Necrotizing enterocolitis is associated with acute brain responses in preterm pigs

BACKGROUND: Necrotizing enterocolitis (NEC) is an acute gut inflammatory disorder that occurs in preterm infants in the first weeks after birth. Infants surviving NEC often show impaired neurodevelopment. The mechanisms linking NEC lesions with later neurodevelopment are poorly understood but may include proinflammatory signaling in the immature brain. Using preterm pigs as a model for preterm infants, we hypothesized that severe intestinal NEC lesions are associated with acute effects on the developing hippocampus. METHODS: Cesarean-delivered preterm pigs (n = 117) were reared for 8 days and spontaneously developed variable severity of NEC lesions. Neonatal arousal, physical activity, and in vitro neuritogenic effects of cerebrospinal fluid (CSF) were investigated in pigs showing NEC lesions in the colon (Co-NEC) or in the small intestine (Si-NEC). Hippocampal transcriptome analysis and qPCR were used to assess gene expressions and their relation to biological processes, including neuroinflammation, and neural plasticity. Microglia activation was quantified by stereology. The neuritogenic response to selected proteins was investigated in primary cultures of hippocampal neurons. RESULTS: NEC development rapidly reduced the physical activity of pigs, especially when lesions occurred in the small intestine. Si-NEC and Co-NEC were associated with 27 and 12 hippocampal differentially expressed genes (DEGs), respectively. These included genes related to neuroinflammation (i.e., S100A8, S100A9, IL8, IL6, MMP8, SAA, TAGLN2) and hypoxia (i.e., PDK4, IER3, TXNIP, AGER), and they were all upregulated in Si-NEC pigs. Genes related to protection against oxidative stress (HBB, ALAS2) and oligodendrocytes (OPALIN) were downregulated in Si-NEC pigs. CSF collected from NEC pigs promoted neurite outgrowth in vitro, and the S100A9 and S100A8/S100A9 proteins may mediate the neuritogenic effects of NEC-related CSF on hippocampal neurons. NEC lesions did not affect total microglial cell number but markedly increased the proportion of Iba1-positive amoeboid microglial cells. CONCLUSIONS: NEC lesions, especially when present in the small intestine, are associated with changes to hippocampal gene expression that potentially mediate neuroinflammation and disturbed neural circuit formation via enhanced neuronal differentiation. Early brain-protective interventions may be critical for preterm infants affected by intestinal NEC lesions to reduce their later neurological dysfunctions

Validation of the new pathology staging system for progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a neurodegenerative disorder associated with neuroglial accumulation of 4-repeat tau protein [2]. Kovacs et al. [1] have recently proposed a new semi-quantitative six-stage system to categorise the severity of PSP pathology. Importantly, the system reduces reliance on regions with high risk of concomitant pathology and focusses on cell type specific tau-pathology.Cambridge Centre for Parkinson-plus (RG95450), and the NIHR Cambridge Biomedical Research Centre (BRC-1215-20014). The Cambridge Brain Bank is supported by the NIHR Cambridge Biomedical Research Centre

Molecular pathology and synaptic loss in primary tauopathies: A [18F]AV-1451 and [11C]UCB-J PET study

