Longitudinal Quantification of Sub‐Regional Hippocampal Amyloid‐Beta Burden in Ex‐Vivo slices from the AppNL‐G‐F Mouse Model of Alzheimer’s Disease

Abstract

AbstractBackgroundAmyloid‐beta (Aβ) pathology is suggested to precede the onset of clinical Alzheimer’s disease symptoms by up to two decades. The humanised AppNL‐G‐F knock‐in model of amyloidopathy has accelerated pathogenesis and can be used to study AD progression. Here we used it to quantify the temporal and spatial characteristics of Aβ plaque accumulation as they first appear in the hippocampus, and as pathology continues to develop.MethodAppNL‐G‐F knock‐in mice and wild‐type mice at 1, 3, 6, and 9 months of age were transcardially perfused with PBS followed by 4% paraformaldehyde (PFA), followed by preparation of coronal slices for immunohistochemistry analysis. Samples were stained with anti‐Aβ antibody (6E10) together with a neuronal marker, NeuN, and DAPI. Images were taken of sub‐hippocampal regions (CA1, CA3, DG), in left/right hemispheres, and ventral/dorsal segments using a confocal microscope (Leica SP8). Summation of intensity across Z‐stacks in Fiji was used to quantify Aβ plaques in regions of interest.ResultWe found age to be a statistically significant factor on determining area density, with hippocampal deposition observed by 3 months. Bin analysis showed a near‐exponential reduction in plaque number with increasing plaque size, increasing with age. Regionally, there was an increase in plaque density in CA3, with non‐linear regression analysis indicating area density for CA3 is most strongly correlated with age. Within the CA1 region, the densest plaque formation was in the pyramidal cell layer. Further analysis at the aged 9‐month time point suggested a differential pathology across the axial plane and greater left‐hemispheric lateralisation.ConclusionThis data provides further evidence for the protracted timeline to which AppNL‐G‐F knock‐in mice recapitulate key AD neuropathologies including insoluble amyloidosis beginning before 3 months in the hippocampus. It also indicates potentially novel differential sub‐regional Aβ accumulation patterns, axial variations, and hemispheric asymmetries, offering mechanistic insights for plaque localisation and differential susceptibility to Aβ. This could aid advancement of Αβ‐targeting therapies.