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Background: Accuracy of clinical diagnosis in neurodegenerative diseases is critically important for patient care and study recruitment. We aimed to investigate the precision of clinical diagnosis of various neurodegenerative conditions using neuropathological diagnosis for reference. Method: All 1310 autopsy cases between 1993 and 2017 from the Neurobiobank München (Munich, Germany) were screened for neurodegenerative diagnoses. Neuropathological diagnoses that occurred in at least five cases were included in the study. Real world clinical diagnoses were extracted from medical records of admitting hospitals in Germany and correlated with neuropathological diagnoses. Sensitivity, specificity and accuracy (using receiver operating characteristic (ROC) curves and area under the curve (AUC) analysis) of clinical diagnoses were calculated. Result: The study included 455 cases with neuropathologically diagnosed Alzheimer's disease (AD, n = 132), argyrophilic grain disease (AGD, n = 6), corticobasal degeneration (CBD, n = 20), frontotemporal lobar degeneration (FTLD, n = 47), Huntington's disease (HD, n = 22), Lewy body disease (LBD, n = 104), motor neuron disease (MND, n = 10), multiple system atrophy (MSA, n = 37) and progressive supranuclear palsy (PSP, n = 77). Clinical diagnoses in these cases comprised AD (n = 136), CBD (n = 17), Creutzfeldt‐Jakob disease (CJD, n = 6), dementia with Lewy bodies (DLB, n = 11), frontotemporal dementia (FTD, n = 44), HD (n = 23), MND (n = 20), MSA (n = 36), Parkinson's disease (PD, n = 92), PSP (n = 60) and vascular dementia (VD, n = 10). Figure 1 illustrates the relationship between clinical (left) and neuropathological diagnoses (right). Figure 2 shows sensitivity, specificity, ROC curves, AUCs including standard errors (SE) and 95% confidence intervals (CI) and p‐values for testing the null hypothesis AUC = 0.5 for clinical diagnoses. Conclusion: Clinical diagnoses of neurodegenerative diseases exhibited a wide span of sensitivity depending on the particular disease (0‐100%) while specificity was high for all clinical diagnoses (89.5‐100%). Accuracy of clinical diagnoses as determined with AUC analysis was very good (AUC>0.9) for HD, MND and MSA, good (AUC = 0.8‐0.9) for AD, DLB/PD and PSP, moderate (AUC = 0.7‐0.8) for FTD, poor (AUC = 0.51‐0.7) for CBD and bad/no discrimination capacity (AUC = 0.5) for AGD. Based on these findings, an increase of sensitivity of clinical diagnoses may be key to improve correct identification of neurodegenerative diseases. This may be possible through development and clinical implementation of molecular biomarkers that are able to indicate the causal proteinopathies of neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Background: β‐amyloid PET (Aβ‐PET) is an important tool for quantification of amyloidosis in the brain of suspected Alzheimer's disease (AD) patients and transgenic AD mouse models. Despite the excellent correlation of Aβ‐PET with gold standard immunohistochemical assessments, the relative contributions of fibrillar and non‐fibrillar Aβ components to the in vivo Aβ‐PET signal remain unclear. Thus, we obtained two murine cerebral amyloidosis models that present with distinct Aβ plaque compositions and performed regression analysis between immunohistochemistry and Aβ PET to determine the biochemical contributions to Aβ‐PET signal in vivo. Method: We investigated groups of AppNL‐G‐F and APPPS1 mice three, six and 12 months of age by longitudinal [18F]‐florbetaben Aβ‐PET and with immunohistochemical analysis of the fibrillar and total Aβ burdens. We then applied group level inter‐modality regression models using age and genotype matched sets of fibrillar/ non‐fibrillar Aβ data (predictors) and Aβ‐PET results (outcome) for both transgenic models. An independent group of double‐hit APPPS1 mice with dysfunctional microglia due to knock‐out of triggering receptor expression on myeloid cells 2 (Trem2‐/‐) served for validation and evaluation of translational impact. Result: Neither fibrillar nor non‐fibrillar Aβ content alone sufficed to explain the Aβ‐PET findings in either transgenic AD model (Figure 1). A regression model compiling fibrillar and non‐fibrillar Aβ together with the estimate of individual heterogeneity and age at scanning could explain a 93% of variance of the Aβ‐PET signal (p<0.001; Figure 2). Fibrillar Aβ burden had a 16‐fold higher contribution to the Aβ‐PET signal when