Pig To Human Cardiac Xenograft Hyperacute Rejection

Objective: Although allotransplantation, with its great basic and clinical success, has become the potential treatment to end-stage organ failure, it also has resulted in a shortage of available organs from deceased human donors. In recent years, attention has been drawn towards xenotransplantation. Pig is investigated as the most likely species to provide organs for human because the anatomy and organ size of pig is similar with human. However, major problems remain to be resolved before successful clinical xenotransplantation can be initiated. The initial immunological barrier of pig-to-human xenotransplantation is hyperacute rejection, which is initiated by natural preformed antibodies directed a carbohydrate epitopes (α-Gal) on the pig vascular endothelium. The binding of antibody to antigen activates the complement cascade, which leads to graft damage.Stachyose is extracted from the root of stachys floridana. It is a kind of nonreductive oligosaccharides. Its constitutional formula is fructose-glucose-galactose-galactose with molecular formula C₂₄H₄₂O₂₁, and molecular weight is 666.59. Stachyose is not toxic and water-soluble. It can inhibit hyperacute rejection of xenotransplantation theoretically since it contains the structure of α-Gal which is similar with the xenogenic antigenic epitope of galactose-α1,3-galacotse. Ourobjective was to investigate the inhibition of stachyose on hyperacute rejection from cell and organ experiments.Methods: PIEC was exposed in human blood plasma and incubated with stachyose or PBS. Then we employed the method of MTT to determine the survival rate of cells, to investigate the protection of stachyose on PIEC. Construct a model of hyperacute rejection of in vitro perfusion pig heart. To investigate the inhibition of stachyose on hyperacute rejection. We determine the histopathobiology and immunohistology of pig hearts which perfused with or without stachyose.Results:1. The survival rate of PIEC increased as the concentration of stachyose increased.2. We have established the model of hyperacute rejection of in vitro perfusion pig heart successfully.3. The survival time of human blood plus stachyose group were longer than control group. The mean time of perfusion hearts in human blood group was (9.5±2.5) min while in human blood plus stachyose perfusion group was (46.8±8.1) min.4. Histopathological studies showed that haemorrhagia, edema, necrosis of endothelial cell, distension of blood vessel were found in human blood perfusion group while there were no obvious pathological changes in human blood plus stachyose group.5. Immunohistochemistry studies also indicated there were obvious deposit of IgG and IgM in human blood perfusion group while in human blood plus stachyose perfusion group no deposit of IgG or IgM were found.Conclusion: Stachyose can competitively bind to natural anti-Gal antibody in human blood, inhibit hyperacute rejection. Stachyose can protect PIEC and pig heart from hyperacute rejection.ObjectiveAllotransplantation, as the most effective measure to end-stage organ failure, has resulted in shortage of organs. Attention has been drawn towards xenotransplantation. Xenotransplantation from pig to human is a potential solution to the worldwide shortage of organs. However, it has many immunology barriers. The imcompatibility of blood type between human and pig may be the reason to failure of organ xenotransplantation, in addition to hyperacute rejection, acute vascular rejection and chronic rejection. The objective of this article was to determine the ABO blood antigen on pig erythrocyte.Methods1. Determine A or B antigen on pig erythrocyteEmploy the method of cell agglutination. Pig erythrocyte and anti-A or anti-B was added to the agglutination plates. The agglutination of pig erythrocyte was visible when erythrocyte distributed on the bottom of the wells to form blood dumps. While erythrocyte precipitated as a small dot as no agglutination happened, which proved that no corresponding antigen was on erythrocyte.2. Determine anti-A or anti-B in plasma of pigEmploy the method of reverse typing to determine the blood antibody in plasma of pig. The plasma of pig was pre-absorbed with packed human type O erythrocyte to remove non-specific binding from anti-human heteroagglutinins.Results1. Detection of the A or B antigen on the surface of porcine erythrocytesWe did not found the blood antigen on pig erythrocyte (n=72).2. Determine anti-A or anti-B in plasma of pigWe determined anti-A or anti-B antibodies in plasma of 72 pigs. 37 pigs were found both anti-A and anti-B antibodies, 14 pigs were found anti-A antibodies, only 3 pigs were found anti-B antibodies, and 18 pigs were found neither anti-A nor anti-B antibodies.ConlusionFrom our experiments, we have demonstrated:Although pig erythrocytes do not express ABO blood antigen which is similar with human, blood group antibodies are in the plasma of pig. We have determined plasma of 72 pigs, 51.4% was found anti-A and anti-B antibody in their plasma; 19.4 was found anti-A antibody; 4.2% was found anti-B antibody; 25% was found neither anti-A nor anti-B antibody.