Islet grafts in MMP-9^−/− mice have an altered vascular phenotype at 2 weeks after transplantation. (A) Confocal z-projection of image stack showing the normal vascular network of a transplanted pancreatic islet in the cremaster muscle 14 days after transplantation. Blood vessels in red are stained with CD31-mAb. (B) Islet vasculature of an islet transplanted to the cremaster muscle of an MMP-9^−/− mouse 14 days after transplantation exhibiting a disturbed vascular network with increased vessel heterogeneity. Bars represent 50 μm. (C) The intra-islet capillaries in islets transplanted to MMP-9^−/− mice (n = 4 mice, 49 vessels) are on average wider than wild-type capillaries (n = 3 mice, 41 vessels). *P < .05. (D) Size-distribution histogram showing heterogeneity in capillary diameters between MMP-9^−/− and wild-type mice.