compared to non‐fibrillar Aβ. However, given the relatively greater abundance of non‐fibrillar Aβ, we estimate that non‐fibrillar Aβ produced 79±25% of the net in vivo Aβ‐PET signal in AppNL‐G‐F mice, and 25±12% in the APPPS1 mice. Corresponding results in groups of APPPS1/Trem2‐/‐ and APPPS1/Trem2+/+ mice validated the calculated regression factors and revealed that the altered fibrillarity due to Trem2 knockout impacts the Aβ‐PET signal (Figure 3). Conclusion: Taken together, the in vivo Aβ‐PET signal derives from the composite of fibrillar and non‐fibrillar Aβ plaque components. While fibrillar Aβ has inherently higher PET tracer binding, the greater abundance of non‐fibrillar Aβ plaque in AD model mice contributes importantly to the PET signal. [ABSTRACT FROM AUTHOR]

Background: All clinical BACE‐inhibitor trials for the treatment of Alzheimer´s Disease have failed due to insufficient efficacy or side effects like worsening of cognitive symptoms. The latter could have been the result of the inhibition of BACE at the synapse where it is expressed in high amounts. We have previously shown that prolonged inhibition of BACE interferes with structural and functional synaptic plasticity (Filser et al. Biol. Psych 2015, Blume et al. Front. Aging Neurosci. 2018), most likely due to the diminished processing of the physiological BACE substrate Seizure protein 6 (Sez6, Zhu et al. Biol. Psych. 2018), which is exclusively processed by BACE1 and it is required for dendritic spine plasticity. The aim of the current study was to elucidate the effects of selective BACE1 inhibitors on dendritic spine plasticity at a dose that affects Sez6 cleavage to various degrees but not completely. Method: By using longitudinal in vivo two‐photon microscopy, we investigated the effect on dendritic spine dynamics of pyramidal layer V neurons in the somatosensory cortex in mice treated with 2 novel highly selective BACE1 inhibitors developed at Shionogi in comparison to Elenbecestat which reduce soluble Sez6 to 27% (Elenbecastat), 17% (Shionogi Compound 1) and 39% (Shionogi Compound2) of baseline levels in untreated animals. For the detection of the soluble Sez6 ectodomain, the BACE cleavage product from full‐length Sez6, Western blot analysis was performed using a highly specific Sez6 antibody generated in the lab of Stefan Lichtenthaler (Pigoni et al. Mol. Neurodeg. 2016). Result: We observed that BACE1 selective inhibitors do not alter dendritic spine density and plasticity in cortical neurons if at least 27% of soluble Sez6 remains. In detail, the density of gained and lost spines does not change under the treatment with Shionogi Compound 2 or Elenbecastat. Also, no differences in the stability of dendritic spines were found during treatment with these two compounds. With Compound 1 however, a significant spine loss occurs after 21 days of treatment. Conclusion: Selective BACE1 inhibitors do not alter dendritic spine plasticity in mice if dosing reduces synaptic BACE1 cleavage of Sez6 not below 27% of baseline soluble Sez6 levels. BACE1 selective inhibitors may be potential novel candidates for clinical trials treating AD if dosing is carefully adjusted to the amount of Sez6 cleavage, which can be easily monitored during the first weeks of treatment. [ABSTRACT FROM AUTHOR]

Background: In vivo assessment of neuroinflammation by 18 kDa translocator protein positron‐emission‐tomography (TSPO‐PET) ligands receives growing interest in preclinical and clinical research of neurodegenerative disorders. Higher TSPO expression in females has been reported for cognitively normal humans, but such effects have not yet been evaluated in rodent models of neurodegeneration and their controls. Thus, we aimed to investigate the impact of sex on TSPO expression in amyloid and tau mouse models and wild‐type (WT). Method: Longitudinal 18F‐GE‐180 TSPO‐PET (18F‐GE180) data of AppNL‐G‐F (amyloid model), P301S (tau model) and C57Bl/6 (WT) mice were evaluated between two and twelve months of age. AppNL‐G‐F received additional longitudinal amyloid‐PET (Aβ‐PET; 18F‐florbetaben). Immunohistochemistry also served for validation of microglial (Iba1, CD68) and tau (AT8) markers at the terminal time point. PET and immunohistochemistry were quantified in cortical regions and compared by linear mixed models (PET) and analysis of variance (immunohistochemistry) between male and female mice. Result: The amyloid model AppNL‐G‐F revealed a distinct cortical increase of TSPO‐PET