Morphological observation and changes of hydroxyproline content in hypertrophic scar of rabbits

Objective To establish animal model for hypertrophic scar and study the characters of its morphology and collagen metabolism. Methods A total of 64 round wounds (diameter of 6 mm each) with total skin loss were made on the ventral side of rabbit ear using a trephine. Morphology and collagen metabolism of scar wounds were studied at 14,21,35,70 and 98 days after operation, respectively. Results There were 76% elevated scars developed (45/59 wounds) on the ventral side of rabbit ear at 21 days and 46% elevated scars disappeared (11/24) at 98 days after operation. There were numerous fibroblast proliferation and whorl arranged collagen fibers at 21 and 35 days. The number of fibroblast decreased, but irregular arranged fibers still presented in the elevated scars at 70 and 98 days after operation. Hydroxyproline content in elevated scars at 21 days was higher than that in normal skin ( P 0.05), and at 35 days was 3 times as that in normal skin and at 98 days was also markedly higher than that in normal skin ( P 0.05). Conclusion Excessive deposition of collagen is a characteristic of hypertrophic scar in rabbits. The conversion of normal scarring to hypertrophic scarring in rabbits occurs at 14～21 days after operation. Both development and regression of hypertrophic scar in rabbit are quicker than that in human.