MYOD1 and chronic obstructive pulmonary disease: In COPD this behavior pattern is muscle-specific: external intercostals show upregulation of proinflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and TNF-receptor expression relates to paired box protein 7 (Pax7), M-cadherin, and MyoD, consistent with a pro-regeneration signaling axis [93,94].