values from 2.5 to 10 months in female mice (+31%), whereas male mice only increased slightly (+6%). The linear mixed model indicated a significant sex x time interaction (T=‐2.953, b/SE=‐0.011/0.004, p=0.0048, Figure 1A), validated by Iba1 and CD68 immunohistochemistry (Figure 2). Aβ‐PET values in the same AppNL‐G‐F mice indicated no significant time x sex interaction (T=0.425, b/SE=0.001/0.003, p=0.673, Figure 3). The P301S tau model showed strong cortical increases of TSPO‐PET from 2 to 8.5 months of age (female: +32%, male: +36%) but no significant sex x time interaction (T=‐0.671, b/SE=‐0.003/0.005, p=0.504, Figure 1B) and no differences in Iba1, CD68 or AT8 were observed. TSPO‐PET values in WT mice indicated an increase with time (female: +23%, male +4%) and a significant time x sex interaction was found (T=‐4.171, b/SE=‐0.009/0.002, p<0.001, Figure 1C). Conclusion: Female mice indicate a sex dependent elevation of glial activation in response to amyloidosis but not to tau pathology which could be related to differences in sex dependency of microglial activation pathways in presence of both proteins. Sex requires attention when microglia activation is evaluated in mouse models of Alzheimer's disease and requires detailed studies in human disease. [ABSTRACT FROM AUTHOR]

Background: BACE1‐inhibitor trials for the treatment of Alzheimer´s Disease (AD) have failed due to insufficient efficacy or side effects like cognitive worsening. However, the scientific evidence to date suggests that BACE1‐inhibition could be an effective preventative measure if applied early enough and in the correct dose. Preclinical studies have associated strong BACE1‐inhibition with decreased dendritic spine density in the cerebral cortex of wildtype mice (GFP‐M) only. Method: We investigated dose‐dependent effects of BACE1‐inhibition on hippocampal dendritic spine dynamics in the APP knock‐in mouse line for the first time. We conducted in vivo two‐photon microscopy in the stratum oriens of hippocampal CA1 neurons in 3.5‐month‐old AppNL‐G‐FGFP‐M mice over 6 weeks to monitor the effect of Bace1 inhibition (NB‐360) in low and high doses on dendritic spine plasticity. Results: Structural spine plasticity is already impaired in CA1 neurons in untreated AppNL‐G‐F mice of this early age. Interestingly, prolonged high‐dose but not low‐dose BACE1‐inhibition was found to enhance spine formation and did not cause spine loss as observed in wildtype control mice. Conclusion: In an early stage of amyloid pathology in a transgenic beta‐amyloid mouse model, BACE1‐inhibition successfully holds the progressive changes in dendritic spine plasticity in hippocampal CA1 neurons. [ABSTRACT FROM AUTHOR]

Background: Lewy body pathology (LBP) occurs in a substantial portion of individuals with autosomal dominant (ADAD) and sporadic Alzheimer disease (sAD) (Ringman, 2016; Cairns, 2015; Leverenz, 2007; Lippa, 1998). Whereas other non‐AD pathologies are frequent in sAD, LBP seems to be the most common co‐pathology in the relatively young ADAD population (Cairns, 2015). Knowledge of clinical and genetic characteristics of LBP in both ADAD and sAD is incomplete. Method: Data from the National Alzheimer's Coordinating Center, the Dominantly Inherited Alzheimer Network, the Queen Square Brain Bank at University College London and the Neurobiobank Munich were leveraged to compare individuals with ADAD and neuropathologically diagnosed sAD with and without LBP. Chi‐squared and Student's t‐test were used for comparison of categorical and continuous variables respectively. Result: The study included 139 ADAD and 4661 sAD autopsy cases. LBP occurred in 59% of ADAD and 38% of sAD cases. LBP was associated with a longer survival in both ADAD (10.1 vs. 8.6 years, p=0.024) and sAD (10.5 vs. 10.2 years, p=0.016). Memory disturbance occurred more frequently as the first clinical AD symptom in both AD variants when LBP was present (ADAD: 90 vs. 65%, p=0.005; sAD: 78 vs. 71%, p<0.001). In both ADAD and sAD, the presence of at least one APOE e4 allele was more common in individuals with LBP (ADAD: 40 vs. 21%, p=0.047; sAD: 57 vs. 46%, p<0.001). In ADAD, frequency of LBP did not differ between individuals with PSEN1 and APP mutations. Conclusion: In this investigation of 139 ADAD and 4661 sAD autopsy cases, LBP occurred in about 60% with ADAD and 40% with sAD. In both ADAD and sAD, the presence of LBP was associated with longer survival, higher frequency of memory disturbance as the first AD symptom and positive APOE e4 status. Further study of these associations may increase our understanding of the role of LBP in AD. [ABSTRACT FROM AUTHOR]

