Neuropathological and biochemical investigation of Hereditary Ferritinopathy cases with ferritin light chain mutation: Prominent protein aggregation in the absence of major mitochondrial or oxidative stress.

AIMS: Neuroferritinopathy (NF) or hereditary ferritinopathy (HF) is an autosomal dominant movement disorder due to mutation in the light chain of the iron storage protein ferritin (FTL). HF is the only late-onset neurodegeneration with brain iron accumulation disorder and study of HF offers a unique opportunity to understand the role of iron in more common neurodegenerative syndromes. METHODS: We carried out pathological and biochemical studies of six individuals with the same pathogenic FTL mutation. RESULTS: CNS pathological changes were most prominent in the basal ganglia and cerebellar dentate, echoing the normal pattern of brain iron accumulation. Accumulation of ferritin and iron was conspicuous in cells with a phenotype suggesting oligodendrocytes, with accompanying neuronal pathology and neuronal loss. Neurons still survived, however, despite extensive adjacent glial iron deposition, suggesting neuronal loss is a downstream event. Typical age-related neurodegenerative pathology was not normally present. Uniquely, the extensive aggregates of ubiquitinated ferritin identified indicate that abnormal FTL can aggregate, reflecting the intrinsic ability of FTL to self-assemble. Ferritin aggregates were seen in neuronal and glial nuclei showing parallels with Huntington's disease. There was neither evidence of oxidative stress activation nor any significant mitochondrial pathology in the affected basal ganglia. CONCLUSIONS: HF shows hallmarks of a protein aggregation disorder, in addition to iron accumulation. Degeneration in HF is not accompanied by age-related neurodegenerative pathology and the lack of evidence of oxidative stress and mitochondrial damage suggests that these are not key mediators of neurodegeneration in HF, casting light on other neurodegenerative diseases characterized by iron deposition.

Tissue microarray (TMA) use in post mortem neuropathology.

BACKGROUND: Tissue microarrays (TMAs), where each block (and thus section) contains multiple tissue cores from multiple blocks potentially allow more efficient use of tissue, reagents and time in neuropathology. NEW METHOD: The relationship between data from TMA cores and whole sections was investigated using 'virtual' TMA cores. This involved quantitative assessments of microglial pathology in white matter lesions and motor neuron disease, alongside qualitative TDP-43 inclusion status in motor neuron disease cases. Following this, a protocol was developed for TMA construction. RESULTS: For microglial pathology we found good concordance between virtual cores and whole sections for volume density using one 1.75 mm core (equivalent to a 2 mm core after accounting for peripheral tissue loss). More sophisticated microglial cell size and measures required two cores. Qualitative results of pTDP-43 pathology showed use of one 1.75 mm core gave a 100 % sensitivity and specificity within grey matter, and 88.3 % sensitivity and 100 % specificity within white matter. A method of producing the TMAs was suitable for immunohistochemistry both manually and by autostainer, with the minimal core loss from the microscope slide. COMPARISON WITH EXISTING METHODS: TMAs have been used infrequently in post mortem neuropathology research. However, we believe TMAs give comparable tissue assessment results and can be constructed, sectioned and stained with relative ease. CONCLUSIONS: We found TMAs could be used to assess both quantitative (microglial pathology) and qualitative pathology (TDP-43 proteinopathy) with greatly reduced quantities of tissue, time and reagents. These could be used for further work to improve data acquisition efficiency.

Expression of p16 and p21 in the frontal association cortex of ALS/MND brains suggests neuronal cell cycle dysregulation and astrocyte senescence in early stages of the disease.

