Neuropathology of Alzheimer's disease and other dementias

Chemical signatures delineate heterogeneous amyloid plaque populations across the Alzheimer's disease spectrum

Amyloid plaque deposition is recognized as the primary pathological hallmark of Alzheimer's disease(AD) that precedes other pathological events and cognitive symptoms. Plaque pathology represents itself with an immense polymorphic variety comprising plaques with different stages of amyloid fibrillization ranging from diffuse to fibrillar, mature plaques. The association of polymorphic Aβ plaque pathology with AD pathogenesis, clinical symptoms and disease progression remains unclear. Advanced chemical imaging tools, such as functional amyloid microscopy combined with MALDI mass spectrometry imaging (MSI), are now enhanced by deep learning algorithms. This integration allows for precise delineation of polymorphic plaque structures and detailed identification of their associated Aβ compositions. We here set out to make use of these tools to interrogate heterogenic plaque types and their associated biochemical architecture. Our findings reveal distinct Aβ signatures that differentiate diffuse plaques from fibrilized ones, with the latter showing substantially higher levels of Aβx-40. Notably, within the fibrilized category, we identified a distinct subtype known as coarse-grain plaques. Both in sAD and fAD brain tissue, coarse grain plaques contained more Aβx-40 and less Aβx-42 compared with cored plaques. The coarse grain plaques in both sAD and fAD also showed higher levels of neuritic content including paired helical filaments (PHF-1)/phosphorylated phospho Tau-immunopositive neurites. Finally, the Aβ peptide content in coarse grain plaques resembled that of vascular Aβ deposits (CAA) though with relatively higher levels of Aβ1-42 and pyroglutamated Aβx-40 and Aβx-42 species in coarse grain plaques. This is the first of its kind study on spatial in situ biochemical characterization of different plaque morphotypes demonstrating the potential of the correlative imaging techniques used that further increase the understanding of heterogeneous AD pathology. Linking the biochemical characteristics of amyloid plaque polymorphisms with various AD etiologies and toxicity mechanisms is crucial. Understanding the connection between plaque structure and disease pathogenesis can enhance our insights. This knowledge is particularly valuable for developing and advancing novel, amyloid-targeting therapeutics.

Protein citrullination marks myelin protein aggregation and disease progression in mouse ALS models

Increased protein citrullination (PC) and dysregulated protein arginine deiminase (PAD) activity have been observed in several neurodegenerative diseases. PC is a posttranslational modification catalyzed by the PADs. PC converts peptidyl-arginine to peptidyl-citrulline, thereby reducing the positive charges and altering structure and function of proteins. Of the five PADs, PAD2 is the dominant isoform in the central nervous system (CNS). Abnormal PC and PAD dysregulation are associated with numerous pathological conditions, including inflammatory diseases and neurodegeneration. Animal model studies have shown therapeutic efficacy from inhibition of PADs, thus suggesting a role of PC in pathogenesis. To determine whether PC contribute to amyotrophic lateral sclerosis (ALS), a deadly neurodegenerative disease characterized by loss of motor neurons, paralysis, and eventual death, we investigated alterations of PC and PAD2 in two different transgenic mouse models of ALS expressing human mutant SOD1^G93A and PFN1^C71G, respectively. PC and PAD2 expression are altered dynamically in the spinal cord during disease progression in both models. PC and PAD2 increase progressively in astrocytes with the development of reactive astrogliosis, while decreasing in neurons. Importantly, in the spinal cord white matter, PC accumulates in protein aggregates that contain the myelin proteins PLP and MBP. PC also accumulates progressively in insoluble protein fractions during disease progression. Finally, increased PC and PAD2 expression spatially correlate with areas of the CNS with the most severe motor neuron degeneration. These results suggest that altered PC is an integral part of the neurodegenerative process and potential biomarkers for disease progression in ALS. Moreover, increased PC may contribute to disease-associated processes such as myelin protein aggregation, myelin degeneration, and astrogliosis.

Astaxanthin, a carotenoid antioxidant, pretreatment alleviates cognitive deficits in aircraft noised mice by attenuating inflammatory and oxidative damage to the gut, heart and hippocampus

BACKGROUND

We first explore whether aircraft noise (AN) induces cognitive deficit via inducing oxidative damage in multiple vital organs including intestines, hearts and hippocampus tissues. Second, we explore whether the AN-induced cognitive deficits and inflammatory and oxidative damage to multiple organs can be alleviated by Astaxanthin (AX) pretreatment.

METHODS

Cognitive deficits were induced by subjecting the mice to AN 2 h daily for 7 consecutive days. An intragastrical dose of AX emulsifier (at the dose of daily feed intake [6 g] of a mouse three times weekly) was given to mice for consecutive 8 weeks prior to the start of AN. Cognitive functions were evaluated by using passive avoidance apparatus, Y-maze, Morris water maze and novel recognition test. Intestinal permeability was determined by measuring the intestinal clearance of fluorescein-isothiocyante. Evans Blue extravasation assay was used to measure the permeability of blood-brain-barrier. Inflammatory and oxidative damage to multiple organs were determined by measuring several pro-inflammatory cytokines and oxidative stress indicators in intestines; hearts and hippocampus.

RESULTS

Mice treated with AN displayed exacerbated stress reactions, cognitive deficits, gut barrier hyperpermeability, increased upload of lipopolysaccharide translocation, systemic pro-inflammatory cytokines overproduction, blood-brain-barrier hyperpermeability, hippocampal neuroinflammation and increased levels of oxidative stress indicators in intestine, heart and hippocampus. All of the above-mentioned disorders caused by AN were significantly (P < 0.05) reversed by AX.

CONCLUSIONS

Our data indicate that AX pretreatment alleviates cognitive deficits in aircraft noised mice by attenuating inflammatory and oxidative damage to intestines, hearts and hippocampal tissues.

Nutrients, Cognitive Function, and Brain Aging: What We Have Learned from Dogs

Due to a difference in genetics, environmental factors, and nutrition, just like in people, dogs age at different rates. Brain aging in people and dogs share similar morphological changes including irreversible cortical atrophy, cerebral amyloid angiopathy, and ventricular enlargement. Due to severe and irreversible brain atrophy, some aging dogs develop cognitive dysfunction syndrome (CDS), which is equivalent to dementia or Alzheimer’s disease (AD) in people. The risk factors and causes of CDS in dogs have not been fully investigated, but age, gender, oxidative stress, and deficiency of sex hormones appears to be associated with increased risk of accelerated brain aging and CDS in dogs. Both AD and CDS are incurable diseases at this moment, therefore more efforts should be focused on preventing or reducing brain atrophy and minimizing the risk of AD in people and CDS in dogs. Since brain atrophy leads to irreversible cognitive decline and dementia, an optimal nutritional solution should be able to not only enhance cognitive function during aging but also reduce irreversible brain atrophy. Up to now, only one nutritional intervention has demonstrated both cognition-enhancing benefits and atrophy-reducing benefits.

