Arthroscopy. 2025 Mar 25. pii: S0749-8063(25)00229-4. [Epub ahead of print]
PURPOSE: This study aimed to investigate the protective effects of extracellular vesicles derived from bone marrow stem cells (BMSC-EVs) on muscle degeneration in a rat model of rotator cuff tendon and suprascapular nerve (SSN) transection (termed the RCT-SSN model), focusing on mitochondrial transfer.
METHODS: The EVs were identified and characterized. RCT-SSN model was established by transecting the supraspinatus, infraspinatus tendons, and suprascapular nerve. Ninety-six rats were divided into four groups (n=24 each): sham surgery, RCT-SSN treated with BMSC-EVs, RCT-SSN treated with EVs from Rhodamine-6G-pretreated BMSCs (Rho-EVs), or phosphate-buffered saline (PBS). Intramuscular injections were administered every two weeks. After 12 weeks, supraspinatus muscles were analyzed for atrophy, fibrosis, oxidative stress, macrophage phenotypes, serum cytokines, and mitochondrial characteristics. In vitro experiments included EVs tracking in macrophages, macrophage phenotype characterization, and inflammatory cytokine profiling.
RESULTS: BMSC-EVs and Rho-EVs displayed similar morphology, but only BMSC-EVs contained functional mitochondria. BMSC-EVs significantly reduced muscle weight loss (0.047 ± 0.010% vs. 0.145 ± 0.013%, P < 0.001), increased muscle fiber cross-sectional area (2037 ± 231.9 μm2 vs. 527.9 ± 92.01 μm2, P < 0.001), and decreased fibrosis (12.09 ± 3.31% vs. 25.69 ± 4.84%, P < 0.001) compared to PBS. BMSC-EVs enhanced superoxide dismutase activity (93.3 ± 11.8 U/mg protein vs. 53.4 ± 8.0 U/mg protein, P < 0.001), improved mitochondrial function, density and structure, and induced an anti-inflammatory macrophage shift, suppressing proinflammatory cytokines in vitro and in vivo. Rho-EVs showed no such effects.
CONCLUSIONS: This study showed that transecting the supraspinatus, infraspinatus tendons, and suprascapular nerve in a rat model induced muscle degeneration and fibrosis. BMSC-EVs, but not Rho-EVs, mitigated these effects by promoting an anti-inflammatory macrophage phenotype and protecting mitochondrial function through mitochondrial transfer.
CLINICAL RELEVANCE: Mitochondrial transfer via BMSC-EVs may offer a therapeutic strategy to prevent muscle degeneration in rotator cuff tear patients.