Effect of mouse strain as a background for Alzheimer's disease models on the clearance of amyloid-β.

Novel animal models of Alzheimer's disease (AD) are relentlessly being developed and existing ones are being fine-tuned; however, these models face multiple challenges associated with the complexity of the disease where most of these models do not reproduce the full phenotypical disease spectrum. Moreover, different AD models express different phenotypes that could affect their validity to recapitulate disease pathogenesis and/or response to a drug. One of the most important and understudied differences between AD models is differences in the phenotypic characteristics of the background species. Here, we used the brain clearance index (BCI) method to investigate the effect of strain differences on the clearance of amyloid β (Aβ) from the brains of four mouse strains. These mouse strains, namely C57BL/6, FVB/N, BALB/c and SJL/J, are widely used as a background for the development of AD mouse models. Findings showed that while Aβ clearance across the blood-brain barrier (BBB) was comparable between the 4 strains, levels of LRP1, an Aβ clearance protein, was significantly lower in SJL/J mice compared to other mouse strains. Furthermore, these mouse strains showed a significantly different response to rifampicin treatment with regard to Aβ clearance and effect on brain level of its clearance-related proteins. Our results provide for the first time an evidence for strain differences that could affect ability of AD mouse models to recapitulate response to a drug, and opens a new research avenue that requires further investigation to successfully develop mouse models that could simulate clinically important phenotypic characteristics of AD.