Fig. 6: Microglial cells phagocyte VaS-associated blood vessels.

a Striatal confocal XY images from Psen1^loxP/loxP; Psen2^–/– mice that were injected with cerebral endothelium-specific adeno-associated control (AAV-BR1-Control; C) or Cre recombinase-expressing (AAV-BR1-Cre; Cre) viruses, perfused with Evans blue (EB; white) and stained with endothelial (IB4; red), microglia (IBA1; green), nuclear (DAPI; blue) markers. Yellow arrowheads indicate microglial IB4⁺ pouches. Lower row images show the dashed white rectangles depicted in the upper row images. Scale bars = 20 and 10 µm in low and high magnification images. b–e Cortical confocal images 8-month-old Cdh5-Cre::ERT2/+; R26-LSL-tdTomato/+; APP-PSEN1/+ tamoxifen-treated mice and stained with a tdTomato antibody (b) or direct tdTomato fluorescence (c–e) (red) and with microglial (IBA1; cyan), astrocytic (GFAP; green —b), lysosomal (CD68; green —e) and nuclear (DAPI; blue) markers. Aß plaques are indicated with a yellow asterisk. Yellow arrowheads indicate internalization of tdTomato⁺ signal by microglial pouches. Lower row images show the dashed white rectangles depicted in the upper row (b, e) or left (c) images. A white arrowhead indicates a tip cell that projects extensions towards an Aß plaque (b). Scale bars (b–e) = 50 µm in low and 10 µm in high magnification images. Regions with high alignment of endothelial cells and microglia are highlighted with dashed yellow rectangles in c. Left panel in d shows a z-projection of a magnified and cropped image from c showing the orthogonal projections and the right panels show different rotated views of 3D reconstructions of the left image (volume, two central panels; surface, right panel). Right graphs (c–e) show the quantification of c the length of tdTomato⁺ vessels occupied by IBA1⁺ signal. Mean  ± SEM. n = 3 mice; ANOVA, post hoc Tukey’s test; d the number of microglial pouches proximal to Aß plaques. Mean ± SEM. n = 3 mice; and e the percentage of microglial IB4⁺/CD68⁺ pouches. Mean ± SEM. n = 3 mice. f Working model of the process of vascular scars (VaS) formation. Numeration continues from Fig. 1f.