MMP9 and Cerebral ischemia: After the upregulation of adhesion molecule expression (e.g. ICAM-1) at the vascular endothelium and breakdown of BBB integrity, with dysfunction of the reconstruction of the extracellular matrix following increased MMP-9 expression, neutrophils may migrate from blood to brain parenchyma where they may further increase the degree of cerebral ischemia by obstructing microvessels and releasing inflammatory mediators [35], [36].