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  • 1
    In: Molecular Psychiatry, Springer Science and Business Media LLC
    Abstract: β-amyloid (Aβ) and tau aggregation as well as neuronal injury and atrophy (ATN) are the major hallmarks of Alzheimer’s disease (AD), and biomarkers for these hallmarks have been linked to neuroinflammation. However, the detailed regional associations of these biomarkers with microglial activation in individual patients remain to be elucidated. We investigated a cohort of 55 patients with AD and primary tauopathies and 10 healthy controls that underwent TSPO-, Aβ-, tau-, and perfusion-surrogate-PET, as well as structural MRI. Z -score deviations for 246 brain regions were calculated and biomarker contributions of Aβ (A), tau (T), perfusion (N1), and gray matter atrophy (N2) to microglial activation (TSPO, I) were calculated for each individual subject. Individual ATN-related microglial activation was correlated with clinical performance and CSF soluble TREM2 (sTREM2) concentrations. In typical and atypical AD, regional tau was stronger and more frequently associated with microglial activation when compared to regional Aβ (AD: β T  = 0.412 ± 0.196 vs. β A  = 0.142 ± 0.123, p   〈  0.001; AD-CBS: β T  = 0.385 ± 0.176 vs. β A  = 0.131 ± 0.186, p  = 0.031). The strong association between regional tau and microglia reproduced well in primary tauopathies (β T  = 0.418 ± 0.154). Stronger individual associations between tau and microglial activation were associated with poorer clinical performance. In patients with 4RT, sTREM2 levels showed a positive association with tau-related microglial activation. Tau pathology has strong regional associations with microglial activation in primary and secondary tauopathies. Tau and Aβ related microglial response indices may serve as a two-dimensional in vivo assessment of neuroinflammation in neurodegenerative diseases.
    Type of Medium: Online Resource
    ISSN: 1359-4184 , 1476-5578
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2023
    detail.hit.zdb_id: 1502531-7
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  • 2
    In: Alzheimer's & Dementia, Wiley, Vol. 17, No. S1 ( 2021-12)
    Abstract: 18‐kDa translocator protein position‐emission‐tomography (TSPO‐PET) imaging emerged for in vivo assessment of neuroinflammation in preclinical and clinical research of Alzheimer’s disease (AD). Higher TSPO‐PET binding as a surrogate of microglial activation in females has been reported for cognitively normal humans (HC), but sex effects have not yet been systematically evaluated in patients with AD. Thus, we aimed to investigate the impact of sex and the body mass index (BMI) on the relationship between β‐amyloid‐accumulation and microglial activation in AD. Method Fifty‐six patients with AD (34 female; BMI 24.9±4.0; age 71.1±7.7 years; 100% Aβ‐positive; MMSE 20.9±5.5) and 13 Aβ‐negative HC (7 female; BMI 24.2±3.3; age 70.6±7.5 years; MMSE 29.0±1.0) underwent TSPO‐PET ( 18 F‐GE‐180) and β‐amyloid‐PET imaging (Aβ‐PET; 18 F‐flutemetamol). The brain was parcellated into 218 cortical regions and standardized‐uptake‐value‐ratios (SUVr, cerebellar reference) were calculated for TSPO‐ and Aβ‐PET. Per AD patient, the averaged regional increase of TSPO‐ and Aβ‐PET SUVr (z‐score) was calculated versus HC. We used the function between regional Aβ‐PET and TSPO‐PET SUVr to determine the Aβ‐plaque dependent microglial response (slope) and the Aβ‐plaque independent microglial response (intercept) at the single patient level (Figure 1). All PET read‐outs were compared between sexes and we tested for a moderation effect of sex on the association between BMI and microglial activation, controlled for age. Result In AD the mean cortical TSPO‐PET z‐score of females (+0.69±0.72) was higher when compared to males (+0.30±0.73; p=0.048; Figure 2), whereas Aβ‐PET z‐scores were similar (female: +4.56±1.76; male: +4.44±2.08). The Aβ‐plaque independent microglial response was stronger in females with AD (intercept: +0.35±0.63) when compared to males (‐0.23±0.71; p=0.0024) whereas the Aβ‐plaque dependent microglial response was indifferent between sexes (Figure 2). BMI and the Aβ‐plaque independent microglial response were significantly associated in females (β=0.35, p=0.043) but not in males (β=‐0.02, p=0.940; BMI*sex interaction: F (3,52) =4.77, p=0.0052; Figure 3). Conclusion Females with AD comprise a higher Aβ‐plaque independent microglia response, whereas the microglial response to fibrillar Aβ is indifferent between sexes. BMI is positively associated with the Aβ‐plaque independent microglia response in females with AD but not in males, indicating that sex and BMI need to be considered when studying neuroinflammation in AD.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2201940-6
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  • 3
    In: Alzheimer's & Dementia, Wiley, Vol. 17, No. S4 ( 2021-12)
