Scarless healing of oral mucosa is characterized by faster resolution of inflammation and control of myofibroblast action compared to skin wounds in the red Duroc pig model

Background: Scar formation following skin trauma can have devastating consequences causing physiological and psychosocial concerns. Currently, there are no accepted predictable treatments to prevent scarring which emphasizes a need for a better understanding of the wound healing and scar formation process. Objectives: Previously it was shown that healing of small experimental wounds in the oral mucosa of red Duroc pigs results in significantly reduced scar formation as compared with equivalent full-thickness skin wounds. In the present study, scar formation was assessed in 17 times larger experimental wounds in both oral mucosa and skin of the red Duroc pigs. Methods: Equivalent experimental wounds were created in the oral mucosa and dorsal skin of red Duroc pigs, and scar formation, localization and abundance of key wound healing cells, transforming growth factor-beta (TGF-beta) and phosphorylated Smad3 (pSmad3) were assessed. Results: Oral mucosal wounds displayed significantly less clinical and histological scar formation than did the corresponding skin wounds. The number of macrophages, mast cells, TGF-beta and pSmad3 immunopositive cells was significantly reduced in the oral mucosal wounds as compared with skin wounds during the maturation stage of the healing process. Although the number of myofibroblasts was significantly elevated, the oral mucosal wounds showed significantly less contraction than did the skin wounds over time. Conclusions: Earlier resolution of the inflammatory reaction and reduced wound contraction may promote scarless oral mucosal wound healing. in addition, scar formation likely depends not only on the number of myofibroblasts but also on the extracellular environment which regulates their function. (C) 2009 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.