Ultrasound-Activated GelMA Hydrogel Loaded with MSC-EVs Promotes Functional Regeneration of Skin Vasculature, Nerves, and Appendages.

Severe skin injuries often lead to dysfunctional healing marked by fibrosis and loss of vascular, neural, and appendage structures. While mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) offer regenerative potential, their therapeutic efficacy is limited by poor delivery efficiency. Here, we present a bioengineered strategy combining ultrasound stimulation with a gelatin methacryloyl (GelMA) hydrogel-EV delivery platform to address these challenges. Ultrasound serves as a mechanobiological primer, enhancing MSC-EVs internalization via calcium-dependent cytoskeletal remodeling, thereby amplifying pro-regenerative pathways such as angiogenesis (such as VEGF), matrix modulation (such as TGF-β/Smad), and neural repair (such as NGF). In vitro, ultrasound (420 kHz, 5 V) synergized with MSC-EVs (60 μg/mL) significantly boosted fibroblast viability, migration, and secretory functions. In a murine full-thickness wound model, the ultrasound-activated GelMA-EV system accelerated re-epithelialization (90% closure by Day 14), induced robust neovascularization and neurogenesis, and facilitated unprecedented hair follicle regeneration. Mechanistic studies revealed ultrasound-driven calcium in-flow and actin depolymerization as key mediators of enhanced MSC-EVs uptake. This synergistic integration of physical and biochemical cues establishes a transformative paradigm for functional skin regeneration, bridging a critical gap in regenerative therapeutics.