A new experimental hypertrophic scar model in guinea pigs

Many aspects of the biology and effective therapy of proliferative scars remain undefined, in part due to a lack of an accurate, practical, reproducible, and economical animal model for systematically studying hypertrophic scars. This study was designed to investigate whether hypertrophic scar formation could be induced in guinea pigs by removal of the panniculus carnosus alone, and by a combination of the removal of the panniculus carnosus with application of coal tar afterwards. Whole thickness skin excision or deep partial thickness injury was used to create the lesions on intact skin. Different anatomic locations were tested in different groups. Scars thus developed were examined morphologically by light microscopy and electron microscopy (TEM and SEM) and biochemically by measuring the activity of glucose-6-phosphate dehydrogenase (G6PD) to check whether these scars had morphological and biochemical properties specific to hypertrophic scars. The albino guinea pigs used in this study were divided into three groups. Removal of the panniculus carnosus was performed from the ventral aspect of the torso in animals in groups I and II. On the skin overlying the area of panniculectomy, circular skin excision was performed in group I, and deep partial thickness burn injury was inflicted in group II, to see whether wounds would heal with hypertrophic scars. In group III, dorsal aspect of the torso were used and wounds were produced by circular skin excisions followed by panniculectomy on both sides but coal tar was applied to only one side. Tissue samples were taken from the scars that were hypertrophic in appearance, and from normal scars and normal skin for comparison. Light and electron microscopic examinations and G6PD activity measurements were performed on these samples. While hypertrophic scar development was not seen in group I and group II, scars with morphological and biochemical properties specific to hypertrophic scars developed in one third of animals in group III after healing of the wounds treated with coal tar. In conclusion, it is shown that it is possible to develop experimental hypertrophic scars in guinea pigs with morphological and biochemical properties similar to those of human proliferative scars. Therefore this model is a new, practical, and economical experimental animal model to study proliferative scars, although improvements are needed to increase yield.