Low-dose ionizing radiation alleviates Aβ42-induced cell death via regulating AKT and p38 pathways in Drosophila Alzheimer's disease models

Ionizing radiation is widely used in medicine and is valuable in both the diagnosis and treatment of many diseases. However, its health effects are ambiguous. Here, we report that low-dose ionizing radiation has beneficial effects in human amyloid-β42 (Aβ42)-expressing Drosophila Alzheimer's disease (AD) models. Ionizing radiation at a dose of 0.05 Gy suppressed AD-like phenotypes, including developmental defects and locomotive dysfunction, but did not alter the decreased survival rates and longevity of Aβ42-expressing flies. The same dose of γ-irradiation reduced Aβ42-induced cell death in Drosophila AD models through downregulation of head involution defective (hid), which encodes a protein that activates caspases. However, 4 Gy of γ-irradiation increased Aβ42-induced cell death without modulating pro-apoptotic genes grim, reaper and hid. The AKT signaling pathway, which was suppressed in Drosophila AD models, was activated by either 0.05 or 4 Gy γ-irradiation. Interestingly, p38 mitogen-activated protein-kinase (MAPK) activity was inhibited by exposure to 0.05 Gy γ-irradiation but enhanced by exposure to 4 Gy in Aβ42-expressing flies. In addition, overexpression of phosphatase and tensin homolog (PTEN), a negative regulator of the AKT signaling pathway, or a null mutant of AKT strongly suppressed the beneficial effects of low-dose ionizing radiation in Aβ42-expressing flies. These results indicate that low-dose ionizing radiation suppresses Aβ42-induced cell death through regulation of the AKT and p38 MAPK signaling pathways, suggesting that low-dose ionizing radiation has hormetic effects on the pathogenesis of Aβ42-associated AD.

Summary: Low-dose ionizing radiation can reduce cell death by regulating AKT/p38 signaling pathway and improve Aβ42-induced symptoms in Drosophila Alzheimer's disease, suggesting that low-dose ionizing radiation may be applicable for treatment.

Protein misfolding, aggregation, and conformational strains in neurodegenerative diseases

A hallmark event in neurodegenerative diseases (NDs) is the misfolding, aggregation, and accumulation of proteins, leading to cellular dysfunction, loss of synaptic connections, and brain damage. Despite the involvement of distinct proteins in different NDs, the process of protein misfolding and aggregation is remarkably similar. A recent breakthrough in the field was the discovery that misfolded protein aggregates can self-propagate through seeding and spread the pathological abnormalities between cells and tissues in a manner akin to the behavior of infectious prions in prion diseases. This discovery has vast implications for understanding the mechanisms involved in the initiation and progression of NDs, as well as for the design of novel strategies for treatment and diagnosis. In this Review, we provide a critical discussion of the role of protein misfolding and aggregation in NDs. Commonalities and differences between distinct protein aggregates will be highlighted, in addition to evidence supporting the hypothesis that misfolded aggregates can be transmissible by the prion principle. We will also describe the molecular basis and implications for prion-like conformational strains, cross-interaction between different misfolded proteins in the brain, and how these concepts can be applied to the development of novel strategies for therapy and diagnosis.

Exercise Improves Recognition Memory and Acetylcholinesterase Activity in the Beta Amyloid-Induced Rat Model of Alzheimer's Disease

Objective

A correlation between physical exercise and cognitive improvement has been found in Alzheimer's disease (AD). This study aimed to investigate the effects of aerobic and resistance exercise on the recognition memory and acetylcholinesterase (AChE) activity in beta amyloid (Aβ) model of AD in rat.

Materials and Methods

Fifty male 8-week-old Wistar rats (250-280 g) were divided into 5 groups (n = 10 each) of control, sham surgery, Aβ-received sedentary, Aβ-received with aerobic exercise and Aβ-received with resistance exercise. AD was induced by intracerebroventricular injection of Aβ_25-35 peptide. The sham surgery group received normal saline using the same route and condition. Two groups of Aβ-received animals were trained by treadmill for aerobic exercise and by ladder for strength exercise for 8 weeks (4 days/week). Novel object recognition (NOR) task was used to assess recognitional memory in groups. AChE activity in the brain tissue was assessed using the Spectrophotometry method.

Results

There was no significant difference in memory index and AChE activity between the sham surgery and control groups (p > 0.05). Also, impairment of NOR indices was seen in the Aβ-injected sedentary rats (p < 0.05). However, both aerobic and strength training improved the exploration index in this test (p < 0.05). Further, AChE activity increased in the Aβ-injected sedentary group but declined in the aerobic and resistance exercise groups (p < 0.01).

Conclusion

Aerobic and resistance exercise could improve recognition memory and decrease AChE activity in Aβ-induced AD in rats. The decrease in AChE activity may be one of the mechanisms by which exercise improves cognition and memory in AD.

Genetic Modifiers in Neurodegeneration

PURPOSE OF REVIEW

To review the evidence for genetic modifier effects in the neurodegenerative diseases Huntington's Disease (HD), Frontotemporal Lobar Degeneration (FTLD), Alzheimer's Disease (AD), and Parkinson's Disease (PD).

RECENT FINDINGS

Increasingly, we understand human disease genetics less through the lens of single-locus/single-trait effects, and more through that of polygenic contributions to disease risk. In addition, specific examples of genetic modifier effects of the chromosome 7 gene TMEM106B on various target genes including those causal for Mendelian classes of FTLD - GRN and c9orf72 - have emerged from both genetic cohort studies and mechanistic examinations of biological pathways.

SUMMARY

Here, we summarize the literature reporting genetic modifier effects in HD, FTLD, AD, and PD. We further contextualize reported genetic modifier effects in these diseases in terms of insight they may lend to the concept of a polygenic landscape for the major neurodegenerative diseases.

