Histological and Biomechanical Evaluation of the Preserved Degenerative Dermis in Rat Autologous Skin Transplant Models after a Deep Second Degree Burn

To describe the histological and biomechanical changes of the preserved degenerative dermis in rat autologous skin transplant models after a deep second-degree burn. 50 SD rats were divided into 5 groups randomly of 10 rats of each: 7-days group, 9-days group, 14-days group, 21-days group, and 60-days group. Deep second-degree burn wounds were prepared on the back of rats sized 3.5cm×3.5cm. Super tangential excision was performed on the burn wound to preserve the degenerative dermis. Then, autologous epidermis was grafted on the wound. After that, the histological changes of the preserved degenerative dermis tissues and the graft areas were observed by macroscopic, light microscope and electron microscope in the 7, 9, 14, 21, 60 days after the operation. Moreover, the tensile properties of healing deeply burned rat skin were also tested for each group at the same time points mentioned above. Results: (1) According to the macroscopic observation, 7 days after the operation, the grafted skin was fused with the area of burn wound; A few hairs were growing out on the skin at the 14th day; the injured skin recovered to normality by the 60th day. (2) Hyaline change occurred in the preserved degenerative dermis tissues based on the observation by light microscope. At the 7th day after operation, the dermis papillae and reticular layer could be discerned; by the 21st day, the thickness, structures and morphology of grafted skin were similar to the normal tissues. (3) 7 days after operation, ballooning changes were observed by the electron microscope in the mitochondria and endoplasmic reticulum of damaged cells and the number of the ribosomes was obviously reduced. The subcellular wound improved continuously and approached normality by the 21st day. (4) 9 days after the operation, the tensible strength and maximal strain of the grafting rat skin approached 70% and 90% of natural skin, respectively. (5) 60 days after the operation, the tensile performance of the healing rat skin recovered to the natural level. Conclusion: The histological and biomechanical changes of the denatured dermis of a deep second degree burn wound may gradually recover to normality after being covered by autologous skin.