AIMS: Cellular senescence plays a role in organismal ageing and has been linked to persistent DNA damage in age-related diseases. Brain senescence has been described in astrocytes and microglia, but it is less well understood in neurones. Evidence suggests that neurones activate a senescence-like mechanism that could contribute to neurodegeneration. We aimed to determine whether a persistent DNA damage response (DDR) and senescence activation are features of motor neurone disease (amyotrophic lateral sclerosis, ALS/MND). METHODS: We examined expression of senescence (p16 and p21) and DNA damage markers (8-OHdG and γH2AX) in motor cortex (MCx), frontal association cortex (FACx) and occipital cortex (OCx) in post-mortem tissue donated by patients with ALS/MND and controls. RESULTS: Nuclear expression of p16 and p21 was detected in glial cells; double immunofluorescence for p16/p21 and glial fibrillary acidic protein (GFAP) suggested that some of these cells were GFAP+ astrocytes. p21 nuclear expression was also found in neurones. Higher levels of p16+ (glia, P = 0.028) and p21+ (glia, P = 0.003; neurones, P = 0.008) cells were found in the FACx of ALS/MND donors but not in the MCx or OCx. Expression of p16 and p21 did not correlate with 8-OHdG or γH2AX. CONCLUSIONS: Expression of p16 and p21 in glia, mainly in astrocytes, suggests senescence induction in these cells; however, neuronal p21 expression might reflect a more general mechanism of age-related cell cycle dysregulation. The significantly higher proportion of cells expressing either p16 or p21 in the FACx of ALS/MND donors could indicate senescence activation and cell cycle dysregulation in early stages of the disease.

Epidemiological pathology of Aß deposition in the ageing brain in CFAS: addition of multiple Aß-derived measures does not improve dementia assessment using logistic regression and machine learning approaches.

Aß-amyloid deposition is a key feature of Alzheimer's disease, but Consortium to Establish a Registry for Alzheimer's Disease (CERAD) assessment, based on neuritic plaque density, shows a limited relationships to dementia. Thal phase is based on a neuroanatomical hierarchy of Aß-deposition, and in combination with Braak neurofibrillary tangle staging also allows derivation of primary age-related tauopathy (PART). We sought to determine whether Thal Aß phase predicts dementia better than CERAD in a population-representative cohort (n = 186) derived from the Cognitive Function and Ageing Study (CFAS). Cerebral amyloid angiopathy (CAA) was quantitied as the number of neuroanatomical areas involved and cases meeting criteria for PART were defined to determine if they are a distinct pathological group within the ageing population. Agreement with the Thal scheme was excellent. In univariate analysis Thal phase performed less well as a predictor of dementia than CERAD, Braak or CAA. Logistic regression, decision tree and linear discriminant analysis were performed for multivariable analysis, with similar results. Thal phase did not provide a better explanation of dementia than CERAD, and there was no additional benefit to including more than one assessment of Aß in the model. Number of areas involved by CAA was highly correlated with assessment based on a severity score (p < 0.001). The presence of capillary involvement (CAA type I) was associated with higher Thal phase and Braak stage (p < 0.001). CAA was not associated with microinfarcts (p = 0.1). Cases satisfying pathological criteria for PART were present at a frequency of 10.2% but were not older and did not have a higher likelihood of dementia than a comparison group of individuals with similar Braak stage but with more Aß. They also did not have higher hippocampal-tau stage, although PART was weakly associated with increased presence of thorn-shaped astrocytes (p = 0.048), suggesting common age-related mechanisms. Thal phase is highly applicable in a population-representative setting and allows definition of pathological subgroups, such as PART. Thal phase, plaque density, and extent and type of CAA measure different aspects of Aß pathology, but addition of more than one Aß measure does not improve dementia prediction, probably because these variables are highly correlated. Machine learning predictions reveal the importance of combining neuropathological measurements for the assessment of dementia.

Combined fused in sarcoma-positive (FUS+) basophilic inclusion body disease and atypical tauopathy presenting with an amyotrophic lateral sclerosis/motor neurone disease (ALS/MND)-plus phenotype.