Imaging markers of cerebrovascular pathologies: Pathophysiology, clinical presentation, and risk factors

Cerebrovascular pathologies (CVPs) are common pathologies associated with age-related cognitive decline along with Alzheimer disease pathologies. The impact of CVP on the prevalence of dementia is increasingly being recognized. The goal of this review is to improve our understanding of the pathophysiological underpinnings and the multimodal magnetic resonance imaging and positron emission tomography imaging changes that are associated with the hallmarks of CVP. This knowledge will facilitate the development of early detection, intervention, and prevention strategies that may contribute to lowering the risk of dementia. In this review, we will first discuss currently known risk factors of CVPs including cardiovascular, lifestyle, genetic, sex differences, and head injury. Next, we will focus on the pathophysiology of CVPs and their impact on neurodegeneration and downstream cognitive impairment. Specifically, we will discuss three of the most common cerebrovascular lesions seen on MRI: white-matter hyperintensity, microbleeds, and infarcts. Finally, we will discuss the unanswered open questions in this field.

Sex hormones and adult hippocampal neurogenesis: Regulation, implications, and potential mechanisms

Neurogenesis within the adult hippocampus is modulated by endogenous and exogenous factors. Here, we review the role of sex hormones in the regulation of adult hippocampal neurogenesis in males and females. The review is framed around the potential functional implications of sex hormone regulation of adult hippocampal neurogenesis, with a focus on cognitive function and mood regulation, which may be related to sex differences in incidence and severity of dementia and depression. We present findings from preclinical studies of endogenous fluctuations in sex hormones relating to reproductive function and ageing, and from studies of exogenous hormone manipulations. In addition, we discuss the modulating roles of sex, age, and reproductive history on the relationship between sex hormones and neurogenesis. Because sex hormones have diverse targets in the central nervous system, we overview potential mechanisms through which sex hormones may influence hippocampal neurogenesis. Lastly, we advocate for a more systematic consideration of sex and sex hormones in studying the functional implications of adult hippocampal neurogenesis.

Induced Pluripotent Stem Cells as a Novel Tool in Psychiatric Research

Reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) provides a valuable opportunity to study neurodevelopmental and neurodegenerative psychiatric diseases by offering an unlimited source for patient-specific neuronal and glial cells. The present review focuses on the recent advancements in modeling psychiatric disorders such as Phelan-McDermid syndrome, Timothy syndrome, Rett syndrome, schizophrenia, bipolar disorder, and dementia. The treatment effects identified in studies on iPSCs using known therapeutic compounds are also summarized in this review. Here we discuss validation of cellular models and explore iPSCs as a novel drug screening tool. Although there are several limitations associated with the current methods used to study mental disorders, using iPSCs as a model system provides the advantage of rewinding and reviewing the development and degeneration of human neural cells.

Brain-derived neurotrophic factor exerts neuroprotective actions against amyloid β-induced apoptosis in neuroblastoma cells

Alzheimer's disease (AD) brains demonstrate decreased levels of brain-derived neurotrophic factor (BDNF) and increased levels of β-amyloid peptide (Aβ), which is neurotoxic. The present study assessed the impact of BDNF on the toxic effects of Aβ_25-35-induced apoptosis and the effects on BDNF-mediated signaling using the MTT assay, western blotting and reverse transcription quantitative polymerase chain reaction. Aβ_25-35 was found to induce an apoptosis, dose-dependent effect on SH-SY5Y neuroblastoma cells, which peaked at a concentration of 20 μM after 24 h. A combination of Aβ_25-35 and BDNF treatment increased the levels of Akt and decreased the level of glycogen synthase kinase-3β (GSK3β) in SH-SY5Y neuroblastoma cells. These findings indicated that BDNF administration exerted a neuroprotective effect against the toxicity of the Aβ_25-35-induced apoptosis in these cells, which was accompanied by phosphoinositide 3-kinase/Akt activation and GSK3β phosphorylation. The mechanisms and signaling pathways underlying neuronal degeneration induced by the Aβ peptide remain to be further elucidated.

Human stem cell models of neurodegeneration: a novel approach to study mechanisms of disease development

The number of patients with neurodegenerative diseases is increasing significantly worldwide. Thus, intense research is being pursued to uncover mechanisms of disease development in an effort to identify molecular targets for therapeutic intervention. Analysis of postmortem tissue from patients has yielded important histological and biochemical markers of disease progression. However, this approach is inherently limited because it is not possible to study patient neurons prior to degeneration. As such, transgenic and knockout models of neurodegenerative diseases are commonly employed. While these animal models have yielded important insights into some molecular mechanisms of disease development, they do not provide the opportunity to study mechanisms of neurodegeneration in human neurons at risk and thus, it is often difficult or even impossible to replicate human pathogenesis with this approach. The generation of patient-specific induced pluripotent stem (iPS) cells offers a unique opportunity to overcome these obstacles. By expanding and differentiating iPS cells, it is possible to generate large numbers of functional neurons in vitro, which can then be used to study the disease of the donating patient. Here, we provide an overview of human stem cell models of neurodegeneration using iPS cells from patients with Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, frontotemporal dementia, Huntington's disease, spinal muscular atrophy and other neurodegenerative diseases. In addition, we describe how further refinements of reprogramming technology resulted in the generation of patient-specific induced neurons, which have also been used to model neurodegenerative changes in vitro.

Quantitative neurofibrillary tangle density and brain volumetric MRI analyses in Alzheimer's disease presenting as logopenic progressive aphasia

Neurofibrillary tangles (NFTs) are one of the key histological lesions of Alzheimer's disease (AD) and are associated with brain atrophy. We assessed regional NFT density in 30 patients with AD, 10 of which presented as the logopenic variant of primary progressive aphasia (lvPPA) and 20 that presented as dementia of the Alzheimer's type (DAT). Regional grey matter volumes were measured using antemortem MRI. NFT density was significantly higher in left temporoparietal cortices in lvPPA compared to DAT, with no differences observed in hippocampus. There was a trend for the ratio of temporoparietal-to-hippocampal NFT density to be higher in lvPPA. The imaging findings mirrored the pathological findings, with smaller left temporoparietal volumes observed in lvPPA compared to DAT, and no differences observed in hippocampal volume. This study demonstrates that lvPPA is associated with a phenomenon of enhanced temporoparietal neurodegeneration, a finding that improves our understanding of the biological basis of lvPPA.

