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Experimental deposition of Alzheimer amyloid β‐ protein in canine leptomeningeal vessels

To study the pathogenesis of cerebral amyloid angiopathy (CAA), organ cultures of canine leptomeninges were incubated with fluorescein-conjugated amyloid β- protein (FAβ, residues 1–40; 10 nM to 200 μM). Fluorescence microscopy showed focal and dose-dependent FAβ binding to blood vessels affected by CAA at FAβ- concentrations as low as 10nM. The new Aβ deposits appeared to be extracellular and were localized to the middle and outer layers of leptomeningeal arterioles. FAβ partially co-localized with apolipoprotein E (ApoE) as revealed by confocal microscopy, suggesting that Aβ in situ binds to ApoE. Young dogs or old dogs without CAA showed no deposition of FAβ. Our results indicate that after initiation of CAA pathology, physiological concentrations of soluble Aβ are sufficient to sustain its further deposition and therefore the progression of CAA.