AIMS: Amyotrophic lateral sclerosis/motor neurone disease (ALS/MND) is characterized by the presence of inclusions containing TDP-43 within motor neurones. In rare cases, ALS/MND may be associated with inclusions containing other proteins, such as fused in sarcoma (FUS), while motor system pathology may rarely be a feature of other neurodegenerative disorders. We here have investigated the association of FUS and tau pathology. METHODS: We report a case with an ALS/MND-plus clinical syndrome which pathologically demonstrated both FUS pathology and an atypical tauopathy. RESULTS: Clinical motor involvement was predominantly present in the upper motor neurone, and was accompanied by extrapyramidal features and sensory involvement, but with only minimal cognitive impairment. The presentation was sporadic and gene mutation screening was negative. Post mortem study demonstrated inclusions positive for FUS, including basophilic inclusion bodies. This was associated with 4R-tauopathy, largely as non-fibrillary diffuse phospho-tau in neurones, with granulovacuolar degeneration in a more restricted distribution. Double-staining revealed that neurones contained both types of protein pathology. CONCLUSION: FUS-positive basophilic inclusion body disease is a rare cause of ALS/MND, but in this case was associated with an unusual atypical tauopathy. The coexistence of two such rare neuropathologies raises the question of a pathogenic interaction.

British Neuropathological Society and International Society of Forensic Radiology and Imaging expert consensus statement for post mortem neurological imaging.

AIMS: To develop an expert consensus statement regarding appropriate clinical and forensic post mortem neurological imaging. METHODS: An expert panel of clinicians were recruited from registered members of the British Neuropathological Society (BNS) and the International Society of Forensic Radiology and Imaging (ISFRI) with post mortem expertise. Following a focus group meeting, 16 core statements were incorporated into an online modified Delphi survey and each panellist was asked to score their level of agreement. Following the first iteration, two statements that failed to reach consensus were modified and re-rated. Consensus was predefined as 75% agreement across responders. RESULTS: Seventeen experts joined the panel and 12 (70.6%) attended the focus group meeting; 14 (82%) completed both iterations of the survey. Consensus was reached for need of adequate clinical history, multidisciplinary discussion, establishment of special interest groups to discuss cases, gathering further evidence to inform imaging choices, establishment of methods for quality assessment in reporting standards and adequate funding for imaging services. The panel agreed that pathologists should be responsible for neuroimaging referrals, collating results of ancillary tests, and producing the final post mortem report. Areas requiring further discussion include the impact of double reporting, indications for neuroimaging and utilities of three-dimensional printing. CONCLUSION: The BNS/ISFRI statement represents current views of an expert panel of health professionals engaged in post-mortem neuroimaging. We hope this provides a working guideline for less experienced operators, stimulates discussion and highlights the most pressing clinical and research questions.

Microinfarcts in an older population-representative brain donor cohort (MRC CFAS): Prevalence, relation to dementia and mobility, and implications for the evaluation of cerebral Small Vessel Disease.

INTRODUCTION: Microinfarcts, small ischaemic foci common in ageing brain, are associated with dementia and gait dysfunction. We determined their relationship with dementia, mobility and cerebrovascular disease in an older population-representative brain donor cohort. These data on microinfarcts were evaluated in relation to pathological assessments of clinically significant cerebral small vessel disease (SVD). METHODS: Microinfarcts were assessed in the MRC Cognitive Function and Ageing Study (n = 331). Nine brain areas were staged according to the number of areas affected. RESULTS: 36% of brains showed at least 1 microinfarct. Higher cortical microinfarct stage was associated with dementia at death (OR 1.41, 95% CI 1.02; 1.96, P = 0.038), whilst cortical and subcortical microinfarct stages were associated with impaired mobility (OR 1.36, 95% CI 1.05-1.74; P 0.018) and falls (OR 1.96, 95% CI 1.11-3.43; P = 0.02). Adding data on microinfarcts to a definition of SVD, based on white matter lesions (WMLs), lacunes and significant arteriosclerosis, were assessed by comparing area under ROC curve (AUC) with and without microinfarcts. SVD was significantly related to dementia status with or without inclusion of microinfarcts. Modelling potential pathological definitions of SVD to predict dementia or impaired mobility indicated optimal prediction using combined assessment of WMLs, lacunes and microinfarcts. CONCLUSION: Cortical (dementia) and subcortical microinfarcts (impaired mobility) are related to diverse clinical outcomes. Optimal pathological assessment of significant SVD in brain ageing is achieved based on WMLs, lacunes and microinfarcts and may not require subjective assessment of the extent and severity of arteriosclerosis.