Absence of beta-amyloid in cortical cataracts of donors with and without Alzheimer's disease

Eye lenses from human donors with and without Alzheimer's disease (AD) were studied to evaluate the presence of amyloid in cortical cataract. We obtained 39 lenses from 21 postmortem donors with AD and 15 lenses from age-matched controls provided by the Banco de Ojos para Tratamientos de la Ceguera (Barcelona, Spain). For 17 donors, AD was clinically diagnosed by general physicians and for 4 donors the AD diagnosis was neuropathologically confirmed. Of the 21 donors with AD, 6 had pronounced bilateral cortical lens opacities and 15 only minor or no cortical opacities. As controls, 7 donors with pronounced cortical opacities and 8 donors with almost transparent lenses were selected. All lenses were photographed in a dark field stereomicroscope. Histological sections were analyzed using a standard and a more sensitive Congo red protocol, thioflavin staining and beta-amyloid immunohistochemistry. Brain tissue from two donors, one with cerebral amyloid angiopathy and another with advanced AD-related changes and one cornea with lattice dystrophy were used as positive controls for the staining techniques. Thioflavin, standard and modified Congo red staining were positive in the control brain tissues and in the dystrophic cornea. Beta-amyloid immunohistochemistry was positive in the brain tissues but not in the cornea sample. Lenses from control and AD donors were, without exception, negative after Congo red, thioflavin, and beta-amyloid immunohistochemical staining. The results of the positive control tissues correspond well with known observations in AD, amyloid angiopathy and corneas with lattice dystrophy. The absence of staining in AD and control lenses with the techniques employed lead us to conclude that there is no beta-amyloid in lenses from donors with AD or in control cortical cataracts. The inconsistency with previous studies of Goldstein et al. (2003) and Moncaster et al. (2010), both of which demonstrated positive Congo red, thioflavin, and beta-amyloid immunohistochemical staining in AD and Down syndrome lenses, is discussed.

An exploratory study on STX6, MOBP, MAPT, and EIF2AK3 and late-onset Alzheimer's disease

Both Alzheimer's disease (AD) and progressive supranuclear palsy (PSP) are a class of neurodegenerative diseases associated with the pathologic aggregation of tau protein in the human brain. They share some clinical and pathologic characteristics. A recent genome-wide association study reported several single-nucleotide polymorphisms at the STX6, MOBP, MAPT, and EIF2AK3 in association with PSP. To explore whether these single-nucleotide polymorphisms are associated with AD risk, we conducted a case-control study to investigate the PSP-associated loci in 1592 Han Chinese subjects. Rs242557 at the MAPT locus was associated with late-onset AD (LOAD) (odds ratio [OR], 1.175; p = 0.026), which appeared to be stronger for LOAD patients with apolipoprotein E (APOE) ε4 allele (OR, 1.510), and this positive association was not changed after adjusting for age, sex, and the APOE ε4-carrier status (additive model: OR, 1.163; p = 0.036; dominant model: OR, 1.315; p = 0.010). Rs1768208 in MOBP and rs7571971 in EIF2AK3 showed association only in the APOE ε4 positive subjects, and these did not appear to be independent of APOE. As for rs1411478 in STX6, we did not explore any association with LOAD. Our exploratory analysis mainly suggests an association of MAPT with LOAD, especially in APOE ε4 carriers. Genotypes at MOBP and EIF2AK3 confer risk predominantly in APOE ε4-positive subjects, with indications of an interaction between APOE and MOBP or EIF2AK3 on AD risk.

Gene expression in the Parkinson's disease brain

The study of gene expression has undergone a transformation in the past decade as the benefits of the sequencing of the human genome have made themselves felt. Increasingly, genome wide approaches are being applied to the analysis of gene expression in human disease as a route to understanding the underlying pathogenic mechanisms. In this review, we will summarise current state of gene expression studies of the brain in Parkinson's disease, and examine how these techniques can be used to gain an insight into aetiology of this devastating disorder.

Functional connectivity during recognition memory in individuals genetically at risk for Alzheimer's disease

The medial temporal lobes (MTL) and frontal cortex have been shown to subserve memory processes. Neurodegenerative diseases, such as Alzheimer's disease (AD), disrupt the neuronal networks that underlie memory processing. The ε4 allele of the apolipoprotein E gene is a genetic risk factor for AD and is associated with decrements in memory and in olfactory function. The present study utilized EQS, a structural equation modeling software program, to examine differences in the neuronal networks between non-demented ε4 carriers and ε4 noncarriers during a cross-modal olfactory recognition memory paradigm. Prior to fMRI scanning, participants were presented with 16 odors. During two scans, participants discriminated between names of odors presented before scanning (targets) or not presented (foils). The results indicate significant connections between bilateral frontal lobes and MTL for ε4 carriers when they misidentified a foil as a target. When ε4 noncarriers correctly identified a target, there were greater associations between the amygdala, MTL, and right frontal lobe; these associations also modeled the brain's response when ε4 noncarriers misidentified a foil as a target. During memory retrieval, affective cues may facilitate retrieval in ε4 noncarriers relative to ε4 carriers. Last, no model was found that best represented the functional network used by ε4 carriers when they correctly identified a target, which may reflect variability of neuronal recruitment within this population.

Age-related changes of neuron numbers in the frontal cortex of a transgenic mouse model of Alzheimer's disease

Alzheimer’s disease (AD) is a neurodegenerative disorder, characterized by amyloid plaque accumulation, intracellular tangles and neuronal loss in selective brain regions. The frontal cortex, important for executive functioning, is one of the regions that are affected. Here, we investigated the neurodegenerative effects of mutant human amyloid precursor protein (APP) and presenilin 1 (PS1) on frontal cortex neurons in APP/PS1KI mice, a transgenic mouse model of AD, expressing two mutations in the human APP, as well as two human PS1 mutations knocked-in into the mouse PS1 gene in a homozygous (ho) manner. Although the hippocampus is significantly affected in these mice, very little is known about the effects of these mutations on selective neuronal populations and plaque load in the frontal cortex. In this study, cytoarchitectural changes were characterized using high precision design-based stereology to evaluate plaque load, total neuron numbers, as well as total numbers of parvalbumin- (PV) and calretinin- (CR) immunoreactive (ir) neurons in the frontal cortex of 2- and 10-month-old APP/PS1KI mice. The frontal cortex was divided into two subfields: layers II–IV and layers V–VI, the latter of which showed substantially more extracellular amyloid-beta aggregates. We found a 34% neuron loss in layers V–VI in the frontal cortex of 10-month-old APP/PS1KI mice compared to 2-month-old, while there was no change in PV- and CR-ir neurons in these mice. In addition, the plaque load in layers V–VI of 10-month-old APP/PS1KI mice was only 11% and did not fully account for the extent of neuronal loss. Interestingly, an increase was found in the total number of PV-ir neurons in all frontal cortical layers of single transgenic APP mice and in layers II–IV of single transgenic PS1ho mice between 2 and 10 months of age. In conclusion, the APP/PS1KI mice provide novel insights into the regional selective vulnerability in the frontal cortex during AD that, together with previous findings in the hippocampus, are remarkably similar to the human situation.

