: Background: In previous studies we have shown that pre‐transplant hamster blood transfusion (HBT) can induce non‐responsiveness in the T cell independent immunecompartment and result in tolerance ...towards hamster cardiac xenografts (Xgs) in T cell deficient athymic nude rats. In this study we test the combination of pre‐transplant HBT with cyclosporin A (CSA) in immunocompetent Lewis rats.
Methods: Before transplantation of a hamster cardiac Xg, 1 ml hamster blood was administered to nude rats or Lewis rats. CSA dissolved in olive oil was given orally at varying doses. Anti‐hamster antibodies were measured by flowcytometry.
Results: In nude rats HBT 3 days before transplantation resulted in 100% long‐term survival >100 days (n = 9). In Lewis rats, HBT resulted in hyperacute rejection (HAR) (n = 6). Treatment of nude rats with CSA at doses varying from five to 20 mg/kg/day and treatment of Lewis rats with CSA five or 10 mg/kg/day did not effect Xg survival. However, treatment of Lewis rats with CSA 20 mg/kg/day led to long‐term survival of five of nine Xgs (p < 0.01). Combination of HBT with CSA 10 mg/kg/day in Lewis rats resulted in long‐term survival of four of seven Xgs. HBT and CSA 20 mg/kg/day resulted in 100% long‐term survival (n = 9). Immunoglobulin M (IgM) increased after HBT and CSA in these Lewis rats, but decreased after transplantation and remained low over time. When CSA was discontinued, IgM increased and Xgs were rejected (n = 3).
Conclusions: This study confirms that pre‐transplant HBT results in long‐term survival of hamster cardiac Xgs in nude rats. HBT and CSA have strong synergistic effects in immunocompetent Lewis rats. Combination of HBT with CSA treatment leads to long‐term Xg survival in Lewis rats, whereas HBT alone results in HAR. The presence of T cells has a dominant influence on Xg survival after pre‐transplant blood transfusion.
Apoptosis is thought to occur during immune-mediated acute rejection of cardiac allografts. In vitro studies have shown that zinc inhibits the activity of the proapoptotic enzyme caspase-3. We ...hypothesized that ZnCl(2) would reduce acute cardiac rejection in vivo via the blockade of caspase-3-dependent apoptosis. (99m)Tc-labeled annexin V was used to measure apoptosis in cardiac allografts through nuclear imaging. Annexin V binds to phosphatidylserines, which are externalized to the outer membrane of apoptotic cells.
Twenty-seven PVG rat hearts were transplanted heterotopically into the abdomen of untreated ACI rats as controls (group 1). Fifteen were scanned and euthanized on postoperative day 4, and 12 were assessed for graft survival. Group 2 and 3 rats (n=15 each) received 1 and 5 mg/kg ZnCl(2) BID IP, respectively. Nine of each of these groups were scanned and euthanized on postoperative day 4, and 6 were studied for allograft survival. Group 4 rats (n=3) received isografts. Region-of-interest analysis demonstrated a dose-dependent reduction in (99m)Tc annexin uptake in ZnCl(2)-treated allografts: 2.43+/-0.37% for group 1, 1. 97+/-0.41% for group 2, 1.21+/-0.47% for group 3, and 0.55+/-0.19% for group 4 (ANOVA, P:=0.001). Graft survival times of 6.4+/-1.7, 9. 3+/-3.0, and 11.5+/-3.4 days for groups 1, 2, and 3, respectively, were also observed (ANOVA, P:=0.001). Caspase-3 activity in the allografts showed a 3.7-fold reduction in group 3 animals compared with group 1 animals (P:=0.004).
Apoptosis that occurs in acute cardiac allograft rejection is reduced with ZnCl(2) in a dose-dependent manner via caspase-3 inhibition.
Nitric oxide (NO) limits the development of graft coronary artery disease (GCAD) in transplanted hearts. We hypothesized that l-arginine polymers administered to cardiac allografts ex vivo would ...translocate across vascular cellular membranes, up-regulate inducible nitric oxide synthase (iNOS) production of NO, and inhibit the development of GCAD.
Three groups of PVG rat donor hearts were incubated with either 0.8 ml phosphate-buffered saline, (PBS, n=12) or 50 microM L-arginine polymer solutions of length five (R5, n=12) or nine (R9, n=12) prior to heterotopic transplantation into ACI recipients. Graft vessels were scored at POD 60 and 90 for percentage luminal narrowing (%LN), intima to media ratio (I/M), and percentage affected vessels (%AV). Translocation efficiency was determined by treatment with biotinylated polymers. NO production of treated aortic segments was determined in vitro by Griess reaction.
Translocation efficiencies were 89+/-19% (R9), 7+/-10% (R5), and 0+/-0% PBS (ANOVA, P<0.001) which corresponded to NO production in treated aortic segments of 0.175+/-0.17 (R9), 0.120+/-0.006 (R5), and 0.135+/-0.035 microM/mg (PBS), (ANOVA, P=0.002). GCAD scores at POD 60 were: %LN: 3.2+/-3.8% (R9), 12.6+/-6.7% (R5), 11.3+/-4.2% (PBS) (ANOVA, P=0.025); I/M: 0.03+/-0.04 (R9), 0.13+/-0.07 (R5), 0.12+/-0.05 (PBS) (ANOVA, P=0.037); %AV: 7+/-7% (R9), 19+/-7%(R5), 22+/-9%(PBS) (ANOVA, P=0.021). Reduction of GCAD parameters was maintained at POD 90.
R9 efficiently translocated across cytoplasmic membranes, enhanced vascular NO production, and decreased neointimal hyperplasia. This ex vivo treatment may have a therapeutic role in preventing GCAD.
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