Inflammation occurs early during the Aβ deposition process in TgCRND8 mice

Alzheimer’s disease (AD) is characterized by a progressive cognitive decline leading to dementia and involves the deposition of amyloid-β (Aβ) peptides into senile plaques. Other neuropathological features that accompany progression of the disease include a decrease in synaptic density, neurofibrillary tangles, dystrophic neurites, inflammation, and neuronal cell loss. In this study, we report the early kinetics of brain amyloid deposition and its associated inflammation in an early onset transgenic mouse model of AD (TgCRND8) harboring the human amyloid precursor protein gene with the Indiana and Swedish mutations. Both diffuse and compact plaques were detected as early as 9–10 weeks of age. Aβ-immunoreactive (Aβ-IR) plaques (4G8-positive) appeared first in the neocortex and amygdala, then in the hippocampal formation, and lastly in the thalamus. Compact plaques (ThioS-positive) with an amyloid core were observed as early as diffuse plaques were detected, but in lower numbers. Amyloid deposition increased progressively with age. The formation of plaques was concurrent with the appearance of activated microglial cells and shortly followed by the clustering of activated astrocytes around plaques at 13–14 weeks of age. This TgCRND8 mouse model allows for a rapid, time-dependent study of the relationship between the fibrillogenic process and the inflammatory response during the brain amyloidogenic process.