Figure 2: Histopathology related to injury. (a) cross-section of normal healthy TA muscle from a wild-type mouse. Skeletal muscle fibers are multinucleated and the nuclei stain blue; the sarcoplasm of each cell stains pink. (b) cross-section from a wild-type TA after injury. There was only minimal evidence of perivascular inflammation (arrows) in the wild-type tissue after injury. (c) cross-section from TA muscle of an mdx mouse. Even without injury, there is mild inflammation, slight increase in endomysial connective tissue, heterogeneity in fiber size, and many centrally nucleated fibers (CNFs, open arrows), all indicative of ongoing degeneration/regeneration within the muscle. (d) cross-section from an mdx TA after injury. Even with a protocol that produces mild changes in morphology to healthy muscle, the mdx muscle suffers much more damage, such as myonecrosis, myophagocytosis, and foci of inflammation surrounding individual muscle fibers (closed arrows). Scale bar = 40 μm.