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

Abstract

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-a), 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-a 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.

Distribution of an analgesic palmitoylethanolamide and other N-acylethanolamines in human placental membranes

“…The fact that analgesic effect of PEA is suppressed in PPAR-α deficient mice [26] supports this hypothesis. PPAR-α is expressed also in the skin (thus the contact site with AM/ACM grafts) [48] where it promotes differentiation of human epidermal keratinocytes [66], and is upregulated at the edge of the wound during wound healing [67,68]. PEA-mediated activation of PPAR-α also results in the repression of pro-inflammatory NF-Kb [69], which again is profitable for wound healing.…”

The granulation (t)issue: A narrative and scoping review of basic and clinical research of the equine distal limb exuberant wound healing disorder

“…A recent study also showed differences in the reepithelialisation process at the molecular level between J o u r n a l P r e -p r o o f horse body and limb wounds. CK10 and loricrin, two markers of late epithelial differentiation, were found to be expressed in some cells at the migrating epithelial tip of body wounds but not of limb wounds, suggesting a more rapid and superior differentiation of keratinocytes in body wounds (Jørgensen et al, 2019b).…”

“…The growth of EGT physically hinders keratinocyte migration as these cells are unable to cover the rapidly proliferating irregular granulation tissue (Hackett, 2011;. Moreover, the mitotic activity of the epithelial cells was markedly lower when the EGT protruded maximally, which may suggest that EGT inhibits the mitosis necessary for reepithelialisation (Wilmink et al, 1999b;Jørgensen et al, 2019b). A recent study also showed differences in the reepithelialisation process at the molecular level between J o u r n a l P r e -p r o o f horse body and limb wounds.…”

Understanding wound healing and cancer in the skin

“…Similarly, keratocytes explanted from the wounds of zebrafish exhibit loss of E-Cadherin expression and an increase in NCAD (McDonald et al, 2013). These results were recapitulated in the wounds of horses, in which the loss of E-Cadherin and increase in NCAD were concentrated in the epithelium directly adjacent to the wound (Jørgensen et al, 2019).…”