Preparation of oxygen-filled adipose-derived stem cells exosome-nanobubbles gel for ultrasound-assisted full-thickness wound healing in rats

Effective wound healing is often hindered by hypoxia, inflammation, and impaired angiogenesis. Although mesenchymal stem cell (MSC)-based therapies have shown potential, their clinical application remains limited. As a result, MSC-derived exosomes, particularly adipose-derived stem cell exosomes (ADSC-Exos), have been proposed as a cell-free alternative; however, they still face limitations, including suboptimal efficiency in targeted delivery. To address these critical obstacles in existing regenerative therapies, we isolated ADSC-Exos from adipose tissue and fabricated a novel ultrasound-responsive, carbomer-based hydrogel incorporating oxygen-enriched ADSC-Exo nanobubbles (Gel-Exo-NB+US). The preclinical wound-healing potential of the developed nanohydrogel was evaluated using a full-thickness wound model in Wistar rats. The engineered hydrogel exhibited favorable physicochemical properties, including shear-thinning and thixotropic behavior, enabling efficient topical application and enhanced tissue adhesion. In a rat full-thickness skin defect model, the combined Gel-Exo-NB and Gel-Exo-NB + US treatments achieved the highest wound-closure rate among all groups, with enhanced re-epithelialization, a reduced scar index, elevated CD31 and α-SMA expression, increased fibroblast proliferation, and increased blood vessel formation. Furthermore, unprecedented hair-follicle regeneration and abundant collagen deposition were observed in the Gel-Exo-NB + US-treated group compared with the Gel-Exo-NB-treated group, highlighting the pivotal role of ultrasound in skin defect regeneration. Notably, the resulting collagen deposition, abundant hair follicles, and thin epidermis suggest potential for scarless wound healing. These therapeutic outcomes are attributed to the synergistic effects of simultaneous ultrasound-mediated exosome therapy and oxygen delivery.