MMP-9-Positive Neutrophil Infiltration Is Associated to Blood-Brain Barrier Breakdown and Basal Lamina Type IV Collagen Degradation During Hemorrhagic Transformation After Human Ischemic Stroke

An abnormal expression of some matrix metalloproteinases (MMPs) is related with hemorrhagic transformation events after stroke. Our aim was to investigate MMP-2 and MMP-9 in the ischemic brain and its relation with blood-brain barrier breakdown after hemorrhagic transformation in human stroke. We assessed 5 cases of fatal ischemic strokes with hemorrhagic complications; brain samples were obtained from infarct, hemorrhagic, and contralateral tissue. MMP-9 and MMP-2 content was analyzed by zymography and immunohistochemistry was performed to localize MMP-9 and to assess collagen IV integrity in the basal lamina. Laser capture microdissection was performed to isolate blood-brain barrier vessels to study these MMPs. Overall, MMP-9 levels were higher both in hemorrhagic and nonhemorrhagic infarcted tissue compared to contralateral areas (P