Back to 2015 Annual Meeting Posters

INTRODUCTION: Diabetic wounds are characterized by a chronic inflammatory state that is maintained by overexpression of pro-inflammatory cytokines generated by macrophages. In normal wound healing, macrophages mobilized from the circulation initially exhibit a pro-inflammatory 'M1' phenotype that is followed by conversion to an anti-inflammatory 'M2' macrophage phenotype to promote tissue repair. We hypothesized that macrophages isolated from human wound tissue and bone marrow from patients with Type 2 Diabetes (T2D) would exhibit increased pro-inflammatory 'M1' characteristics and decreased 'M2' repair phenotypes.
METHODS: Human wound tissue and bone marrow were obtained from 6 patients (N=3 with T2D; N=3 non-T2D) following amputation under our IRB-approved protocol. Immune cell isolations were performed immediately following surgery. Flow cytometry was performed on CD68⁺ wound macrophages isolated from chronic wound tissue. Cells were stained for two well-established M2 markers (M2- CD163⁺, CD206⁺). RT-PCR quantification of IL12 (M1 cytokine) expression in human bone marrow-derived macrophages (BMDM) was performed 6 hours after stimulation with lipopolysaccharide (LPS).
RESULTS: Human CD68⁺ macrophages isolated from T2D wounds showed a significant decrease in these M2 scavenger receptors compared to macrophages in wounds in non-T2D individuals. Functionally, upon stimulation with LPS, human T2D BMDM demonstrated exaggerated production of IL12, a key pro-inflammatory cytokine, compared to non-T2D controls. (Figure 1)
CONCLUSIONS: Macrophages appear to be poised towards an M1 phenotype and mount a distinct pro-inflammatory response in human T2D chronic wound tissue. Manipulation of macrophage function/phenotypes could allow for development of new therapies to prevent chronic inflammation in diabetic wounds.