Supplementary Figure 3: Extended data from Fig. 1. SFRP1 specifically localizes to APs, blood vessels and choroid plexus.

A-D; F-H) Paraffin sections of the frontal cortex from BBV-VI AD patients (A-C; F-H) and age matched controls (D) coimmunostained for SFRP1 and Aβ, ThioS or probed with secondary antibodies only, as indicated in the panels. Note that SFRP1 specifically localizes to blood vessels identified by the autofluorescence of elastin¹⁶ (A). B,C) No signal was detected with secondary antibodies, supporting the specificity of SFRP1 localization. D) No detectable signal was found in control sections. E) Western blot analysis of SFRP1 presence in choroid plexus extracts from AD (n=5) patients and cognitive normal controls (n=4), normalized to α-Tubulin. Data are means ± SEM and were analyzed with two-sided Student-t test, finding no significant differences. F-H) SFRP1 specifically accumulates in the core of Aβ+ and ThioS+ APs (white arrowheads) and their surroundings (yellow arrows in F,G) and forms aggregates that are poorly ThioS+ (arrowhead in H). These experiments were repeated 4 times with similar results. Scale bar: 50 μm A-C; 100 μm D-G.