Parisi, Joseph E.

The specific effect of TDP-43 pathology on grey matter volume in individuals without frontotemporal lobar degeneration is unclear. Bejanin et al. reveal a major and independent contribution of TDP-43 to neurodegeneration and shed light on the regional distribution of TDP-43-related atrophy in older adults.

Abstract Introduction Neuroimaging biomarkers are important for early diagnosis of Alzheimer's disease, and comparing multimodality neuroimaging to autopsy data is essential. Methods We compared the pathologic findings from a prospective autopsy cohort (n = 100) to Pittsburgh compound B PET (PiB‐PET), 18 F‐fluorodeoxyglucose PET (FDG‐PET), and MRI. Correlations between neuroimaging biomarkers and neuropathologic schemes were assessed. Results PiB‐PET showed strong correlations with Thal amyloid phase and Consortium to Establish a Registry for Alzheimer's Disease score and categorized 44% of Thal phase 1 participants as positive. FDG‐PET and MRI correlated modestly with Braak tangle stage in Alzheimer's type pathology. A subset of participants with “none” or “sparse” neuritic plaque scores had elevated PiB‐PET signal due to diffuse amyloid plaque. Participants with findings characterized as “suspected non‐Alzheimer's pathophysiology” represented 15% of the group. Discussion PiB‐PET is associated with Alzheimer's disease, neuritic plaques, and diffuse plaques. FDG‐PET and MRI have modest correlation with neuropathologic schemes. Participants with findings characterized as suspected non‐Alzheimer's pathophysiology most commonly had primary age‐related tauopathy.

Abstract While the accumulation and aggregation of amyloid-β and tau are central events in the pathogenesis of Alzheimer’s disease, there is increasing evidence that cerebrovascular pathology is also abundant in Alzheimer’s disease brains. In brain capillaries, endothelial cells are connected closely with one another through transmembrane tight junction proteins forming the blood–brain barrier. Because the blood–brain barrier tightly regulates the exchange of molecules between brain and blood and maintains brain homeostasis, its impairment is increasingly recognized as a critical factor contributing to Alzheimer’s disease pathogenesis. However, the pathological relationship between blood–brain barrier properties and Alzheimer’s disease progression in the human brain is not fully understood. In this study, we show that the loss of cortical tight junction proteins is a common event in Alzheimer’s disease, and is correlated with synaptic degeneration. By quantifying the amounts of major tight junction proteins, claudin-5 and occludin, in 12 brain regions dissected from post-mortem brains of normal ageing (n = 10), pathological ageing (n = 14) and Alzheimer’s disease patients (n = 19), we found that they were selectively decreased in cortical areas in Alzheimer’s disease. Cortical tight junction proteins were decreased in association with the Braak neurofibrillary tangle stage. There was also a negative correlation between the amount of tight junction proteins and the amounts of insoluble Alzheimer’s disease-related proteins, in particular amyloid-β40, in cortical areas. In addition, the amount of tight junction proteins in these areas correlated positively with those of synaptic markers. Thus, loss of cortical tight junction proteins in Alzheimer’s disease is associated with insoluble amyloid-β40 and loss of synaptic markers. Importantly, the positive correlation between claudin-5 and synaptic markers, in particular synaptophysin, was present independent of insoluble amyloid-β40, amyloid-β42 and tau values, suggesting that loss of cortical tight junction proteins and synaptic degeneration is present, at least in part, independent of insoluble Alzheimer’s disease-related proteins. Collectively, these results indicate that loss of tight junction proteins occurs predominantly in the neocortex during Alzheimer’s disease progression. Further, our findings provide a neuropathological clue as to how endothelial tight junction pathology may contribute to Alzheimer’s disease pathogenesis in both synergistic and additive manners to typical amyloid-β and tau pathologies.