Anti-aβ therapeutics in Alzheimer's disease: the need for a paradigm shift

Most current Alzheimer's disease (AD) therapies in advanced phases of development target amyloid β-peptide (Aβ) production, aggregation, or accumulation. Translational models suggest that anti-Aβ therapies may be highly effective if tested as agents to prevent or delay development of the disease or as therapies for asymptomatic patients with very early signs of AD pathology. However, anti-Aβ therapeutics are currently being tested in symptomatic patients where they are likely to be much less effective or ineffective. The lack of alignment between human clinical studies and preclinical studies, together with predictions about optimal trial design based on our understanding of the initiating role of Aβ aggregates in AD, has created a treatment versus prevention dilemma. In this perspective, we discuss why it is imperative to resolve this dilemma and suggest ways for moving forward in the hopes of enhancing the development of truly effective AD therapeutics.

Evidence for three loci modifying age-at-onset of Alzheimer's disease in early-onset PSEN2 families

Families with early-onset Alzheimer's disease (AD) sharing a single PSEN2 mutation exhibit a wide range of age-at-onset, suggesting that modifier loci segregate within these families. While APOE is known to be an age-at-onset modifier, it does not explain all of this variation. We performed a genome scan within nine such families for loci influencing age-at-onset, while simultaneously controlling for variation in the primary PSEN2 mutation (N141I) and APOE. We found significant evidence of linkage between age-at-onset and chromosome 1q23.3 (P < 0.001) when analysis included all families, and to chromosomes 1q23.3 (P < 0.001), 17p13.2 (P = 0.0002), 7q33 (P = 0.017), and 11p14.2 (P = 0.017) in a single large pedigree. Simultaneous analysis of these four chromosomes maintained strong evidence of linkage to chromosomes 1q23.3 and 17p13.2 when all families were analyzed, and to chromosomes 1q23.3, 7q33, and 17p13.2 within the same single pedigree. Inclusion of major gene covariates proved essential to detect these linkage signals, as all linkage signals dissipated when PSEN2 and APOE were excluded from the model. The four chromosomal regions with evidence of linkage all coincide with previous linkage signals, associated SNPs, and/or candidate genes identified in independent AD study populations. This study establishes several candidate regions for further analysis and is consistent with an oligogenic model of AD risk and age-at-onset. More generally, this study also demonstrates the value of searching for modifier loci in existing datasets previously used to identify primary causal variants for complex disease traits.

Use it or lose it: environmental enrichment as a means to promote successful cognitive aging

Environmental enrichment has become increasingly utilized in rodent models of aging and neurodegenerative disease in order to prevent or reverse cognitive decline and neuronal dysfunction. However, the potential application of this body of work to human cognitive aging has rarely been discussed. The present article provides an overview of the rodent research that has tested the effects of environmental enrichment on hippocampal and neocortical function, and the types of memories mediated by these brain regions. Although data from models of neurodegenerative disease are presented, primary emphasis is given to studies of aging rodents and to methodological issues (e.g., age, treatment duration, treatment type) central to the mnemonic effectiveness of enrichment treatment. The implications of this work for human cognitive aging are discussed.

Molecular cross talk between misfolded proteins in animal models of Alzheimer's and prion diseases

The central event in protein misfolding disorders (PMDs) is the accumulation of a misfolded form of a naturally expressed protein. Despite the diversity of clinical symptoms associated with different PMDs, many similarities in their mechanism suggest that distinct pathologies may cross talk at the molecular level. The main goal of this study was to analyze the interaction of the protein misfolding processes implicated in Alzheimer's and prion diseases. For this purpose, we inoculated prions in an Alzheimer's transgenic mouse model that develop typical amyloid plaques and followed the progression of pathological changes over time. Our findings show a dramatic acceleration and exacerbation of both pathologies. The onset of prion disease symptoms in transgenic mice appeared significantly faster with a concomitant increase on the level of misfolded prion protein in the brain. A striking increase in amyloid plaque deposition was observed in prion-infected mice compared with their noninoculated counterparts. Histological and biochemical studies showed the association of the two misfolded proteins in the brain and in vitro experiments showed that protein misfolding can be enhanced by a cross-seeding mechanism. These results suggest a profound interaction between Alzheimer's and prion pathologies, indicating that one protein misfolding process may be an important risk factor for the development of a second one. Our findings may have important implications to understand the origin and progression of PMDs.

Epigenetic regulation in the pathophysiology of Alzheimer's disease

With the aging of the population, the growing incidence and prevalence of Alzheimer's disease (AD) increases the burden on individuals and society as a whole. To date, the pathophysiology of AD is not yet fully understood. Recent studies have suggested that epigenetic mechanisms may play a pivotal role in its course and development. The most frequently studied epigenetic mechanisms are DNA methylation and histone modifications, and investigations relevant to aging and AD are presented in this review. Various studies on human postmortem brain samples and peripheral leukocytes, as well as transgenic animal models and cell culture studies relevant to AD will be discussed. From those, it is clear that aging and AD are associated with epigenetic dysregulation at various levels. Moreover, data on e.g. twin studies in AD support the notion that epigenetic mechanisms mediate the risk for AD. Conversely, it is still not fully clear whether the observed epigenetic changes actually represent a cause or a consequence of the disease. This is mainly due to the fact that most clinical investigations on epigenetics in AD are conducted in samples of patients already in an advanced stage of the disease. Evidently, more research is needed in order to clarify the exact role of epigenetic regulation in the course and development of AD. Research on earlier stages of the disease could provide more insight into its underlying pathophysiology, possibly contributing to the establishment of early diagnosis and the development of more effective treatment strategies.

