[Construction of an engineered probiotic strain for efficiently delivering chemokine CXCL12 and application of the strain in diabetic chronic wound healing].

Diabetic chronic wounds are characterized by difficult healing, recurrent progression, and high rates of disability and mortality, which make their clinical treatment a medical challenge urgent to be addressed. However, the complex local microenvironment conditions of chronic wounds, such as high protease activity and persistent inflammatory responses, result in low bioavailability of exogenous cytokines (e.g., chemokine CXCL12) at the wound site, limiting their clinical application. In this study, we utilized Lactobacillus plantarum WCFS1 as the chassis to develop an efficient CXCL12 delivery system based on synthetic biology. Subsequently, we evaluated the role of the engineered probiotic strain in promoting the chronic wound healing in diabetic mice. Firstly, we fused the endogenous secretion signal peptide lp_3050 (SP_{lp_3050}) of L. plantarum WCFS1 and the commonly used secretion signal peptide usp45 (SP_usp45) of lactic acid bacteria with the reporter gene gusA and inserted them into the pTRK892-P_32(pgm) plasmid by molecular cloning. Then, we prepared the engineered strains and characterized the efficacy of the two signal peptides in driving the secretion of GusA. The results showed that SP_{lp_3050} efficiently drove the secretion of GusA in L. plantarum WCFS1, increasing the activity of GusA in the culture supernatant by nearly five times compared with that of SP_{lp_3050}. Further, we fused SP_{lp_3050} and codon-optimized CXCL12 gene to construct an engineered probiotic strain Lpw-CXCL12 for CXCL12 delivery. The results demonstrated that the content of CXCL12 in the culture supernatant reached (13.40±0.20) μg/mL. Finally, we found that the engineered probiotic strain Lpw-CXCL12 accelerated chronic wound healing in a diabetic mouse model. In conclusion, these results support an engineered probiotic strain in promoting diabetic chronic wound healing, providing a new strategy and technological foundation for the management of diabetic chronic wounds in the future.