Cerebrospinal fluid (CSF) has been extensively studied to explore biochemical alterations in subjects with neurodegenerative disorders. In Alzheimer's disease, levels of increased CSF tau protein and ...decreased levels of β‐amyloid 1–42 (Aβ42) have been shown to correlate with brain plaque formation and tangle pathology. Intracellular Lewy inclusions containing aggregated α‐synuclein (α‐syn) represent a pathological hallmark of Parkinson's disease (PD). In most – but not all – studies published to date total CSF α‐syn concentrations have been found to be decreased in disorders related to α‐syn pathology, that is, PD, dementia with Lewy bodies and multiple system atrophy. However, these reports show extensive signal overlap among tested individuals, thereby diminishing its potential for routine use in clinical practice.
To investigate potential biological (i.e., non‐technical) confounders of reported CSF levels for α‐syn, Aβ42, and tau in PD and related disorders, we carried out a methodical review of known factors that underlie signal variability and speculate on those that have not yet been tested. We discuss several biological factors, such as neuropathology, demographics, clinical phenotype, progression and duration of disease, concomitant illnesses and, last but not least, pharmacotherapy, which in isolation or combination can substantially alter values for CSF proteins of interest. Enhanced implementation of standardized clinical protocols, streamlined operating procedures, and further progress in the development of validated assays for CSF proteins have the potential to (i) inform us as to the pathogenesis of disease, (ii) support the laboratory‐based diagnosis for symptomatic subjects in the future, and (iii) facilitate breakthrough therapies to alter the course of neurodegenerative disorders, such as PD and Alzheimer's disease.
Cerebrospinal fluid (CSF) has been extensively studied to explore biochemical alterations in subjects with neurodegenerative disorders. To investigate potential biological confounders of reported CSF levels for α‐synuclein (α‐Syn), amyloid‐β 1‐42(Aβ42) and tau protein in Parkinson's disease and related disorders, we reviewed the current literature for known factors that underlie signal variability and speculate on those that have not yet been tested.
This article is part of a special issue on Parkinson disease.
Cerebrospinal fluid (CSF) has been extensively studied to explore biochemical alterations in subjects with neurodegenerative disorders. To investigate potential biological confounders of reported CSF levels for α‐synuclein (α‐Syn), amyloid‐β 1‐42(Aβ42) and tau protein in Parkinson's disease and related disorders, we reviewed the current literature for known factors that underlie signal variability and speculate on those that have not yet been tested.
This article is part of a special issue on Parkinson disease.
The goals of this study were to determine the effects of prolongedfixation time and to optimize antigen retrieval (AR) methods on immunohistochemical (IHC) staining of common neurodegenerative ...disease markers. A panel of commercial antibodies (Abs) to amyloid-β, ubiquitin, p62/sequestosome, tau, and α-synuclein was applied to a 2-mm tissue microarray using several AR methods. The IHC outcomes were assessed in sections that included 2 types of specimens taken from 20 postmortem brainsshort-term fixation ofup to 70 days before paraffin embedment and long-term fixation of up to 14 years in formalin. Good amyloid-β IHC staining was obtained with all amyloid-β Abs applied when a formic acid AR method was used, even after 14 years of fixation. Ubiquitin immunoreactivity was also optimally labeled with this method. The p62/sequestosome IHC outcome was optimal for tissue fixed up to 10 years, but only when the p62-lck-ligand-Ab with heat AR method was used. All hyperphosphorylated tau Abs tested worked with fixation up to 10 years, in particular with the heat AR method, whereas Abs against tau isoforms RD3 and RD4 were applicable only when the fixation time was 6months or shorter. α-Synuclein-immunoreactive structures were visualized up to 14 years but only by the use of Syn42-Ab after formic acid AR or after a combination of heat and formic acid methods.
ABSTRACTThere is no consensus on the pathologic conditions or severity implied by the term “hippocampal sclerosis” (HS). In this study, a panel of experienced neuropathologists evaluated inter-rater ...agreement for pathologic diagnoses in the hippocampus and proposes consensus recommendations on the use of the term “HS.” In a group of 251 cases of HS selected from a large autopsy cohort (1,388; 18%), a coordinating group identified 5 patterns of degenerative or vascular pathology. Four independent neuropathologists assessed a single set of hematoxylin and eosin–stained sections following descriptive definitions to classify the appearances and assign the diagnosis of HS, if appropriate. Diagnostic agreement (range, 36%–70%) was highest for vascular lesions. Subsequent joint review of all cases highlighted the need to identify neurodegenerative lesions using immunohistochemistry. Initial agreement in assigning the diagnosis of HS varied from 0% to 86%. After a joint review, the group recommended that the term “HS” should be applied to all cases with complete/near-complete neuronal loss and gliosis in the subfields of the cornu Ammonis but not to hippocampal microinfarction. Therefore, the etiology of HS must be defined in association with a neurodegenerative process or as “lacking neurodegenerative markers,” a pathologic condition presumed to arise from hypoxic/ischemic mechanisms.
Accurate differentiation between neurodegenerative diseases is developing quickly and has reached an effective level in disease recognition. However, there has been less focus on effectively ...distinguishing the prodromal state from later dementia stages due to a lack of suitable biomarkers. We utilized the Disease State Index (DSI) machine learning classifier to see how well quantified metabolomics data compares to clinically used cerebrospinal fluid (CSF) biomarkers of Alzheimer's disease (AD). The metabolic profiles were quantified for 498 serum and CSF samples using proton nuclear magnetic resonance spectroscopy. The patient cohorts in this study were dementia (with a clinical AD diagnosis) (N = 359), mild cognitive impairment (MCI) (N = 96), and control patients with subjective memory complaints (N = 43). DSI classification was conducted for MCI (N = 51) and dementia (N = 214) patients with low CSF amyloid-β levels indicating AD pathology and controls without such amyloid pathology (N = 36). We saw that the conventional CSF markers of AD were better at classifying controls from both dementia and MCI patients. However, quantified metabolic subclasses were more effective in classifying MCI from dementia. Our results show the consistent effectiveness of traditional CSF biomarkers in AD diagnostics. However, these markers are relatively ineffective in differentiating between MCI and the dementia stage, where the quantified metabolomics data provided significant benefit.
