Extracellular vesicles from hydroxycamptothecin primed umbilical cord stem cells enhance anti-adhesion potential for treatment of tendon injury

Background Peritendinous fibrosis represents a fibrotic healing process that usually occurs after tendon injury or surgery. This worldwide challenge hampers the functional rehabilitation and the mobility of extremities. However, effective treatment is still lacking at present. The aim of our study was to explore the effect of extracellular vesicles derived from hydroxycamptothecin primed human umbilical cord stem cells (HCPT-EVs) on post-traumatic tendon adhesion. Methods Extracellular vesicles derived from unprimed human umbilical cord mesenchymal stem cells (Unprimed EVs) or HCPT-EVs were isolated and characterized. A rat model of Achilles tendon injury was used to confirm the anti-adhesion effect of HCPT-EVs and compared with that of Unprimed EVs in vivo. In vitro, the inhibitory effects of HCPT-EVs on fibroblast proliferation, viability, and myofibroblast differentiation upon TGF-β1 stimulation were compared with the effects of Unprimed EVs. For mechanistic analysis, the expression of endoplasmic reticulum stress (ERS)-associated proteins was examined among the effector cargos of HCPT-EVs and Unprimed EVs. The ERS antagonist salubrinal was used to determine the ERS dependence of the anti-adhesion effects of HCPT-EVs. Results There were no obvious differences between Unprimed EVs and HCPT-EVs in terms of morphology, particle size, characteristic protein expression, and cellular uptake. HCPT-EVs exhibited a fortified anti-adhesion effect after Achilles tendon injury compared with Unprimed EVs. Fibroblast proliferation and viability and myofibroblast differentiation were all inhibited by HCPT-EVs. These properties were superior for HCPT-EVs relative to Unprimed EVs. Mechanistically, HCPT-EVs contained more ERS-associated protein than Unprimed EVs and activated the ERS pathway in fibroblast to counteract myofibroblast differentiation. Conclusion This study demonstrates that HCPT-EVs show high anti-adhesion potential for the treatment of tendon injury by provoking ERS in fibroblasts. HCPT-EVs represent a promising strategy for clinical use in treating adhesion-related diseases.