Regional differences in wound oxygenation during normal healing in an equine model of cutaneous fibroproliferative disorder

Abstract

Wound repair in horse limbs is often complicated by the development of exuberant granulation tissue (EGT) and excessive scarring while body wounds tend to repair uneventfully. EGT resembles the human keloid. While the events leading to keloid formation are not fully elucidated, tissue hypoxia has been proposed as a major contributing factor. The objective of this study was to investigate tissue oxygen saturation in healing full-thickness wounds created on the horse limb and body, using near-infrared spectroscopy. Spectroscopic reflectance data were collected from both anatomic sites at specific times following wounding. The oxygen saturation values of limb wounds were significantly inferior to those of body wounds during the early period of healing, indicating a temporary, relative state of hypoxia in the former during the inflammatory phase of repair. Horses present a weak, persistent inflammatory response to wounding, especially at the limb level. The relative hypoxia present acutely in limb wounds of horses may promote a feeble yet prolonged inflammatory response, which could interfere with and retard the subsequent phases of healing. Ongoing low-grade inflammation in horse wounds is accompanied by up-regulation of various inflammatory and profibrotic mediators, which might ultimately promote the development of fibroproliferative disorders such as EGT.