Journal of Neuropathology and Experimental Neurology最新文献

Gallyas silver staining and AT8 immunostaining are frequently used to stage tau pathology in post-mortem Alzheimer disease (AD) brains. Because of differential labeling of tau aggregation types, however, these methods result in strikingly different patterns of pathology when used in adjacent sections of the same brain. How Gallyas versus AT8 staining impacts the quantification of tau pathology distribution across brain areas and affect analysis of tau and cognitive impairment is unknown. We performed a side-by-side comparison of AT8 versus Gallyas-stained hippocampal sections from 34 patients from the University of Southern California (USC) Alzheimer's Disease Research Center (ADRC). Using images of Gallyas and AT8 stained sections, we computed overall tau density in hippocampal subregions as well as manual tangle counts and compared each of them to cognitive variables like Clinical Dementia Rating and Mini Mental State Exam in the patients. We found that AT8 had a much higher density of staining overall, and the two stains had differing distributions, with increased AT8 in Brodmann area 35 and CA1. Both stains related to cognition differentially, and Gallyas density was significantly related to post-mortem interval. These findings contribute to our understanding of how tau pathology stain choice might influence the characterization of AD.

Prion diseases are rare neurodegenerative disorders that share misfolding of the normal cellular prion protein into disease-causing isoforms known as "prions" as the critical pathophysiological event. Definite diagnosis can only be achieved through neuropathological confirmation. The neuropathological features of prion disease are well described; however, some molecular subtypes are typified by characteristic neuropathological features that are subtle or absent. Prion seeding assays have excellent specificity and have considerably improved premortem diagnostic accuracy but they have reduced sensitivity for some uncommon prion disease molecular subtypes. We developed a formalin-fixed, paraffin-embedded tissue-based prion seeding assay to serve as a complementary diagnostic tool for prion diseases. Fixed brain tissue was prepared through an optimized process involving careful defacing of tissue blocks prior to sampling and then stepwise deparaffinization and homogenization. Fixed tissue homogenates are then tested in an adapted version of a diagnostic cerebrospinal fluid (CSF) prion seeding assay, which utilizes full-length recombinant hamster prion protein as substrate. Two examples illustrate the utility of the assay by confirming prion seeding in fixed brain tissue from previously neuropathologically misdiagnosed obligate carriers of 2 different prion protein gene mutations. The importance of careful tissue sampling to rigorously maintain the diagnostic specificity of this assay is also highlighted.

Changes in the peripheral metabolome, particularly in the blood, may provide biomarkers for assessing lesion severity and predicting outcomes after spinal cord injury (SCI). Using principal component analysis (PCA) and Orthogonal Partial Least Squares Discriminatory Analysis (OPLS-DA), we sought to discover how SCI severity and location acutely affect the nuclear magnetic resonance-acquired metabolome of the blood, spinal cord, and liver at 6 h post-SCI in mice. Unsupervised PCA of the spinal cord metabolome separated mild (30 kdyne) and severe (70 kdyne) contusion injury groups but did not distinguish between lesion level. However, OPLS-DA could discriminate thoracic level T2 from T9 lesions in both blood plasma (accuracy 86 ± 6%) and liver (accuracy 89 ± 5%) samples. These differences were dependent on alterations in energy metabolites (lactate and glucose), lipoproteins, and lipids. Lactate was the most discriminatory between mild and severe injury at T2, whereas overlapping valine/proline resonances were most discriminatory between injury severities at T9. Plasma lactate correlated with blood-spinal cord barrier breakdown and plasma glucose with microglial density. We propose that peripheral biofluid metabolites can serve as biomarkers of SCI severity and associated pathology at the lesion site; their predictive value is most accurate when the injury level is also considered.

Cholinergic degeneration in the nucleus basalis of Meynert (NBM) is clinically linked to cognitive impairment and gait dysfunction in Alzheimer's disease and Parkinson's disease. Modeling cholinergic degeneration in an animal model may provide powerful opportunities to study the clinical-physiological role of the NBM and lead to new therapies. We describe a procedure to inject ME20.4 Saporin, an immunotoxin that specifically binds to and depletes cholinergic neurons stereotactically into the NBM of a rhesus monkey (Macaca mulatta). A digital non-human primate brain atlas was co-registered to the brain of the monkey. A custom-designed cranial chamber was also implanted to the skull to guide the injection. The effects of the ME20.4 Saporin injections were evaluated in vivo with PET-CT using [18F]-FEOBV as a radiotracer. This approach yielded reliable spatial accuracy and successful delivery of ME20.4 Saporin into the NBM. [18F]-FEOBV PET analyses revealed reduced radiotracer uptake in the NBM. Postmortem assessment showed a reduction of ME20.4-positive cells within the NBM. No clear effects on cognitive testing were observed. This Saporin-mediated selective destruction of cholinergic neurons in the NBM, using MRI-guidance and a cranial chamber, offers a promising method to study the pathophysiology of NBM degeneration and possible therapeutic interventions.

Neuropathologic features diagnostic of parkinsonian disorders infrequently occur in isolation; hyperphosphorylated tau (p-tau) and amyloid plaques are often observed in combination with α-synuclein deposition. Co-pathologies in neurodegenerative diseases are now recognized as the norm rather than an exception, but existing neuropathological assessment tools do not capture the complexity of concurrent co-pathologies. Characterization of this co-pathology is critical, as it has the potential to identify synergistic mechanisms. We developed a hierarchical cytoarchitectural classification system, which we applied to an autopsy series of military veterans with parkinsonism (n = 26), focusing on Lewy and neurofibrillary pathologies. We defined co-pathology as Type A (co-morbid), Type B (co-regional), Type C (co-cellular), or Type D (co-aggregate). The regional distributions of each co-pathology subtype were assessed using double-label immunohistochemistry in the frontal cortex, hippocampal formation, and midbrain. The frontal cortex demonstrated only subtypes A-C (no co-aggregates), whereas the midbrain and hippocampus showed all subtypes of copathology (A-D). In summary, we show marked differences in the prevalence and levels of mixed α-synuclein and tau pathology in this cohort. Our classification system has the potential to be applied broadly for the study of co-pathology in neurodegenerative disorders.

Alcohol use disorder (AUD) is characterized by an inability to stop consuming alcohol. Neuroimaging studies of patients with AUD show mild grey and white matter atrophy, while pathological studies suggest that atrophy is restricted to the white matter. The effects on individual brain cells are largely unknown. Mild neuronal loss has been described in the prefrontal cortex but this has not been consistent. Studies quantifying oligodendrocytes, astrocytes, and microglia are rare. These knowledge gaps impede therapeutic advancements. Here, we piloted the use of tissue microarrays, immunohistochemistry, and automated image analysis to systematically quantify cell profiles in human postmortem tissue. We sampled 173 grey and white matter cores across 5 cerebral regions from 4 male AUD cases and 4 age-matched controls. We found no obvious differences in the regional profiles of neurons, astrocytes, oligodendrocytes, or microglia. However, mean microglial densities across all regions were higher in AUD (P=.0024). There were visual signs of reactive astrocytosis in AUD cases but mean cell body sizes were unchanged. Our findings suggest that alcohol-related brain damage is not due to a loss of any of major cell classes. Larger studies focusing on subtype-specific markers and advanced image analysis tools are required.