Development of an artificial dermis composed of hyaluronic acid and collagen

This study aimed to investigate the efficacy of an artificial dermis composed of hyaluronic acid (HA) and collagen (Col) with or without epidermal growth factor (EGF), both in in vitro and in vivo. The cross-linked high molecular weight HA spongy sheet was prepared by freeze-drying. The spongy sheet was immersed in a mixed solution of high molecular weight HA, low molecular weight HA, and heat-denatured Col, and then lyophilized to obtain a two-layered spongy sheet. Cross-linking among Col molecules was induced by ultraviolet irradiation to prepare the artificial dermis (Type I). In a similar manner, a two-layered artificial dermis containing EGF (Type II) was prepared using a similar mixed solution containing EGF. The in vitro experiments demonstrated that EGF released from the Type II artificial dermis stimulates fibroblasts to produce increased amounts of vascular endothelial growth factor and hepatocyte growth factor. The therapeutic efficacy of artificial dermis was evaluated in animal tests using Sprague Dawley (SD) rats. The dorsal skin of the SD rat was shaved and then exposed to boiling water for 3 s to induce a deep dermal burn. The necrotic tissue was then excised 3 days later. Each artificial dermis was applied to the skin defect for 7 days and assessed for its ability to generate a wound bed. The in vivo experiments demonstrated that the Type II artificial dermis promotes angiogenesis to a greater extent at an early stage (within 3 days), and also suppresses the inflammatory reaction more successfully compared with the Type I artificial dermis. In further animal tests, an autologous skin graft was performed by excising a piece of skin from the abdominal region and then grafting it onto the wound bed prepared using each artificial dermis for 7 days. Although the Type II artificial dermis had the highest potential to promote angiogenesis, in this animal study, each artificial dermis induced excellent wound bed formation acceptable for autologous skin grafting.