01.12 Murine and Human Diabetic Wounds Display Decreased Tregs and Increased T_H17 Cells.

E. C. Barrett¹, W. J. Melvin¹, F. M. Davis¹, C. Audu¹, A. Kimball¹, A. Joshi², A. Obi¹, K. Gallagher^{1,2 1}University 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 T_H17 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 FoxP3^EGFP 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 FoxP3^EGFP reporter mice, we have identified that in normal wound repair, FoxP3+CD4+Tregs are increased and T_H17 cells are decreased on day 5, during the resolution phase of normal tissue repair. In contrast, in diabetic wounds, Tregs are decreased and T_H17 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 (T_H17) and decreased FoxP3+CD4+Tregs. 

Conclusion: These results identify that T_H17 cells are increased in murine and human diabetic wounds and may contribute to the excess inflammation in diabetic wounds that prevents healing.