Histological Assessment of Supraspinatus Muscle

The supraspinatus (n = 5 per group) muscles were flash-frozen and cryosectioned as described previously.^{29 (link)} Masson trichrome (G1345, Solarbio, China) and Oil Red O (ORO; G1260, Solarbio) stains were used to assess fibrosis, atrophy, and fatty infiltration in supraspinatus muscles. Slides were covered with 10% glycerol in PBS (for ORO) or 50% resinene in xylene (for Masson trichrome) and observed on an optical microscope. Cross-sections were chosen randomly from mid-bellies of supraspinatus. Pictures were analyzed with ImageJ software (National Institutes of Health, USA) as described previously.^{29 (link),30 (link)}