Topical Formulations of Water-Soluble Chitin as a Wound Healing Assistant -Evaluation on Open Wounds Using a Rabbit Ear Model-

Water-soluble chitin (WSC) was prepared by carefully deacetylating chitins to about $50\%$ of N-acetyl content. Topical formulations based on WSC were prepared and their effects on wound healing were evaluated on a rabbit ear model. Full-thickness, open skin wounds were made on the ears of rabbits and WSC ointments were embedded in the open wounds. The application of WSC ointments significantly accelerated wound healing and wound contraction. The areas of epithelial-ization and granulation tissues in WSC ointment group are remarkably larger than those in control group (no treatment) and in placebo group (treated with ointment-base materials). A large number of grown granulation tissues including dense fibroblast deposition were observed under the thickened epithelium of the wound treated with WSC ointments. The number of inflammatory cells in WSC ointment group was significantly decreased compared with those in control and placebo groups, indicating that WSC would give low stimuli to wounds and prevent excessive scar formation. Neovascularization was the most prominent in WSC ointment group. Wound contraction in WSC ointment group was much larger than those in control and placebo groups. Overall results demonstrate that the topical formulation based on WSC is considered to become an excellent dressing as a wound healing assistant.