The Geneva brain collection

Fluid preservation in brain banking: a review

Fluid preservation is nearly universally used in brain banking to store fixed tissue specimens for future research applications. However, the effects of long-term immersion on neural circuitry and biomolecules are not well characterized. As a result, there is a need to synthesize studies investigating fluid preservation of brain tissue. We searched PubMed and other databases to identify studies measuring the effects of fluid preservation in nervous system tissue. We categorized studies based on the fluid preservative used: formaldehyde solutions, buffer solutions, alcohol solutions, storage after tissue clearing, and cryoprotectant solutions. We identified 91 studies containing 197 independent observations of the effects of long-term storage on cellular morphology. Most studies did not report any significant alterations due to long-term storage. When present, the most frequent alteration was decreased antigenicity, commonly attributed to progressive crosslinking by aldehydes that renders biomolecules increasingly inaccessible over time. To build a mechanistic understanding, we discuss biochemical aspects of long-term fluid preservation. A subset of lipids appears to be chemical altered or extracted over time due to incomplete retention in the crosslinked gel. Alternative storage fluids mitigate the problem of antigen masking but have not been extensively characterized and may have other downsides. We also compare fluid preservation to cryopreservation, paraffin embedding, and resin embedding. Overall, existing evidence suggests that fluid preservation provides maintenance of neural architecture for decades, including precise structural details. However, to avoid the well-established problem of overfixation caused by storage in high concentration formaldehyde solutions, fluid preservation procedures can use an initial fixation step followed by an alternative long-term storage fluid. Further research is warranted on optimizing protocols and characterizing the generalizability of the storage artifacts that have been identified.

The UT health Psychological Autopsy Interview Schedule (UTH- PAIS) - Description and reliability of diagnoses and transdiagnostic personality measures

Few studies have used psychological autopsies to evaluate large and diverse populations on transdiagnostically relevant variables such as personality, temperament, and trauma exposure; rather, they tend to focus on specific psychiatric disorders or manner of death. We therefore developed the UT Health Psychological Autopsy Interview Schedule (UTH-PAIS). The measure is described, and our results show that the PAIS diagnoses and dimensions can be reliably assessed. Furthermore, we were able to show that our sample of donated brains overall matches the demographic characteristics of a larger pool of individuals receiving a medical autopsy. In the Discussion we review the strengths and potential limitations of the study and outline in which context the PAIS will prove to be useful.

The 18 kDa translocator protein is associated with microglia in the hippocampus of non-demented elderly subjects

Increase in the brain expression of the 18 kDa translocator protein (TSPO) is considered as a marker of neuroinflammation in the context of brain diseases, such as Alzheimer's disease (AD). However, in non-demented subjects with Alzheimer's neuropathology, TSPO accumulation in hippocampus subdivisions has not been fully characterized. To determine if TSPO is associated with the presence of amyloid β plaques and/or phosphorylated Tau accumulation, we analyzed hippocampal sections using immunohistochemistry of 14 non-demented subjects with positive staining for Aβ and/or phosphorylated Tau. TSPO expression was heterogenous with higher accumulation in the CA2/3 and subiculum subfields of the hippocampus. Its distribution closely resembled that of the microglial IBA1 marker and of the Aβ42 amyloid form. In addition, positive correlations were observed between TSPO and IBA1 densities in CA4, CA2/3 and the subiculum but not with either the astrocyte GFAP marker or the AD-type Aβ and Tau markers. This study sustains the hypothesis that TSPO is mainly associated with microglia and in Aβ42-rich subdivisions in the hippocampus of non-demented elderly individuals.

Fluorescence-activated cell sorting to reveal the cell origin of radioligand binding

Many studies have explored the role of TSPO (18 kDa translocator protein) as a marker of neuroinflammation using single-photon emission computed tomography (SPECT) or positron emission tomography (PET). In vivo imaging does not allow to determine the cells in which TSPO is altered. We propose a methodology based on fluorescence-activated cell sorting to sort different cell types of radioligand-treated tissues. We compared left/right hippocampus of rats in response to a unilateral injection of lipopolysaccharide (LPS), ciliary neurotrophic factor (CNTF) or saline. We finally applied this methodology in human samples (Alzheimer's disease patients and controls). Our data show that the pattern of TSPO overexpression differs across animal models of acute neuroinflammation. LPS induces a microglial expansion and an increase in microglial TSPO binding. CNTF is associated with an increase in TSPO binding in microglia and astrocytes in association with an increase in the number of microglial binding sites per cell. In humans, we show that the increase in CLINDE binding in Alzheimer's disease concerns microglia and astrocytes in the presence of a microglial expansion. Thus, the cellular basis of TSPO overexpression is condition dependent, and alterations in TSPO binding found in PET/SPECT imaging studies cannot be attributed to particular cell types indiscriminately.