Core cerebrospinal fluid (CSF) biomarkers - Aβ42, Tau, and phosphorylated Tau (pTau) - have been recently incorporated in the revised criteria for Alzheimer's disease (AD). However, their widespread ...clinical application lacks standardization. Pre-analytical sample handling and storage play an important role in the reliable measurement of these biomarkers across laboratories.
In this study, we aim to surpass the efforts from previous studies, by employing a multicenter approach to assess the impact of less studied CSF pre-analytical confounders in AD-biomarkers quantification.
Four different centers participated in this study and followed the same established protocol. CSF samples were analyzed for three biomarkers (Aβ42, Tau, and pTau) and tested for different spinning conditions temperature: room temperature (RT) vs. 4°C; speed: 500 vs. 2000 vs. 3000 g, storage volume variations (25, 50, and 75% of tube total volume), as well as freezing-thaw cycles (up to five cycles). The influence of sample routine parameters, inter-center variability, and relative value of each biomarker (reported as normal/abnormal) was analyzed.
Centrifugation conditions did not influence biomarkers levels, except for samples with a high CSF total protein content, where either non-centrifugation or centrifugation at RT, compared to 4°C, led to higher Aβ42 levels. Reducing CSF storage volume from 75 to 50% of total tube capacity decreased Aβ42 concentration (within analytical CV of the assay), whereas no change in Tau or pTau was observed. Moreover, the concentration of Tau and pTau appears to be stable up to five freeze-thaw cycles, whereas Aβ42 levels decrease if CSF is freeze-thawed more than three times.
This systematic study reinforces the need for CSF centrifugation at 4°C prior to storage and highlights the influence of storage conditions in Aβ42 levels. This study contributes to the establishment of harmonized standard operating procedures that will help reducing inter-lab variability of CSF-AD biomarkers evaluation.
Insulin resistance (IR) has previously been associated with an increased risk of developing Alzheimer's disease (AD), although the relationship between IR and AD is not yet clear. Here, we examined ...the influence of IR on AD using plasma and cerebrospinal fluid (CSF) biomarkers related to IR and AD in cognitively healthy men. We also aimed to characterise the shared protein signatures between IR and AD.
Fifty-eight cognitively healthy men, 28 IR and 30 non-IR (age and APOE ε4 matched), were drawn from the Metabolic Syndrome in Men study in Kuopio, Finland. CSF AD biomarkers (amyloid β-peptide (Aβ), total tau and tau phosphorylated at the Thr181 epitope) were examined with respect to IR. Targeted proteomics using ELISA and Luminex xMAP assays were performed to assess the influence of IR on previously identified CSF and plasma protein biomarker candidates of AD pathology. Furthermore, CSF and plasma SOMAscan was performed to discover proteins that associate with IR and CSF AD biomarkers.
CSF AD biomarkers did not differ between IR and non-IR groups, although plasma insulin correlated with CSF Aβ/tau across the whole cohort. In total, 200 CSF and 487 plasma proteins were differentially expressed between IR and non-IR subjects, and significantly enriched pathways, many of which have been previously implicated in AD, were identified. CSF and plasma proteins significantly associated with CSF AD biomarkers were also discovered, and those sensitive to both IR and AD were identified.
These data indicate that IR is not directly related to the level of CSF AD pathology in cognitively healthy men. Proteins that associated with both AD and IR are potential markers indicative of shared pathology.
Genetic variants in the granulin (GRN) gene have been shown to increase the risk of Alzheimer's disease (AD). Here, we report that the A allele of rs5848 in GRN reduces plasma granulin levels in a ...dose-dependent manner in a clinically-defined AD sample cohort. Similarly, the mRNA levels of granulin were decreased with respect to A allele of rs5848 in the inferior temporal cortex of neuropathologically confirmed AD patients. Our findings suggest that the A allele of rs5848 is functionally relevant by reducing the expression of granulin.
To determine the extent of neurodegeneration of the visual association cortex, we assessed hyperphosphorylated tau-immunoreactive (HPtau-IR) neurofibrillary tangles in Brodmann Areas 18/19 in ...nondemented and demented subjects. At least occasional HPtau-IR neurofibrillary tangles were seen in 24% of 59 nondemented subjects with ages at death ranging from 42 to 87 years. The incidence increased to 41% in the 32 nondemented subjects who had HPtau-IR pathology in the hippocampal region. Demented subjects with Braak Stages 0 to III and corticobasal degeneration, frontotemporal lobar degeneration with TAR DNA binding protein 43, vascular cognitive impairment, or dementia with Lewy bodies also had HPtau-IR pathology in Brodmann Areas 18/19. These results support the concept that the occipital association area may have enhanced vulnerability to neurodegeneration. Neuropathologic assessment of these areas is, therefore, recommended, particularly in subjects suspected or known to have had mild cognitive impairment. Occasional HPtau-IR lesions were also seen in the medial temporal gyrus. Thus, the question as to whether scattered HPtau-IR lesions in either temporal or occipital cortex indicate a neurodegenerative disease remains unresolved. Further systematic clinicopathologic studies are needed for an understanding of regional susceptibility to neurodegeneration and the significance of scattered HPtau-IR brain lesions.
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