APOE and Alzheimer disease: Interestingly, loss of pericytes in human AD is significantly higher in apoE4 carriers compared to apoE3 carriers, which is associated with greater degree of BBB breakdown [56, 64], and increased risk for CAA, as shown both in human apoE4 compared to apoE3 carriers [65–69], and APP mouse models on apoE4 compared to apoE3 background [66, 70].