Burns are injuries on the skin or other tissues. Burns are divided into superficial, partial, and full-thickness, characterized by the depth of the affected tissues. Histological analysis is critical to assess the burn wound healing process. Thus, a systematic evaluation system is imperative for burn research. In the present study, a total of thirty Sprague-Dawley rats were randomly divided into five groups. Deep partial-thickness burn wound was induced on the dorsal part of the rats. Six animals from each group were sacrificed on the 3rd, 7th, 11th, 14th and 21st day post-burn, respectively. Half of the wound tissue was immediately fixed in buffered neutral formalin for hematoxylin & eosin staining. The healing of the epidermis was evaluated with scores ranging from 0 to 7 based on the state of crust on wound surface, the degree of epithelialization as well as the formation of rete ridges. Meanwhile, healing of the dermis was also evaluated with scores ranging from 0 to 7 according to the proportion of adipose cells, inflammatory cells and fibroblasts, the state of collagen deposition as well as the formation of hair follicles. Furthermore, temporal changes of histological score of epidermis and dermis in the skin tissue with deep partial-thickness burn was evaluated. In conclusion, a new comprehensive system for assessing microscopic changes in the healing process of deep partial-thickness burn wound in hematoxylin & eosin staining slides was established, which simplified the scoring process and helped to obtain reproducible and accurate results in the burn study.
Our previous study has demonstrated that epidermal growth factor (EGF) with tocotrienol-rich fraction (TRF) cream formulation accelerating postburn wound healing with deep partial-thickness burn in rats. Current study was conducted to determine the gene expression levels related to burn wound healing process. A total of 180 Sprague-Dawley rats were randomly divided into 6 groups: untreated control, treated with Silverdin cream, base cream, base cream with 0.00075% EGF, base cream with 3% TRF or base cream with 0.00075% EGF, and 3% TRF, respectively. Burn wounds were created and the above-mentioned creams were applied once daily. Six animals from each group were sacrificed on days 3, 7, 11, 14, and 21 postburn. RNA was extracted from wound tissues and quantitative real-time polymerase chain reaction was performed to analyze the 9 wound healing-related genes against time postburn. Results demonstrated that topically applied EGF + TRF formulation downregulated the expression levels of IL-6 (interluekin-6), TNF-α (tumor necrosis factor-α) and iNOS (inducible nitric oxide synthase) throughout the whole healing process. TGF-β1 (transforming growth factor-β) and VEGF-A (vascular endothelial growth factor-A) were reduced on day 14 postburn. On the contrary, increased expression of Collagen-1 in the early stage of wound healing was observed with no effects on epidemal growth factor receptor (EGFR). The results showed beneficial application of EGF + TRF cream in the treatment of burn wound since it accelerated wound healing by relieving oxidative stress, decreasing inflammation, and promoting proper tissue modelling in the burn wound.
Burn injuries are one of the most devastating injuries in the world. A uniform burn wound is essential for burn research. The objective of this study was to describe a new model for inducing deep partial-thickness burns in rats. Burn wounds were performed on the dorsal part of Sprague-Dawley rats using a constructed heating device in our laboratory. Digital images of each animal were captured every day for macroscopic evaluation and for assessment of the wound contraction rate. Six animals were sacrificed on days 1, 3, 7, 11, 14, and 21 after onset of burn and their skin tissues were harvested for histological analysis. Uniform deep partial-thickness burns could be achieved in Sprague-Dawley rats under the condition of a contact temperature of 70°C, with the weight of heating devices of 300 g, and a duration of 10 s. Macroscopic evaluation recorded the general appearance of the deep partial-thickness burns. Evaluation of the wound contraction rate showed that the deep partial-thickness wound area was reduced by 90.39% of the original wound area by day 21 after burn. Microscopic evaluation by hematoxylin-eosin staining revealed the histological changes during the wound healing process. This is a standardized and reproducible model for inducing deep partial-thickness burns in Sprague-Dawley rats.