Fibroblast Dynamics Following Partial and Deep Burn Injury in a Reconstructed Human Skin Model

Background: Burn injuries are characterized by extensive and prolonged inflammatory responses that impair wound healing, especially in deep burns. Understanding the post-burn fibroblast dynamics in wound healing is critical to improve recovery and minimize scarring. This study aimed to develop a 3D reconstructed human skin (RhS) burn model to mimic superficial, partial-thickness, and deep burn injuries and assess fibroblast behavior over one week. Methods: RhS consisted of a reconstructed epidermis on a fibroblast populated collagen hydrogel dermis. Papillary (fibroblast activation protein; FAP +) and reticular (FAP-) fibroblasts located themselves in the upper and lower regions respectively within the dermal compartment in line with native skin. Burns of increasing temperatures (70 °C, 110 °C, and 140 °C) were introduced and RhS was analyzed up to one-week post-burn. Results: Lactate dehydrogenase (LDH) staining for metabolic active cells in tissue sections enabled distinct histological zones to be observed in RhS with partial (110 °C) and deep burns (140 °C): including a viable fibroblast zone (zone V), a mixed dead and viable fibroblast zone (zone M), and a necrotic zone (zone N). Fibroblast migration from the wound edge (M) into the viable area (V) and changes in fibroblast phenotype, particularly an increase in papillary fibroblast markers (FAP +), were observed, with a marked increased expression of Ki67 in fibroblasts at the burn wound edge (M). Additionally, burn temperature influenced the protein secretion of inflammatory and tissue remodeling mediators SAA, NGAL, MRP8/13, ICAM-1, CCL20, and MMP-9. Conclusion: The RhS burn model enables complex fibroblast dynamics post-burn to be investigated in an organotypic model, providing a platform for studying burn pathophysiology which can be used for evaluating potential therapeutic strategies for enhancing burn wound healing and minimizing scarring in the future.