A novel animal scar model after major burn with a high success rate of >70 % during an observation period of 300 days.

Abstract

Among all types of injuries, burns are one of the most prone to inducing scars. However, there is an absence of appropriate animal models for research. This study aimed to establish an easy and reliable animal model for major burn-induced scarring and evaluate its characteristics systematically. Rats were subjected to deep second-degree burns covering approximately 30 % of the total body surface area (TBSA) using hot liquid (94℃-98℃). Wounds were meticulously dressed, and the dressing was changed every 1-3 days. Multivariate analysis was performed to explore the critical factors for modelling. Macroscopic features and their temporal evolution were observed from day 0 to day 300 after modelling. Skin ultrasound was used to assess physicochemical properties. Haematoxylin-eosin (HE) staining, Masson staining, and immunohistochemistry staining were performed to evaluate general histological characteristics and the dynamic distribution of specific cells. Western blotting and picrosirius red staining were performed to quantify the content and ratio of collagen Ⅰ and collagen Ⅲ. Scar formation around 40 days post-burn, higher rat weight, and wound dressing change frequency were associated with a high success rate of modelling. Macroscopically, scars exhibited distinctive pinkish pigmentation, increased firmness, absence of new hair growth, and long-term contraction. Ultrasound imaging and histopathological staining revealed an increase in the thickness of the epidermis and dermis. Compared with normal skin, diminished dermal density and water content, and elevated transepidermal water loss rate, haemoglobin content, and elastic retraction rate were revealed in scars. Microscopically, scars manifested marked thickening of the epidermis and dermis, diminished skin appendages, and abundant collagen fibre bundles. Activated fibroblasts and microvessels were significantly increased in scars compared with those in normal skin; moreover, collagen Ⅰ and collagen Ⅲ content and collagen Ⅰ to collagen Ⅲ ratio were increased. The burn scar model in rats we constructed and continuously observed for 300 days replicates the intricate biological characteristics of scars post-burn, with simple and reliable methodology and a high success rate of more than 70 %.