Human umbilical cord mesenchymal stem cell exosomes promote elastin production and acute skin wound healing via TGFβ1-Smad pathway

Skin wound healing is a complex physiological process influenced by multiple factors, including the patient's overall health status. Exosomes derived from human umbilical cord mesenchymal stem cells (hUCMSC-Exos) have demonstrated significant potential in enhancing wound repair. This study investigates the mechanisms through which hUCMSC-Exos facilitate skin wound healing and evaluates their potential application in combination with hydrogels for clinical treatment. Human foreskin fibroblasts (HFF-1) were treated with varying concentrations of hUCMSC-Exos to evaluate their impact on cell proliferation, assessed via the CCK-8 assay. Exosome uptake by HFF-1 cells was visualized using PKH-26 dye staining, while flow cytometry was employed to analyze cell cycle changes. Cell migration was evaluated through scratch and Transwell assays. Gene expression levels of Collagen I, Elastin, and Fibronectin were quantified by qRT-PCR, while Elastin secretion was measured by ELISA. Western blotting was used to examine proteins in the TGFβ1-Smad signaling pathway. The role of SP1 in regulating Elastin gene expression was investigated by testing the SP1 inhibitor Plicamycin and examining hUCMSC-Exos ability to counteract its effect. Additionally, a chromatin immunoprecipitation (ChIP) assay was performed to analyze SP1 binding at the Elastin gene promoter. In vivo, the efficacy of hUCMSC-Exos combined with hydrogels in promoting wound healing was assessed using a mouse skin wound model. hUCMSC-Exos significantly enhanced HFF-1 cell proliferation at concentrations exceeding 1 × 10⁹ particles/mL and increased the proportion of cells in the S and G2/M phases. HFF-1 cells readily absorbed these exosomes, leading to improved cell migration. Treatment with hUCMSC-Exos upregulated the gene expression of Collagen I, Fibronectin, and Elastin. The SP1 inhibitor Plicamycin reduced Elastin gene expression, an effect that was reversed by hUCMSC-Exos. In vivo, the combination of hUCMSC-Exos and hydrogels accelerated wound healing, enhanced collagen organization, and promoted the formation of elastic fibers and blood vessels. hUCMSC-Exos facilitate skin wound healing by promoting SP1 binding to the Elastin gene promoter, thereby upregulating Elastin expression and supporting extracellular matrix remodeling. These findings suggest a promising therapeutic role for hUCMSC-Exos in clinical applications for wound healing.