    Abstract: Cortico‐basal degeneration (CBD) and progressive supranuclear palsy (PSP) are 4R‐tauopathies characterized by progressive tau pathology spread that typically starts in the subcortex. Pre‐clinical studies suggest that tau spreads across connected neurons in an activity‐dependent manner, indicating that the brains’ connectome may mediate tau spreading. Supporting this, we found in Alzheimer’s disease that PET‐assessed cortical tau spreads across functionally connected regions. Here, we assessed whether connectivity mediates cortical/subcortical tau spreading also in 4R‐tauopathies, by combining resting‐state fMRI connectivity with i) 2 nd generation in vivo tau‐PET (PI2620) in CBS and PSP and ii) post‐mortem tau assessments in PSP. Method We assessed PI2620 tau‐PET in 24 CBS‐patients, 28 PSP‐patients and 15 healthy controls. Voxel‐wise tau‐PET differences were determined between patients vs. controls and mean tau‐PET SUVRs were assessed for 232 cortical/subcortical‐ROIs (Fig. 1A). Semi‐quantitative post‐mortem AT8‐stained neuronal tau was assessed in two additional, non‐overlapping PSP samples (Munich: n=96; & UPENN: n=97). Neuropathological ROIs were reconstructed in MRI‐standard‐space (Figs. 1B & C). Functional connectivity was assessed between tau‐PET‐ROIs and neuropathological‐ROIs using out‐of‐sample resting‐state fMRI from 69 elderly amyloid‐ and tau‐negative controls. Using linear regression, we assessed the association between ROI‐to‐ROI connectivity and covariance in tau‐PET or post‐mortem tau levels in spatially corresponding ROI pairs. For tau‐PET, we further tested at the subject level, whether functional connectivity of tau epicenters (i.e. ROIs with highest tau‐PET in a given subject) predicted tau deposition in connected regions, using linear mixed models controlling for age, gender and random intercept. Result PSP and CBS patients showed elevated tau‐PET compared to controls (Fig. 2). Higher functional connectivity was associated with higher covariance in tau‐PET in PSP and CBS (b=0.402‐0.715, Fig. 3A‐D, all p 〈 0.001). For post‐mortem data, higher ROI‐to‐ROI functional connectivity was also associated higher covariance in tau in both PSP samples (b=0.468 & 0.765, p 〈 0.001, Fig. 3E & F). Using tau‐PET we found further that connectivity patterns of subject‐level subcortical tau epicenters was associated with subject‐level tau‐PET uptake in connected regions (Fig. 4B‐E, all p 〈 0.001). Conclusion Highly functionally connected brain regions share similar tau levels in 4R‐tauopathies as indicated by tau‐PET and post‐mortem assessments, suggesting that brain connectivity is associated with inter‐regional tau spreading in 4R‐tauopathies.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2201940-6
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  • 4
    In: Annals of Neurology, Wiley, Vol. 92, No. 5 ( 2022-11), p. 768-781
    Abstract: Alzheimer disease (AD) is characterized by amyloid β (Aβ) plaques and neurofibrillary tau tangles, but increasing evidence suggests that neuroinflammation also plays a key role, driven by the activation of microglia. Aβ and tau pathology appear to spread along pathways of highly connected brain regions, but it remains elusive whether microglial activation follows a similar distribution pattern. Here, we assess whether connectivity is associated with microglia activation patterns. Methods We included 32 Aβ‐positive early AD subjects (18 women, 14 men) and 18 Aβ‐negative age‐matched healthy controls (10 women, 8 men) from the prospective ActiGliA (Activity of Cerebral Networks, Amyloid and Microglia in Aging and Alzheimer's Disease) study. All participants underwent microglial activation positron emission tomography (PET) with the third‐generation mitochondrial 18 kDa translocator protein (TSPO) ligand [ 18 F]GE‐180 and magnetic resonance imaging (MRI) to measure resting‐state functional and structural connectivity. Results We found that inter‐regional covariance in TSPO‐PET and standardized uptake value ratio was preferentially distributed along functionally highly connected brain regions, with MRI structural connectivity showing a weaker association with microglial activation. AD patients showed increased TSPO‐PET tracer uptake bilaterally in the anterior medial temporal lobe compared to controls, and higher TSPO‐PET uptake was associated with cognitive impairment and dementia severity in a disease stage‐dependent manner. Interpretation Microglial activation distributes preferentially along highly connected brain regions, similar to tau pathology. These findings support the important role of microglia in neurodegeneration, and we speculate that pathology spreads throughout the brain along vulnerable connectivity pathways. ANN NEUROL 2022;92:768–781
    Type of Medium: Online Resource
    ISSN: 0364-5134 , 1531-8249
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 2037912-2
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  • 5
    In: Nature Communications, Springer Science and Business Media LLC, Vol. 13, No. 1 ( 2022-03-15)
    Abstract: Tau pathology is the main driver of neuronal dysfunction in 4-repeat tauopathies, including cortico-basal degeneration and progressive supranuclear palsy. Tau is assumed to spread prion-like across connected neurons, but the mechanisms of tau propagation are largely elusive in 4-repeat tauopathies, characterized not only by neuronal but also by astroglial and oligodendroglial tau accumulation. Here, we assess whether connectivity is associated with 4R-tau deposition patterns by combining resting-state fMRI connectomics with both 2 nd generation 18 F-PI-2620 tau-PET in 46 patients with clinically diagnosed 4-repeat tauopathies and post-mortem cell-type-specific regional tau assessments from two independent progressive supranuclear palsy patient samples ( n  = 97 and n  = 96). We find that inter-regional connectivity is associated with higher inter-regional correlation of both tau-PET and post-mortem tau levels in 4-repeat tauopathies. In regional cell-type specific post-mortem tau assessments, this association is stronger for neuronal than for astroglial or oligodendroglial tau, suggesting that connectivity is primarily associated with neuronal tau accumulation. Using tau-PET we find further that patient-level tau patterns are associated with the connectivity of subcortical tau epicenters. Together, the current study provides combined in vivo tau-PET and histopathological evidence that brain connectivity is associated with tau deposition patterns in 4-repeat tauopathies.
