A majority of current disease-modifying therapeutic approaches for age-related neurodegenerative diseases target their characteristic proteopathic lesions (α-synuclein, Tau, Aβ). To monitor such ...treatments, fluid biomarkers reflecting the underlying disease process are crucial. We found robust increases of neurofilament light chain (NfL) in CSF and blood in murine models of α-synucleinopathies, tauopathy, and β-amyloidosis. Blood and CSF NfL levels were strongly correlated, and NfL increases coincided with the onset and progression of the corresponding proteopathic lesions in brain. Experimental induction of α-synuclein lesions increased CSF and blood NfL levels, while blocking Aβ lesions attenuated the NfL increase. Consistently, we also found NfL increases in CSF and blood of human α-synucleinopathies, tauopathies, and Alzheimer’s disease. Our results suggest that CSF and particularly blood NfL can serve as a reliable and easily accessible biomarker to monitor disease progression and treatment response in mouse models and potentially in human proteopathic neurodegenerative diseases.
•Increased NfL in CSF and blood of proteopathic neurodegenerative diseases•Increased NfL in CSF and blood coincides with onset of proteopathic lesions in brain•NfL as disease progression and treatment response marker•Translational value and predictability of current mouse models in clinical settings
Bacioglu et al. (2016) report NfL increases in CSF and blood of murine models and human α-synucleinopathies, tauopathies, and β-amyloidosis. NfL in bodily fluid constitutes a biomarker of neurodegeneration reflecting the translational value and potential impact of current mouse models in clinical settings.
Brain Aβ deposition is a key early event in the pathogenesis of Alzheimer´s disease (AD), but the long presymptomatic phase and poor correlation between Aβ deposition and clinical symptoms remain ...puzzling. To elucidate the dependency of downstream pathologies on Aβ, we analyzed the trajectories of cerebral Aβ accumulation, Aβ seeding activity, and neurofilament light chain (NfL) in the CSF (a biomarker of neurodegeneration) in Aβ-precursor protein transgenic mice. We find that Aβ deposition increases linearly until it reaches an apparent plateau at a late age, while Aβ seeding activity increases more rapidly and reaches a plateau earlier, coinciding with the onset of a robust increase of CSF NfL. Short-term inhibition of Aβ generation in amyloid-laden mice reduced Aβ deposition and associated glial changes, but failed to reduce Aβ seeding activity, and CSF NfL continued to increase although at a slower pace. When short-term or long-term inhibition of Aβ generation was started at pre-amyloid stages, CSF NfL did not increase despite some Aβ deposition, microglial activation, and robust brain Aβ seeding activity. A dissociation of Aβ load and CSF NfL trajectories was also found in familial AD, consistent with the view that Aβ aggregation is not kinetically coupled to neurotoxicity. Rather, neurodegeneration starts when Aβ seeding activity is saturated and before Aβ deposition reaches critical (half-maximal) levels, a phenomenon reminiscent of the two pathogenic phases in prion disease.
The molecular architecture of amyloids formed in vivo can be interrogated using luminescent conjugated oligothiophenes (LCOs), a unique class of amyloid dyes. When bound to amyloid, LCOs yield ...fluorescence emission spectra that reflect the 3D structure of the protein aggregates. Given that synthetic amyloid-β peptide (Aβ) has been shown to adopt distinct structural conformations with different biological activities, we asked whether Aβ can assume structurally and functionally distinct conformations within the brain. To this end, we analyzed the LCO-stained cores of β-amyloid plaques in postmortem tissue sections from frontal, temporal, and occipital neocortices in 40 cases of familial Alzheimer’s disease (AD) or sporadic (idiopathic) AD (sAD). The spectral attributes of LCO-bound plaques varied markedly in the brain, but the mean spectral properties of the amyloid cores were generally similar in all three cortical regions of individual patients. Remarkably, the LCO amyloid spectra differed significantly among some of the familial and sAD subtypes, and between typical patients with sAD and those with posterior cortical atrophy AD. Neither the amount of Aβ nor its protease resistance correlated with LCO spectral properties. LCO spectral amyloid phenotypes could be partially conveyed to Aβ plaques induced by experimental transmission in a mouse model. These findings indicate that polymorphic Aβ-amyloid deposits within the brain cluster as clouds of conformational variants in different AD cases. Heterogeneity in the molecular architecture of pathogenic Aβ among individuals and in etiologically distinct subtypes of AD justifies further studies to assess putative links between Aβ conformation and clinical phenotype.
SignificanceSingle-cell transcriptomics has revealed specific glial activation states associated with the pathogenesis of neurodegenerative diseases, such as Alzheimer's and Parkinson's disease (AD ...and PD). What is still needed are clinically relevant biomarkers for deciphering such glial states in AD and PD patients. To this end, we applied proteome analysis in cerebrospinal fluid (CSF) of mouse models of AD and PD pathology. This allowed us to identify a panel of glial CSF proteins that largely match the transcriptomic changes. The identified proteins can also be quantified in human CSF and show changes in AD patients, supporting their relevance as biomarker candidates to stage glial activation in patients with neurodegenerative diseases.
Amyloid-β (Aβ) deposits are a relatively late consequence of Aβ aggregation in Alzheimer's disease. When pathogenic Aβ seeds begin to form, propagate and spread is not known, nor are they ...biochemically defined. We tested various antibodies for their ability to neutralize Aβ seeds before Aβ deposition becomes detectable in Aβ precursor protein-transgenic mice. We also characterized the different antibody recognition profiles using immunoprecipitation of size-fractionated, native, mouse and human brain-derived Aβ assemblies. At least one antibody, aducanumab, after acute administration at the pre-amyloid stage, led to a significant reduction of Aβ deposition and downstream pathologies 6 months later. This demonstrates that therapeutically targetable pathogenic Aβ seeds already exist during the lag phase of protein aggregation in the brain. Thus, the preclinical phase of Alzheimer's disease-currently defined as Aβ deposition without clinical symptoms-may be a relatively late manifestation of a much earlier pathogenic seed formation and propagation that currently escapes detection in vivo.
