Exercise mimetics and JAK inhibition attenuate IFN-γ-induced wasting in engineered human skeletal muscle.

Chronic inflammatory diseases often lead to muscle wasting and contractile deficit. While exercise can have anti-inflammatory effects, the underlying mechanisms remain unclear. Here, we used an in vitro tissue-engineered model of human skeletal muscle ("myobundle") to study effects of exercise-mimetic electrical stimulation (E-stim) on interferon-γ (IFN-γ)-induced muscle weakness. Chronic IFN-γ treatment of myobundles derived from multiple donors induced myofiber atrophy and contractile loss. E-stim altered the myobundle secretome, induced myofiber hypertrophy, and attenuated the IFN-γ-induced myobundle wasting and weakness, in part by down-regulating JAK (Janus kinase)/STAT1 (signal transducer and activator of transcription 1) signaling pathway amplified by IFN-γ. JAK/STAT inhibitors fully prevented IFN-γ-induced myopathy, confirming the critical roles of STAT1 activation in proinflammatory action of IFN-γ. Our results reveal a previously unknown mechanism of the cell-autonomous anti-inflammatory effects of muscle exercise and establish the utility of human myobundle platform for studies of inflammatory muscle disease and therapy.