Basic research on xenotransplantation u sing genetic engineering and its future application in clinic meidicine

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Xenotransplantation is considered to be promising as an alternative method to solve the shortage of donor organs. The purpose of this research is to get the basic knowledge for clinical application of xenotransplantation. We investigated the mechanisms of (1) hyperacute rejection and (2) cellular response including delayd rejection and immunological tolerance, and attempted the new strategy for successful xenotransplantation. The obtained results are as follows,(1) Crry gene in rats and decay accelerating factor (DAF) gene in guinea pigs were analyzed. The experimental model, which shows that complement activation can be suppressed when complement inhibitory proteins of recipient are genetically inserted into donor organ, was established. Genetic analysis of alpha 1,3 galactosyl transferase (alpha 1,3 GT), which forms main xenoantigens, namely alpha 1,3 galactosyl (alpha Gal) antigens, wes performed in mice and pigs. We are now producing knock out mice of alpha 1,3 GT function and cons … More tructing a targeting vector for knock out in pigs. Since we also elucidated several splicing variants in porcine alpha 1,3 GT,we are now examining the functional difference between these variants. As gene transfection of alpha 1,2 fucosyl transferase (alpha 1,2 FT), which is capable of competitive inhibition of alpha 1,3 GT,caused the decreased expression of alpha Gal antigens in pig cultured cells, we are establishing alpha 1,2 FT transgenic pigs. However, as decreased sialylation in cultured endothelial cells by alpha 1,2 FT gene transfer inhibited the capacity of tube formation, further experiment will be necessary for modification of carbohydrate antigens in cell surface. In guinea pig to rat combination, inhibition of coagulation as well as complement system was proved to be important to suppress hyperacute rejection.(2) Donor specific immunological tolerance was found to be acquired by inhibition of adhesion molecules on donor antigen presenting cells in rat to mouse combination.The method of microcapsulated islets transplantation into subcutaneously guided greater omentum was proved to be useful. The optimal condition of adenovirus vector for gene transfer to donor organs was determined. The simultaneous transplantation of bone marrow cells or gene transfer of donor MHC using retrovirus vector was beneficial for induction of immunological tolerance. Less