Hairless Descendants of Mexican Hairless Dogs: An Experimental Model for Studying Hypertrophic Scars

BACKGROUND/OBJECTIVE: In previous studies, the author noticed hypertrophic scar formation in hairless dogs. The purpose of this study was to evaluate both grossly and histopathologically hypertrophic scars in hairless dogs to explore any similarities with hypertrophic scars in humans and to introduce these dogs as an appropriate model for further investigation on hypertrophic scarring. METHODS: Full-thickness wounds were made on the dorsolumbar skin of hairless dogs. Hypertrophic scarring was examined with three methods: clinical observations, dihydroxyphenylalanine (DOPA)-positive melanocytes, and skin histopathology. RESULTS: Hairless dogs clinically developed the formation of hyperpigmented and hypertrophic scars that did not extend beyond the original wound margins. In hypertrophic scars of hairless dogs, the split epidermal sheet showed an increased number of DOPA-positive melanocytes with well-developed dendrites exhibiting activated melanocytes. There were very few DOPA-positive melanocytes in the repaired skin of haired dogs. Histopathologic examinations demonstrated that hypertrophic scars were fully reepithelialized and granulation tissue formation was accompanied by inflammatory cell infiltration. There was remodeling of thick collagens and fine elastic fibers in the course of hypertrophic scar formation. CONCLUSION: Experimental hypertrophic scars produced in hairless dogs have morphologic properties similar to those of human hypertrophic scars.