Trafficking of immune cells across the blood-brain barrier is modulated by neurofibrillary pathology in tauopathies

Tauopathies represent a heterogeneous group of neurodegenerative disorders characterized by abnormal deposition of the hyperphosphorylated microtubule-associated protein tau. Chronic neuroinflammation in tauopathies is driven by glial cells that potentially trigger the disruption of the blood-brain barrier (BBB). Pro-inflammatory signaling molecules such as cytokines, chemokines and adhesion molecules produced by glial cells, neurons and endothelial cells, in general, cooperate to determine the integrity of BBB by influencing vascular permeability, enhancing migration of immune cells and altering transport systems. We considered the effect of tau about vascular permeability of peripheral blood cells in vitro and in vivo using primary rat BBB model and transgenic rat model expressing misfolded truncated protein tau. Immunohistochemistry, electron microscopy and transcriptomic analysis were employed to characterize the structural and functional changes in BBB manifested by neurofibrillary pathology in a transgenic model. Our results show that misfolded protein tau ultimately modifies the endothelial properties of BBB, facilitating blood-to-brain cell transmigration. Our results suggest that the increased diapedesis of peripheral cells across the BBB, in response to tau protein, could be mediated by the increased expression of endothelial signaling molecules, namely ICAM-1, VCAM-1, and selectins. We suggest that the compensation of BBB in the diseased brain represents a crucial factor in neurodegeneration of human tauopathies.

Early Alzheimer-type lesions in cognitively normal subjects

Amyloid deposits and tau-immunoreactive neurofibrillary tangles, together with neuronal and synaptic loss, are the neuropathological hallmarks of Alzheimer's disease (AD). Both proteins are present in the normal brain during aging. However, the temporal sequence of their involvement in the onset of AD pathology remains controversial. To define whether amyloid β protein deposits or tau protein lesions appear first during normal brain aging, we performed an immunohistological study on serial sections from 105 autopsy brains (age range: 40-104 years) from patients free of clinical signs of cognitive decline, using anti-tau (AT8) and anti-amyloid (4G8) antibodies in the hippocampus, entorhinal cortex, inferior temporal cortex (Brodmann area 20), prefrontal cortex (Brodmann area 9), occipital cortex (Brodmann areas 17 and 18), and in the brainstem. All cases older than 48 years displayed at least a few neurofibrillary tangles, which appeared more frequently in the entorhinal than in the transentorhinal cortex. Tau pathology in these areas preceded tau inclusions in the brainstem. Furthermore, the first site of the apparition of tau pathology is inconsistent, being the entorhinal cortex in most cases, and in fewer cases, the transentorhinal region. There was no case presenting with amyloid deposition in the absence of neurofibrillary tangles, lending evidence to the fact that neurofibrillary tangles appear earlier than amyloid plaques during normal brain aging. However, the role of amyloid in promoting tau deposition cannot be excluded in some cases but may not represent the sole mechanism of disease induction and progression.

Mapping the landscape of cerebral amyloid angiopathy research: an informetric analysis perspective

To quantitatively analyse the research output and major trends in the field of cerebral amyloid angiopathy (CAA) over six decades, from 1954 to 2014, using advanced informetrics methods, we systematically identified CAA-related articles from PubMed, collected metadata and performed productivity analysis, copublication analysis, and network and content analysis over defined time periods. Linear regression was used to investigate these relationships. Changes in CAA research themes (2000-2014) were defined using a topic modelling technique. A total of 2340 CAA papers were published between 1954 and 2014. The mean number (3.03; 95% CI 2.62 to 3.45; p<0.0001) and mean rate (0.13%; 95% CI 0.11% to 0.15%; p<0.0001) of CAA publications increased yearly. Analysis of copublication networks over 5-year periods from 1990 to 2014, revealed a great increase in the total number of connected investigators publishing on CAA (coefficient 16.74; 95% CI 14 to 19.49; p<0.0001) as well as the interactions between them (coefficient 73.53; 95% CI 52.03 to 89.03; p<0.0001). Further analysis of the network characteristics showed that in the past 15 years, copublication networks became not only larger, but also more connected and coherent. Content analysis identified 16 major CAA research themes and their differential evolution in the past 15 years, with the following main trends: (A) limited focus on vascular cognitive impairment; (B) a shift in emphasis towards neuroimaging, cerebral microbleeds and diagnostic aspects and away from pathological aspects; and (3) a reduced emphasis on basic biology apart from an increased focus on mouse models and perivascular drainage. Our study reveals the rapidly developing nature of the CAA research landscape, providing a novel quantitative and objective basis for identifying unmet needs and new directions. Our findings support the idea of a collaborative culture in the field, encouraging international research initiatives.

