Study On Tissue Engineered Dermal Substitutes

Closure of full-thickness skin defects is important for the treatment of patients with burn, traumatic injury, chronic skin ulcer or hyperthopic scar. The traditional approach is grafting autologous skin, which often results in heavy pigmentation and scarring in donor sites, and the amount of skin obtained by this method is limited for patients with large area skin injuries. The technique of skin tissue engineering has been a new method to provide adequate skin grafts and improve wound healing quality. The development of dermal replacement is particular crucial to skin tissue engineering. Various dermal analogs have been developed and used as dermal template to cover full-thickness wounds successfully. But it is too expensive to afford. Therefore, development of economical dermal replacement with good quality is necessary.In this study, the bilayer collagen-chitosan sponge scaffold was fabricated with type I collagen and chitosan, the structures and properties of the scaffold were studied. Dermal fibroblasts were isolated from SD rat skin, then the cells were transplanted into the sponge scaffold to construct the tissue engineered dermal substitutes in vitro. The artificial skin was transplanted into full-thickness wounds of SD rats. The main results of the thesis are as follows:1. A porous scaffold with suitable pore sizes and internconnected pore structure was prepared with collagen and chitosan by freeze-drying, and glutaraldehyde (GA) was added to the scaffold as cross-linking bridges. The test indicated the scaffold had good mechanical property and water-absorbing ability. The biological evaluation tests showed that the collagen-chitosan dermal scaffold had no cytotoxicity and no remarkable sensitization for rabbit skin. Subcutaneous implantation indicated the collagen-chitosan dermal scaffold had good tissue compatibility. However, the scaffold was still observed on 28th day, which demonstrated that it could be biodegradated and absorbed slowly.2. Dermal fibroblasts were isolated from SD rat skin successfully. We transplanted the fibroblasts on the collagen-chitosan scaffold to construct the dermal substitute in vitro. The artificial dermal substitute with functionally vitality could be called a living artificial dermal substitute.3. The skin defect model was established in SD rats. The capcity of the artificial dermal substitute promoting tissue regeneration was evaluated by transplanting it on the back of the SD rats. The results of the experiment showed that the artificial dermal substitute was good at adhering the tissue and absorbing liquid and it could promote the wounds healing. The result of the histological observation showed that the artificial dermal substitute could guide the ingrowth of fresh tissues and promote the growth of epidermal cells and fibroblasts.According to the results of this study, we concluded that the living artificialdermal substitute had not only good properties of physics and chemistry but alsogood biocompatibility. So it could become an artificial dermal substitute applied inrepairing the skin defect.