Del-1 nanoparticles/silk fibroin hydrogel accelerates the healing of chronic skin wounds by promoting inflammation regression

Abstract

Objective To investigate the effect of silk fibroin hydrogel loaded with developmental endothelial locus-1 (Del-1) nanoparticles on the healing of chronic skin wounds in mice. Methods The back skin of BALB/c mice (6-8 weeks old) was pressed with a magnet for 12 h and then relaxed for 12 h, for 4 consecutive days to establish a chronic pressure ulcer wound. After infliction, the mice were randomly divided into 3 groups (n=8), and the skin wounds were treated with PBS, silk fibroin hydrogel or Del-1 nanoparticles/silk fibroin hydrogel. The wound healing was recorded with camera to calculate the wound healing rate. In 9 d after treatment, HE and Masson staining were used to observe the wound healing, and immunofluorescence staining for CD14 and TNF-α was used to compare the appearance frequency of skin macrophages and the expression of inflammatory factors. After Tert-butyl peroxide (TBHP) was used to stimulate mouse macrophage RAW 264.7 cells and mouse vascular endothelial C166 cells, C166 cells were transfected with lentival vector to overexpress Del-1. Crystal violet staining was used to observe the migration of macrophages. RT-qPCR was used to detect the expression of inflammatory factor IL-6. Results The wound healing was significantly faster in the Del-1 nanoparticles/silk fibroin hydrogel group than the silk fibroin hydrogel group and the PBS group (P < 0.01). The expression levels of TNF-α and CD14 in the wound surface were lower (P < 0.01), but collagen deposition and tissue repair were better in the Del-1 nanoparticles/silk fibroin hydrogel group than the silk fibroin hydrogel group and the PBS group (P < 0.01). In vitro experiments, macrophages migrated to endothelial cells stimulated by TBHP, but the migration rate of macrophages was significantly lower in the Del-1 overexpression group (P < 0.01). RT-qPCR confirmed that Del-1 inhibited the transcription of IL-6 (P < 0.01). Conclusion Del-1 nanoparticles/silk fibroin hydrogel can significantly accelerate the healing of skin wounds, and its mechanism may be through promoting the regression of inflammation and tissue repair.

Keywords

• del-1
• silk fibroin
• chronic wound healing
• macrophage
• inflammatory regression