For example, the chronic muscle wasting disease that occurs in the mdx mouse model of Duchenne muscular dystrophy involves progressive muscle fibrosis that is accompanied by an accumulation of intramuscular M2‐biased macrophages that express TGFβ and arginase (Vidal et al., 2008; Villalta et al., 2009) and the ablation of arginase expression causes large reductions in the pathological fibrosis of dystrophic skeletal muscles (Wehling‐Henricks et al., 2010). This evidence concerns the gene TGFB1 and Duchenne muscular dystrophy.