MMP9 and androgen insensitivity syndrome: In the early stage of AIS, neutrophils first migrate and aggregate to vascular lesions, aggravating brain damage by releasing proteases, ROS, and cell adhesion molecules (17); moreover, neutrophils can also infiltrate into the ischemic area, directly destroy the blood–brain barrier (BBB) by enhancing the expression of matrix metalloproteinase 9 (MMP-9), and cause secondary brain injury or hemorrhagic transformation (18).