In an immunohistochemical study of patients with fatal ischemic stroke, MMP-9-positive neutrophils were shown to infiltrate around the cerebral microvessels, resulting in the loss of type IV collagen in the basement membrane and the formation of cerebral hemorrhage, which indicates that the degradation of ECM mediated by MMP-9 may be related to hemorrhagic transformation (88) (Figures 1 and 2). Here, MMP9 is linked to ischemic stroke.