APOE and Alzheimer disease: Our finding that pericyte number was greater in the SFG in AD compared to controls is contrary to other studies where a decline in the number of pericytes was observed in the frontal cortex and hippocampus in human AD (Sengillo et al., 2013), with an APOE4 genotype appearing to exacerbate this pericyte loss (Halliday et al., 2016).