Review: Astrocytes in Alzheimer's disease and other age-associated dementias: a supporting player with a central role.

Astrocytes have essential roles in the central nervous system and are also implicated in the pathogenesis of neurodegenerative disease. Forming non-overlapping domains, astrocytes are highly complex cells. Immunohistochemistry to a variety of proteins can be used to study astrocytes in tissue, labelling different cellular components and sub-populations, including glial fibrillary acidic protein, ALDH1L1, CD44, NDRG2 and amino acid transporters, but none of these labels the entire astrocyte population. Increasing heterogeneity is recognized in the astrocyte population, a complexity that is relevant both to their normal function and pathogenic roles. They are involved in neuronal support, as active components of the tripartite synapse and in cell interactions within the neurovascular unit (NVU), where they are essential for blood-brain barrier maintenance and neurovascular coupling. Astrocytes change with age, and their responses may modulate the cellular effects of neurodegenerative pathologies, which alone do not explain all of the variance in statistical models of neurodegenerative dementias. Astrocytes respond to both the neurofibrillary tangles and plaques of Alzheimer's disease, to hyperphosphorylated tau and Aß, eliciting an effect which may be neuroprotective or deleterious. Not only astrocyte hypertrophy, in the form of gliosis, occurs, but also astrocyte injury and atrophy. Loss of normal astrocyte functions may contribute to reduced support for neurones and dysfunction of the NVU. Understanding how astrocytes contribute to dementia requires an understanding of the underlying heterogeneity of astrocyte populations, and the complexity of their responses to pathology. Enhancing the supportive and neuroprotective components of the astrocyte response has potential translational applications in therapeutic approaches to dementia.

Expression microdissection isolation of enriched cell populations from archival brain tissue.

BACKGROUND: Laser capture microdissection (LCM) is an established technique for the procurement of enriched cell populations that can undergo further downstream analysis, although it does have limitations. Expression microdissection (xMD) is a new technique that begins to address these pitfalls, such as operator dependence and contamination. NEW METHOD: xMD utilises immunohistochemistry in conjunction with a chromogen to isolate specific cell types by extending the fundamental principles of LCM to create an operator-independent method for the procurement of specific CNS cell types. RESULTS: We report how xMD enables the isolation of specific cell populations, namely neurones and astrocytes, from rat formalin fixed-paraffin embedded (FFPE) tissue. Subsequent reverse transcriptase-polymerase chain reaction (RT-PCR) analysis confirms the enrichment of these specific populations. RIN values after xMD indicate samples are sufficient to carry out further analysis. COMPARISON WITH EXISTING METHOD: xMD offers a rapid method of isolating specific CNS cell types without the need for identification by an operator, reducing the amount of unintentional contamination caused by operator error, whilst also significantly reducing the time required by the current basic LCM technique. CONCLUSIONS: xMD is a superior method for the procurement of enriched cell populations from post-mortem tissue, which can be utilised to create transcriptome profiles, aiding our understanding of the contribution of these cells to a range of neurological diseases. xMD also addresses the issues associated with LCM, such as reliance on an operator to identify target cells, which can cause contamination, as well as addressing the time consuming nature of LCM.

PTEN regulates AMPA receptor-mediated cell viability in iPS-derived motor neurons.

