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

Abstract: 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 μg/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 Galα1‐3Gal xenoantigen (αGal) from porcine lung which had been perfused and retained for 30 min with human blood was assessed by enzyme‐linked immunosorbent assay using αGal‐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 αGal 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.     

The Role of Antibodies and Von Willebrand Factor in Discordant Pulmonary Xenotransplantation

Pulmonary xenotransplantation is one potential solution to the paucity of donors but is currently limited by rapid failure of the graft. Unlike cardiac and renal xenotransplants, pulmonary xenografts release large quantities of swine von Willebrand factor (vWF). Swine vWF binds xenoreactive antibodies and is capable of activating primate platelets. The contribution of swine vWF to lung xenograft dysfunction is not entirely clear. To probe the role vWF plays in xenograft dysfunction, we traced the fate of xenoantibodies in vWF+ and von Willebrand factor-deficient (vWFD) swine lungs. These studies showed that the vast majority of xenoantibodies bind the vWF released from the vWF+ swine lung, and thus do not remain bound on lung endothelium. The vWF complexed to xenoantibody remained capable of aggregating primate platelets. With this information, we performed swine-to-baboon lung transplants using vWF+ and vWFD donors. Without vWF present to complex xenoantibodies, a picture of hyperacute rejection more typical of heart and kidney xenografts, with antibody deposition along the graft endothelium, interstitial hemorrhage, and edema occurred. These findings suggest that porcine vWF plays a major role in the pathogenesis of pulmonary xenograft dysfunction, and suggests promising strategies to treat lung xenograft dysfunction.     

清除补体避免猪到猕猴异种心脏移植超急性排斥反应的实验研究

目的 观察纯化的眼镜蛇毒因子(CVF)对猪到狱猴异种心脏移植超急性排斥反应的影响。方法 以幼猪为供者，施行猪到狱猴腹腔内异位心脏移植，实验组(n＝4)使用CVF完全清除受者体内补体，对照组(n＝5)不使用CVF，两个组术后均采用环抱素A、甲泼尼龙和环磷酰胺抑制排斥反应，通过检测血清C3、C4水平及总补体活性验证CVF的效果，移植心停跳时切取移植心进行病理检查。结果 在使用CVF后，实验组血清C3降为0，总补体活性CH50值也几乎为0，末发现明显毒副反应，移植猪心存活时间平均为lld，最长达13d，病理学提示均发生了延迟性异种排斥反应；对照组3个移植心在移植后60min内发生超急性排斥反应，另2个分别存活22h及6d。结论 纯化的CVF有良好的清除补体的作用，且末见明显副作用；使用CVF可克服猪到狱猴异种心脏移植超急性排斥反应的发生。     

中华眼镜蛇蛇毒因子在豚鼠—大鼠异种心脏移植中的作用

目的 应用中眼镜蛇蛇毒因子（CVF）消耗补体,观察豚鼠心脏在移植入Wistar大鼠腹腔内后对超急性排斥反应的变化。方法 按0．2μg/g体重CVF大鼠腹腔内分两次间隔6小时注射,18小时后进行心脏移植。脾切除及腹腔内注射环磷酰胺（Cy）均在移植前一天进行。设计分为四组：A组为对照组,不用任何药物;B组仅用CVF;C组应用CVF＋Cy＋脾切除;D组Cy＋脾切除。Cy的用量为60mg/kg体重腹腔内注射。检测各组受体的供心存活时间,并在供心停跳后取出行光镜、电镜检查。结果 A、B、C、D各组供心存活时间分别为15－3120分钟。供心存活时间的统计学分析：A组与B、C两组比较P值＜0．01,A组与D组比较,B组与C组比较P值＞0．05,B组与D组比较,C组与D组比较P值＜0．01。光镜、电镜结果提示：B、C组与A、D组有明显不同。结论 CVF能明显抑制补体活性,减轻或延缓超急性排斥反应的发生,使供体器官存活时间延长。CVF具有异种器官移植的基础研究和临床开发意义。     