Reduced hippocampal CA2, CA3, and dentate gyrus activity in asymptomatic people at genetic risk for Alzheimer's disease

Previous functional magnetic resonance imaging (MRI) studies in healthy subjects with the apolipoprotein Eepsilon4 (APOE-4) genetic risk for Alzheimer's disease have shown increased activation during memory task performance in broadly distributed cortical regions. These findings have been hypothesized to reflect compensatory recruitment of intact brain regions that presumably result from subtle neural dysfunction reflecting incipient disease. In this study, we used high-resolution functional MRI in APOE-4 carriers and non-carriers to measure activity in hippocampal subregions (CA fields 1, 2, 3; dentate gyrus [DG], and subiculum) and adjacent medial temporal lobe (parahippocampal and entorhinal) subregions. We found reduced left CA2, CA3, and dentate gyrus (CA23DG) activity in cognitively intact APOE-4 carriers. These results suggest that reduced neural activity in hippocampal subregions may underlie the compensatory increase in extrahippocampal activity in people with a genetic risk for Alzheimer's disease prior to the onset of cognitive deficits.

An association study of common variation at the MAPT locus with late-onset Alzheimer's disease

The MAPT gene that encodes Tau is located on chromosome 17q21, in a region, which has evolved to form two major haplotypes, H1 and H2. There is strong evidence that the H1 haplotype, and a sub-haplotype (H1C), are overrepresented and associated with increased risk for the sporadic tauopathies, progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD). Both PSP and CBD cases display Tau pathology similar to Late-Onset Alzheimer's Disease (LOAD). However, numerous association studies investigating the genetic involvement of MAPT in LOAD have generated conflicting results. Here we have used a large LOAD case-control sample to genotype SNPs that have been shown to define H1/H2 status and intra-H1 variability. Single marker association analyses found no evidence that any of the SNPs are associated with risk of LOAD. When gender and APOE4 status were taken into account we observed suggestive association for SNP rs242557 (P = 0.02). Stratification of the sample revealed association with rs242557 only in APOE4 positive individuals (P = 0.01 recessive model), however this result would not survive multiple correction. There was no significant difference in H1/H2 haplotype distribution between cases and controls. We also tested the association of specific sub-haplotypes on the H1 background and likewise results were negative. No effect was observed on disease age of onset for any of the markers studied. In summary, we find no evidence for allelic or haplotypic association, with SNPs in the MAPT gene and LOAD. SNP rs242557 is nominally significant in the APOE4 positive individuals. None of the SNPs studied modified AAO for LOAD.

Direct and indirect roles of cyclin-dependent kinase 5 as an upstream regulator in the c-Jun NH2-terminal kinase cascade: relevance to neurotoxic insults in Alzheimer's disease

Significant increase in JNK, c-Jun, and Cdk5 activities are reported in Alzheimer's disease (AD). Inhibition of c-Jun prevents neuronal cell death in in vivo AD models, highlighting it as a major JNK effector. Both JNK and Cdk5 promote neurodegeneration upon deregulation; however, Cdk5 has not been mechanistically linked to JNK or c-Jun. This study presents the first mechanism showing Cdk5 as a major regulator of the JNK cascade. Deregulated Cdk5 induces biphasic activation of JNK pathway. The first phase revealed c-Jun as a direct substrate of Cdk5, whose activation is independent of reactive oxygen species (ROS) and JNK. In the second phase, Cdk5 activates c-Jun via ROS-mediated activation of JNK. Rapid c-Jun activation is supported by in vivo data showing c-Jun phosphorylation in cerebral cortex upon p25 induction in transgenic mice. Cdk5-mediated biphasic activation of c-Jun highlights c-Jun, rather than JNK, as an important therapeutic target, which was confirmed in neuronal cells. Finally, Cdk5 inhibition endows superior protection against neurotoxicity, suggesting that Cdk5 is a preferable therapeutic target for AD relative to JNK and c-Jun.

Interactions between the amyloid precursor protein C-terminal domain and G proteins mediate calcium dysregulation and amyloid beta toxicity in Alzheimer's disease

Alzheimer's disease is characterized by neuropathological accumulations of amyloid beta(1-42) [A beta(1-42)], a cleavage product of the amyloid precursor protein (APP). Recent studies have highlighted the role of APP in A beta-mediated toxicity and have implicated the G-protein system; however, the exact mechanisms underlying this pathway are as yet undetermined. In this context, we sought to investigate the role of calcium upregulation following APP-dependent, A beta-mediated G-protein activation. Initial studies on the interaction between APP, A beta and Go proteins demonstrated that the interaction between APP, specifically its C-terminal -YENPTY- region, and Go was reduced in the presence of A beta. Cell death and calcium influx in A beta-treated cells were shown to be APP dependent and to involve G-protein activation because these effects were blocked by use of the G-protein inhibitor, pertussis toxin. Collectively, these results highlight a role for the G-protein system in APP-dependent, A beta-induced toxicity and calcium dysregulation. Analysis of the APP:Go interaction in human brain samples from Alzheimer's disease patients at different stages of the disease revealed a decrease in the interaction, correlating with disease progression. Moreover, the reduced interaction between APP and Go was shown to correlate with an increase in membrane A beta levels and G-protein activity, showing for first time that the APP:Go interaction is present in humans and is responsive to A beta load. The results presented support a role for APP in A beta-induced G-protein activation and suggest a mechanism by which basal APP binding to Go is reduced under pathological loads of A beta, liberating Go and activating the G-protein system, which may in turn result in downstream effects including calcium dysregulation. These results also suggest that specific antagonists of G-protein activity may have a therapeutic relevance in Alzheimer's disease.

Clinicopathologic correlations in a large Alzheimer disease center autopsy cohort: neuritic plaques and neurofibrillary tangles "do count" when staging disease severity

There is uncertainty regarding the association of cognitive decline in Alzheimer disease (AD) with classic histopathologic features- neurofibrillary tangles (NFTs) and "neuritic" amyloid plaques (NPs). This uncertainty fuels doubts about the diagnostic importance of NFTs and NPs and leads to confusion regarding hypotheses of AD pathogenesis. Three hundred ninety subjects who underwent longitudinal premortem clinical workup and postmortem quantitative neuropathologic assessment served as the group to address this issue. Subjects with concomitant brain disease(s) were analyzed independently to more accurately assess the contribution of distinct pathologies to cognitive decline. More than 60% of patients of all age groups had important non-AD brain pathologies. However, subjects without superimposed brain diseases showed strong correlations between AD-type pathology counts (NFTs > NPs) and premortem Mini-Mental State Examination scores. The observed correlation was stronger in isocortex than in allocortex and was maintained across age groups including patients older than 90 years. A theoretical model is proposed in which our results are interpreted to support the "amyloid cascade hypothesis" of AD pathogenesis. Our data show that there are many important contributory causes to cognitive decline in older persons. However, NFTs and NPs should not be dismissed as irrelevant in AD based on clinicopathologic correlation.

