MSTN and chronic obstructive pulmonary disease: The expression of myostatin has a tendency to be higher in COPD myoblasts than in healthy individual myoblasts [0.47 a.u. (0.33–0.86) versus 0.33 a.u. (0.22–0.40); P = 0.083; Fig. 4A], and is significantly more elevated in COPD myotubes compared to healthy individual myotubes [0.87 a.u. (0.62–0.96) versus 0.52 a.u. (0.42–0.65); P = 0.050; Fig. 4B].