Seed-induced Aß deposition is modulated by microglia under environmental enrichment in a mouse model of Alzheimer's disease.

ABSTRACT

Alzheimer's disease (AD) is characterized by severe neuronal loss as well as the accumulation of amyloid-ß (Aß), which ultimately leads to plaque formation. Although there is now a general agreement that the aggregation of Aß can be initiated by prion-like seeding, the impact and functional consequences of induced Aß deposits (Aß seeding) on neurons still remain open questions. Here, we find that Aß seeding, representing early stages of plaque formation, leads to a dramatic decrease in proliferation and neurogenesis in two APP transgenic mouse models. We further demonstrate that neuronal cell death occurs primarily in the vicinity of induced Aß deposits culminating in electrophysiological abnormalities. Notably, environmental enrichment and voluntary exercise not only revives adult neurogenesis and reverses memory deficits but, most importantly, prevents Aß seeding by activated, phagocytic microglia cells. Our work expands the current knowledge regarding Aß seeding and the consequences thereof and attributes microglia an important role in diminishing Aß seeding by environmental enrichment.