MMP3 and Alzheimer disease: MMP‐2 has been demonstrated to be a key element in the induction of BBB permeability alterations and disruption of TJs.23, 24, 25 It is secreted by ECs in cultures upon stimulation with Aβ peptides.26 AD patients showed higher plasma MMP‐2 levels, although contradicting results have also been reported.27, 28 We measured the levels of secreted MMP‐2, MMP‐3, and MMP‐9 from day 2 to day 6 of coculture in the bEC media of AD and WT models.