Effects of Epidermal Growth Factor on horse skin from different anatomical locations

Healing can be impaired in horses depending on the anatomical location of the wound. Wounds on the limb may develop exuberant granulation tissue that does not re-epithelialize, evolving in aberrant scarring, known as “proud flesh”. This preliminary ex vivo study investigates the effects of Epidermal Growth Factor (EGF) on epidermal thickness and re-epithelialisation of cultured horse skin.Skin strips were obtained from a euthanized horse exempt of dermatological lesions. From the mentioned strips, six-mm full-thickness punch biopsies were obtained from body and limb skin and cultured in a serum free medium, then treated for 6 days (D): 10ng/mL or 20 ng/mL Epidermal Growth Factor (EGF) either alone or with 10μg/mL Dexamethasone (DMS). Culture medium and treatments were replaced every other day. Epidermal thickness and the length of neoformed peripheral epidermis (μm) were measured at D3, D5 and D7.The higher dose of EGF modified epidermal thickness in skin from both locations at D5: a statistically significant increase was observed for body skin while a decrease was observed for limb skin. Analogously, a signifi-cant increase of the neoformed peripheral epidermis (epithelial tongue) was observed at D5 for body skin; although a decrease was seen in limb skin, it failed to reach statistical significance. Statistically significant changes were not observed at both D3 or D7.Our findings confirm the dif-ferences between body and limb skin morpho-physiology reported in horses. Moreover, while body skin responded to EGF as hypothesised, limb skin showed an unexpected response.