3D Fibrin/Gelatin Hydrogel System Enhances the Therapeutic Potency of DPSC-Derived Extracellular Vesicles Compared to 2D Culture in Accelerating Diabetic Wound Healing via Angiogenesis and Immune Modulation

Background: Impaired angiogenesis and persistent inflammation are hallmarks of chronic diabetic wounds. Extracellular vesicles derived from dental pulp stem cells (DPSC-EVs) represent a promising cell-free therapy for tissue repair; however, their clinical translation is hindered by suboptimal yields and attenuated bioactivity associated with conventional two-dimensional (2D) culture. This study investigated whether a biomimetic three-dimensional (3D) fibrin/gelatin hydrogel system could optimize the therapeutic potency of DPSC-EVs for diabetic wound healing. Methods: DPSCs were encapsulated within 3D fibrin/gelatin scaffolds, followed by comprehensive characterization of cell viability and morphology. 3D-EVs and 2D-EVs were isolated via ultracentrifugation and validated by transmission electron microscopy and nanoparticle tracking analysis. The pro-angiogenic capacity of 3D-EVs was evaluated using human umbilical vein endothelial cells (HUVECs) under high-glucose (HG) stress. Additionally, the immunomodulatory effects were assessed by monitoring macrophage polarization in lipopolysaccharide-stimulated RAW 264.7 cells. The therapeutic efficacy was further validated in vivo using a streptozotocin (STZ)-induced diabetic mouse model with full-thickness cutaneous wounds. Results: The 3D fibrin/gelatin hydrogel provided a supportive microenvironment that significantly augmented the secretory productivity of DPSCs. Compared to 2D-EVs, 3D-EVs exhibited superior functional resilience in restoring HUVEC migration and tube formation under HG-induced oxidative stress. Furthermore, 3D-EVs effectively orchestrated the macrophage transition from a pro-inflammatory M1 phenotype toward an anti-inflammatory M2 phenotype, thereby modulating the immune microenvironment. In vivo, topical administration of 3D-EVs markedly accelerated wound closure, promoted re-epithelialization, and enhanced microvascular density and collagen maturation in diabetic mice. Conclusions: Our findings demonstrate that the 3D fibrin/gelatin culture system effectively primes the therapeutic profile of DPSC-EVs. These engineered vesicles accelerate diabetic wound healing by synergistically promoting angiogenesis and resolving chronic inflammation, offering a robust and potent cell-free strategy for the management of chronic diabetic ulcers.