Figure 4. Microglia Are the Major Contribu tors of Apoe Expression in the Vicinity of β-amyloid Plaques.

(A–F) Combined RNAscope and immunofluorescent analyses of Apoe expression by microglia and astrocytes in the vicinity of β-amyloid plaques. Expressions of Apoe, the microglia marker Itgam (A–C), and the astrocyte marker Slc1a3 (D and E) were visualized using RNAscope probes, while plaques were visualized by staining with the anti-Aβ antibody 6E10. Nuclei were visualized with DAPI. Photos are representative of three mice per genotype. (A and D) are representative images of App^NL-G-F CA1 stained for microglia (Itgam) and astrocytes (Slc1a3), respectively. (B) Zoom-in of the boxed area in (A), taken as a separate image with a higher magnification lens. Similarly, (E) is a zoom-in of the boxed area in (D). (C) and (D) are representative images of male wild type C57Bl/6J CA1, stained for microglia (Itgam) and astrocytes (Slc1a3), respectively. Scale bars in (A), (C), (D), and (F) represent 50 μm, while in (B) and (E) represent 20 μm.

(G) Quantification of Apoe staining intensity per cell, classified based on the genotype (App^NL-G-F or C57BL/6J), cell type (microglia [mglia] or astrocyte [astro]), and distance from a plaque (ring). For wild-type mice, measurements were made by selecting random regions of interest (ROIs) in the same brain areas as in App^NL-G-F. Measurements were made from at least 25 plaques or ROIs for each condition (App^NL-G-F mglia, C57BL/6J mglia, App^NL-G-F astro, and C57BL/6J astro), collected from 3 mice per genotype.

(H) Number of microglia and astrocytes next to plaques. As in (G), cells were classified based on genotype and distance from plaques (App^NL-G-F) or random ROIs (C57BL/6J).