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.

Validation of a Vertical Progression Porcine Burn Model

“…The collagen fibers were viewed under normal as well as polarized light. 14 Apoptosis was identified from immunohistochemical staining, and apoptotic zones were defined as areas with more than 10 percent of cells staining positively for apoptosis. The depth of the beginning and end of these zones was recorded.…”

Immediate Burn Excision Fails to Reduce Injury Progression

“…Scar Surface Area Photographs of each wound were taken before the full-thickness excision biopsy ( Figure 3A) and after fixation of the biopsy with formalin ( Figure 3B). 21 ImageJ software (National Institute of Health, Bethesda, MD) was used to calculate the total surface area of the scar (in square centimeter).…”

Collagen bundle morphometry in skin and scar tissue: a novel distance mapping method provides superior measurements compared to Fourier analysis

“…(2002a,b) showed that the zeroth‐order maximum of Fourier analysis can be used reliably for determining the orientation of the collagen bundles and that it is a valid measurement method for this purpose. Fourier analysis has been widely applied to determine the orientation of structures and, besides using it for the objective assessment of collagen orientation in diseased skin and scars (van Zuijlen et al , 2002a,b; Har‐Shai et al , 2003; van Zuijlen et al , 2003; Ng et al , 2005; Har‐Shai et al , 2006; Singer & McClain., 2006,), it has been used to quantify the orientation of structures in other types of tissue, such as ligaments (Chaudhuri et al , 1987), the annulus fibrosus (Guerin & Elliott, 2006) and vascular endothelial cells (Palmer & Bizios, 1997).…”