Development of a porcine incisional wound model and novel scarring scales

Abstract

A major goal of wound management is to reduce scarring. Prior to evaluating novel anti-scarring therapies, we developed a porcine incisional wound model and scarring outcome measures. Forty-eight full-thickness incisions (3 cm in length) and excisional wounds (3 x 0.5 cm) were created on two animals and closed with sutures (n=24) or tissue adhesive (n=24). Scars were evaluated using two validated clinical scar scales and a novel scale developed for animals. Full-thickness biopsies were obtained at 5 and 8 weeks for determination of scar morphology using H&E and Congo red staining with and without polarized light. Scar tissue was classified based on the collagen fiber morphology and "redness" ratio, which is a measure of the relative distribution of collagen fiber in all three spatial dimensions. The clinical cosmetic scales were highly reliable, yet nondiscriminatory. The novel gross cosmetic and histomorphological scores were both highly reliable (0.75 and 0.70, respectively), yet poorly correlated with each other (0.17). The "redness" ratio and cross-sectional surface area measurements were also highly reliable (r=0.96 and 0.99, respectively) but unrelated to cosmetic outcomes. However, the "redness ratio" did correlate with the histomorphologic appearance of the scars, with poorer appearing clinical scars receiving lower ratios (ANOVA p=0.001). Significant differences in cosmetic scores were noted between excisional and incisional wounds favoring incisions (p=0.0019). We describe a novel porcine model for incisional and excisional wounds. The new clinical and histomorphologic outcomes were highly reliable yet poorly correlated. In general, incisional wounds healed with less apparent scarring than excisional wounds.