Extracellular vesicles from 3D cultured dermal papilla cells improve wound healing via Krüppel-like factor 4/vascular endothelial growth factor A -driven angiogenesis

BACKGROUND: Non-healing wounds are an intractable problem of major clinical relevance. Evidence has shown that dermal papilla cells (DPCs) may regulate the wound-healing process by secreting extracellular vesicles (EVs). However, low isolation efficiency and restricted cell viability hinder the applications of DPC-EVs in wound healing. In this study, we aimed to develop novel 3D-DPC spheroids (tdDPCs) based on self-feeder 3D culture and to evaluate the roles of tdDPC-EVs in stimulating angiogenesis and skin wound healing. METHODS: To address the current limitations of DPC-EVs, we previously developed a self-feeder 3D culture method to construct tdDPCs. DPCs and tdDPCs were identified using immunofluorescence staining and flow cytometry. Subsequently, we extracted EVs from the cells and compared the effects of DPC-EVs and tdDPC-EVs on human umbilical vein endothelial cells (HUVECs) in vitro using immunofluorescence staining, a scratch-wound assay and a Transwell assay. We simultaneously established a murine model of full-thickness skin injury and evaluated the effects of DPC-EVs and tdDPC-EVs on wound-healing efficiency in vivo using laser Doppler, as well as hematoxylin and eosin, Masson, CD31 and α-SMA staining. To elucidate the underlying mechanism, we conducted RNA sequencing (RNA-seq) of tdDPC-EV- and phosphate-buffered saline-treated HUVECs. To validate the RNA-seq data, we constructed knockdown and overexpression vectors of Krüppel-like factor 4 (KLF4). Western blotting, a scratch-wound assay, a Transwell assay and a tubule-formation test were performed to detect the protein expression, cell migration and lumen-formation ability of KLF4 and vascular endothelial growth factor A (VEGFA) in HUVECs incubated with tdDPC-EVs after KLF4 knockdown or overexpression. Dual-luciferase reporter gene assays were conducted to verify the activation effect of KLF4 on VEGFA. RESULTS: We successfully cultured tdDPCs and extracted EVs from DPCs and tdDPCs. The tdDPC-EVs significantly promoted the proliferation, lumen formation and migration of HUVECs. Unlike DPC-EVs, tdDPC-EVs exhibited significant advantages in terms of promoting angiogenesis, accelerating wound healing and enhancing wound-healing efficiency both in vitro and in vivo. Bioinformatics analysis and further functional experiments verified that the tdDPC-EV-regulated KLF4/VEGFA axis is pivotal in accelerating wound healing. CONCLUSIONS: 3D cultivation can be utilized as an innovative optimization strategy to effectively develop DPC-derived EVs for the treatment of skin wounds. tdDPC-EVs significantly enhance wound healing via KLF4/VEGFA-driven angiogenesis.