Excitatory transmission in the brain is commonly mediated by the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors. In amyotrophic lateral sclerosis (ALS), AMPA receptors allow cytotoxic levels of calcium into neurons, contributing to motor neuron injury. We have previously shown that oculomotor neurons resistant to the disease process in ALS show reduced AMPA-mediated inward calcium currents compared with vulnerable spinal motor neurons. We have also shown that PTEN (phosphatase and tensin homolog deleted on chromosome 10) knockdown via siRNA promotes motor neuron survival in models of spinal muscular atrophy (SMA) and ALS. It has been reported that inhibition of PTEN attenuates the death of hippocampal neurons post injury by decreasing the effective translocation of the GluR2 subunit into the membrane. In addition, leptin can regulate AMPA receptor trafficking via PTEN inhibition. Thus, we speculate that manipulation of AMPA receptors by PTEN may represent a potential therapeutic strategy for neuroprotective intervention in ALS and other neurodegenerative disorders. To this end, the first step is to establish a fibroblast-iPS-motor neuron in vitro cell model to study AMPA receptor manipulation. Here we report that iPS-derived motor neurons from human fibroblasts express AMPA receptors. PTEN depletion decreases AMPA receptor expression and AMPA-mediated whole-cell currents, resulting in inhibition of AMPA-induced neuronal death in primary cultured and iPS-derived motor neurons. Taken together, our results imply that PTEN depletion may protect motor neurons by inhibition of excitatory transmission that represents a therapeutic strategy of potential benefit for the amelioration of excitotoxicity in ALS and other neurodegenerative disorders.

Brain haemosiderin in older people: pathological evidence for an ischaemic origin of magnetic resonance imaging (MRI) microbleeds.

INTRODUCTION: Magnetic resonance imaging (MRI) cerebral microbleeds (CMB) arise from ferromagnetic haemosiderin iron assumed to derive from extravasation of erythrocytes. Light microscopy of ageing brain frequently reveals foci of haemosiderin from single crystalloids to larger, predominantly perivascular, aggregates. The pathological and radiological relationship between these findings is not resolved. METHODS: Haemosiderin deposition and vascular pathology in the putamen were quantified in 200 brains donated to the population-representative Medical Research Council Cognitive Function and Ageing Study. Molecular markers of gliosis and tissue integrity were assessed by immunohistochemistry in brains with highest (n = 20) and lowest (n = 20) levels of putamen haemosiderin. The association between haemosiderin counts and degenerative and vascular brain pathology, clinical data, and the haemochromatosis (HFE) gene H63D genotype were analysed. The frequency of MRI CMB in 10 cases with highest and lowest burden of putamen haemosiderin, was compared using post mortem 3T MRI. RESULTS: Greater putamen haemosiderin was significantly associated with putaminal indices of small vessel ischaemia (microinfarcts, P < 0.05; arteriolosclerosis, P < 0.05; perivascular attenuation, P < 0.001) and with lacunes in any brain region (P < 0.023) but not large vessel disease, or whole brain measures of neurodegenerative pathology. Higher levels of putamen haemosiderin correlated with more CMB (P < 0.003). CONCLUSIONS: The MRI-CMB concept should take account of brain iron homeostasis, and small vessel ischaemic change in later life, rather than only as a marker for minor episodes of cerebrovascular extravasation. These data are of clinical relevance, suggesting that basal ganglia MRI microbleeds may be a surrogate for ischaemic small vessel disease rather than exclusively a haemorrhagic diathesis.

Calcium dysregulation in relation to Alzheimer-type pathology in the ageing brain.

AIMS: Calcium dyshomeostasis is implicated in the pathogenesis of several neurodegenerative disorders including Alzheimer's disease. However, much of the previous research has focused on changes in neuronal calcium signalling. In a recent microarray study we identified dysregulation of several key signalling pathways including the Ca(2+) signalling pathway in astrocytes as Alzheimer-type pathology developed. In this study we sought to determine the expression of calpain-10 and calcium/calmodulin-dependent kinase alpha (CamKIIα) in relation to Alzheimer-type pathology in a population-based study. METHODS: Using post mortem temporal cortex samples derived from the Medical Research Council Cognitive Function and Ageing Study (MRC-CFAS) ageing brain cohort we examined calpain-10 and CamKIIα gene and protein expression using quantitative polymerase chain reaction and immunohistochemistry. RESULTS: We demonstrate that astrocytic expression of calpain-10 is up-regulated, and CamKIIα down-regulated with increasing Braak stage. Using immunohistochemistry we confirm protein expression of calpain-10 in astrocytes throughout the temporal cortex and demonstrate that calpain-10 immunoreactivity is correlated with both local and global measures of Alzheimer-type pathology. In addition, we identify a subpopulation of calpain-10 immunoreactive interlaminar astrocytes that extend processes deep into the cortex. CamKIIα is predominantly neuronal in localization and is associated with the presence of diffuse plaques in the ageing brain. DISCUSSION: Dysregulated expression of key calcium signalling molecules occurs with progression of Alzheimer-type pathology in the ageing brain, highlighting the need for further functional studies of astrocytic calcium signalling with respect to disease progression.

