Angiogenesis is vital for tissue repair but insufficient in chronic wounds due to paradoxical growth factor overexpression yet reduced neovascularization. Therapeutics physiologically promoting revascularization remain lacking. This study aims to investigate the molecular mechanisms underlying fibroblast-derived exosome-mediated angiogenesis during wound repair.

To assess the effects of fibroblasts derived exosomes on wound healing and angiogenesis, a full-thickness mouse skin injury model was established, followed by pharmacological inhibition of exosome secretion. The number and state of blood vessels in wounds were assessed by immunofluorescence, immunohistochemistry, hematoxylin–eosin staining, and laser Doppler imaging system. The high-throughput miRNA sequencing was carried out to detect the miRNA profiles of fibroblast-derived exosomes. The roles of candidate miRNAs, their target genes, and relevant pathways were predicted by bioinformatic online software. The knockdown and overexpression of candidate miRNAs, co-culture system, matrigel assay, pharmacological blockade, cell migration, EdU incorporation assay, and cell apoptosis were employed to investigate their contribution to angiogenesis mediated by fibroblast-derived exosomes. The expression of vascular endothelial growth factor A (VEGFA), vascular endothelial growth factor receptor 2 (VEGFR2), hypoxia-inducible factor 1α (HIF-1α), von Hippel–Lindau (VHL), and proline hydroxylases 2 was detected by western blot, co-immunoprecipitation, immunofluorescence, real-time quantitative polymerase chain reaction, flow cytometry, and immunohistochemistry. Furthermore, a full-thickness mouse skin injury model based on type I diabetes mellitus induced by streptozotocin was established for estimating the effect of fibroblast-derived exosomes on chronic wound healing.

Pharmacological inhibition of exosome biogenesis markedly reduces neovascularization and delays murine cutaneous wound closure. Topical administration of fibroblast-secreted exosomes rescues these defects. Mechanistically, exosomal microRNA-24-3p suppresses VHL E3 ubiquitin ligase levels in endothelial cells to stabilize hypoxia-inducible factor-1α and heighten vascular endothelial growth factor signaling. MicroRNA-24-3p-deficient exosomes exhibit attenuated pro-angiogenic effects. Strikingly, topical application of exosomes derived from fibroblasts onto chronic wounds in diabetic mice improves neovascularization and healing dynamics.

Overall, we demonstrate central roles for exosomal miR-24-3p in stimulating endothelial HIF-VEGF signaling by inhibiting VHL-mediated degradation. The findings establish fibroblast-derived exosomes as promising acellular therapeutic candidates to treat vascular insufficiency underlying recalcitrant wounds.

Wound healing is a sophisticated biological process characterized by the orchestrated interplay of diverse cellular components, growth factors, and signaling cascades. Recent research has highlighted the pivotal role of fibroblast exosomes in mediating intercellular communication and facilitating tissue regeneration. This investigation aimed to elucidate the therapeutic efficacy of fibroblast exosomes in enhancing wound repair mechanisms, with a particular emphasis on their differential effects in normal and diabetic wound healing paradigms.

A mouse full-thickness skin defect model was used to evaluate the effects of fibroblast exosomes on wound re-epithelialization, granulation tissue formation, and epidermal barrier function. Molecular and cellular experiments were conducted to analyze the roles of exosomes in epidermal stem cell proliferation, migration, differentiation, and antioxidant stress, with further validation of the associated signaling pathways. The therapeutic efficacy was additionally confirmed in a type 1 diabetic mouse model.

Fibroblast exosomes significantly enhanced wound re-epithelialization by promoting the proliferation, migration, and differentiation of epidermal stem cells. Additionally, exosomes increased fibroblast abundance and myofibroblast activation, facilitating granulation tissue formation as well as improving extracellular matrix (ECM) deposition and the biomechanical properties of healed skin. Furthermore, exosomes improved epidermal barrier function by upregulating tight junction proteins (e.g. Claudin-1 and ZO-1) and reducing transepidermal water loss (TEWL). In diabetic mouse models, exosomes accelerated wound closure, restored ECM deposition and biomechanical integrity, and repaired epidermal barrier function. Mechanistically, exosomes target the 3′ untranslated region (UTR) of Keap1 mRNA through miR-29a-3p and activate the KEAP1/Nrf2 antioxidant pathway, mitigating oxidative stress and protecting epidermal stem cells from reactive oxygen species (ROS)-induced damage.

Fibroblast exosomes alleviate oxidative damage by modulating the KEAP1/Nrf2 pathway through miR-29a-3p and enhancing epidermal stem cell function. These exosomes exhibit remarkable therapeutic potential in accelerating wound healing and improving healing quality under both normal and diabetic conditions, offering a robust foundation for innovative therapeutic strategies.

To investigate the mechanisms underlying the reduced biomechanical properties and impaired wound healing in the dorsal skin of streptozocin (STZ)-induced type 1 diabetes mellitus (T1DM) mice.

Forty male C57BL/6 mice (8 weeks old, weighing 20~25 g) were randomly divided into wild-type (WT, n=20) and T1DM (n=20) groups. After the mice were inflicted with full-thickness skin resection (circular, 1 cm in diameter, in both sides of the back midline), atomic force microscopy (AFM) and scanning electron microscopy (SEM) were employed to assess the Young's modulus, relaxation rate, and collagen arrangement of the skin, and HE, Masson's trichrome, Sirius red, Gordon-Sweet, and Victoria blue staining were all applied to evaluate the epidermis and granulation tissue, total collagen content, ratio of type Ⅲ to type Ⅰ collagen, reticular fiber content, and elastic fiber content. Immunohistochemical assay and Western blotting were conducted to quantify the expression of type Ⅰ and type Ⅲ collagen proteins. Flow cytometry and immunofluorescence staining of paraffin sections were performed to detect the transformation of myofibroblast in wound tissues.

On day 21 post-wounding, the dorsal skin of T1DM mice exhibited significantly reduced stiffness, strength, and resilience compared to the conditions in the WT group (P<0.05). During and after healing, T1DM mice showed decreased collagen and elastic fibers, an increased ratio of type Ⅲ to type Ⅰ collagen, and increased reticular fibers, all with statistical significance (P<0.05). Additionally, there was a significant reduction in myofibroblast transformation during the early stages of wound healing in the T1DM group (P<0.05).

T1DM inhibits the transformation of fibroblasts into myofibroblasts, leading to impaired wound healing and reduced biomechanical properties in the dorsal skin of mice.