Amnesia in frontotemporal dementia: shedding light on the Geneva historical data

Recent accumulated evidence indicates that episodic memory impairments could be part of the initial clinical expression of frontotemporal dementia (FTD). An early study on this issue was carried out by Constantinidis and colleagues in 1974, but it was subsequently overlooked for a long period of time. The scope of the present research was: (a) to explore the presence of early episodic memory impairments in the entire population of neuropathologically confirmed FTD patients from the Geneva brain collection; and (b) to expand the present insight on the association between the initial symptomatology and various characteristics, namely gender, age at onset, disease duration, and presence of Pick body neuropathology. A careful review of the records of 50 FTD patients hospitalized at the Department of Psychiatry of the Bel-Air Hospital, Geneva, Switzerland, from 1929 to 1999, was conducted. Further in-depth neuropathological analysis with novel immunohistological methods was carried out in 37 of the cases. The data showed that memory impairments were the first clinical symptom in several of the patients. In addition, this specific phenotypic expression of FTD was associated with the female gender, advanced age, and positive Pick body neuropathology. The current findings give the opportunity to historically vindicate the early work of Constantinidis and colleagues. In addition, the novel observations about the association of episodic memory impairments with the female gender and positive Pick body neuropathology add to the existing knowledge about this phenotypic expression of FTD.

Neuropathology of dementia in a large cohort of patients with Parkinson's disease

The aim of our study was to establish the contribution of distinct pathological aggregates (cortical Lewy bodies (LB), neuronal tau-inclusions and β-amyloid plaque (Aβ) deposition) in dementia related to Parkinson's disease (PD) in a large autopsy cohort. We studied the brains of 155 PD patients, 109 of whom were clinically demented. The total LB score, the Braak stages for neurofibrillary tangles (NFT) and the Thal phases for Aβ deposition were assessed in each case, according to previously published guidelines. All the three lesion types were more abundant in the demented PD group, compared to the non-demented PD group, but neocortical LB pathology was the most important substrate of dementia. A significant correlation was found between the severity of Aβ phases, NFT stages and cortical LB scores. In a subgroup of severely demented PD patients, cortical tau burden was much higher than in the rest of the group. Extensive cortical NFTs associate unavoidably with dementia. Some patients remain cognitively intact despite high cortical LB score. In conclusion, our data strongly support a combining, yet distinct role of neocortical LBs and tau deposits.

Etiologies of Parkinsonism in a century-long autopsy-based cohort

We investigated the distribution of different etiologies underlying Parkinsonism in a hospital-based autopsy collection, studied the demographic data and evaluated diagnostic accuracy using histopathological examination as the gold standard. Out of a total of 9359 consecutive autopsy cases collected between 1914 and 2010, we identified 261 individuals who carried a clinical diagnosis of a Parkinsonian syndrome at death. A detailed neuropathological examination revealed idiopathic Parkinson's disease (PD) in 62.2%, progressive supranuclear palsy (PSP) in 4.2%, multiple system atrophy (MSA) in 2.3%, corticobasal degeneration (CBD) in 1.2%, postencephalitic Parkinsonism (PEP) in 2.7%, vascular Parkinsonism (VaP) in 8.8% and Alzheimer-type pathology (ATP) of the substantia nigra in 8%. The diagnostic accuracy of PD in our cohort was lower (71.2%) than those reported in previous studies, although it tended to increase during the last decades up to 85.7%. Of particular interest, we found that PD, while being the most frequent cause of Parkinsonism, was greatly overdiagnosed, with VaP and ATP being the most frequent confounding conditions.