The role of antibodies in dysfunction of pig-to-baboon pulmonary transplants

OBJECTIVE: Pulmonary transplantation has become the preferred treatment for end-stage lung disease, but application of the procedure is limited because of a paucity of donors. One way to solve donor limitations is to use animal organs as a donor source or xenotransplantation. The current barrier to pulmonary xenotransplantation is the rapid failure of the pulmonary xenograft. Although antibodies are known to play a role in heart and kidney xenograft rejection, their involvement in lung dysfunction is less defined. This project was designed to define the role of antibodies in pulmonary graft rejection in a pig-to-baboon model. METHODS: Orthotopic transgenic swine left lung transplants were performed in baboons depleted of antibodies by one of three techniques before transplantation: (1) ex vivo swine kidney perfusion, (2) total immunoglobulin-depleting column perfusion, and (3) ex vivo swine lung perfusion. Results were compared with those of transgenic swine lung transplants in unmodified baboons. RESULTS: All three techniques of antibody removal resulted in depletion of xenoreactive antibodies. Only pretransplantation lung perfusion improved pulmonary xenograft function compared with lung transplantation in unmodified baboons. CONCLUSIONS: The pathogenesis of pulmonary injury in a swine-to-primate transplant model is different from that in renal and cardiac xenografts. Depletion of antibodies alone does not have a beneficial effect and may actually be detrimental.     

Prolonged Function of Macrophage, von Willebrand Factor-Deficient Porcine Pulmonary Xenografts

Porcine von Willebrand factor (vWF) activates human and primate platelets. Having determined the importance of pulmonary intravascular macrophages (PIMs) in pulmonary xenotransplantation, we evaluated whether, in the absence of PIMs, vWF might play a role in pulmonary xenograft dysfunction. Utilizing a left single-lung transplant model, baboons depleted of anti-alphaGal antibodies received lungs from either vWF-deficient (n = 2); MCP-expressing (n = 5); MCP PIM-depleted (n = 5); or vWF-deficient PIM-depleted swine (n = 3). Two out of three of the PIM-depleted, pvWF deficient grafts survived longer than any previously reported pulmonary xenografts, including PIM-depleted xenografts expressing human complement regulatory proteins. Depletion of PIM's from vWF-deficient lungs, like depletion of PIM's from hMCP lungs, resulted in abrogation of the coagulopathy associated with pulmonary xenotransplantation. Thus, in terms of pulmonary graft survival, control of adverse reactions involving pvWF appears to be equally or even more important than is complement regulation using hMCP expression. However, based on the rapid failure of PIM-sufficient, pvWF-deficient pulmonary xenografts, pVWF-deficient pulmonary xenografts appear to be particularly sensitive to macrophage-mediated damage. These data provide initial evidence that vWF plays a role in the 'delayed' (24 h) dysfunction observed in pulmonary xenotransplantation using PIM depleted hMCP organs.     

Hyperacute rejection is attenuated in GalT knockout swine lungs perfused ex vivo with human blood

BACKGROUND: Hyperacute rejection (HAR) is one of the principal obstacles to successful xenotransplantation. Homozygous alpha-1,3-galactosyltransferase knockout (GalT-KO) miniature swine now offer the prospect of overcoming this barrier to xenotransplantation. In this study, the short-term function of GalT-KO swine lungs was evaluated in a well-established ex vivo model of swine-to-human lung xenotransplantation. METHODS: Lungs from homozygous GalT-KO swine (n = 3) and control lungs from pigs of the background strain used to create the GalT-KO pig line (n = 2) were perfused ex vivo with freshly collected heparinized human blood. Graft function was assessed by various physiologic measurements, serial histologic and immunohistochemical evaluation, and assays of complement and platelet activation. RESULTS: Xenoperfused control swine lungs exhibited HAR with graft survival times <5 minutes. In contrast, GalT-KO swine lungs retained their function for approximately 2 hours, on average. GalT-KO swine lungs showed decreased complement and platelet activation compared with controls. Nonetheless, activation of complement and coagulation cascades was not completely eliminated in the GalT-KO swine lungs. CONCLUSIONS: The survival of xenoperfused GalT-KO swine lungs was significantly prolonged, as compared with control lungs expressing Gal. This appears to have been due largely to substantially reduced complement activation. Nonetheless, the xenoperfused GalT-KO lungs still showed some evidence of complement fixation and intravascular coagulopathy by the time of graft demise.     