The enigma of vascular cognitive disorder and vascular dementia

The prevalence, morphology and pathogenesis of vascular dementia (VaD), recently termed vascular cognitive impairment, are a matter of discussion, and currently used clinical diagnostic criteria show moderate sensitivity (average 50%) and variable specificity (range 64-98%). In Western clinic-based series, VaD is suggested in 8-10% of cognitively impaired aged subjects. Its prevalence in autopsy series varies from 0.03 to 58%, with reasonable values of 8-15%, while in Japan it is seen in 22-35%. Neuropathologic changes associated with cognitive impairment include multifocal and/or diffuse disease and focal lesions: multi-infarct encephalopathy, white matter lesions or arteriosclerotic subcortical (leuko)encephalopathy, multilacunar state, mixed cortico-subcortical type, borderline/watershed lesions, rare granular cortical atrophy, post-ischemic encephalopathy and hippocampal sclerosis. They result from systemic, cardiac and local large or small vessel disease. Recent data indicate that cognitive decline is commonly associated with widespread small ischemic/vascular lesions (microinfarcts, lacunes) throughout the brain with predominant involvement of subcortical and functionally important brain areas. Their pathogenesis is multifactorial, and their pathophysiology affects neuronal networks involved in cognition, memory, behavior and executive functioning. Vascular lesions often coexist with Alzheimer disease (AD) and other pathologies. Minor cerebrovascular lesions, except for severe amyloid angiopathy, appear not essential for cognitive decline in full-blown AD, while both mild Alzheimer pathology and small vessel disease may interact synergistically. The lesion pattern of "pure" VaD, related to arteriosclerosis and microangiopathies, differs from that in mixed-type dementia (AD with vascular encephalopathy), more often showing large infarcts, which suggests different pathogenesis of both types of lesions. Due to the high variability of cerebrovascular pathology and its causative factors, no validated neuropathologic criteria for VaD are available, and a large variability across laboratories still exists in the procedures for morphologic examination and histology techniques.

Actin-binding proteins coronin-1a and IBA-1 are effective microglial markers for immunohistochemistry

This study identifies the actin-binding protein, coronin-1a, as a novel and effective immunohistochemical marker for microglia in both cell cultures and in formaldehyde-fixed, paraffin-embedded tissue. Antibodies to coronin-1a effectively immunostained microglia in human, monkey, horse, rat, and mouse tissues, even in tissues stored for long periods of time. The identity of coronin-1a-immunoreactive cells as microglia was confirmed using double immunolabeling with cell type-specific markers as well as by morphological features and the distribution of immunoreactive cells. These properties are shared by another actin-binding protein, IBA-1. Unlike IBA-1, coronin-1a immunoreactivity was also detected in lymphocytes and certain other hematopoietic cells. The results indicate that both coronin-1a and IBA-1 are robust markers for microglia that can be used in routinely processed tissue of humans and animals. Because both coronin-1a and IBA-1 are actin-binding proteins that play a role in rearrangement of the membrane cytoskeleton, it suggests that these proteins are critical to dynamic properties of microglia.

Haplotype-based association analysis of the MAPT locus in late onset Alzheimer's disease

BACKGROUND

Late onset Alzheimer's disease (LOAD) is a common sporadic form of the illness, affecting individuals above the age of 65 yrs. A prominent hypothesis for the aetiopathology of Alzheimer's disease is that in the presence of a beta-amyloid load, individuals expressing a pathogenic form of tau protein (MAPT) are at increased risk for developing the disease. Genetic studies in this pursuit have, however, yielded conflicting results. A recent study showed a significant haplotype association (H1c) with AD. The current study is an attempt to replicate this association in an independently ascertained cohort.

RESULTS

In this report we present the findings of a haplotype analysis at the MAPT locus. We failed to detect evidence of association of the H1c haplotype at the MAPT locus with LOAD. None of the six SNPs forming the H1c haplotype showed evidence of association with disease. In addition, nested clade analysis suggested the presence of independent mutations at multiple points in the haplotype network or homoplasy at the MAPT locus. Such homoplasy can confound single SNP tests for association. We do not detect evidence that the set of SNPs forming the H1c haplotype in general or rs242557 in particular are pathogenic for LOAD.

CONCLUSION

In conclusion, we employed two contemporary haplotype analysis tools to perform haplotype association analysis at the MAPT locus. Our data suggest that the tagged SNPs forming the H1c haplotype do not have a causal role in the pathogenesis of LOAD.

Diffuse beta-amyloid plaques and hyperphosphorylated tau are unrelated processes in aged dogs with behavioral deficits

Single and double-labeling immunocytochemistry has been used to learn about the localization, distribution, and possible relationship between beta-amyloid protein (Abeta) deposition and tau hyperphosphorylation in the canine cerebral cortex with age. Behavioral impairment, as reported by the owners and tested in all dogs, correlated with increased Abeta burden in old dogs. Abeta plaques were diffuse and they were not accompanied by modifications in synaptic protein expression. Plaques were not associated with increased active mitogen activated protein kinase (MAPK/ERK-P) and p38 kinase (p38-P) expression, and tau hyperphosphorylation in neighboring cell processes. Yet tau hyperphosphorylation, as revealed with phospho-specific antibodies to tauThr181 and tauSer396, increased with age in individual neurons. Moreover, the subcellular pattern shifted from perinuclear localization to granular cytoplasmic and nuclear distribution with age. Our results in dog suggest that Abeta diffuse plaque formation and tau hyperphosphorylation are independent events, both occurring during the process of aging. Although increased cognitive dysfunction is associated with increased tau hyperphosphorylation, further investigation is needed to understand whether tau hyperphosphorylation is causative of cognitive impairment or an independent process related to aging.

Pick disease: a brief overview

This article is a brief review of the clinical, radiographic, and pathologic features of Pick disease. It is directed toward residents and fellows in training as well as practicing physicians who might wish to find a concise treatise on this clinicopathologic entity. The pathogenesis and genetics of this disorder are discussed. Included are medical journal articles accessed from computerized medical literature searches of articles published in the last 10 years. Pertinent images have been included where necessary. Although ubiquitously discussed in medical school and residency, Pick disease is nevertheless a relatively uncommon clinicopathologic entity. Recognition of its clinical and pathologic manifestations is critical in correctly diagnosing this illness and subsequently educating family members of the deceased.

