Hypoxia-Challenged sEVs-Engineered Nanofiber Scaffolds Accelerate Diabetic Wound Healing via Reversing Cellular Dysfunction of Skin Repair Cells

The persistent hyperglycemic microenvironment in diabetic wounds causes dysfunction of repair cells, resulting in impaired angiogenesis and disorganized extracellular matrix (ECM) deposition. Small extracellular vesicles (sEVs) derived from hypoxia-challenged chorionic plate mesenchymal stem cells (CP-MSC-sEVs Hypo ) have been explored as novel acellular therapeutics. However, the effects of oxygen tension during culturing parent cells on the pro-regenerative efficacy and mechanisms of CP-MSC-sEVs have not been systematically investigated. In addition, their rapid clearance and limited interaction with target cells at wound sites constrained therapeutic efficacy. In this study, oxygen tension was first optimized systematically during the precondition of CP-MSCs to improve the pro-regenerative properties of the derived sEVs Hypo . Then, sEVs Hypo -engineered nanofiber scaffolds were fabricated to achieve the sustained release of sEVs Hypo at wound sites by polydopamine (PDA)-mediated interfacial adhesion. In vitro experiments revealed that sEVs obtained under 5% oxygen tension (sEVs Hypo-5% ) exhibited the most pronounced angiogenic and collagen-regenerative performance. Furthermore, small RNA sequencing and bioinformatic analyses revealed that miR-21-5p was the most abundant miRNA in sEVs Hypo-5% , and functional rescue assays validated that miR-21-5p was the key mediator of endothelial activation and ECM remodeling. To improve the bioavailability of sEVs Hypo-5% , PDA was leveraged to immobilize sEVs Hypo-5% onto a biocompatible, ECM-mimicking poly(ε-caprolactone) nanofiber scaffold to achieve high loading efficacy and sustained release. In a full-thickness diabetic wound model, the sEVs Hypo-5% -loaded nanoscaffold accelerated wound closure and achieved superior pro-healing effects on D14 via enhancing neovascularization and ECM deposition, as confirmed by histological and immunofluorescence analyses. Collectively, this sEVs Hypo-5% -loaded nanoscaffold achieved efficient immobilization and sustained delivery of sEVs Hypo-5% to promote angiogenesis and matrix repair by endogenously delivering miR-21-5p at diabetic wound sites, with strong potential for clinical translation.