Cerebral amyloid β(42) deposits and microvascular pathology in ageing baboons

M. Ndung'u, W. Hartig, F. Wegner, J. M. Mwenda, R. W. C. Low, R. O. Akinyemi and R. N. Kalaria (2012) Neuropathology and Applied Neurobiology38, 487-499 Cerebral amyloid beta(42) deposits and microvascular pathology in ageing baboons Background: Previous studies have extensively reported the deposition of amyloid beta (A beta) peptide with carboxyl- and amino-terminal heterogeneity in cortical and cerebrovascular deposits in Alzheimer's disease (AD) and in non-human primates except baboons. Methods: We examined the immunocytochemical distribution of A beta peptides and A beta oligomers in brain tissue from three subspecies of 18- to 28-year-old baboons (Papio) and in other monkeys including the squirrel (Saimiri sciureus) and rhesus (Macaca mulatta) for comparison. Results: A general preponderance of A beta(42) in parenchymal deposits and many vascular deposits in all cortical lobes was evident in the baboons. A beta oligomeric immunoreactivity was also apparent like to amyloid plaques. We found that the amino acid sequence of the A beta domain of the baboon amyloid precursor protein is similar to that of man. In contrast to A beta, immunoreactivity to hyperphosphorylated tau protein was largely intracellular and rare in these baboons. Brain tissues from squirrel and rhesus monkeys examined in parallel exhibited mostly vascular and parenchymal deposits containing A beta(42) peptides. Our results were comparable to AD, but showed that even in younger monkeys exhibiting few deposits, A beta(42) was evident in both parenchymal deposits and cerebral amyloid angiopathy. Perivascular amyloid deposits were frequent and often accompanied by microvascular abnormalities in the form of collapsed degenerated capillaries. Conclusions: Similar to other primates above and below in the phylogenetic order, our observations and evaluation of the literature implicate pathogenicity of A beta(42) peptide associated with microvascular degeneration in baboons. We suggest baboons are useful animals to investigate the dynamics of AD-related pathology.