Neuropeptides neurotensin and substance P accelerate diabetic wound healing by modulating immunity and the skin microbiome

Diabetic foot ulcers (DFUs) are a common and debilitating complication of diabetes mellitus, typified by impaired healing, persistent inflammation, and skin microbiota dysbiosis. Although some neuropeptides are immunomodulatory, their effects on skin microbiota and wound resolution remain largely unexplored. We examined the therapeutic potential of the neuropeptides neurotensin (NT) and substance P (SP) in reshaping inflammatory and microbial dynamics and accelerating wound closure in a healthy and streptozotocin-induced diabetic mice model. Full-thickness cutaneous wounds were induced on both groups, followed by daily topical applications of saline (CT), NT, or SP. Wound closure was monitored and changes in skin bacterial communities characterized using next-generation sequencing. Wound tissue samples were collected for immunohistochemical analysis. Topical application of NT or SP significantly accelerated wound healing, with the most pronounced effects in diabetic animals. Both neuropeptides reduced the number of pro-inflammatory cells, lowering M1 macrophages in diabetic wounds from 16.4 ± 4 to 12.1 ± 3 with NT and 10.9 ± 3 with SP, while increasing M2 macrophages from 11.6 ± 4 to 18.1 ± 4 (NT) and 21.6 ± 5 (SP). SP exerted the most pronounced immunomodulatory effect, normalizing the M1/M2 ratio and reducing the number of CD3⁺ T cells (12.4 ± 3) and neutrophils (12.1 ± 3) to levels comparable to non-diabetic skin. Concurrently, SP treatment induced substantial microbiota remodeling in diabetic wounds, reducing Staphylococcus by circa 34%, Aerococcaceae_unclassified by 6.8%, Aerococcus by 1.5% and nearly eliminating Weissella. These reductions were accompanied by an over twofold increase in commensal genera (Lactobacillus, Micrococcaceae_unclassified, Actinobacteria_unclassified), shifting the microbial community toward a more non-diabetic profile. Our findings suggest that NT and especially SP, enhance diabetic wound healing through dual local immunomodulation and microbiota restructuring.