Altered concentrations of amyloid-β (Aβ) peptide and Tau protein in the cerebrospinal fluid (CSF) are thought to be predictive markers for Alzheimer's disease (AD). Transgenic mice overexpressing ...human amyloid precursor protein (APP) have been used to model Aβ pathology, but concomitant changes in Aβ and Tau in CSF have been less well studied. We measured Aβ and Tau in the brains and CSF of two well-characterized transgenic mouse models of AD: one expressing human APP carrying the Swedish mutation (APP23) and the other expressing mutant human APP and mutant human presenilin-1 (APPPS1). Both mouse models exhibit Aβ deposition in the brain, but with different onset and progression trajectories. We found an age-related 50 to 80% decrease in Aβ42 peptide in mouse CSF and a smaller decrease in Aβ40, both inversely correlated with the brain Aβ load. Surprisingly, the same mice showed a threefold increase in total endogenous murine Tau in CSF at the stages when Aβ pathology became prominent. The results mirror the temporal sequence and magnitude of Aβ and Tau changes in the CSF of patients with sporadic and dominantly inherited AD. This observation indicates that APP transgenic mice may be useful as a translational tool for predicting changes in Aβ and Tau markers in the CSF of AD patients. These findings also suggest that APP transgenic mouse models may be useful in the search for new disease markers for AD.
The intracerebral injection of β-amyloid-containing brain extracts can induce cerebral β-amyloidosis and associated pathologies in susceptible hosts. We found that intraperitoneal inoculation with ...β-amyloid-rich extracts induced β-amyloidosis in the brains of β-amyloid precursor protein transgenic mice after prolonged incubation times.
With molecular treatments coming into reach for spinocerebellar ataxia type 3 (SCA3), easily accessible, cross‐species validated biomarkers for human and preclinical trials are warranted, ...particularly for the preataxic disease stage. We assessed serum levels of neurofilament light (NfL) and phosphorylated neurofilament heavy (pNfH) in ataxic and preataxic subjects of two independent multicentric SCA3 cohorts and in a SCA3 knock‐in mouse model. Ataxic SCA3 subjects showed increased levels of both NfL and pNfH. In preataxic subjects, NfL levels increased with proximity to the individual expected onset of ataxia, with significant NfL elevations already 7.5 years before onset. Cross‐sectional NfL levels correlated with both disease severity and longitudinal disease progression. Blood NfL and pNfH increases in human SCA3 were each paralleled by similar changes in SCA3 knock‐in mice, here also starting already at the presymptomatic stage, closely following ataxin‐3 aggregation and preceding Purkinje cell loss in the brain. Blood neurofilaments, particularly NfL, might thus provide easily accessible, cross‐species validated biomarkers in both ataxic and preataxic SCA3, associated with earliest neuropathological changes, and serve as progression, proximity‐to‐onset and, potentially, treatment‐response markers in both human and preclinical SCA3 trials.
Synopsis
This cross‐species study establishes neurofilament blood levels (NfL/pNfH) as biomarkers of neuronal damage in spinocerebellar ataxia type 3 (SCA3) in humans and mice, both at the manifest and premanifest disease stage. NfL levels capture proximity to symptom onset and disease progression.
Blood levels of neurofilament light (NfL) and phosphorylated neurofilament heavy (pNfH) were assessed in manifest and premanifest subjects of two multicentric SCA3 cohorts and in SCA3 knock‐in mice.
NfL and pNfH levels were increased at the manifest disease stage, with NfL levels reflecting both clinical disease severity and disease progression.
NfL elevations in the premanifest stage were present already 7.5 years before the individual expected onset, with levels increasing further in temporal proximity to symptom onset.
NfL and pNfH increases in the SCA3 mouse model started also already at the premanifest stage, closely following ataxin‐3 aggregation and even preceding Purkinje cell loss in the brain.
This cross‐species study establishes neurofilament blood levels (NfL/pNfH) as biomarkers of neuronal damage in spinocerebellar ataxia type 3 (SCA3) in humans and mice, both at the manifest and premanifest disease stage. NfL levels capture proximity to symptom onset and disease progression.
We have generated a novel transgenic mouse model on a C57BL/6J genetic background that coexpresses KM670/671NL mutated amyloid precursor protein and L166P mutated presenilin 1 under the control of a ...neuron‐specific Thy1 promoter element (APPPS1 mice). Cerebral amyloidosis starts at 6–8 weeks and the ratio of human amyloid (A)β42 to Aβ40 is 1.5 and 5 in pre‐depositing and amyloid‐depositing mice, respectively. Consistent with this ratio, extensive congophilic parenchymal amyloid but minimal amyloid angiopathy is observed. Amyloid‐associated pathologies include dystrophic synaptic boutons, hyperphosphorylated tau‐positive neuritic structures and robust gliosis, with neocortical microglia number increasing threefold from 1 to 8 months of age. Global neocortical neuron loss is not apparent up to 8 months of age, but local neuron loss in the dentate gyrus is observed. Because of the early onset of amyloid lesions, the defined genetic background of the model and the facile breeding characteristics, APPPS1 mice are well suited for studying therapeutic strategies and the pathomechanism of amyloidosis by cross‐breeding to other genetically engineered mouse models.
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