Figure 6.

Fn14^−/− mice have delayed muscle regeneration. Cardiotoxin-treated muscles at indicated days after injury of wild-type (A–D) and Fn14^−/− (E–H) mice are shown. Detailed views of B and F are shown in (I) and (J) respectively to show regenerating, central nucleate myotubes, some of which are indicated by arrows. Images are representative of three independent experiments with seven mice per genotype in total. Scale bar: 200 μm (A–C, E–G), 100 μm (D, H). (K) The number of central nucleated myotubes in Fn14^−/− mice was significantly lower than in wild-type muscles at 5 and 7 days, but not 14 days, after cardiotoxin. Error bars=s.d.; ^**=P<0.01 by Student's t-test; n as indicated. (L) Myofibers that express embryonic myosin heavy chain (eMyHC), an additional marker of regenerating myotubes (dark brown stain), were more abundant in wild-type than in Fn14^−/− muscles at 4 days after injury.