Alzheimer's Disease (AD) is clinically characterized as a predominantly amnestic (memory impairment) syndrome at presentation that progresses to affect other cognitive domains. AD is pathologically defined by the presence of amyloid plaques and neurofibrillary tangles of hyperphosphorylated tau (pTau) in stereotypical brain regions. AD shows clinical and pathological diversity, including non-amnestic subtypes, severity of tau pathology across brain regions, and co-pathologies such as aggregates of hyper-phosphorylated transactive response DNA-binding protein 43 (pTDP-43). This study aims to examine the association between pTau and pTDP-43 using new highly quantitative approaches. By examining the combined pathology, we hope to identify patterns of pTau related to pTDP-43 across the different clinical and pathologic subtypes. The University of Washington Alzheimer's Disease Research Center clinical core autopsy cohort was characterized and subdivided into amnestic and non-amnestic syndrome subtypes. The subjects were analyzed to identify the prevalence of pTDP-43 and its correlation to the subject's cognitive data and patterns of progression. This analysis was used to select a subset of 29 cases with non-amnestic dementia and a matched subset with an amnestic subtype for more in-depth neuropathological and molecular profiling of several brain regions. Using the HALO platform, I generated quantitative measures of pTau in the frontal, temporal, and parietal cortex, as well as the hippocampus. The integration of these findings aims to understand how pTDP-43 pathology influences tau distribution based on clinical presentation These results will allow us to select a small set of cases for further work that will include using NanoString GeoMx Digital Spatial Profiling to identify potential pathways relevant to the association between pTDP-43 and pTau severity concerning mechanisms of clinical and pathologic heterogeneity in AD. These insights will allow for further research of these pathways to determine their biological relevance and ways to mitigate their effects.

Alzheimer’s disease (AD) is the most common cause of dementia in the aging population, characterized pathologically by the presence of amyloid plaques and tau neurofibrillary tangles in the brain. However, AD often coexists with other pathologies contributing to dementia, such as hyperphosphorylated aggregates of the protein TDP-43. TDP-43 induces a dementia syndrome similar to AD and the combination of AD and TDP-43 is associated with accelerated cognitive decline, greater brain atrophy, and increased AD pathologic burden. AD and TDP-43 pathology are definitively diagnosed post-mortem upon neuropathologic examination but there is a great need to be able to identify these pathologies in living patients using biomarkers. Currently there are accepted biomarkers for AD, including measures of amyloid beta and hyperphosphorylated tau proteins in cerebrospinal fluid (CSF), but there are no biomarkers for TDP-43. Leveraging the reliability of CSF in detecting pathologic proteins, we hypothesize that measurable hallmarks of underlying TDP-43 pathology also exist in CSF. We tested four groups of brain donors (n=36 per group) defined by presence or absence of AD and TDP-43 pathology at autopsy: healthy controls, AD only (amyloid plaques and tau tangles), TDP-43 only, and AD+TDP-43. Post-mortem CSF samples are analyzed for TDP-43, hyperphosphorylated tau (pTau-181), and the brain injury marker glial fibrillary acidic protein (GFAP) using the Quanterix SR-XTM Biomarker Detection System. Because these assays are intended for ante-mortem samples, the first aim of the study was to determine optimal sample preparation for post-mortem samples, followed by the second aim to determine if there are concentration differences between proteins in CSF across groups. Successful identification of reliable TDP-43 biomarkers in living patients would improve neurodegenerative disease diagnostics, enabling accurate underlying pathology diagnosis and facilitating tracking disease progression and treatment response as therapies for AD, TDP-43, and other causes of dementia emerge.

According to the World Health Organization, Alzheimer’s Disease (AD) is the most common form of dementia – a major and growing cause of disability and dependency among older people globally. The Seattle AD Brain Cell Atlas (SEA-AD) project is a collaboration between the University of Washington (UW) and the Allen Institute for Brain Science (AIBS) aimed at discovering early vulnerable cell types in AD. In SEA-AD, we hope to further our understanding of the etiology and early progression of AD to ultimately identify targets for effective therapeutic intervention. Eighty-four participant brain donors with a postmortem interval less than 12 hours from the UW AD Research Center (12/84) and Kaiser Adult Changes in Thought (72/84) studies were included in the SEA-AD cohort. At the time of procurement, one hemisphere was frozen in super-cooled isopentane for transcriptomic analysis at AIBS; the contralateral hemisphere was fixed in 10% neutral buffered formalin for neuropathologic assessment at UW. The middle temporal gyrus, medial entorhinal cortex, and hippocampus were sampled, processed, embedded in paraffin, and sectioned for  immunohistochemical (IHC) studies. Seven antibodies, including duplexed stains, targeting amyloid b (6e10) and microglia (IBA1), pTau (AT8) and pTDP-43 (1D3), monoplexed a-synuclein (LB509), astrocytes (GFAP), neurons (NeuN), and triplexed histochemical stain: hematoxylin, eosin, and Luxol fast blue were deployed to assess the neuropathology associated with the presence and progression of AD and related neuropathologic changes. The data obtained from the quantitative assessment of the IHC staining is integrated with the transcriptomic data generated by the Allen Institute to enhance our understanding of the cellular vulnerabilities and associated molecular processes of AD. Public access to this neuropathological data through the SEA-AD resource potentiates research efforts to understand and identify the mechanisms of AD progression.