PDGFRB and Alzheimer disease: Clinical data from patients have shown that soluble‐PDGRFβ (sPDGRFβ), as a marker of pericyte degeneration, is elevated in the cerebrospinal fluid (CSF) of patients with Alzheimer's disease and mild cognitive impairment and correlates with imaging‐based assessments of BBB permeability.[16, 18] The finding supports the involvement of PDGF‐BB/PDGFRβ signaling in disease pathology and suggests that this important signaling pathway regulating BBB may undergo substantial alteration with advancing age.