FIGURE 4.

Iba‐1/TREM2 periplaque microglia were barely present in brain sections treated with old‐Tg sample. (A) Schematic representation of the regionalization of the plaque‐associated area for quantification. Three concentric circles were drawn outwards the outline of the plaque, with a radius of 10, 20, and 30 μm each. Then, microglia on plaque was assessed, as well as microglia at a distance of 10, 20, and 30 μm. (B) Fluorescence microscopy images stained with X‐34 and immunolabeled for Iba1 and TREM2 in 3xTg‐AD mice treated with PBS (B1) and with brain homogenates from AD patient (B2) and old‐Tg mice (B3) in the ipsilateral side. (C) Quantification of Iba1 load (c1), TREM2 load (c2), and TREM2/Iba1 ratio (c3). (D) Schematic timeline of the MTT assay. BV‐2 cells were seeded into a 96‐well plate and, after 3 h, brain extracts were added to the cells at a final concentration of 0.1 μg/μL. After incubation for 72 h, MTT was added to each well and further incubated for 4 h. Then, acid isopropanol was added and absorbance at 550 nm was measured. (E) BV‐2 cells treated with human, old‐Tg samples (0.1 μg/μL), and the control sample with no seeds. (F) BV‐2 cells treated with old‐Tg immunodepleted samples for Aβ, tau, and both Aβ and tau. H, human; I, ipsilateral; ID, immunodepleted; M, mouse. The values represent means ± SEM. N = 4–6 per group (C), N = 3–6 per group (E, F). Scale bar: 10 μm (B1–B3), 20 μm (B1a–B1c, B2a–B2c, B3a–B3c).