Effect of Hyperkalemia and Hemolysis Caused by Hyperacute Rejection on Cardiac Function in Pig to Human Ex Vivo Xenogeneic Cardiac Perfusion Model

BACKGROUND AND OBJECTIVES: Hyperacute rejection (HAR) is a major obstacle to successful xenotransplantation of vascularized organs. This study was conducted to observe the effect of hemolysis of perfused human whole blood on pig heart function, and determine the major risk factors for preservation of xenoperfused cardiac function using ex-vivo pig to human xenogeneic cardiac perfusion model. MATERIALS AND METHODS: Harvested pig hearts were perfused with normal human whole blood (group 1), two different types of pre-treated human whole blood (group 2: immunoglobulins were depleted by plasmapheresis, group 3: pre-treated with plasmapheresis, GAS914, cobra venom factor (CVF) and steroid), and normal porcine whole blood as control (group 4) for 3 hours. RESULTS: Duration of heart beat was significantly prolonged in group 2 and group 3. Histological examination showed widespread HAR features but was gradually delayed in groups 2 and 3 compared to group 1. The absolute levels of serum creatine kinase-MB and Troponin I increased gradually, and was lower in group 3. Serum hemoglobin levels were rapidly increased in groups 3 and 4, compared to group 1. Extracellular potassium level increased sharply from the beginning of blood perfusion in groups 1, 2 and 3, compared to group 4. CONCLUSION: Pretreatment of human whole blood, including immunoglobulin depletion, CVF and steroid reduced and delayed the destruction of pig myocardium by HAR. However, the increased extracellular potassium levels in groups 1, 2 and 3 reflected that these treatments could not prohibit myocardial injury by HAR.

Mechanism of Humoral and Cellular Immune Modulation Provided by Porcine Sertoli Cells

The understanding of main mechanisms that determine the ability of immune privilege related to Sertoli cells (SCs) will provide clues for promoting a local tolerogenic environment. In this study, we evaluated the property of humoral and cellular immune response modulation provided by porcine SCs. Porcine SCs were resistant to human antibody and complement-mediated formation of the membrane attack complex (38.41+/-2.77% vs. 55.02+/-5.44%, p=0.027) and cell lysis (42.95+/-1.75% vs. 87.99 +/-2.25%, p<0.001) compared to immortalized aortic endothelial cells, suggesting that porcine SCs are able to escape cellular lysis associated with complement activation by producing one or more immunoprotective factors that may be capable of inhibiting membrane attack complex formation. On the other hand, porcine SCs and their culture supernatant suppressed the up-regulation of CD40 expression (p<0.05) on DCs in the presence of LPS stimulation. These novel findings, as we know, suggest that immune modulatory effects of porcine SCs in the presence of other antigen can be obtained from the first step of antigen presentation. These might open optimistic perspectives for the use of porcine SCs in tolerance induction eliminating the need for chronic immunosuppressive drugs.

Role of Complement Regulatory Proteins in the Survival of Murine Allo-transplanted Sertoli Cells

Sertoli cells (SC) are known to contain immunoprotective properties, which allow them to survive as allografts without the use of immunosuppressive drugs. Experiments were designed to determine which factors are related to prolonged survival of allogeneic SC. Balb/c derived Sertoli (TM4) and colon cancer (CT-26) cell lines were implanted beneath the kidney capsule of non-immunosuppressed C57BL/6 mice and compared their survival as allografts. Compared to TM4 graft, which survived more than 7 days after transplantation, CT-26 showed massive infiltration of polymorphonuclear cells, necrosis and enlargement of draining lymph nodes. Cultured cell lines showed no differences in their expression patterns of FasL, TGF beta1, clusterin and two complement regulatory proteins (CRP, i.e., membrane cofactor protein, MCP; decay accelerating factor, DAF), but protectin (CD59), another member of CRP was expressed only on TM4. These results suggest that CD59 and unknown factors may contribute to the prolonged survival of SC in non-immunoprivileged sites.