Lack of unique neuropathology in amyotrophic lateral sclerosis associated with p.K54E angiogenin (ANG) mutation.

AIMS: Five to 10% of cases of amyotrophic lateral sclerosis are familial, with the most common genetic causes being mutations in the C9ORF72, SOD1, TARDBP and FUS genes. Mutations in the angiogenin gene, ANG, have been identified in both familial and sporadic patients in several populations within Europe and North America. The aim of this study was to establish the incidence of ANG mutations in a large cohort of 517 patients from Northern England and establish the neuropathology associated with these cases. METHODS: The single exon ANG gene was amplified, sequenced and analysed for mutations. Pathological examination of brain, spinal cord and skeletal muscle included conventional histology and immunohistochemistry. RESULTS: Mutation screening identified a single sporadic amyotrophic lateral sclerosis case with a p.K54E mutation, which is absent from 278 neurologically normal control samples. The clinical presentation was of limb onset amyotrophic lateral sclerosis, with rapid disease progression and no evidence of cognitive impairment. Neuropathological examination established the presence of characteristic ubiquitinated and TDP-43-positive neuronal and glial inclusions, but no abnormality in the distribution of angiogenin protein. DISCUSSION: There is only one previous report describing the neuropathology in a single case with a p.K17I ANG mutation which highlighted the presence of eosinophilic neuronal intranuclear inclusions in the hippocampus. The absence of this feature in the present case indicates that patients with ANG mutations do not always have pathological changes distinguishable from those of sporadic amyotrophic lateral sclerosis.

Mesial temporal astrocyte tau pathology in the MRC-CFAS ageing brain cohort.

BACKGROUND: Glial tau pathology is seen in certain tauopathies and in ageing. We determined its frequency in ageing mesial temporal lobe and its relationship to other tau pathologies in the MRC-CFAS population-representative neuropathology cohort. METHODS: Mesial temporal lobe, including hippocampus, amygdala, entorhinal cortex and white matter, was examined using immunohistochemistry with the AT8 antibody to phospho-tau and RD3 and RD4 antibodies to 3R and 4R tau isoforms. Gallyas silver stain was used to detect fibrillar aggregates. RESULTS: Thorn-shaped astrocytes (TSA), positive with AT8, RD4 and Gallyas, were present in 49% of cases. They were particularly prevalent in subpial, periventricular and white matter perivascular locations and were less frequent in grey matter. Coiled bodies were seen in 18.8%. TSA were not related to Braak neurofibrillary tangle or hippocampal tangle pathology stages. TSA in grey matter were associated with coiled bodies (p = 0.011) and argyrophilic grains (p = 0.048), which were identified in 11.5% of cases. They did not correlate with dementia. CONCLUSIONS: Astrocyte tau pathology is common in the ageing mesial temporal lobe. Its formation is independent of Alzheimer-type pathology. It is a 4R tauopathy, which may form part of a mesial temporal age-related 4R tauopathy that includes oligodendroglial tau and argyrophilic grains.

Isolation of enriched glial populations from post-mortem human CNS material by immuno-laser capture microdissection.

