Matrigel plug angiogenesis in C3-deficient mice. Angiogenesis was assessed using the in vivo Matrigel plug assay as described under “In vivo Matrigel plug assay.” (A) Six hours after Matigel implantation, WT and C3^−/− mice were injected with control liposomes or clodronate liposomes to deplete macrophages and after 7 days angiogenesis was assessed within the explanted Matrigels. Data are mean ± SEM (n = 14 Matrigels per group) and are shown as percentage of control. Area of neovascularization in WT mice treated with control liposomes represents the 100% control. *P < .01; ns, not significant. (B) Frozen sections of the explanted Matrigels were stained with H&E. C3^−/− mice showed significantly more Matrigel plug neovascularization. Scale bars, 150 μm.