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Updated: Jul 18, 2025
Protocol to Create Chronic Wounds in Diabetic Mice
Published on: September 25, 2019
Reduced Bioactive Microbial Products (Pathogen-Associated Molecular Patterns) Contribute to Dysregulated Immune
Ruchi Roy1, Foyez Mahmud1, Janet Zayas2
1Division of Hematology, Oncology and Cell Therapy, Department of Medicine, Rush University Medical Center, Chicago, Illinois, USA.
Abstract:
Diabetic chronic ulcers are plagued with persistent nonresolving inflammation. However, diabetic wound environment early after injury suffers from inadequate inflammatory responses due to reductions in proinflammatory cytokines levels. Diabetic neutrophils have known impairments in bactericidal functions. We hypothesized that reduced bacterial killing by diabetic neutrophils, due to their bactericidal functional impairments, results in reduced bioactive bacterial products, known as pathogen-associated molecular patterns, which in turn contribute to reduced signaling through toll-like receptors, leading to inadequate production of proinflammatory cytokines in infected diabetic wound early after injury. We tested our hypothesis in db/db type 2 obese diabetic mouse wound infection model with Pseudomonas aeruginosa. Our data indicate that despite substantially higher levels of infection, toll-like receptor 4-mediated signaling is reduced in diabetic wounds early after injury owing to reduced bioactive levels of lipopolysaccharide. We further demonstrate that topical treatment with lipopolysaccharide enhances toll-like receptor 4 signaling, increases proinflammatory cytokine production, restores leukocyte trafficking, reduces infection burden, and stimulates healing in diabetic wounds. We posit that lipopolysaccharide may be a viable therapeutic option for the treatment of diabetic foot ulcers if it is applied topically after the surgical debridement process, which is intended to reset chronic ulcers into acute fresh wounds.
Insights
Diabetic wound healing is impaired by reduced bacterial signaling. Topical lipopolysaccharide (LPS) treatment can restore inflammatory responses and promote healing in diabetic ulcers.
Area of Science:
- Wound healing research
- Immunology
- Diabetology
Background:
- Diabetic chronic ulcers exhibit persistent inflammation.
- Early diabetic wounds show inadequate inflammatory responses due to low proinflammatory cytokines.
- Diabetic neutrophils have impaired bactericidal functions.
Purpose of the Study:
- To investigate the hypothesis that reduced bacterial killing by diabetic neutrophils leads to decreased pathogen-associated molecular patterns (PAMPs).
- To determine if reduced PAMPs cause impaired toll-like receptor (TLR) signaling and inadequate cytokine production in diabetic wounds.
- To evaluate the therapeutic potential of lipopolysaccharide (LPS) in a diabetic wound infection model.
Main Methods:
- Utilized a db/db type 2 obese diabetic mouse wound infection model with Pseudomonas aeruginosa.
- Assessed toll-like receptor 4 (TLR4) signaling and lipopolysaccharide (LPS) levels in diabetic wounds.
- Investigated the effects of topical LPS treatment on inflammation, infection, and healing.
Main Results:
- Diabetic wounds showed reduced TLR4 signaling and lower bioactive LPS levels despite higher infection rates.
- Topical LPS treatment enhanced TLR4 signaling, increased proinflammatory cytokines, and improved leukocyte trafficking.
- LPS treatment reduced infection burden and stimulated wound healing in diabetic mice.
Conclusions:
- Reduced bacterial products, specifically LPS, contribute to impaired TLR4 signaling and inflammation in diabetic wounds.
- Topical LPS application is a potential therapeutic strategy for diabetic foot ulcers after debridement.
- Restoring inflammatory signaling through LPS may overcome impaired healing in diabetic wounds.
