Protective Effect and Molecular Mechanism of Mesenchymal Stem Cell-Derived Extracellular Vesicles in Diabetic Foot Ulcers

This study explores the protective mechanism of mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) in diabetic foot ulcer (DFU). Human umbilical cord MSCs (HucMSCs) were identified via osteogenesis and adipogenic differentiation, as well as flow cytometry. EVs were isolated from HucMSCs and characterized using transmission electron microscopy, nanoparticle tracking analysis, and Western blotting. Fluorescence microscopy revealed the uptake of PKH67-labeled EVs and Cy3-labeled microRNA-21-5p (miR-21-5p) by human skin fibroblasts (HSFs). EVs were cocultured with HSFs, and cell proliferation and migration were assessed using Cell Counting Kit-8, colony formation, scratch, and Transwell assays. miR-21-5p overexpression in EVs was evaluated for its role in promoting HSF functions. The expression levels of miR-21-5p, Krüppel-like factor 6 (KLF6), α-smooth muscle actin, and collagen type I alpha 1 chain were analyzed via quantitative real-time PCR and Western blotting. The interaction between miR-21-5p and KLF6 was confirmed through a dual-luciferase reporter gene assay. HucMSC-derived EVs enhanced the proliferation and migration of HSFs under high glucose by delivering miR-21-5p, which targeted and inhibited KLF6. Overexpression of KLF6 counteracted the pro-proliferative and migratory effects of EVs carrying miR-21-5p. Overall, these findings suggest that HucMSC-EVs promote HSF proliferation and migration by downregulating KLF6 via miR-21-5p delivery, offering a potential therapeutic strategy for DFU.