Isolating individual populations of cells from post-mortem (PM) central nervous system (CNS) tissue for transcriptomic analysis will provide important insights into the pathogenesis of neurodegenerative diseases. To date, research on individual CNS cell populations has been hindered by the availability of suitable PM material, unreliable sample preparation and difficulties obtaining individual cell populations. In this paper we report how rapid immunohistochemistry combined with laser capture microdissection (immuno-LCM) enables the isolation of specific cell populations from PM CNS tissue, thereby enabling the RNA profile of these individual cell types to be investigated. Specifically, we detail methods for isolating enriched glial populations (astrocytes, oligodendrocytes and microglia) and confirm this cell enrichment by polymerase chain reaction (PCR). In addition, the study details the numbers of each glial population required to obtain 50ng RNA, a suitable amount of starting material required to carry out microarray analysis that potentially may identify alterations of cell-specific genes and pathways associated with a range of neurodegenerative disorders.

Staging and natural history of cerebrovascular pathology in dementia.

OBJECTIVE: Most pathologic studies indicate that significant vascular changes are found in the majority of elderly persons, either alone or in association with neurodegenerative processes such as Alzheimer disease (AD) or dementia with Lewy bodies (DLB). Cumulative burden of cerebrovascular lesions can explain cognitive decline described as vascular cognitive impairment, but because there is a lack of consensus in the best way to quantify vascular pathology, the relationship between cognitive decline and cerebrovascular disease remains uncertain. We developed a rating scheme for cerebrovascular lesions using postmortem brains from patients with dementia from 2 European tertiary care memory clinics. METHODS: A total of 135 brains with a neuropathologic diagnosis of vascular dementia (VaD) (n = 26), AD + VaD (n = 39), DLB + VaD (n = 21), AD + DLB + VaD (n = 9), AD (n = 19), and DLB (n = 21) were investigated in this study. Cerebrovascular lesions were rated on large sections from the hippocampus, the temporal lobe, the frontal lobe, and basal ganglia. RESULTS: In patients with dementia, vessel wall modifications such as arteriolosclerosis or amyloid angiopathy are the most common and presumably the earliest changes. Modifications in perivascular spaces and myelin loss are the next most common. Lacunar or regional infarcts may occur as a consequence of an independent process or in the final phase of small vessel diseases. CONCLUSION: A staging system based on this conceptual model of cerebrovascular pathology could enable the neuropathologic quantification of the cerebrovascular burden in dementia. Further studies are needed to determine whether this system can be used in large-scale studies to understand clinical-cerebrovascular pathologic correlations.

Association between APOE genotype, neuropathology and dementia in the older population of England and Wales.

AIMS: Apolipoprotein E (APOE) genotype is the major genetic risk factor for sporadic Alzheimer's disease (AD) but it is unclear how this is mediated. Most studies of APOE genotype have used case-control design to compare groups differing by two variables: i.e. dementia and AD pathology, so it is unclear to which of these variables APOE genotype is more strongly related. The prospective Medical Research Council Cognitive Function and Ageing Study neuropathology cohort is population-based sample in which donations are unbiased by dementia status. METHODS: We investigated the association between APOE genotypes and neuropathological and cognitive data in this cohort (n = 310). RESULTS: APOEε4 was associated with an increased risk of diffuse plaques, neuritic plaques, tangles and cerebral amyloid angiopathy. APOEε4 was not associated with infarcts, lacunes, haemorrhages or small vessel disease. APOEε2 appeared to have a protective effect on AD pathology and also on the risk of cortical atrophy. APOE genotype had a non-significant effect on the presence of dementia after adjusting for AD pathology. CONCLUSIONS: APOE genotype is associated with each of the key features of AD pathology but not with cerebrovascular disease other than cerebral amyloid angiopathy. The excess risk of dementia in those with an APOEε4 allele is explained by the pathological features of AD. However, it remains unclear to what extent cognitive dysfunction is caused by these specific pathological features or more directly by closely related APOE-associated mechanisms.

Population variation in oxidative stress and astrocyte DNA damage in relation to Alzheimer-type pathology in the ageing brain.

