The effects of thermal injury on immature rat ear cartilage

The purpose of this study was to research regeneration and growing properties of an immature rat ear cartilage and its adjacent tissue after a thermal injury. Fifteen 30-day-old male Sprague-Dawley rats were used. Burn wounds were created by applying a heated plaque. All the rats, based on their tissue sampling day, were placed in two groups for histopathologic evaluation. In group I (n = 5), the burned right auricles were amputated on the first day,and the left auricles were amputated as a control at the same time. In group II (n = 10), the burned right auricles were amputated on the 30th day, and the left auricles were amputated as a control at the same time. Epithelization of skin was completed in period ranging between 12 and 15 days in all burned ears. The skin appendages were few throughout the affected area.Chondroid tissue regenerated from perichondrium and increased capillary vessels were observed.On the first day of the burn injury, electron microscopic findings were karyopyknosis, karyorrhexis, and karyolysis of the nucleus, and there were also signs of necrosis. New chondroblasts were formed around the collagen fibrils in the scar tissue on the 30th day. CD-31 immunohistochemical staining showed increased capillary vessels in the burned ear. The peripheral nerve fibers decreased and regenerative signs of nerves were shown with the use of S-100 immunohistochemical staining. Differentiation of chondroblasts to chondrocytes occurs in the burned immature ear, and new cartilage tissue regenerates from perichondrium. In addition, regenerative signs of nerves appear.