MMP-9 expression correlates with higher blood vessel density during in vivo wound healing. (A) MMP-9 immunostaining of cryosections from 5- and 10-d wounds in control, α3eKO, α9eKO, or α3/α9eKO mice. Bar, 100 µm. e, epidermis; wb, wound bed. (B and C) MMP-9 staining was quantified for each genotype as percentages of positive staining per field within 5-d (B) or 10-d (C) wound beds. Means ± SEM are shown. n ≥ 5 mice per genotype. One-way analyses of variance followed by Newman-Keuls’s multiple comparisons test were used. *, P < 0.05 compared with nonasterisked groups.