Immunohistochemical analysis of MMP-9, VEGFR-2, VCAM-1, and eNOS in tissue samples from patients with cAVM. (a) The representative immunohistochemistry of MMP-9, VEGFR-2, VCAM-1, and eNOS in tissue samples from twenty patients with cAVM and twenty controls. (b) The relative expression level of MMP-9, VEGFR-2, VCAM-1, and eNOS protein. The scores for each case in A according to the intensity and extent of staining were multiplied to obtain weighted scores and t-test was used for statistical analysis. The four proteins (MMP-9, VCAM-1, VEGFR-2, and eNOS) were validated in twenty group samples (one control sample and one cAVM sample per group) by immunohistochemistry, and the same trend was observed in each group. Three of the twenty validated groups are shown. MMP-9: Matrix metalloproteinase-9; VCAM-1: Vascular cell adhesion molecule-1;VEGFR-2: Vascular endothelial growth factor receptor-2; eNOS: Endothelial nitric oxide synthase; AVM: Arteriovenous malformation.