Defect Repairing Ability Of Allograft Tissue Engineering Bi-layered Skin And Evaluation Of Its Immunologic Rejection

Tissue Engineering is a modern subject. It includes a scaffold that provides an architecture on which seeded cells can be organized and developed into the desired organ or tissue prior to implant. The scaffold provides an initial biomechanical profile for the replacement tissue until the cells produce an adequate extracellular matrix. Tissue engineered organs can help people to resolve the proplem of lack of organs for transplantation.In our study, we have cultured a tissue engineered composited skin in labatary. To examine its bioactivity, we have made an animal model of tissue engineered skin allograft and succeeded in allografting the tissue engineered rat skin.Experiment 1, we made an animal model of skin allograft with Wistar and SD rats. The autograft skin of SD rats healed, but the skin grafted from SD rats to Wistar rats had been completely rejected. Through this experiment, we have affirmed the feasibility of the skin allograft model of these two groups of rat.Experiment 2, an in vitro construct of human skin of full thickness has been engineered using tissue engineering techniques. Epithelial cells and fibroblasts wereisolated from the back skin of relatively lower immunogenicity newborn SD rats. Fibroblasts were seeded into bovine I type collagen gel and cultured for 3 days. Epithelial cells were seeded on the surface of collagen gel and cultured for another 2 days, then expose the equivalent skin to air-liquid interface to generate a protective cornified layer. The equivalent skin consists of epithelium and dermis. Its characteristics were similar to the normal skin. Epithelium. Tissue-engineering skin of full thickness, which use newborn SD rats back skin as the sources of epithelial cells and fibroblasts with bovine I type collagen as carrier, was a fine biological living skin equivalent and can be used to repair the defects of full thickness skin.Experiment 3. transplanted the tissue engineered rat skin to adult Wistar rats and compared it with autograft and allograft skin through observing their developments and their histological changements. The allograft skin has significant rejection, but tissue engineered skin has no obvious rejection.Experiment 4, detected the change of TNF-a and IL-2 in graft skin of the three groups with immunohistochemical and Western blot methods, and detected the change of these two factors in serum with radioimmunoassay. Through these experiments, have found that these two factors had significant effects in the rejection of skin graft.Experiment 5,T lymphocytes play a very important role in immunological rejections of organ graft. In this experiment we have observed the T lymphocyte subpopulations infiltrated in rejection reaction of these three skin graft groups and analyzed their relationship with the rejection reactions. The result showed that CD4+ T lymphocytes plays a more important role in the immological rejection of skin allograft.Experiment 6, comparing the expression of selectin-P and selectin-E in tissue engineered skin with normal skin allograft of rats through immunohistochemical motheds. The selectins expressed changed with the immunological rejection. It can be concluded from these results that selectins must have some relationships with the-7-immunological rejection of skin allograft.In our study, we have developed tissue engineered skin of newborn SD rats and succeeded in transplanting it to Wistar rats. The bioactivity and histocompatibility of this tissue engineered skin also have been proved.