Figure 5.
Infiltrating neutrophils are the primary source of MMP-9 in the ischemic brain. The cellular localization of MMP-9 immunoreactivity in the ischemic brain was examined by double-labeling immunofluorescence. A, There was strong and extensive colocalization between MMP-9 and the specific neutrophil marker, SJC, but not with neuronal (neuN), astrocytic (GFAP), or microglial (Iba1) markers. There was also strong colocalization of MMP-9 with the vascular basement membrane protein, laminin. B, Depletion of neutrophils using an anti-PMN antibody abolished the cellular and vascular MMP-9 immunoreactivity in the brain, but there was no effect with an isotype control antibody. C, There was a strong correlation between the number of MMP+ cells and the number of neutrophils in the cortex of vehicle- and IL-1β-treated mice. R2 = 0.91; p < 0.01, Pearson correlation. All double-labeling immunofluorescence images are from the cortex ipsilateral to MCAo of IL-1β-treated mice 24 h after MCAo. Scale bars: A, 25 μm; B, 100 μm.