| Summary: | <p>Cooling of burns is key to acute burn management, and is a widely accepted practice in modern medicine. Cooled burns are less painful, heal more quickly, require fewer skin grafts, and leave less scarring. The vast majority of research in this area has used animal models, and focussed on optimising cooling, rather than investigating its mechanism. Cooling is not without risks and limitations, and understanding the mechanism might lead to pharmacological alternatives.</p> <p>We aimed to develop a standardised human model for burning and cooling, and used this to investigate the transcriptional and proteomic effects of burning and cooling. This model used redundant skin discarded during surgery, and purpose-built apparatus for burn creation and cooling. Microvascular and other histological changes were demonstrated in response to burning, and modified by cooling. RNA and protein extracts from cooled and uncooled samples of burned and unburned skin were analysed with RNAseq and LC/MS3 techniques, respectively. Findings were validated with immunohistochemistry and qPCR.</p> <p>We demonstrated that there was a significant change in 22% of the transcriptome of the skin, with gene ontologies related to wounding, angiogenesis, inflammation, haemostasis, innate immune response, degranulation and chemotaxis among those significantly upregulated. Downregulated ontologies included keratinisation, epidermal differentiation, hair follicle development and cornified envelope. Cooling of burns significantly increased the transcription of genes related to hair follicle differentiation while reducing the transcription of heat-shock proteins.</p> <p>Burning caused significant activation of the complement and coagulation cascades, while cooling reduced the scale of these changes. Immunohistochemistry confirmed complement proteins, including the membrane-attack complex (MAC) localised to the immediate area of the blistered epidermis, as were fibrinogen and platelets, with evidence of early neutrophil migration.</p> <p>We have demonstrated the role of complement and coagulation activation as a damage-amplifying agent following thermal injury, and the role of cooling in attenuating this effect. The preservation of transcription of follicle-related genes indicates preservation of epidermal appendages as sites of re-epithelialisation.</p> <p>Complement blockade is already utilised in the management of autoimmune conditions, and transplant rejection, and could modify the complement activation in burns, reducing injury-progression, and the associated systemic effects, and improving patient outcomes.</p>
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