Immunohistochemical demonstration of the presence of inflammatory cells in muscles of wild-type and uPA-deficient mice after glycerol-induced injury.

Detection of macrophages (Mac-1+) (A) and neutrophils (Gr-1+) (B) in transverse sections of control and injured skeletal muscles of wild-type (WT) and uPA-deficient mice at the indicated times after injury. Mac-1–expressing cells increased 2 days after injury in muscle of WT and uPA-deficient mice; however, the number of Mac-1–positive cells was lower in uPA−/− mice muscle. Gr-1–expressing cells were maximal 12 hours after injury in both WT and uPA-deficient mice, though there were fewer Gr-1–positive cells in the uPA-deficient mice. (C) Detection of endothelial (CD31⁺) cells in skeletal muscle of WT and uPA-deficient mice. No significant differences in the number of CD31-stained microvessels were found between uPA-deficient and WT mice. Original magnification, 400×. (D) Quantitative analysis of Mac-1–positive cells in regenerating muscles of WT ▪ and uPA-deficient ░ mice. Muscles were analyzed for Mac-1 immunofluorescence at 0 and 2 days after injury. Mac-1–positive cells were counted in 10 random fields per section, and data from 12 sections per muscle were pooled. Mean values for both limbs were to provide a mean value for each animal (3 animals were studied at each time point). Histograms show the percentage of reduction (46%) of Mac-1–positive cells in uPA−/− mice with respect to WT mice.