Combination of an engineered Lactococcus lactis expressing CXCL12 with light‐emitting diode yellow light as a treatment for scalded skin in mice

Summary Impaired wound closure is an increasingly crucial clinical challenge. Recently, wound healing has shifted towards innovative treatments that exploit nanotechnology, biomaterials, biologics and phototherapy. Here, we constructed an engineered MG1363‐pMG36e‐mCXCL12 strain with pMG36e plasmid encoding stromal cell‐derived factor 1α (named CXCL12) and evaluated the synergistic effects of light‐emitting diode (LED) yellow light and MG1363‐pMG36e‐mCXCL12 on scald wounds in mice. The results indicated that the combined treatment with LED yellow light with mCXCL12 delivering strain accelerated wound closure, tissue remodelling, re‐epithelialization and hair follicle regeneration and inhibited over‐inflammation oppositely in the central and surrounding wounds by macroscopic, histopathologic and immunohistochemistry parameters. Furthermore, combination therapy increased the epidermal growth factor and Ki67‐positive cells and upregulated beta‐catenin (β‐catenin), cellular‐myelocytomatosis (c‐Myc), wingless‐type MMTV integration site family member 1 (Wnt1), Jagged 1, neurogenic locus notch homolog protein 1 (Notch 1) and hairy and enhancer of split 1 (Hes 1) protein levels of the Wnt and Notch signalling pathways. It also facilitated collagen fibrogenesis and deposition and improved the activities of hydroxyproline, superoxide dismutase and glutathione peroxidase in scalded granulation tissue, in addition to reducing the inflammatory factors interleukin 1 beta (IL‐1β) and tumour necrosis factor alpha (TNF‐α). The combined treatment effectively reduced skin pathogens Ralstonia and Acinetobacter to further reduce the risk of infection. Overall, combination of LED yellow light and MG1363‐pMG36e‐mCXCL12 represents a potential strategy for the treatment of cutaneous wounds.