Overexpression of APPwt. APPswe in cortical cell cultures decreases the spine density of neighboring healthy wild-type neuron, in an APP-dependent manner. A, Representative confocal images of cultured cortical neurons where the neuron on the left is overexpressing either LA-GFP only (LA-GFP), APPwt-mCh (APPwt), APPswe-mCh (APPswe), or APP KO neurons that overexpress APPswe-mCh (APP KO+swe), and the neuron on the right is only overexpressing LA-GFP (healthy neuron). Scale bar, 10 µm. B, Bar graphs (mean ± SEM) show the spine density of healthy neurons depending on the distance from (LA-GFP, APPwt, APPswe, or APP KO+swe) neurons (n = at least 3 neurons/condition from three different cultures). Two-way ANOVA and Tukey's post hoc test for multiple comparisons. Spine density of healthy neurons according to the distance from the APP-overexpressing neuron (F_(6,168) = 5.309; p < 0.0001; treatment: F_(5,168) = 51.6, p < 0.0001, interaction: F_(30,168) = 3.484, p < 0.0001). From 0 to 10 μm: LA-GFP versus APPwt, p < 0.0001; LA-GFP vs APPswe, p < 0.0001; APPswe vs APP KO+swe, p < 0.0001. From 20 to 30 μm: LA-GFP vs APPwt, p = 0.0487; LA-GFP vs APPswe, p < 0.0001. From 30 to 40 μm: LA-GFP vs APPswe, p < 0.0001. *p < 0.05, ***p < 0.001 when compared with control condition (both neurons only overexpress LA-GFP) at equivalent distance. ###p < 0.001 when healthy neurons in APP KO plus the swe condition are compared with healthy neurons in the APPswe condition.