where Are We Going?

Down syndrome (DS) is a form of accelerated aging, and people with DS are highly prone to aging-related conditions that include vascular and neurological disorders. Due to the overexpression of several genes on Chromosome 21, for example genes encoding amyloid precursor protein (APP), superoxide dismutase (SOD), and some of the interferon receptors, those with DS exhibit significant accumulation of amyloid, phospho-tau, oxidative stress, neuronal loss, and neuroinflammation in the brain as they age. In this review, we will summarize the major strides in this research field that have been made in the last few decades, as well as discuss where we are now, and which research areas are considered essential for the field in the future. We examine the scientific history of DS bridging these milestones in research to current efforts in the field. We extrapolate on comorbidities associated with this phenotype and highlight clinical networks in the USA and Europe pursuing clinical research, concluding with funding efforts and recent recommendations to the NIH regarding DS research.

Single-nucleus chromatin accessibility and transcriptomic characterization of Alzheimer's disease.

The gene-regulatory landscape of the brain is highly dynamic in health and disease, coordinating a menagerie of biological processes across distinct cell types. Here, we present a multi-omic single-nucleus study of 191,890 nuclei in late-stage Alzheimer's disease (AD), accessible through our web portal, profiling chromatin accessibility and gene expression in the same biological samples and uncovering vast cellular heterogeneity. We identified cell-type-specific, disease-associated candidate cis-regulatory elements and their candidate target genes, including an oligodendrocyte-associated regulatory module containing links to APOE and CLU. We describe cis-regulatory relationships in specific cell types at a subset of AD risk loci defined by genome-wide association studies, demonstrating the utility of this multi-omic single-nucleus approach. Trajectory analysis of glial populations identified disease-relevant transcription factors, such as SREBF1, and their regulatory targets. Finally, we introduce single-nucleus consensus weighted gene coexpression analysis, a coexpression network analysis strategy robust to sparse single-cell data, and perform a systems-level analysis of the AD transcriptome.

Generation of a humanized Aß expressing mouse demonstrating aspects of Alzheimer's disease-like pathology.

The majority of Alzheimer's disease (AD) cases are late-onset and occur sporadically, however most mouse models of the disease harbor pathogenic mutations, rendering them better representations of familial autosomal-dominant forms of the disease. Here, we generated knock-in mice that express wildtype human Aß under control of the mouse App locus. Remarkably, changing 3 amino acids in the mouse Aß sequence to its wild-type human counterpart leads to age-dependent impairments in cognition and synaptic plasticity, brain volumetric changes, inflammatory alterations, the appearance of Periodic Acid-Schiff (PAS) granules and changes in gene expression. In addition, when exon 14 encoding the Aß sequence was flanked by loxP sites we show that Cre-mediated excision of exon 14 ablates hAß expression, rescues cognition and reduces the formation of PAS granules.

Neuropathology of Aging in Cats and its Similarities to Human Alzheimer's Disease.

Elderly cats develop age-related behavioral and neuropathological changes that ultimately lead to cognitive dysfunction syndrome (CDS). These neuropathologies share similarities to those seen in the brains of humans with Alzheimer's disease (AD), including the extracellular accumulation of ß-amyloid (Aß) and intraneuronal deposits of hyperphosphorylated tau, which are considered to be the two major hallmarks of AD. The present study assessed the presence and distribution of Aß and tau hyperphosphorylation within the cat brain (n = 55 cats), and how the distribution of these proteins changes with age and the presence of CDS. For this, immunohistochemistry was performed on seven brain regions from cats of various ages, with and without CDS (n = 10 with CDS). Cats accumulate both intracytoplasmic and extracellular deposits of Aß, as well as intranuclear and intracytoplasmic hyperphosphorylated tau deposits. Large extracellular aggregates of Aß were found in elderly cats, mainly in the cortical brain areas, with occasional hippocampal aggregates. This may suggest that these aggregates start in cortical areas and later progress to the hippocampus. While Aß senile plaques in people with AD have a dense core, extracellular Aß deposits in cats exhibited a diffuse pattern, similar to the early stages of plaque pathogenesis. Intraneuronal Aß deposits were also observed, occurring predominantly in cortical brain regions of younger cats, while older cats had few to no intraneuronal Aß deposits, especially when extracellular aggregates were abundant. Intracytoplasmic hyperphosphorylated tau was found within neurons in the brains of elderly cats, particularly in those with CDS. Due to their ultrastructural features, these deposits are considered to be pre-tangles, which are an early stage of the neurofibrillary tangles seen in AD. The largest numbers of pre-tangles are found mainly in the cerebral cortex of elderly cats, whereas lower numbers were found in other regions (i.e., entorhinal cortex and hippocampus). For the first time, intranuclear tau was found in both phosphorylated and non-phosphorylated states within neurons in the cat brain. The highest numbers of intranuclear deposits were found in the cortex of younger cats, and this tended to decrease with age. In contrast, elderly cats with pre-tangles had only occasional or no nuclear labelling.

