Biofilm-modified macrophage (BAM) phenotype and function in diabetic wounds
About 85% of lower-limb amputations in patients with diabetes are preceded by infected foot ulceration. Emerging studies highlight the significant risk that biofilm infection poses to the non-healing diabetic ulcers. Macrophages (Mphi) are highly plastic innate immune cells that play a central role in tissue repair. These cells of innate immune system serve as the primary defenders against infection. Bacterial pathogens have evolved multiple strategies to evade and subvert host immune system. Emerging studies indicate a role of methicillin-resistant SA (MRSA) biofilms in evading Mphi bacterial effector mechanisms by transforming Mphi towards an alternatively activated M2 phenotype. Strategies of modifying activation state of Mphi have been suggested to be effective in developing anti-biofilm therapeutics. A thorough characterization and phenotyping of chronic wound biofilm modified Mphi (BAMs) is warranted. We seek to understand how does the diabetic wound environment influences BAM phenotype and function. A fine balance between ECM synthesis and degradation is essential to achieve optimal repair. An imbalance in either direction may result in scarring or poor healing outcomes. M2 Mphi may exist as ECM promoting (ECM-promote) vs ECM degrading (ECM-degrade) subpopulations. Striking preliminary data using a preclinical burn biofilm model demonstrated that wounds infected with biofilm overproducing stain of SA rexB- mutant resulted in a massive loss of collagen in the healing granulation tissue compared to the low biofilm producing SA SarA- mutant strain. To be able to pharmacologically stimulate the right kind of behavior in wound ECM turnover, a thorough characterization of ECM-promote vs ECM-degrade mphi is necessary, as well as an understanding of the signals they require for ECM turnover. The following two specific aims will be addressed: AIM 1. Determine if functionally active wmphi isolated from biofilm-infected diabetic wounds show ECM-degrade phenotype causing wound collagen degradation. AIM 2. Investigate whether increased presence of ECM-degrade wound mphi phenotypes in biofilm-infected human diabetic wounds are associated with educed wound collagen levels and increased wound recurrence.

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