01.12 Murine and Human Diabetic Wounds Display Decreased Tregs and Increased TH17 Cells.

E. C. Barrett1, W. J. Melvin1, F. M. Davis1, C. Audu1, A. Kimball1, A. Joshi2, A. Obi1, K. Gallagher1,2 1University Of Michigan,Vascular Surgery,Ann Arbor, MI, USA 2University Of Michigan,Microbiology And Immunology,Ann Arbor, MI, USA

Introduction:  Non-healing wounds in patients with Type 2 Diabetes (T2D) are a major cause of increasing morbidity and mortality.  We and others have identified that a wound CD4+Treg cell phenotype is important for normal tissue repair, however the predominant CD4+ T cell phenotype in T2D wounds is unclear. Thus, we hypothesized that in diabetic wounds Tregs are decreased, while a TH17 phenotype predominates and serves to promote excess inflammation and impairs healing. 

Methods:  Using a murine wound healing model, wound Mφs were analyzed by flow cytometry from control and diet-induced obese (DIO) mice (a model of T2D) and FoxP3EGFP reporter mice (n= 40/group).  Human T2D and non-T2D wounds were isolated and single cell RNA sequencing was performed. Statistical significance was determined using Student’s t-test or ANOVA. 

Results: Using our FoxP3EGFP reporter mice, we have identified that in normal wound repair, FoxP3+CD4+Tregs are increased and TH17 cells are decreased on day 5, during the resolution phase of normal tissue repair. In contrast, in diabetic wounds, Tregs are decreased and TH17 are increased on day 5. Further, we found increased IL17A production by diabetic CD4+T cells compared to control wounds. Single-cell transcriptional profiling of human diabetic wounds revealed increased RORγt+CD4+T cells (TH17) and decreased FoxP3+CD4+Tregs. 

Conclusion: These results identify that TH17 cells are increased in murine and human diabetic wounds and may contribute to the excess inflammation in diabetic wounds that prevents healing.