The H1c haplotype at the MAPT locus is associated with Alzheimer's disease

Although it is clear that microtubule associated protein tau (MAPT) is involved in Alzheimer's disease (AD) pathology, it has not been clear whether it is involved genetically. We have recently examined the MAPT locus in progressive supranuclear palsy and found that a haplotype (H1c) on the background of the well-described H1 clade is associated with PSP. Here we report that the same haplotype is associated with the risk of AD in two autopsy confirmed series of cases with ages at death >65 years.

Overlap between neurodegenerative disorders

Neurodegenerative disorders are characterized by the formation of distinct pathological changes in the brain, including extracellular protein deposits, cellular inclusions, and changes in cell morphology. Since the earliest published descriptions of these disorders, diagnosis has been based on clinicopathological features, namely, the coexistence of a specific clinical profile together with the presence or absence of particular types of lesion. In addition, the molecular profile of lesions has become an increasingly important feature both in the diagnosis of existing disorders and in the description of new disease entities. Recent studies, however, have reported considerable overlap between the clinicopathological features of many disorders leading to difficulties in the diagnosis of individual cases and to calls for a new classification of neurodegenerative disease. This article discusses: (i) the nature and degree of the overlap between different neurodegenerative disorders and includes a discussion of Alzheimer's disease, dementia with Lewy bodies, the fronto-temporal dementias, and prion disease; (ii) the factors that contribute to disease overlap, including historical factors, the presence of disease heterogeneity, age-related changes, the problem of apolipoprotein genotype, and the co-occurrence of common diseases; and (iii) whether the current nosological status of disorders should be reconsidered.

Adult neurogenesis: from precursors to network and physiology

The discovery that the adult mammalian brain creates new neurons from pools of stemlike cells was a breakthrough in neuroscience. Interestingly, this particular new form of structural brain plasticity seems specific to discrete brain regions, and most investigations concern the subventricular zone (SVZ) and the dentate gyrus (DG) of the hippocampal formation (HF). Overall, two main lines of research have emerged over the last two decades: the first aims to understand the fundamental biological properties of neural stemlike cells (and their progeny) and the integration of the newly born neurons into preexisting networks, while the second focuses on understanding its relevance in brain functioning, which has been more extensively approached in the DG. Here, we propose an overview of the current knowledge on adult neurogenesis and its functional relevance for the adult brain. We first present an analysis of the methodological issues that have hampered progress in this field and describe the main neurogenic sites with their specificities. We will see that despite considerable progress, the levels of anatomic and functional integration of the newly born neurons within the host circuitry have yet to be elucidated. Then the intracellular mechanisms controlling neuronal fate are presented briefly, along with the extrinsic factors that regulate adult neurogenesis. We will see that a growing list of epigenetic factors that display a specificity of action depending on the neurogenic site under consideration has been identified. Finally, we review the progress accomplished in implicating neurogenesis in hippocampal functioning under physiological conditions and in the development of hippocampal-related pathologies such as epilepsy, mood disorders, and addiction. This constitutes a necessary step in promoting the development of therapeutic strategies.

A comparative study of age-related brain pathology--are neurodegenerative diseases present in nonhuman animals ?

Although some aged dogs definitely have dementia-like conditions, they have rather different brain histopathology from that seen in Alzheimer's disease including the shape of senile plaques, severity of neuron loss and absence of neurofibrillary tangles. Aged wild-type mice never show such brain lesions at all. In addition, no cases of Parkinson's disease have been reported in nonhuman animals yet. The reason for this might be non-parallel aging of the whole body and brain. If such nonhuman animals had a longer life span, like humans, typical Alzheimer's and Parkinson's lesions would be formed in the brain. As the rate of deposition of the misfolded proteins causing the lesions might be slow, nonhuman animals normally die before the lesions appear.

Hypoglycemia induces transient neurogenesis and subsequent progenitor cell loss in the rat hippocampus

Neurogenesis after brain injury not only leads to the replacement of damaged cells but might also contribute to functional recovery, suggesting the possibility of endogenous neural repair. We investigated the extent of hippocampal neural regeneration in a rat model of hypoglycemia. Two weeks after 30 min of insulin-induced isoelectric electroencephalogram, extensive neuronal loss was observed in the hippocampus, including area CA1 and dentate gyrus (DG). A transient increase in progenitor cell proliferation in the DG subgranular zone (SGZ) was detected, leading to an increase of immature neuroblasts 1-2 weeks after hypoglycemic insult. Most of the surviving newborn cells assumed a neuronal phenotype within 1 month in DG, a few cells near the site of granule-cell death becoming astroglia or microglia. No neuronal regeneration was observed in the CA1 after hypoglycemia, although dividing cells appeared to be astroglia or microglia in CA1 and dentate hilus. At 4 weeks after hypoglycemia, proliferative activity in the SGZ diminished below baseline in experimental versus control rats, with a subsequent reduction of neuroblasts. Morphological findings (doublecortin staining) suggest permanent progenitor cell loss in some areas of SGZ. Reduced neurogenesis in DG and lack of neuronal regeneration in CA1 may impede cognitive recovery after severe hypoglycemia injury.

Extracellular Deposits of Aβ Produced in Cultures of Alzheimer Disease Brain Vascular Smooth Muscle Cells

Alzheimer disease (AD) and Down syndrome (DS) brains contain deposits of amyloid-beta peptide that are located extracellularly in the neuropil and in blood vessels walls. A small fraction of brain Abeta is detected intracellularly in neurons, smooth muscle cells, and microglia. The roles of these extracellular and intracellular pools of Abeta in pathogenesis of AD-type dementia are controversial. Cell culture models of vascular amyloidosis-beta revealed intracellular, but not extracellular deposition of Abeta. Here we demonstrate for the first time, formation of extracellular deposits of Abeta in primary cultures of vascular smooth muscle cells isolated from AD cases with cerebrovascular amyloid angiopathy. Extracellular Abeta deposition required the use of cultures that produced high quantities of Abeta, which contained at least 50% of cells forming intracellular Abeta deposits, and providing extracellular matrix proteins. During 12 days of culture in this system, we observed accumulation of nonfibrillar, granular deposits in extracellular matrix, similar to early stages of vascular amyloidogenesis in vivo. This is a valuable system to study the effects of various potential amyloidogenic factors on formation of extracellular Abeta deposits.