The relationship between in vivo synaptic density and tau burden in primary tauopathies is key to understanding the impact of tauopathy on functional decline and in informing new early therapeutic strategies. In this cross-sectional observational study, we determine the in vivo relationship between synaptic density and molecular pathology, in the primary tauopathies of Progressive Supranuclear Palsy (PSP) and Corticobasal Degeneration (CBD), as a function of disease severity. Twenty three patients with PSP, and twelve patients with Corticobasal Syndrome (CBS) were recruited from a tertiary referral centre. Nineteen education, sex and gender-matched control participants were recruited from the National Institute for Health Research ‘Join Dementia Research’ platform. Cerebral synaptic density and molecular pathology, in all participants, were estimated using PET imaging with the radioligands [11C]UCB-J and [18F]AV-1451, respectively. Patients with CBS also underwent amyloid PET imaging with [11C]PiB to exclude those with likely Alzheimer’s pathology – we refer to the amyloid negative cohort as having CBD although acknowledge other pathologies exist. Disease severity was assessed with the PSP rating scale; regional non-displaceable binding potentials (BPND) of [11C]UCB-J and [18F]AV-1451 were estimated in regions of interest from the Hammersmith Atlas, excluding those with known off-target binding for [18F]AV-1451. As an exploratory analysis, we also investigated the relationship between molecular pathology in cortical brain regions, and synaptic density in subcortical areas. Across brain regions, there was a positive correlation between [11C]UCB-J and [18F]AV-1451 BPND (ß = 0.4, t = 3.6, p = 0.001), independent of age or time between PET scans. However, this correlation became less positive as a function of disease severity in patients (ß = - 0.02, t = -2.9, p = 0.007, R = -0.41). Between regions, cortical [18F]AV-1451 binding was negatively correlated with synaptic density in subcortical areas (caudate nucleus, putamen). Brain regions with higher synaptic density are associated with a higher [18F]AV-1451 binding in PSP/CBD, but this association diminishes with disease severity. Moreover, higher cortical [18F]AV-1451 binding correlates with lower subcortical synaptic density. Longitudinal imaging is required to confirm the mediation of synaptic loss by molecular pathology. However, the effect of disease severity suggests a biphasic relationship between synaptic density and molecular pathology with synapse rich regions vulnerable to accrual of pathological aggregates, followed by a loss of synapses in response to pathology. Given the importance of synaptic function for cognition, our study elucidates the pathophysiology of primary tauopathies and may inform the design of future clinical trials.Cambridge Centre for Parkinson-Plus (RG95450); the National Institute for Health Research Cambridge Biomedical Research Centre (BRC-1215-20014); the PSP Association (“MAPT-PSP” study), and the Association of British Neurologists, Patrick Berthoud Charitable Trust (RG99368)

Locus coeruleus pathology in progressive supranuclear palsy, and its relation to disease severity

Abstract: The locus coeruleus is the major source of noradrenaline to the brain and contributes to a wide range of physiological and cognitive functions including arousal, attention, autonomic control, and adaptive behaviour. Neurodegeneration and pathological aggregation of tau protein in the locus coeruleus are early features of progressive supranuclear palsy (PSP). This pathology is proposed to contribute to the clinical expression of disease, including the PSP Richardson’s syndrome. We test the hypothesis that tau pathology and neuronal loss are associated with clinical heterogeneity and severity in PSP. We used immunohistochemistry in post mortem tissues from 31 patients with a clinical diagnosis of PSP (22 with Richardson’s syndrome) and 6 control cases. We quantified the presence of hyperphosphorylated tau, the number of pigmented cells indicative of noradrenergic neurons, and the percentage of pigmented neurons with tau-positive inclusions. Ante mortem assessment of clinical severity using the PSP rating scale was available within 1.8 (±0.9) years for 23 patients. We found an average 49% reduction of pigmented neurons in PSP patients relative to controls. The loss of pigmented neurons correlated with disease severity, even after adjusting for disease duration and the interval between clinical assessment and death. The degree of neuronal loss was negatively associated with tau-positive inclusions, with an average of 44% of pigmented neurons displaying tau-inclusions. Degeneration and tau pathology in the locus coeruleus are related to clinical heterogeneity of PSP. The noradrenergic deficit in the locus coeruleus is a candidate target for pharmacological treatment. Recent developments in ultra-high field magnetic resonance imaging to quantify in vivo structural integrity of the locus coeruleus may provide biomarkers for noradrenergic experimental medicines studies in PSP

Neuroinflammation and protein aggregation co-localize across the frontotemporal dementia spectrum.

