Pre-treatment of porcine pulmonary xenograft with desmopressin: a novel strategy to attenuate platelet activation and systemic intravascular coagulation in an ex-vivo model of swine-to-human pulmonary xenotransplantation.

BACKGROUND: Von Willebrand factor (vWF) has been proposed as a major contributor to the development of coagulopathy in pulmonary xenotransplantation. Pretreatment of donor swine with 1-deamino-8-d-arginine vasopressin (DDAVP), an analog of vasopressin, can reduce the content of vWF in pulmonary xenografts. Here, we investigate the effects of DDAVP pre-treatment in an ex-vivo perfusion model of pulmonary xenotransplantation. METHODS: We set up and performed the ex-vivo perfusion using porcine pulmonary accessory lobes and fresh human whole blood (n = 12). Half of the donor swine were given 3 mug/kg DDAVP intravenously for 3 days before ex-vivo perfusion (DDAVP group) and half of them were left untreated (control group). The porcine lung was perfused with fresh blood for 1 h and changes in the following parameters were monitored: pulmonary arterial pressure, pulmonary vascular resistance, blood cell counts, fibrinogen, antithrombin, platelet factor 4, D-dimer, C3a, C4d, and xenoreactive IgM. The release of Galalpha1-3Gal xenoantigen (alphaGal) from porcine lung which had been perfused and retained for 30 min with human blood was assessed by enzyme-linked immunosorbent assay using alphaGal-binding lectin. RESULTS: Both DDAVP and control groups showed typical findings of immediate pulmonary dysfunction: an increase of pulmonary vascular resistance and sequestration of leukocytes and platelets after ex-vivo perfusion. However, in the DDAVP group, the increase of platelet factor 4, C3a, and C4d after perfusion was attenuated compared to that in the control group. The release of alphaGal after blood retention was significantly lower in the DDAVP group than that of the control group. CONCLUSION: Pre-infusion of DDAVP to the donor swine was beneficial in attenuating platelet activation as well as complement/coagulation activation. These effects of DDAVP are likely to relate to the reduction of porcine vWF content in the xenograft. Therefore, the modulation of vWF secretion in donor lungs could be an additional therapeutic way to reduce systemic coagulopathy in pulmonary xenotransplantation.

Aurintricarboxylic acid inhibits endothelial activation, complement activation, and von Willebrand factor secretion in vitro and attenuates hyperacute rejection in an ex vivo model of pig-to-human pulmonary xenotransplantation.

BACKGROUND: In the xenotransplantation of vascularized organs, such as the lung, a large area of endothelial cell layer is a big hurdle to be overcome. We investigated the potential protective effect of aurintricarboxylic acid (ATA), a known inhibitor of platelet adhesion, on endothelial damage induced by xenogeneic serum. We also assessed its role in hyperacute xenograft rejection using a porcine ex vivo lung perfusion model. METHODS: Porcine endothelial cells were incubated with human serum and other inflammatory stimuli. For the evaluation of von Willebrand factor (vWF) secretion and tissue factor (TF) expression, we used human endothelial cells. E-selectin expression, complement activation, TF expression and platelet activation were investigated by flow cytometry. In an ex vivo porcine lung perfusion model, the porcine lungs were perfused with fresh human whole blood: unmodified blood (n = 5), ATA-treated blood (n = 5), and ATA and lepirudin-treated blood (n = 5). RESULTS: Aurintricarboxylic acid significantly inhibited TNF-alpha- or lipopolysaccharide-induced endothelial E-selectin expression in a dose-dependent manner. ATA also prevented human serum induced-E-selectin expression and human monocytic cell adhesion to porcine endothelial cells. Moreover, ATA abolished thrombin-induced vWF secretion as well as complement activation. However, ATA induced endothelial TF expression and platelet activation in vitro. In ex-vivo experiments, ATA treatment improved pulmonary function and attenuated sequestration of leukocytes. Although ATA did not influence thrombin generation, we were able to minimize its activity by adding lepirudin to the blood with ATA. CONCLUSIONS: Our study demonstrated in vitro protective effect of ATA on the inhibition of endothelial activation and vWF secretion and confirmed detrimental effect of ATA on induction of endothelial TF and platelet activation. The combination of ATA and lepirudin may act beneficially by preventing coagulation perturbation while maintaining improved xenograft survival.

Pre-treatment of donor with 1-deamino-8-d-arginine vasopressin could alleviate early failure of porcine xenograft in a cobra venom factor treated canine recipient.

OBJECTIVE: Unlike cardiac or renal xenotransplants, the depletion of complement using cobra venom factor (CVF) does not improve pulmonary xenograft survival. Several cases suggest that the swine von Willebrand factor (vWF) may play a major role in presenting a different pathogenesis of pulmonary xenograft dysfunction from other organs. To evaluate the role of vWF and the complement system in mediating hyperacute vascular injury of pulmonary xenografts and elucidate pathogenesis of the injury, we performed swine-to-canine orthotropic single lung xenotransplantation after pre-treatment of 1-deamino-8-d-arginine vasopressin (DDAVP) and CVF. METHODS: We set up three groups for lung xenotransplantation: group I served as the control group; group II, recipients pre-treated with CVF; group III, donors pre-treated with DDAVP (9 mg/kg, 3 days)/recipients pre-treated with CVF (60 u/kg). Hemodynamic data, coagulation and complement system parameters, and grafted lung pathologies were examined serially for 3h after transplantation. RESULTS: DDAVP infusion reduced the vWF content in swine lung tissue in vivo (7.7+/-2.4 AU/mg vs 16.0+/-5.6 AU/mg, P < 0.0001). Infusion of CVF 24 h prior to transplantation effectively depleted the recipient's serum C3 and complement hemolytic activity below the detectable range. Regardless of the use of CVF, both groups I and II transplanted with unmodified grafts showed an immediate drop in leukocytes and platelet counts after transplantation. However, in group III, in recipients transplanted with DDAVP pre-treated swine lung, the platelet count did not decrease after transplantation (P = 0.0295). The decrease of plasma antithrombin and fibrinogen tended to be attenuated in group III. Light microscopic examination revealed extensive vascular thromboses in both capillary and larger vessels, as well as early pulmonary parenchymal damage in groups I and II, but were rarely observed in group III. CONCLUSIONS: Complement inhibition alone was not enough to alleviate intravascular thrombosis, the main pathology in pulmonary xenotransplantation. Pre-infusion of DDAVP to the donor animal was effective in preventing platelet sequestration and attenuated intravascular thrombosis. It is suggested that the strategies targeting vWF would be promising for successful pulmonary xenotransplantation.