ADSC-EVs Activate Autophagy Via the AKT/FOXO1 Pathway to Inhibit Tendon Fibrosis

Background: Extracellular vesicles (EVs) from adipose-derived mesenchymal stem cells (ADSCs) play an important role in tendon healing and regeneration. However, the role of EVs in regulating tendon fibrosis during autophagy has not previously been reported. Purpose: To investigate the effect of EVs from ADSCs (ADSC-EVs) on the autophagy-mediated regulation of tendon fibrosis. Study Design: Controlled laboratory study. Methods: We extracted ADSCs and tenocytes from Sprague-Dawley rats, isolated EVs, and verified their uptake by tenocyts tendon fibroblasts. To assess the effects of ADSC-EVs on tendon fibroblasts, we conducted an EdU (5-ethynyl-2′-deoxyuridine) assay, scratch assay, and transwell assay to evaluate cell proliferation and migration. The activation of autophagy, a fundamental function of eukaryotic cells, by ADSC-EVs was investigated through western blotting, transmission electron microscopy, and transfection with green fluorescent protein–red fluorescent protein–LC3B. Finally, an in vivo experiment was conducted using a patellar tendon healing model. Hematoxylin and eosin staining and biomechanical testing were performed to assess tendon healing. Results: In vitro, ADSC-EVs enhanced the proliferation and migration of tendon fibroblasts after uptake. In vivo, ADSC-EVs were mixed with a gelatin methacryloyl hydrogel, applied to the injured patellar tendon, and exposed to ultraviolet irradiation for coagulation. Biomechanical testing, immunohistochemistry, and hematoxylin and eosin staining confirmed that ADSC-EVs promoted effective tendon healing. Conclusion: We demonstrated that ADSC-EVs reduced fibrosis during tendon healing by activating autophagy, thereby promoting high-quality healing. Clinical Relevance: Our findings confirm that ADSC-EVs can reduce fibrosis and inflammation during tendon healing, which may be a promising treatment approach to improve the quality of tendon healing. Therefore, ADSC-EVs have the potential to be used as cell-free biotherapeutics.