Background: In the neurodegenerative conditions Alzheimer disease (AD), Lewy body disease (LBD) including the neuropathologically indistinguishable Parkinson disease and dementia with Lewy bodies, frontotemporal lobar degeneration (FTLD), corticobasal degeneration (CBD), progressive supranuclear palsy (PSP) and multiple system atrophy (MSA) figures for seizure risk are inconsistent, rare or lacking. This is particular true if neuropathologically confirmed diagnoses are stipulated. Therefore, our goal was to determine the lifetime risk for epileptic seizures and to investigate associated clinical parameters in neuropathologically diagnosed neurodegenerative diseases. Method: Cases from the Neurobiobank Munich, Germany, were matched with information from clinical files regarding the occurrence of epileptic seizures. The aforementioned diseases were compared for lifetime seizure risk. The predictive value of the first clinical symptom regarding lifetime risk for seizures was analyzed and associations between the occurrence of seizures and survival was investigated. Result: We analyzed 454 neuropathologically diagnosed cases with sufficient clinical data available. 144 had AD, 103 LBD, 93 PSP, 53 FTLD, 36 MSA, and 25 CBD. Lifetime risk for epileptic seizures was 31.3% in AD, 20.0% in CBD, 12.6% in LBD, 11.3% in FTLD, 8.3% in MSA and 7.5% in PSP. Patients with AD had a statistically significantly higher lifetime risk for seizures compared to patients with FTLD (p=0.005), LBD (p=0.001), MSA (p=0.005) and PSP (p<0.001). An increased lifetime seizure risk was found in patients with cognitive first symptoms when compared to those with non‐cognitive first symptoms (21.1% vs. 11.0%). A decreases lifetime risk for seizures was observed in cases with motor first symptoms when compared to those with non‐motor first symptoms (10.3% vs. 20.5%). MSA patients with seizures survived longer when compared to those without (12.3 vs. 7.0 years; p = 0.017). Conclusion: In this clinical neuropathological correlation study, nearly every third AD patient and approximately every fifth patient with a neurodegenerative disease experienced epileptic seizures in the disease course. Therefore, epileptic seizures are an important comorbidity in neurodegenerative conditions, in particular in AD. Assessment of the first clinical symptom may improve early estimation of the lifetime seizure risk in the studied neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Background: The novel PSEN1single amino acid deletion mutation F175del causes autosomal dominant Alzheimer disease (ADAD) in the late thirties. In vitroF175del features an unusual pattern of APP fragments including an increased production of Aβ39. This Aβ species was found particularly in brain vessels and therefore may contribute to the development of cerebral amyloid angiopathy (CAA). Method: Neuropathological examination was performed in a patient with ADAD caused by PSEN1F175del who died at the age of 45 years. Clinical, neuropsychological, genetic and biomarker findings in this patient as well effects of the PSEN1deletion mutation on Aβ processing were described before (Vöglein et al, Neurobiology of Aging, 2019). Result: Copious cored/compact and diffuse Aβ plaques were found in the cerebral cortex. Interestingly, there were plentiful streaky and several cored/compact and diffuse Aβ plaques also in the cerebellum. A large number of cortical neuropil threads and neurons with fibrillary cytoplasmatic tau aggregates as well as several neuritic plaques were detected (ABC score: A3/B3/C3). CAA with Aβ depositions in the leptomeningeal and cortical vessel walls was detected (Thal phase 2). Furthermore, several Lewy bodies and Lewy neurites were found in the cerebral cortex (Braak stage 6). Conclusion: The neuropathological hallmarks of AD, Aβ plaques and neurofibrillary degeneration, were present in PSEN1 F175del associated ADAD. CAA was found that could be in causal connection with the enhanced Aβ 39 generation caused by the mutation as shown in cell culture. Further, an unusually high cerebellar Aβ burden was detected. In summary, we provide neuropathological characteristics of ADAD caused by PSEN1 F175del and potentially unveiled an effect of an altered Aβ processing that was shown in vitro on brain pathology. [ABSTRACT FROM AUTHOR]