Effective enzymatic debridement of burn wounds depends on the denaturation status of collagen.

The treatment of burn wounds by enzymatic debridement using bromelain has shown promising results in our burn center. However, inadequate debridement occurred in a few cases in which the etiology of the burn was attributed to relatively low temperature burns. We hypothesized that bromelain is ineffective in burns in which collagen denaturation, which occurs approximately at 65°C, has not taken place. Our objective was to assess whether there is a relationship between the denaturation of collagen and the ability of bromelain to debride acute scald burn wounds of different temperatures. Ex vivo human skin from four different donors was cut into 1x1 cm samples, and scald burns were produced by immersion in water at temperatures of 40°C, 50°C, 60°C, 70°C, and 100°C for 20 minutes. Denaturation of collagen was assessed with histology, using hematoxylin and eosin (H&E) staining and a fluorescently labeled collagen hybridizing peptide (CHP), and with second harmonic generation (SHG) microscopy. Burned samples and one control sample (room temperature) were weighed before and after application of enzymatic debridement to assess the efficacy of enzymatic debridement. After enzymatic debridement, a weight reduction of 80% was seen in the samples heated to 70°C and 100°C, whereas the other samples showed a reduction of 20%. Unfolding of collagen, loss of basket-weave arrangement, and necrosis was seen in samples heated to 60°C or higher. Evident CHP fluorescence, indicative of collagen denaturation, was seen in samples of 60°C, 70°C and 100°C. SHG intensity, signifying intact collagen, was significantly lower in the 70°C and 100°C group (P <.05) compared to the lower temperatures. In conclusion, denaturation of collagen in skin samples occurred between 60°C and 70°C and strongly correlated with the efficacy of enzymatic debridement. Therefore, enzymatic debridement with the use of bromelain is ineffective in scald burns lower than 60°C.

Comparing the antibacterial and healing properties of medical-grade honey and silver-based wound care products in burns.

Burns are a major global healthcare concern, often complicated by the presence of bacteria such as Pseudomonas aeruginosa in the wounds. Silver-based dressings are commonly used in the treatment of burns but can cause skin irritation and delay healing time. Medical-grade honey (MGH) provides an interesting alternative. This study investigated the antimicrobial effects and possible cytotoxicity of L-Mesitran Soft (MGH-gel) and its individual components, Medihoney (Manuka), Flammazine (silver sulphadiazine), and silver nitrate (AgNO3) in an ex vivo human burn wound model. Bacterial survival and wound healing parameters, including re-epithelialization and keratinocyte proliferation were assessed. L-Mesitran, Flammazine, and AgNO3 reduced P. aeruginosa numbers below detection levels. L-Mesitran Soft exhibited a significantly stronger antimicrobial effect compared to Medihoney. The individual components of L-Mesitran contributed significantly to its antibacterial efficacy, thus suggesting synergistic activities. Moreover, L-Mesitran, Flammazine, and AgNO3 slightly inhibited re-epithelialization while Medihoney treatment resulted in a complete lack of re-epithelialization and keratinocyte proliferation. Furthermore, clinical cases illustrated the effectiveness of MGH therapy in infected burns. Overall, L-Mesitran Soft had similar effects as silver-based products on bacterial load and epidermal regeneration, but outperformed Medihoney. Therefore, supplemented MGH could be used as an effective alternative to silver-based dressings for P. aeruginosa-infected burns.

Full Skin Equivalent Models for Simulation of Burn Wound Healing, Exploring Skin Regeneration and Cytokine Response.

Healing of burn injury is a complex process that often leads to the development of functional and aesthetic complications. To study skin regeneration in more detail, organotypic skin models, such as full skin equivalents (FSEs) generated from dermal matrices, can be used. Here, FSEs were generated using de-epidermalized dermis (DED) and collagen matrices MatriDerm® and Mucomaix®. Our aim was to validate the MatriDerm- and Mucomaix-based FSEs for the use as in vitro models of wound healing. Therefore, we first characterized the FSEs in terms of skin development and cell proliferation. Proper dermal and epidermal morphogenesis was established in all FSEs and was comparable to ex vivo human skin models. Extension of culture time improved the organization of the epidermal layers and the basement membrane in MatriDerm-based FSE but resulted in rapid degradation of the Mucomaix-based FSE. After applying a standardized burn injury to the models, re-epithelization occurred in the DED- and MatriDerm-based FSEs at 2 weeks after injury, similar to ex vivo human skin. High levels of pro-inflammatory cytokines were present in the culture media of all models, but no significant differences were observed between models. We anticipate that these animal-free in vitro models can facilitate research on skin regeneration and can be used to test therapeutic interventions in a preclinical setting to improve wound healing.

Monocytes and T cells incorporated in full skin equivalents to study innate or adaptive immune reactions after burn injury.

Introduction: Thermal injury often leads to prolonged and excessive inflammation, which hinders the recovery of patients. There is a notable absence of suitable animal-free models for investigating the inflammatory processes following burn injuries, thereby impeding the development of more effective therapies to improve burn wound healing in patients. Methods: In this study, we established a human full skin equivalent (FSE) burn wound model and incorporated human peripheral blood-derived monocytes and T cells. Results: Upon infiltration into the FSEs, the monocytes differentiated into macrophages within a span of 7 days. Burn-injured FSEs exhibited macrophages with increased expression of HLA-DR+ and elevated production of IL-8 (CXCL8), in comparison to uninjured FSEs. Among the T cells that actively migrated into the FSEs, the majority were CD4+ and CD25+. These T cells demonstrated augmented expression of markers associated with regulatory T cell, Th1, or Th17 activity, which coincided with significant heightened cytokine production, including IFN-γ, IL-4, IL-6, IL-8, IL-10, IL-12p70, IL-17A, IP-10 (CXCL10), and TGF-ß1. Burn injury did not impact the studied effector T cell subsets or cytokine levels. Discussion: Collectively, this study represents a significant advancement in the development of an immunocompetent human skin model, specifically tailored for investigating burn-induced innate or adaptive immune reactions at the site of burn injury.