To be able to select the most appropriate age of Alzheimer’s disease (AD) in vivo models for efficacy analyses of new drugs, it is of utmost relevance to know the model’s brain pathology in detail. We therefore evaluated the brain pathology of the well-established and often used 5xFAD mouse model from early adulthood until old age.
5xFAD mice contain five AD-linked mutations, three in the APP695 gene, and two in the PSEN1 gene whose expressions are driven by the neuron-specific Thy1 promoter. The model is already well characterized and often used for the analysis of new drugs against AD as it displays several common AD pathologies, such as cognitive impairment, increased amyloid-β levels and amyloid plaques, neuroinflammation, but also neurodegeneration as well as vascular and tau pathology.
The detailed analyses of the model’s amyloid plaque pathology in the cortex by 6E10, LOC, and Thioflavin S in four age groups show a first slight increase of LOC and Thioflavin S immunoreactive (IR) area already at the age of 3 months. By the age of 7 months, all three markers show a highly increased IR area compared to age-matched non-transgenic (ntg) littermates (Figure 1). The IR area of all markers further increases with age.
Figure 1: Progression of amyloid plaque development in the cortex of 5xFAD mice. 6E10 (A), LOC (B), and Thioflavin S (C) immunoreactive area in percent in the cortex of 1.5 to 9 months old 5xFAD mice of mixed sex. Mean ± SEM. n = 8 per group; 5 slides per animal. Two-way ANOVA followed by the Bonferroni’s post hoc test. ***p <0.001.
Additional analyses of inflammatory processes reveal that also activated microglia, astrocytosis, as well as cerebral amyloid angiopathy (CAA) as measured by Iba1, GFAP and amyloid on collagen IV labelling, respectively, are prominent pathologies in the cortex of 7 and 9 months old 5xFAD mice (Figure 2). The IR area of GFAP is even already increased in the cortex of 5xFAD mice at the age of 3 months compared to age-matched ntg littermates. All pathologies further increase with age.
Figure 2: Progression of inflammatory processes in the cortex of 5xFAD mice. Iba1 (A), GFAP (B), and amyloid on collagen 4 normalized to collagen 4 (C) immunoreactive area in percent in the cortex of 1.5 to 9 months old 5xFAD mice of mixed sex. Quantification of collagen 4 by itself did not show significant differences compared to ntg littermates and over age (data not shown). Mean ± SEM. n = 8 per group; 5 slides per animal. Two-way ANOVA followed by the Bonferroni’s post hoc test. *p <0.05, ***p <0.001.
Similar results of all markers were also observed in the hippocampus (data not shown).
Based on these results, 5xFAD mice can be utilized to test drugs for their efficacy to prevent or decrease disease progression as well as reduce already existing AD pathology.
More details about the pathology of this model are available in our 5xFAD animal model brochure that we are happy to share upon request.