Effect of an anti-C5a monoclonal antibody indicates a prominent role for anaphylatoxin in pulmonary xenograft dysfunction

BACKGROUND: In contrast to renal or cardiac xenografts, the inhibition of complement using cobra venom factor (CVF) accelerates pulmonary xenograft failure. By activating C3/C5 convertase, CVF depletes complement while additionally generating C5a and other anaphylatoxins, to which pulmonary xenografts may be uniquely susceptible. The current study investigates the role of C5a in pulmonary xenograft failure in baboons. METHODS: Left orthotopic pulmonary xenografts using swine lungs expressing human CD46 were performed in baboons receiving: I) no other treatment (n=4), II) immunodepletion (n=5), and III) immunodepletion plus a single dose of mouse anti-human C5a monoclonal antibody (anti-C5a, 0.6 mg/kg administered intravenously) (n=3). The extent to which anti-C5a inhibits baboon C5a was assessed in vitro using a hemolytic reaction involving baboon serum and porcine red blood cells and by ELISA. RESULTS: Baboons in Group III exhibited significantly prolonged xenograft survival (mean=722+/-121 min, P=0.02) compared to baboons in Group I (mean=202+/-24 min) and Group II (mean=276+/-79 min). Furthermore, baboons in Groups I and II experienced pronounced hemodynamic compromise requiring inotropic support whereas those in Group III remained hemodynamically stable throughout experimentation without the need for additional pharmacologic intervention. CONCLUSIONS: These findings indicate that C5a exacerbates pulmonary xenograft injury and compromises recipient hemodynamic status. Moreover, blockade of anaphylatoxins, such as C5a, offers a promising approach for future investigations aimed at preventing pulmonary xenograft injury in baboons.     

延长非协调性异种心脏移植存活时间的研究

目的 寻找延长非协调性异种心脏移植存活时间的方法。方法 实验分Ａ、Ｂ、Ｃ、Ｄ４组,将异种心脏（豚鼠－大鼠）移植于颈部。Ａ组：移植前受体用眼镜蛇蛇毒因子（ＣＶＦ）１５０ｕｇ．ｋｇ－１．ｄ＾－１,腹膜腔内注射（ｉ．ｐ）,每天分２次,相隔３ｄ,共４次;Ｂ组：在Ａ组的基础上,移植前１ｈ加用己酮可可碱（ＰＴＸ）５０ｍｇ／ｋｇ（ｉ．ｐ）,然后每隔６ｈ按２５ｍｇ／ｋｇ（ｉ．ｐ）至发生排斥反应为止;Ｃ组：在Ａ组的     

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

Abstract: 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‐α‐ 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.     

蛇毒因子、全身照射、胸腺修饰预处理受者对异种小动物心脏移植的作用

目的　利用眼镜蛇蛇毒因子 (CVF)、全身照射 (WBI)、异基因胸腺修饰等途径预处理受者 ,探讨这些处理对非协调性异种心脏移植物存活期及免疫排斥反应的影响。方法　供者为三色豚鼠 ,受者为SD大鼠 ,随机配对分成空白组 (O组 ) ;单用CVF的对照组 (A组 ) ;CVF +全身照射组 (B组 ) ;CVF +全身照射 +胸腺注射组 (C组 )。各组分别行大鼠腹腔内异位异种心脏移植术。观察各组供心存活时间及排斥后的光镜及电镜表现。结果　 (1)存活时间 :B组、C组和A组均较O组明显延长 (P <0 .0 1) ;B组和C组又较A组明显延长 (P <0 .0 5 ) ;但C组与B组比较 ,差异无显著性 (P >0 .0 5 )。 (2 )病理表现 :O组呈超急性排斥反应 ,另三组均呈延迟性异种排斥改变。结论　在本模型中 ,使用CVF可克服超急性排斥反应 ,联用全身照射可进一步延长供心存活时间 ;但在此基础上加用异基因胸腺修饰对延长供心存活时间无显著意义。     

Disseminated intravascular coagulation in association with pig-to-primate pulmonary xenotransplantation