Distribution of microglial phenotypes as a function of age and Alzheimer's disease neuropathology in the brains of people with Down syndrome.

INTRODUCTION: Microglial cells play an important role in the development of Alzheimer's disease (AD). People with Down syndrome (DS) inevitably develop AD neuropathology (DSAD) by 40 years of age. We characterized the distribution of different microglial phenotypes in the brains of people with DS and DSAD. METHODS: Autopsy tissue from the posterior cingulate cortex (PCC) from people with DS, DSAD, and neurotypical controls was immunostained with the microglial marker Iba1 to assess five microglia morphological types. RESULTS: Individuals with DS have more hypertrophic microglial cells in their white matter. In the gray matter, individuals with DSAD had significantly fewer ramified microglia and more dystrophic microglia than controls and the younger individuals with DS. The DSAD group also exhibited more rod-shaped and amoeboid cells than the AD group. DISCUSSION: Individuals with DS and DSAD show a microglial phenotype that distinguishes them from non-DS controls.

DNA extraction from sternum bone for identification of a saponified body: use of a modified protocol.

This paper discusses our approach and results obtained when attempting to identify a saponified human body recovered from the sea, without arms and legs. Bones, especially the long ones, are the only sources of DNA available in several cases involving unidentified bodies in advanced state of putrefaction. In this case, since the body was found without limbs, attempts were made to extract DNA from the sternum bone. The DNA was extracted using a modified version of the NucleoSpin® DNA Trace Kit (Macherey Nagel™) protocol and an STR analysis was performed. Thanks to this modified protocol a complete DNA profile was obtained from the sternum bone, while only partial results were obtained from blood and teeth. The DNA profile obtained from the sternum was compared with the DNA of the putative son searching for a genetic match. Five incompatibilities were detected so it was possible to exclude the kinship. In conclusion this could be a useful technique in personal identification through DNA analysis in case of poor quality and quantity of bone.

miR-181a negatively modulates synaptic plasticity in hippocampal cultures and its inhibition rescues memory deficits in a mouse model of Alzheimer's disease.

MicroRNAs play a pivotal role in rapid, dynamic, and spatiotemporal modulation of synaptic functions. Among them, recent emerging evidence highlights that microRNA-181a (miR-181a) is particularly abundant in hippocampal neurons and controls the expression of key plasticity-related proteins at synapses. We have previously demonstrated that miR-181a was upregulated in the hippocampus of a mouse model of Alzheimer's disease (AD) and correlated with reduced levels of plasticity-related proteins. Here, we further investigated the underlying mechanisms by which miR-181a negatively modulated synaptic plasticity and memory. In primary hippocampal cultures, we found that an activity-dependent upregulation of the microRNA-regulating protein, translin, correlated with reduction of miR-181a upon chemical long-term potentiation (cLTP), which induced upregulation of GluA2, a predicted target for miR-181a, and other plasticity-related proteins. Additionally, Aß treatment inhibited cLTP-dependent induction of translin and subsequent reduction of miR-181a, and cotreatment with miR-181a antagomir effectively reversed the effects elicited by Aß but did not rescue translin levels, suggesting that the activity-dependent upregulation of translin was upstream of miR-181a. In mice, a learning episode markedly decreased miR-181a in the hippocampus and raised the protein levels of GluA2. Lastly, we observed that inhibition of miR-181a alleviated memory deficits and increased GluA2 and GluA1 levels, without restoring translin, in the 3xTg-AD model. Taken together, our results indicate that miR-181a is a major negative regulator of the cellular events that underlie synaptic plasticity and memory through AMPA receptors, and importantly, Aß disrupts this process by suppressing translin and leads to synaptic dysfunction and memory impairments in AD.