Myofibroblast-Targeting Extracellular Vesicles: A Promising Platform for Cardiac Fibrosis Drug Delivery.

Current pharmacological treatments for cardiac fibrosis are often limited by their efficacy and specificity, leading to marked side effects. Fibroblast activation protein (FAP) is specifically expressed on activated myofibroblasts (myoFbs) but not on resting cardiac fibroblasts, making it a promising target for cardiac fibrosis therapy. In this study, we engineered extracellular vesicles (EVs) conjugated with an anti-FAP single-chain variable fragment, termed αFAP-EVs, which specifically target myoFbs. Our results demonstrated that αFAP-EVs successfully targeted activated myoFbs in vitro and localized to fibrotic regions in isoproterenol-induced mouse hearts in vivo. To further enhance delivery efficiency, αFAP-EVs were combined with clodronate-loaded liposomes (αFAP-EL@CLD) to reduce liver accumulation and improve cardiac fibrotic site targeting. αFAP-EL@CLD loaded with cholesterol-methylated- and phosphorothioate-modified miR-29b (Agomir-29b) or the transforming growth factor beta 1 receptor inhibitor GW788388 significantly inhibited myoFb activation and reduced fibrosis in isoproterenol-induced mouse models. Importantly, these drug-loaded αFAP-EL@CLD vesicles exhibited high therapeutic efficacy with minimal systemic toxicity, attributed to their stability and targeted delivery capabilities. These findings suggest that αFAP-EL@CLD vesicles are promising candidates for cardiac fibrosis therapy, offering a foundation for future clinical applications.