    Type of Medium: Online Resource
    ISSN: 2041-1723
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 2553671-0
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  • 6
    In: NeuroImage: Clinical, Elsevier BV, Vol. 38 ( 2023), p. 103402-
    Type of Medium: Online Resource
    ISSN: 2213-1582
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2023
    detail.hit.zdb_id: 2701571-3
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  • 7
    In: Neurology, Ovid Technologies (Wolters Kluwer Health), Vol. 102, No. 1 ( 2024-01-9)
    Abstract: Corticobasal syndrome (CBS) with underlying 4-repeat tauopathy is a progressive neurodegenerative disease characterized by declining cognitive and motor functions. Biomarkers for assessing pathologic brain changes in CBS including tau-PET, 18 kDa translocator protein (TSPO)-PET, structural MRI, neurofilament light chain (NfL), or glial fibrillary acidic protein (GFAP) have recently been evaluated for differential diagnosis and disease staging, yet their association with disease trajectories remains unclear. Therefore, we performed a head-to-head comparison of neuroimaging (tau-PET, TSPO-PET, structural MRI) and plasma biomarkers (NfL, GFAP) as prognostic tools for longitudinal clinical trajectories in β-amyloid (Aβ)–negative CBS. Methods We included patients with clinically diagnosed Aβ-negative CBS with clinical follow-up data who underwent baseline structural MRI and plasma-NfL analysis for assessing neurodegeneration, [ 18 F]PI-2620-PET for assessing tau pathology, [ 18 F]GE-180-PET for assessing microglia activation, and plasma-GFAP analysis for assessing astrocytosis. To quantify tau and microglia load, we assessed summary scores of whole-brain, cortical, and subcortical PET signal. For structural MRI analysis, we quantified subcortical and cortical gray matter volume. Plasma NfL and GFAP values were assessed using Simoa-based immunoassays. Symptom progression was determined using a battery of cognitive and motor tests (i.e., Progressive Supranuclear Palsy Rating Scale [PSPRS] ). Using linear mixed models, we tested whether the assessed biomarkers at baseline were associated with faster symptom progression over time (i.e., time × biomarker interaction). Results Overall, 21 patients with Aβ-negative CBS with ∼2-year clinical follow-up data were included. Patients with CBS with more widespread global tau-PET signal showed faster clinical progression (PSPRS: B/SE = 0.001/0.0005, p = 0.025), driven by cortical rather than subcortical tau-PET. By contrast, patients with higher global [ 18 F]GE-180-PET readouts showed slower clinical progression (PSPRS: B/SE = −0.056/0.023, p = 0.019). No association was found between gray matter volume and clinical progression. Concerning fluid biomarkers, only higher plasma-NfL (PSPRS: B/SE = 0.176/0.046, p 〈 0.001) but not GFAP was associated with faster clinical deterioration. In a subsequent sensitivity analysis, we found that tau-PET, TSPO-PET, and plasma-NfL showed significant interaction effects with time on clinical trajectories when tested in the same model. Discussion [ 18 F]PI-2620 tau-PET, [ 18 F]GE-180 TSPO-PET, and plasma-NfL show prognostic potential for clinical progression in patients with Aβ-negative CBS with probable 4-repeat tauopathy, which can be useful for clinical decision-making and stratifying patients in clinical trials.
    Type of Medium: Online Resource
    ISSN: 0028-3878 , 1526-632X
    RVK:
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2024
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