093 Myofibroblasts in Female Red Duroc Pig Scars

Abstract

Introduction: Myofibroblasts are a subtype of fibroblasts, which appear temporally during wound healing. Young hypertrophic scar contains a large number of myofibroblasts and the number declines over time. It has been shown that deep partial-thickness wounds on the female, red Duroc pig heal with thick scars, which is similar to hypertrophic scar. As part of our validation of the Duroc model of hypertrophic scarring, we evaluated myofibroblasts in wounds on the Duroc pigs. Methods: Superficial (0.015″ to 0.030″) and deep (0.045″ to 0.060″) wounds were created on the backs of 12 Durocs. Biopsies were taken at weeks 1, 2, 4, 15, and 21 postwounding. Samples were analyzed by immunochemical staining for alpha smooth muscle actin (a-SMA, for myofibroblasts) and heat-shock protein (HSP47, for fibroblasts). HSP47 positive cells were counted at 40X and the fraction of a-SMA positive cells out of fibroblasts was evaluated at 10X. Statistical significance was calculated with the Kruskal-Wallis test. Results: The counts of HSP47 and a-SMA positive cells are shown in the table below. In brief, in deep wounds most of the HSP47 positive cells were a-SMA positive at 1 and 2 weeks but this declined rapidly thereafter. In shallow wounds there were far fewer cells positive for a-SMA and the decline was even more rapid. 1W 2W 4W 15W 21W Number Shallow 105 ± 22 151 ± 59 106 ± 23 57 ± 20 44 ± 4 HSP47 Deep 524 ± 45 449 ± 35 231 ± 73 108 ± 30 55 ± 8 P value <0.05 <0.05 <0.05 <0.05 Percent Shallow 23% 3% 0 0 0 a-SMA Deep 90% 74% 10% 0 0 P value <0.05 <0.05 Conclusions: a-SMA positive fibroblasts (myofibroblasts) are present in deep Duroc wounds and the temporal pattern is similar to that reported for human hypertrophic scar. This further validates the female red Duroc model of human hypertrophic scarring.