FN1 and fibrosis: Remarkably, this single swap led to a significant reduction in fibronectin protein accumulation to similar levels as the APOE3/3 baseline (0.60 ± 0.058-fold change, corresponding to a 40% decrease relative to APOE4/4, p = 0.0344; Figure 3E), demonstrating that APOE4 vascular fibrosis is driven by myofibroblasts.