Re-Epithelialisation in a Yorkshire Pig Full-Thickness Excisional Wound Model Is Associated With Keratinocyte Activation, Oxidative Stress, and Biomacromolecule Oxidation.

Pig skin represents the best analogue for human skin both anatomically and physiologically, with this model used extensively for pre-clinical testing of therapeutics and biomaterials. However, the molecular processes underlying re-epithelialisation in pigs are still not well described compared to murine models. Our objective was to characterise the re-epithelialisation process in porcine full-thickness excisional wounds in Yorkshire pigs. Immunohistochemistry markers for keratinocyte differentiation, activation and oxidative stress were used at 7 days and 28 days post-wounding, and in healthy control skin to characterise protein expression. We show at day 7, re-epithelialisation is associated with reduced cytokeratin 10, E-cadherin and filaggrin and an increase in cytokeratin 14, cytokeratin 16 and cytokeratin 17. At day 28, cytokeratin 16 remained expressed, but cytokeratin 14 only associated with basal keratinocytes and cytokeratin 10 with suprabasal keratinocyte layers. At day 7, both phospho-nuclear factor kappa B and the antioxidant transcription factor nuclear factor-erythroid 2-related factor 2 show nuclear translocation at the wound edge, which is attenuated by day 28. Concomitant with these observations, we show that re-epithelialisation is associated with guanosine oxidation, protein nitration, and lipid peroxidation at both day 7 and 28. Our observations confirm the baseline expression profile of keratinocytes during normal healing of full-thickness excisional wounds in Yorkshire pigs. Characterisation of similar markers in human healing will improve our understanding of the validity of the Yorkshire pig model for use in the testing of therapeutics for impaired skin healing in humans.