AIMS: Increasing evidence suggests a role for oxidative damage to DNA in brain ageing and in neurodegenerative disorders, including Alzheimer's disease. Most studies have focussed on the reduced capacity for DNA repair by neurones, and have not taken into account the effect of oxidative stress on astrocytes, and their contribution to pathology. METHODS: We examined levels of oxidative stress, DNA damage and DNA repair mechanisms in astrocytes in a population-based sample derived from the Medical Research Council Cognitive Function and Ageing Neuropathology Study. RESULTS: We demonstrate wide variation in parameters for oxidative stress and DNA damage in astrocytes in the ageing population. We show that there is a significant reduction (P = 0.002) in the lipid peroxidation marker malondialdehyde with increasing Braak stage in Alzheimer's disease. Furthermore, we demonstrate that expression of the DNA damage-associated molecules H2AX and DNA-dependent protein kinase do not increase with increasing Braak stage, rather there is evidence of a nonsignificant reduction in DNA-dependent protein kinase expression by neurones and astrocytes, and in H2AX by neurones with increasing levels of Alzheimer's type pathology. CONCLUSIONS: These findings suggest that the changes in oxidative stress and the astrocyte DNA damage response are not accounted for as an accumulating effect due to established Alzheimer-type pathology. We hypothesize that astrocyte damage, leading to impaired function, may contribute to the development of ageing brain pathology in some individuals.

Astrocyte phenotype in relation to Alzheimer-type pathology in the ageing brain.

Astrocyte pathology occurs in association with Alzheimer's disease (AD) and in brain ageing, but is poorly characterised. We sought to define the detailed cellular pathology of astrocytes, the extent of population variation and the relationship to Alzheimer-type changes in a population-based cohort. Three staining patterns were associated with GFAP and excitatory amino acid transporter 2 (EAAT2): minimal, moderate or extensive immunoreactivity. GFAP and EAAT2 expression were inversely related (p=0.015), with trends to increased expression of GFAP (p=0.019) and decreased expression of EAAT2 (p=ns) with increasing Braak stage. GFAP and EAAT2 correlated incompletely with beta-amyloid and tau immunoreactivity. However, gliosis increased with increasing burden of neuritic (p=0.011), but not diffuse (p=ns), plaques. Double-staining revealed distinct subsets of astrocytes; GFAP(+)EAAT(-), GFAP(-)EAAT(+), or GFAP(+)EAAT(+). In contrast to the variation in GFAP and EAAT2, levels of EAAT1 and S100B showed consistent staining patterns. Alzheimer-type pathology only partially explains the variation in gliosis and astrocyte functional markers, suggesting that other factors contribute to the population variance in astrocyte pathology.

Population variation in glial fibrillary acidic protein levels in brain ageing: relationship to Alzheimer-type pathology and dementia.

BACKGROUND: The cellular pathology of astrocytes in brain ageing and their role in modulating the brain's response to neurodegenerative pathology remain incompletely understood. METHODS: Using quantitative ELISA, we have investigated glial fibrillary acidic protein (GFAP) expression in the population-based neuropathology cohort of the Medical Research Council Cognitive Function and Ageing Study to determine: (1) the population variation in the astroglial hypertrophic response, (2) its relationship to the presence of Alzheimer-type pathology, and (3) its association with cognition. RESULTS: Increasing GFAP was found with increasing Braak stage, levels increasing even at early stages. Within Braak stages, GFAP did not differ between demented and non-demented individuals, but there was greater variance in GFAP in the demented. Possession of ApoE epsilon4 was associated with slightly increased GFAP levels (not significant) for given amyloid beta protein loads. CONCLUSION: In a population-based sample, increasing gliosis precedes development of Alzheimer lesions. Population variation in GFAP with varying Alzheimer lesion burdens suggests that they are not the only driver for astrogliosis. GFAP was not independently predictive of dementia, but the variation in astrocytic responses may be a factor modulating brain responses to neurodegenerative pathology.