Administration of HGF-blocking antibody to WT mice. WT mice were subjected to cardiotoxin muscle injury and treated with intraperitoneal injection of either HGF-blocking antibody or control IgG daily, and muscles collected at 5 days after injury. (Top) Muscle homogenates subjected to c-met immunoprecipitation and then Western blotting for c-met or phosphotyrosine (pTyr). Note that treatment with HGF-blocking antibody reduced c-met phosphorylation. (Middle) Muscle cryosections stained with hematoxylin and eosin for morphologic analysis. Note the impairment of muscle regeneration in WT mice after treatment with HGF-blocking antibody. Scale bar represents 50 μm. (Bottom) Quantitative analysis of morphology. Regenerating fibers identified as central nucleated fibers and counted in 2 sections per muscle and expressed as number per millimeter muscle area. Damaged area estimated by subtracting summed area of normal and regenerating fibers from total muscle area. Bars represent mean ± SE; n = 4 to 6 per group. *Mean value significantly different from that for WT mice (P < .05).