Epithelial‐to‐mesenchymal transition and keratinocyte differentiation in equine experimental body and limb wounds healing by second intention

Background The re‐epithelialization process in equine wound healing is incompletely described. For epithelial cells to migrate during embryogenesis they undergo epithelial‐to‐mesenchymal transition (EMT); this phenotypic transition occurs during wound healing in humans and rodents, but it has not been investigated in horses. Hypothesis/objectives To investigate keratinocyte differentiation and EMT in equine experimental excisional limb and body wounds healing by second intention. Animals Six adult research horses. Methods and materials Immunohistochemical analysis was used to detect expression of the differentiation markers cytokeratin (CK)10, CK14, loricrin and peroxisome proliferator‐activated receptor alpha (PPAR‐α), and of the EMT markers E‐cadherin and N‐cadherin in normal limb and body skin, and biopsies from limb and body wounds. Results Loricrin and CK10 were expressed in normal skin and periwound skin but not in migrating epithelium of body and limb wounds. However, they reappeared at the migrating epithelial tip of body wounds only. CK14 and PPAR‐α had uniform distribution throughout the migrating epithelium. N‐cadherin was not expressed in normal unwounded skin but was detected in periwound skin adjacent to the wound margin. E‐cadherin expression decreased at the wound margin. Conclusions and clinical importance Presence of N‐cadherin suggests that cadherin switching occurred during wound healing, this may be an indication that EMT occurs in horses. To the best of the authors’ knowledge, this has never been described in horses before and warrants further investigation to assess the clinical implications. The tip of the migrating epithelium in body wounds appeared more differentiated than limb wounds, which could be part of the explanation for the superior healing of body wounds. Résumé Contexte Le processus de re‐épithélialisation dans la cicatrisation des plaies chez le cheval n'est pas entièrement décrit. Pour que les cellules épithéliales migrent au cours de l'embryogénèse, elles passent par une transition épithéliale‐mésenchymateuse (EMT); cette transition phénotypique se produit au cours de la cicatrisation chez l'homme et les rongeurs mais n'a pas été étudiée chez le cheval. Hypothèses/Objectifs Etudier la différenciation kératinocytaire et l’EMT au cours de plaies expérimentales et la cicatrisation par seconde intention chez le cheval. Sujets Six chevaux de recherche adultes. Matériel et méthode Une analyse immunohistochimique a été utili