Negative-pressure wound therapy enhances local inflammatory responses in acute infected soft-tissue wound

Clinical studies found that negative-pressure wound therapy (NPWT) displayed significant clinical benefits in the healing of infected wounds. However, the effect of NPWT on local inflammatory responses in acute infected soft-tissue wound has not been investigated thoroughly. The purpose of this study was to test the impact of NPWT on local expression of proinflammatory cytokines, amount of neutrophils, and bacterial bioburden in wound from acute infected soft-tissue wounds. Full-thickness wounds were created on the back of rabbits, and were inoculated with Staphylococcus aureus strain ATCC29213. The wounds were treated with sterile saline-moistened gauze dressings and NPWT with continuous negative pressure (-125 mmHg). Wound samples were harvested on days 0 (6 h after bacterial inoculation), 2, 4, 6, and 8 at the center of wound beds before irrigation for real-time PCR analysis of gene expression of IL-1β, IL-8, and TNF-α. Wound biopsies were examined histologically for neutrophil quantification in different layers of tissue. Quantitative bacterial cultures at the same time point were analyzed for bacterial clearance. Application of NPWT to acute infected wounds in rabbits was compared with treatment with sterile saline-moistened gauze, over an 8-day period. NPWT-treated wounds exhibited earlier and greater peaking of IL-1β and IL-8 expression and decrease in TNF-α expression over the early 4 days (P < 0.05). Furthermore, histologic examination revealed that significantly increased neutrophil count was observed in the shallow layer in wound biopsies of NPWT treatment at day 2 (P < 0.001). In addition, there was a statistically significant decrease of bacteria load from baseline (day 0) at days 2 and 8 in NPWT group (P < 0.05). In conclusion, this study demonstrates that NPWT of acute infected soft-tissue wounds leads to increased local IL-1β and IL-8 expression in early phase of inflammation, which may trigger accumulation of neutrophils and thus accelerate bacterial clearance. Meanwhile, the success of NPWT in the treatment of acute wounds can attenuate the expression of TNF-α, and the result may partly explain how NPWT can avoid significantly impairing wound healing.