Amyloid Beta (Aβ) Protein- and Amyloid Precursor Protein (APP)- Immunoreactive Structures in the Brains of Aged Tree Shrews

Background: Amyloid beta (Aβ) accumulates in the human brain in an age-dependent manner during normal aging. However, Aβ accumulation has not been observed in rodents during normal aging. Tree shrews, the experimental animals studied here, are as small as rats but have a longer life span than rodents. Methods: We investigated Aβ accumulations in the brains of young and aged tree shrews by amyloid histochemistry and immunohistochemistry using antibodies to Aβ-42, Aβ-40, Aβ-16 and amyloid precursor protein (APP). Results: In the brain of young tree shrews, there were no Aβ- immunoreactive (-ir) and APP-ir profiles. In the brains of aged tree shrews, Aβ-42-ir neuronal profiles were observed in the cortex, subiculum, basal ganglia, mammillary body and hypothalamus, but there were only a few weak Congo red-positive amyloid deposits. Aβ-42-, Aβ-40-, Aβ-16- and APP-ir blood vessels were observed. Conclusions: An early stage of amyloid accumulation occurs in the brains of aged tree shrews, indicating that this animal may be a good model for studying the start of Aβ accumulation.