Thioflavin-positive tau aggregates complicating quantification of amyloid plaques in the brain of 5XFAD transgenic mouse model

Jisu Shin,Youngsoo Kim,Sohui Park,Heeyang Lee

doi:10.1038/s41598-021-81304-6

Abstract

Transgenic mouse models recapitulating Alzheimer’s disease (AD) pathology are pivotal in molecular studies and drug evaluation. In transgenic models selectively expressing amyloid-β (Aβ), thioflavin S (ThS), a fluorescent dye with β-sheet binding properties, is widely employed to observe amyloid plaque accumulation. In this study, we investigated the possibility that a commonly used Aβ-expressing AD model mouse, 5XFAD, generates ThS-positive aggregates of β-sheet structures in addition to Aβ fibrils. To test this hypothesis, brain sections of male and female 5XFAD mice were double-stained with ThS and monoclonal antibodies against Aβ, tau, or α-synuclein, all of which aggregates are detected by ThS. Our results revealed that, in addition to amyloid plaques, 5XFAD mice express ThS-positive phospho-tau (p-tau) aggregates. Upon administration of a small molecule that exclusively disaggregates Aβ to 5XFAD mice for six weeks, we found that the reduction level of plaques was smaller in brain sections stained by ThS compared to an anti-Aβ antibody. Our findings implicate that the use of ThS complicates the quantification of amyloid plaques and the assessment of Aβ-targeting drugs in 5XFAD mice.

Highlights

Transgenic mouse models recapitulating Alzheimer’s disease (AD) pathology are pivotal in molecular studies and drug evaluation
To compare the type and the quantity of protein aggregates stained by thioflavin S (ThS) and aforementioned antibodies in the brain of 5XFAD, male (n = 3) and female (n = 3) 5XFAD mice were sacrificed at 7–8 months and 5–6 months of age, respectively
In 5XFAD mouse brain, β-sheet-rich protein aggregates detected by ThS were thought to be Aβ plaques, which can be stained by 6E10

Summary

Introduction

Transgenic mouse models recapitulating Alzheimer’s disease (AD) pathology are pivotal in molecular studies and drug evaluation. We investigated the possibility that a commonly used Aβ-expressing AD model mouse, 5XFAD, generates ThS-positive aggregates of β-sheet structures in addition to Aβ fibrils. To test this hypothesis, brain sections of male and female 5XFAD mice were double-stained with ThS and monoclonal antibodies against Aβ, tau, or α-synuclein, all of which aggregates are detected by ThS. To identify the protein component of ThS-positive aggregates, male 5XFAD mice from 7 to 8 months of age and female from 5 to 6 months of age were prepared Their brain sections were double-stained by ThS with anti-Aβ(1–16) monoclonal antibody 6E10, anti-Aβ(17–24) monoclonal antibody 4G8, anti-phosphorylated tau monoclonal antibody AT8, or anti-α-synuclein monoclonal antibody (Table 1). Whole Cortex Hippocampus double-stained by ThS with either 6E10 or AT8 to compare the differences between the number of ThS-positive aggregates and each antibody stained accumulates

Methods

Results

Conclusion