ACUTE AND CHRONIC ANIMAL-MODELS FOR EXCESSIVE DERMAL SCARRING - QUANTITATIVE STUDIES

Excessive scarring in the form of keloids and hypertrophic scars conti nues to be a clinical problem for some patients. The lack of an animal model for such scarring has been an obstacle to studying the cellular and molecular biology of these entities. Precious observations made b y the authors that some surgical scars in the rabbit ear remain raised for months after wounding prompted us to investigate whether the rabb it ear might provide a model by which to study excessive dermal scarri ng. After establishing the model in preliminary study, 40 excisional w ounds, 6 mm in diameter, were created over the ventral surface of rabb it ears. Elevated scars were treated with either intralesional triamci nolone acetonide or saline at day 16 postwounding. On day 22, 25 scar wounds were used for thorough histomorphometric analysis, 15 wounds we re eliminated prior to analysis because of invagination of epithelial tissue, which made analysis difficult. Total area of scar and Hypertro phic Index, a ratio comparing scar prominence with the thickness of ad jacent unwounded tissue, were measured for 25 (62 percent) of the resu lting scars. Both total area of scar and Hypertrophic Index were found to be significantly decreased in the steroid-treated group (p < 0.02 and < 0.03, respectively). In a chronic form of this model, in which l arger excisions were taken, an excessive accumulation of both new coll agen and cartilage over 9 months was observed. An animal model for exc essive dermal scarring that allows quantitation of scar formation and, at an early stage, call be modulated in a predictable way with intral esional corticosteroid treatment is presented. This model may parallel hypertrophic scarring in humans and thus might provide a tool by whic h to study its pathophysiology and objectively evaluate therapeutic mo dalities.