BACKGROUND: Profound coagulopathy has been proposed as a barrier to xenotransplantation. Disseminated intravascular coagulation (DIC) has been observed with the rejection of renal and bone marrow xenografts but has not yet been described in pulmonary xenografts. METHODS: This study examined the coagulation parameters in five baboons that received pulmonary xenografts and one baboon that was exposed to porcine lung during an extracorporeal perfusion. Platelet counts, prothrombin times (PT), and levels of fibrinogen, D-dimers, and thrombin-antithrombin III complex (TAT) were analyzed. In addition, serum levels of plasminogen activator inhibitor-1 (PAI-1), thrombomodulin (TM), tissue plasminogen activator (tPA), and tissue factor (TF) were determined. RESULTS: Hyperacute pulmonary xenograft dysfunction, which occurred within 0-9 hr of graft reperfusion, was associated with clinically evident DIC. This coagulopathy was characterized by thrombocytopenia, decreased fibrinogen levels, elevations in PT, and increases in D-dimers and TAT. Furthermore, transient increases in PAI-1, increases in TM, and increases in tPA were observed in the serum of some but not all recipients. None of the baboons demonstrated measurable increases in soluble TF. CONCLUSIONS: Although DIC in renal or bone marrow xenotransplantation develops over a period of days, DIC associated with hyperacute pulmonary xenograft dysfunction develops within hours of graft reperfusion. Thus, the DIC in pulmonary xenotransplantation may represent a unique and/or accelerated version of the coagulopathy observed with renal and bone marrow xenotransplantation.     

Prevention of acute lung injury in swine: depletion of pulmonary intravascular macrophages using liposomal clodronate

BACKGROUND: Swine contain large numbers of pulmonary intravascular macrophages (PIMs) that mediate the physiological response observed in acute lung injury (ALI). As the hyperacute dysfunction observed in pulmonary xenotransplantation is similar to endotoxin-induced ALI, PIMs may play a critical role in pulmonary xenograft dysfunction. We used liposomal clodronate to eliminate the PIM population in a model of acute swine lung injury. MATERIALS AND METHODS: Experimental swine (n = 6) received liposomal clodronate (1.25 g/10 kg) and control swine (n = 5) received saline containing liposomes before infusion of lipopolysaccharide (450 ng/kg). RESULTS: Control swine demonstrated higher peak pulmonary artery pressures (41.8 +/- 2.2 versus 16.8 +/- 1.2 mm Hg; P < 0.0001) and higher peak pulmonary vascular resistances (1405 +/- 209 versus 353 +/- 81 dynes. s. cm(-5); P = 0.0016) in response to lipopolysaccharide infusion. Clodronate treated swine also had significantly lower serum levels of tumor necrosis factor-alpha, interleukin-6, and thrombin. CONCLUSIONS: Liposomal clodronate effectively attenuates acute swine lung injury induced by endotoxin. This method of depletion of the PIM population presents a promising new treatment of swine lungs before xenotransplantation.     

Accommodation after lung xenografting from hamster to rat

BACKGROUND: Long-term xenograft survival can be achieved in hamster hearts transplanted into rats treated with cobra venom factor (CVF) and cyclosporine A (CsA). This phenomenon of "accommodation" is associated with expression of protective genes such as bcl-2, bcl-X(L), and heme-oxygenase-1. We examined whether accommodation could be induced in hamster-to-rat lung xenografts and whether the pattern of protective genes is similar to cardiac xenografts. METHODS: We used hamster-to-rat cardiac and lung xenotransplantation models. Cardiac xenotransplants were treated with CVF+CsA and compared with untreated controls. Lung xenotransplants were treated with either CVF+CsA or FK506 and cyclophosphamide (Cp) and compared with untreated controls. All recipients were killed by 21 days after transplantation. We examined graft survival and protein expression of protective genes, and we performed histologic and immunohistologic analyses. RESULTS: Rejection occurred rapidly in untreated rats. CVF+CsA or FK506+Cp treatment significantly influenced graft survival. Eight of 12 CVF+CsA-treated heart transplants survived 21 days. Seven of 16 CVF+CsA-treated lung grafts and five of 12 FK506+Cp-treated lung xenografts survived 21 days. We observed significant protein expression of bcl-2, bcl-X(L), and heme-oxygenase-1 in cardiac xenografts treated with CVF+CsA at 2, 14, and 21 days after transplantation, compared with normal hamster hearts. We also observed significant expression of these proteins in lung xenografts treated with either CVF+CsA or FK506+Cp at 21 days after transplantation, compared with normal lungs. CONCLUSIONS: Accommodation may be a general phenomenon for all organs, mediated through protective genes. Induction of accommodation does not require disruption of the complement system.     

