Figure 3.

Rescue of vascular and neuronal phenotype in Lrp1^lox/lox; Tie2-Cre mice by endothelial-specific LRP1 gene replacement. (A and B) Endothelial expression of GFP (left, green), HA-tagged mLRP1 (right, green), and lectin⁺ endothelium (purple) in the cortex of 4-mo-old Lrp1^lox/lox; Tie2-Cre mice after AAV2-BR1-GFP (left) or AAV2-BR1-mLRP1 (LRP1 minigene, right) treatment (A), and quantification of HA-mLRP1⁺ area colocalized with lectin⁺ endothelial capillary profiles (<6 µm in diameter) in the cortex (Ctx) and hippocampus (Hp; B). Scale bar = 25 µm. Mean ± SEM; n = 3 mice/group. (C–E) IgG (left, purple) and fibrinogen (right, purple) perivascular capillary deposits (C) and quantification (D and E) in 4-mo-old Lrp1^lox/lox; Tie2-Cre and Lrp1^lox/lox mice after AAV2-BR1-GFP (top) or AAV2-BR1-mLRP1 (bottom) treatment. Green, lectin⁺ endothelium. Scale bar = 20 µm. Mean ± SEM, n = 14 mice/group. (F) High-magnification confocal images from Lrp1^lox/lox; Tie2-Cre mouse treated with AAV2-BR1-mLRP showing that vessel segments that reexpress HA-mLRP1 (asterisks) were no longer leaky compared with a vessel segment that does not express HA-mLRP1 (arrow) that leaks fibrinogen. Scale bar = 10 µm. (G–I) NeuN⁺ neurons and SMI312⁺ neurites (G) and quantification of NeuN⁺ neurons and SMI312⁺ neurites in the cortex and hippocampus of 4-mo-old Lrp1^lox/lox and Lrp1^lox/lox; Tie2-Cre mice after AAV2-BR1-GFP (top panels) or AAV2-BR1-mLRP1 (bottom panels) treatment (H and I). Scale bar = 50 µm. Mean ± SEM, n = 14 mice/group. (J–M) Burrowing (J), nest construction (K), novel object location (L), and recognition (M) in 4-mo-old Lrp1^lox/lox; Tie2-Cre and Lrp1^lox/lox mice after AAV2-BR1-GFP or AAV2-BR1-mLRP1 treatment. Mean ± SEM; n = 14 mice/group. In B, significance was determined by Student’s t test. In D, E, and H–M, significance was determined by one-way ANOVA followed by Bonferroni post hoc test. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.