Transforming growth factor-β signaling is upregulated in sporadic inclusion body myositis.

Introduction: In this study we aimed to determine whether transforming growth factor-β (TGF-β) signaling is dysregulated in sporadic inclusion body myositis (sIBM) muscle samples.

Methods: We examined TGF-β signaling markers in muscle samples from 24 sIBM patients and compared them with those from 10 dermatomyositis (DM) patients using immunohistochemistry and Western blot analyses.

Results: Compared with the DM muscle fibers, the sIBM muscle fibers exhibited greater TGF-β, TGF-β receptor type I (TβRI), and TGF-β receptor type II (TβRII) immunoreactivity in the cytoplasm, as well as greater phosphorylated Smad2 (pSmad2) immunoreactivity in the myonuclei. The signal intensities of TGF-β, TβRI, and TβRII immunoreactivity correlated significantly with muscle fiber cross-sectional areas. Western blot analyses indicated higher expression levels of TGF-β, TβRI, TβRII, and pSmad2 in the sIBM muscle samples than in the DM muscle samples.

Conclusions: These data indicate that upregulation of TGF-β signaling may be an important molecular event in sIBM. Muscle Nerve 55: 741-747, 2017.