32. Negative Pressure Wound Therapy Regulates Yes-Associated Protein and Engrailed-1 Pathways to Prevent Scarring in Diabetic Wounds

Purpose: Hypertrophic and keloid scarring have significant functional and aesthetic morbidity and can substantially impact patients’ quality of life. These debilitating sequelae of surgery may be managed through modification of the wound microenvironment via mechanical forces such as Negative Pressure Wound Therapy (NPWT). In this study, we applied continuous NPWT to murine diabetic wounds to investigate the effects on pathways underlying scarring and fibrosis. Methods: 20 diabetic (db/db) mice received a 1x1cm2 full-thickness excisional dorsal skin wound and were divided into two groups. One group received occlusive covering (Control group), and one group received continuous NPWT (-125 mmHg, 24hours, 7 days; NPWT group). The wounds were monitored for 10 days after excision, after which the tissue was harvested for histological and molecular analysis. Results: Immunofluorescent staining demonstrated that the NPWT group had significantly higher Yes-associated protein (YAP; 2±1 vs 1±1 RFI; p=0.03), fibronectin deposition (2±1 vs 1±1 RFI; p=0.03), collagen deposition (34±4 vs 20±4 RFI; p<0.0001), and cellular proliferation (15±7 vs 5±2 RFI; p=0.002) of the wound bed compared to the Control group. Furthermore, the Control group had significantly higher Engrailed-1 expression (En1; 10±4 vs 2±1 En1+/HPF; p=0.0001) compared to the NPWT group. Additionally, western blotting showed that the NPWT group upregulated RhoA (p=0.03) and YAP (p=0.02) and down-regulated Caspase-3 (p=0.03) compared to the Control group. Conclusions: Past research has illustrated that the mechanical signaling protein YAP induces En1+ fibroblasts and is linked to fibrosis and scarring, while increased caspase-3 is involved in keloid formation. In this study, we find that NPWT affects cell proliferation and apoptosis, which may affect scar formation. More specifically, we determined that NPWT results in the upregulation of YAP and downregulation of En1, suggesting that mechanical forces such as NPWT may uncouple YAP from En1. NPWT also decreased caspase-3. Thus, NPWT may limit scarring through fibroblast turnover.