The clinical syndromes of frontotemporal dementia are clinically and neuropathologically heterogeneous, but processes such as neuroinflammation may be common across the disease spectrum. We investigated how neuroinflammation relates to the localization of tau and TDP-43 pathology, and to the heterogeneity of clinical disease. We used PET in vivo with (i) 11C-PK-11195, a marker of activated microglia and a proxy index of neuroinflammation; and (ii) 18F-AV-1451, a radioligand with increased binding to pathologically affected regions in tauopathies and TDP-43-related disease, and which is used as a surrogate marker of non-amyloid-β protein aggregation. We assessed 31 patients with frontotemporal dementia (10 with behavioural variant, 11 with the semantic variant and 10 with the non-fluent variant), 28 of whom underwent both 18F-AV-1451 and 11C-PK-11195 PET, and matched control subjects (14 for 18F-AV-1451 and 15 for 11C-PK-11195). We used a univariate region of interest analysis, a paired correlation analysis of the regional relationship between binding distributions of the two ligands, a principal component analysis of the spatial distributions of binding, and a multivariate analysis of the distribution of binding that explicitly controls for individual differences in ligand affinity for TDP-43 and different tau isoforms. We found significant group-wise differences in 11C-PK-11195 binding between each patient group and controls in frontotemporal regions, in both a regions-of-interest analysis and in the comparison of principal spatial components of binding. 18F-AV-1451 binding was increased in semantic variant primary progressive aphasia compared to controls in the temporal regions, and both semantic variant primary progressive aphasia and behavioural variant frontotemporal dementia differed from controls in the expression of principal spatial components of binding, across temporal and frontotemporal cortex, respectively. There was a strong positive correlation between 11C-PK-11195 and 18F-AV-1451 uptake in all disease groups, across widespread cortical regions. We confirmed this association with post-mortem quantification in 12 brains, demonstrating strong associations between the regional densities of microglia and neuropathology in FTLD-TDP (A), FTLD-TDP (C), and FTLD-Pick's. This was driven by amoeboid (activated) microglia, with no change in the density of ramified (sessile) microglia. The multivariate distribution of 11C-PK-11195 binding related better to clinical heterogeneity than did 18F-AV-1451: distinct spatial modes of neuroinflammation were associated with different frontotemporal dementia syndromes and supported accurate classification of participants. These in vivo findings indicate a close association between neuroinflammation and protein aggregation in frontotemporal dementia. The inflammatory component may be important in shaping the clinical and neuropathological patterns of the diverse clinical syndromes of frontotemporal dementia

In vivo 18F-flortaucipir PET does not accurately support the staging of progressive supranuclear palsy

Progressive Supranuclear Palsy (PSP) is a neurodegenerative disorder characterised by neuro-glial tau pathology. A new staging system for PSP pathology at post-mortem has been described and validated. We used a data-driven approach to test whether post-mortem pathological staging in PSP can be reproduced in vivo with 18F-flortaucipir PET. Methods: N=42 patients with probable PSP and N=39 controls underwent 18F-flortaucipir PET. Conditional inference tree analyses on regional binding potential values identified absent/present pathology thresholds to define in vivo staging. Following the staging system for PSP pathology, the combination of absent/present values across all regions was evaluated to assign each participant to in vivo stages. Analysis of variance was applied to analyse differences among means of disease severity between stages. In vivo staging was compared with post-mortem staging in N=9 patients who also had post-mortem confirmation of the diagnosis and stage. Results: Stage assignment was estimable in 41 patients: N=10 patients were classified in stage I/II, N=26 in stage III/IV, N=5 in stage V/VI, while N=1 was not classifiable. An explorative sub-staging identified N=2 patients in stage I, N=8 in stage II, N=9 in stage III, N=17 in stage IV and N=5 in stage V. However, the nominal 18F-flortaucipir derived stage was not associated with clinical severity and was not indicative of pathology staging at post-mortem. Conclusion: 18F-flortaucipir PET in vivo does not correspond to neuropathological staging in PSP. This analytic approach, seeking to mirror in vivo the neuropathology staging with PET-to-autopsy correlational analyses might enable in vivo staging with next-generation PET tracers for tau, but further evidence and comparison with post-mortem data are needed.This study was co-funded by the Cambridge University Centre for Parkinson-Plus (RG95450); the National Institute for Health Research (NIHR) Cambridge Biomedical Research Centre (BRC-1215-20014), including their financial support for the Cambridge Brain Bank; the PSP Association (“MAPT-PSP” award); the Alzheimer’s Research UK East-Network pump priming grant; the Wellcome trust (220258); the Medical Research Council (MR/P01271X/1; G1100464); the Association of British Neurologists, Patrick Berthoud Charitable Trust (RG99368); Alzheimer’s Society (443 AS JF 18017); the Evelyn Trust (RG84654), and RCUK/UKRI (via a Research Innovation Fellowship awarded by the Medical Research Council to CHWG - MR/R007446/1); the Guarantors of Brain (G101149). The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care