The localization of molecularly distinct microglia populations to Alzheimer's disease pathologies using QUIVER

Chromogen-based double immunohistochemical detection of mitochondrial respiratory chain deficiencies in human brain tissue

Studies of the mitochondrial respiratory chain (MRC) have given important insights into the pathology of mitochondrial and neurodegenerative disorders. Immunohistochemical methods for staining MRC complexes are particularly valuable for assessing quantitative changes in situ, especially in complex tissues with cellular heterogeneity, such as the brain. However, traditional approaches have notable limitations. Chromogen-based staining, while preserving tissue morphology, has been restricted to a single antigen per section, preventing co-assessment of MRC complexes and mitochondrial mass on the same section. Immunofluorescence, which allows multiplex staining of multiple targets, partially addresses this limitation but compromises tissue morphology and can be highly variable in postmortem brain samples. To address these challenges, we have established a dual-antigen, chromogen-based immunohistochemical method that allows simultaneous assessment of each MRC complex and the mitochondrial marker voltage-dependent anion channel 1 (VDAC1) on the same section. As proof of concept, we apply this method on brain tissue from patients with neurological disease caused by mutations in the mitochondrial DNA polymerase gamma (POLG). Our findings demonstrate that this approach is both reliable and robust. Moreover, this method enables more precise identification of MRC deficiencies in neurons and significantly reduces the amount of tissue required for analysis, a critical advantage when working with scarce human brain samples.

Assessing Co-Localization of ITM2B With Alzheimer's Disease and Limbic-Predominant Age-Related TDP-43 Encephalopathy Neuropathologic Changes

Mutations in the Integral membrane protein 2B (ITM2B) gene are linked to the development of familial British and Danish dementias, two relatively early-onset dementia disorders known also to be associated with Tau neurofibrillary tangles (NFTs). However, to date, the involvement of ITM2B in limbic-predominant age-related TDP-43 encephalopathy neuropathologic changes (LATE-NC) remains unclear. To address this question, we used brain samples from the University of Kentucky Alzheimer's Disease Research Center community-based autopsy cohort. We investigated the patterns and co-localizations of ITM2B immunohistochemistry in subiculum, CA1, CA2, CA3 and dentate gyrus of the hippocampus from brains with Alzheimer's disease neuropathologic changes (ADNC), LATE-NC, and comorbid ADNC+LATE-NC, as well as low-pathology controls (n = 4 per disease state). There was frequent co-localization between ITM2B protein and intracellular Tau pathology in ADNC; however, there was a far weaker rate of co-localization between ITM2B and TDP-43 pathology. There also was, as previously described, an association between ITM2B immunostaining and neuritic-appearing amyloid plaques. Additionally, co-localization of intracellular ITM2B pathology with Thioflavin-S in NFTs suggested a potential role for ITM2B in marking neurons undergoing transition from relatively healthy (early NFT-bearing cells) to more severely affected (later NFT-bearing) cellular disease states. This study indicates that ITM2B has a relatively specific pattern of involvement in Tau-related neurodegeneration and in neuritic amyloid plaques, while implying minimal, if any, role for ITM2B in the synergistic relationship between Tau and TDP-43 pathologies.

A pathologic study of Perivascular pTDP-43 Lin bodies in LATE-NC

BACKGROUND

TAR DNA-Binding Protein 43 (TDP-43) pathological inclusions are a distinctive feature in dozens of neurodegenerative pathologies, including limbic-predominant age-related TDP-43 encephalopathy neuropathologic change (LATE-NC). Prior investigations identified vascular-associated TDP-43-positive micro-lesions, known as "Lin bodies," located on or near the brain capillaries of some individuals with LATE-NC. This study aimed to investigate the relationship between the accumulation of Lin bodies and glial cells in LATE-NC and the potential co-localization with ferritin, a protein associated with iron storage. Using multiplexed immunohistochemistry and digital pathology tools, we conducted pathological analyses to investigate the relationship between Lin bodies and glial markers (GFAP for astrocytes, IBA1 for microglia) and ferritin. Analyses were conducted on post-mortem brain tissues collected from individuals with pathologically confirmed Alzheimer's disease neuropathological changes (ADNC) and LATE-NC.

RESULTS

As shown previously, there was a robust association between Lin bodies and GFAP-positive astrocyte processes. Moreover, we also observed Lin bodies frequently co-localizing with ferritin, suggesting a potential link to compromised vascular integrity. Subsequent analyses demonstrated increased astrocytosis near Lin body-positive vessels compared to those without Lin bodies, particularly in ADNC cases. These results suggest that the accumulation of Lin bodies may elicit an increased glial response, particularly among astrocytes, possibly related to impaired vascular integrity.

CONCLUSIONS

Lin bodies are associated with a local reactive glial response. The strong association of Lin bodies with ferritin suggests that the loss of vascular integrity may be either a cause or a consequence of the pTDP-43 pathology. The reactive glia surrounding the affected vessels could further compromise vascular function.

The interaction between ageing and Alzheimer's disease: insights from the hallmarks of ageing

Ageing is a crucial risk factor for Alzheimer's disease (AD) and is characterised by systemic changes in both intracellular and extracellular microenvironments that affect the entire body instead of a single organ. Understanding the specific mechanisms underlying the role of ageing in disease development can facilitate the treatment of ageing-related diseases, such as AD. Signs of brain ageing have been observed in both AD patients and animal models. Alleviating the pathological changes caused by brain ageing can dramatically ameliorate the amyloid beta- and tau-induced neuropathological and memory impairments, indicating that ageing plays a crucial role in the pathophysiological process of AD. In this review, we summarize the impact of several age-related factors on AD and propose that preventing pathological changes caused by brain ageing is a promising strategy for improving cognitive health.

A neuropathologic feature of brain aging: multi-lumen vascular profiles

Cerebrovascular pathologies other than frank infarctions are commonly seen in aged brains. Here, we focus on multi-lumen vascular profiles (MVPs), which are characterized by multiple vessel lumens enclosed in a single vascular channel. Little information exists on the prevalence, risk factors, and co-pathologies of MVPs. Therefore, we used samples and data from the University of Kentucky Alzheimer's Disease Research Center (n = 91), the University of Kentucky Pathology Department (n = 31), and the University of Pittsburgh Pathology Department (n = 4) to study MVPs. Age at death was correlated with MVP density in the frontal neocortex, Brodmann Area 9 (r = 0.51; p < 0.0001). Exploratory analyses were performed to evaluate the association between conventional vascular risk factors (e.g., hypertension, diabetes), cardiovascular diseases (e.g., heart attack, arrhythmia), and cerebrovascular disease (e.g., stroke); the only nominal association with MVP density was a self-reported history of brain trauma (Prevalence Ratio = 2.1; 95 CI 1.1-3.9, before correcting for multiple comparisons). No specific associations were detected between neuropathological (e.g., brain arteriolosclerosis) or genetic (e.g., APOE) variables and MVP density. Using a tissue clearing method called SeeDB, we provide 3-dimensional images of MVPs in brain tissue. We conclude that MVPs are an age-related brain pathology and more work is required to identify their clinical-pathological correlation and associated risk factors.