SPP1 and Alzheimer disease: Microglia and PVMs possess phagocytosis properties to a certain extent and are vital for maintaining brain homeostasis after birth.87 Microglia can take up parenchymal ISF amyloid-β, whereas PVMs can degrade perivascular amyloid-β.88 When it comes to the crosstalk between microglia and PVMs, recent evidence in a mouse model of Alzheimer’s disease indicated that the expression of secreted phosphoprotein 1 (SPP1/osteopontin) was upregulated in PVMs, which strengthened the phagocytic function of microglia, resulting in synaptic loss.89