Application and Single-Cell Regulation Mechanism of Engineered EVs Combined With 4D-Printed Hydrogel for Infected...

Burns represent a complex and disabling global public health problem, presenting substantial clinical challenges attributed to disrupted tissue microenvironment and persistent wound infections, which impair the synergistic interaction between fibroblasts (Fb) and keratinocytes (KC). FGF2 and its homologues widely used for burns show weak wound-repair efficacy, owing to poor targeting and degradation by bacteria and proteases. In this study, FGF2-modified extracellular vesicles (F-EVs) were engineered from human adipose mesenchymal stem cells (ADMSCs) via electrostatic adsorption, and further combined with 4D-printed hydrogels to construct a 4D@F-EVs system. This system was designed to reconstruct the burn tissue microenvironment, exert antibacterial effects, and restore the crosstalk between Fb and KC. In vitro and in vivo analysis confirmed that the 4D@F-EVs were precisely delivered to Fb, promoting cell proliferation and facilitating the reconstruction of the burn tissue microenvironment. Single-cell RNA sequencing (scRNA-seq) analysis revealed that the regulatory effect of 4D@F-EVs on skin regeneration involves the activation of the PI3K-Akt signaling pathway and the promotion of crosstalk between Keratinocyte Growth Factor-positive (KGF⁺) Fb and Keratinocyte Growth Factor Receptor-positive (KGFR⁺⁾ KC. Collectively, this work offers an original clinical approach for infected burn wounds by reconstructing the impaired microenvironment and restoring intercellular crosstalk.