MMP9 and Alzheimer disease: Among other cells, microglia have also been observed to secrete metalloproteases (MMPs), such as matrix metallopeptidase-2 (MMP-2) and matrix metallopeptidase-9 (MMP-9), which have been reported to be activated in AD and IS, degrading the basement membrane, therefore increasing BBB permeability and NVU dysfunction (Lorenzl et al., 2003; Hernandez-Guillamon et al., 2010; Yang and Rosenberg, 2015; Turner and Sharp, 2016; Montaner et al., 2019; Freitas-Andrade et al., 2020; Sarvari et al., 2020; Carcel-Marquez et al., 2021).