Temporal Dynamics and Interrelations of Cytokines, Neutrophil Proteins, Exudation, and Bacterial Colonization in Epidermal Wound Healing

Sigrid Lundgren^1,2Ganna Petruk¹Karl Wallblom^1,2José F Cardoso¹Ann-Charlotte Strömdahl¹Fredrik Forsberg¹Congyu Luo¹Bo Nilson²Erik Hartman¹Jane Fisher¹Manoj Puthia¹Karim Saleh¹Artur Schmidtchen^1,2*

• ¹Department of Clinical Sciences, Faculty of Medicine, Lund University, Lund, Skane County, Sweden
• ²Skåne University Hospital, Lund, Skane County, Sweden

Introduction: Inflammation is integral to wound healing; yet, its dynamics in normally healing epidermal wounds are not fully characterized. To this end, we analyzed longitudinal wound fluid samples collected from epidermal suction blister wounds in healthy volunteers. Materials and methods: A total of 48 control wounds were induced by suction blister method in 24 healthy volunteers—1 on each thigh. Immunoassay, MALDI-TOF mass spectrometry, and microbiological methods were applied to analyze cytokine dynamics, neutrophil activity, and bacterial colonization and levels in wound swabs and dressings during epidermal wound healing, focusing on viable cultivable wound bacteria.Results: Cytokine levels peaked on day 5, followed by a decline on day 8. Wound exudation, measured by protein content, increased from day 2, peaking on day 5. The neutrophil-derived proteins myeloperoxidase, elastase, and heparin-binding protein (HBP) peaked on day 5, correlating with interleukin (IL)-8, a key neutrophil chemoattractant. The identified bacteria consisted primarily of commensal bacteria, including various staphylococci. Levels of such bacteria rose from day 2, peaking on days 5-8, and aligned with increases in the cytokines tumor necrosis factor α, IL-1β, and IL-10 at the peak of inflammation on day 5. Conclusions: This study uncovers the coordinated dynamics of cytokines, neutrophil activity, and major commensal bacteria in epidermal wound healing and identifies HBP—a marker for neutrophil activation and endothelial leakage—for the first time in normally healing epidermal wounds.