(A–D) Representative images of colonic sections (n = 5 wounds per group from 3 mice per group in 3 experiments) 4 days after injury from WT mice treated with (A) vehicle or (C) VEGFR inhibitor tivozanib. Sections were stained with anti-CD31 antisera (red, blood vessels), anti–HIF-1α antisera (green, hypoxic cells), and bisbenzimide (blue, nuclei). Dashed white lines outline wound beds, dashed yellow lines outline the muscularis propria, and dashed white boxes indicate the areas shown at higher magnification in B and D. (E) Number of blood vessels within the wound bed per wound bed length in vehicle-treated and tivozanib-treated mice. n = 5 wounds per group from 3 mice per group in 3 experiments. **P < 0.01, Student’s t test. (F) Number of HIF-1α–positive cells per wound bed length in vehicle-treated and tivozanib-treated mice. **P < 0.01, Mann-Whitney test. (G–I) Representative images of colonic sections (3–4 mice per groups in 3 experiments) from WT mice given (G) vehicle (n = 6 wounds from 3 mice), (H) tivozanib (n = 6 wounds from 3 mice), or (I) tivozanib and PGI₂ analog (n = 9 wounds from 4 mice) 6 days after injury stained with anti–α-SMA antibodies (red, smooth muscle) and bisbenzimide (blue, nuclei). (J) Relative α-SMA staining of the outer muscle layer in indicated groups of mice 6 days after injury. n = 6–9 wounds per group from 3–4 mice per group in 3 experiments. P = 0.0001, 1-way ANOVA. ***P < 0.001, Tukey’s post-test. (K) Schematic depicting the model of penetrating ulcer formation. PGI₂ stimulates VEGF production in the wound bed, which stimulates angiogenesis and prevents muscle necrosis. Scale bar: 100 μm (A, C, and G–I); 25 μm (B and D). Mean ± SEM.