O-linked glycosylation and functional incompatibility of porcine von Willebrand factor for human platelet GPIb receptors

BACKGROUND: Xenograft rejection is associated with vascular inflammation, thrombocytopenia and the accelerated consumption of coagulation factors. Primary biological incompatibilities of the xenograft in the regulation of clotting appear to amplify pathological processes associated with rejection. The functional incompatibility of porcine von Willebrand factor (vWF) expressed within the xenograft vasculature may heighten interactions with the primate platelet receptor GPIb, hence augmenting formation of platelet microthrombi and vascular injury. Here, we address the functional impact of O-linked glycosylation of the vWF A1 domain on primate platelet activation. METHODS: Recombinant human or porcine vWF A1-domains were transiently over-expressed in COS-7 cells as FLAG-tagged fusion protein, linked to plasma membranes via GPI anchors. O-linked glycosylation was blocked by the addition of phenyl-alpha-GalNAc2 to cultures. Expressed vWF-A1 domains were characterized utilizing cytofluometric- and Western blot analyses. RESULTS: Cytofluometric analysis confirmed equivalent levels of human and porcine vWF A1-domain expression irrespective of the levels of O-linked glycosylation. Differential glycosylation patterns of vWF-A1 under these conditions were confirmed by Western blot analyses. Native porcine vWF A1-domains had enhanced human platelet activation potential when compared with human recombinant vWF A1. However, the loss of O-linked glycosylation abolished differences in aggregatory responses between human and porcine vWF A1 domains. CONCLUSIONS: Various degrees of O-linked glycosylation of vWF-A1-domains modulate levels of functional interaction with platelet receptor GPIb and consequent platelet aggregation responses in vitro. These data may have implications for outcomes of xenotransplantation. We speculate that alterations in glycosylation of vWF and other adhesion proteins associated with the targeting of the alpha1,3-Gal-epitope in mutant swine may have salutatory effects on the primate platelet activation observed in these xenografts.     

Donor‐derived infections and infectious risk in xenotransplantation and allotransplantation

Post‐transplantation infections are common in allograft recipients and should be expected in all immunocompromised hosts. Based on the need for immunosuppression in xenotransplantation, procedures developed to enhance safety in allotransplantation can be applied in future xenotransplantation clinical trials. Standardized approaches can be developed to guide the evaluation of common infectious syndromes in xenograft recipients. The opportunity created by screening of swine intended as xenograft donors has equal applicability to allotransplantation—notably broader screening strategies for allograft donors such as use of advanced sequencing modalities including broad‐range molecular probes, microarrays, and high‐throughput pyrosequencing. Considerations in management of allotransplant‐ and xenotransplant‐associated infections are largely the same. Experience in xenotransplantation will continue to inform thinking regarding donor‐derived infections in allotransplantation. We expect that experience in managing complex allotransplant recipients will similarly inform clinical trials in xenotransplantation.     

Complement depletion in a porcine model of septic acute respiratory disease

In a porcine model of severe septic acute respiratory failure produced by continuous infusion of live Pseudomonas aeruginosa, the role of the complement system was studied by pretreating animals with cobra venom factor (CVF) to deplete C3. Three groups of spontaneously breathing animals were monitored with Swan-Ganz and arterial thermodilution catheters. Group I was pretreated with 80 U/kg of CVF iv 16-18 hours before testing. Group II received Ps. aeruginosa iv (2 X 10(8)/20 kg/minute). Group III was pretreated with CVF and later given the Pseudomonas infusion. The CH50 as a measure of complement activity was less than 7% of normal level in Groups I and III. No changes in respiratory variables occurred in Group I. In Group II, the mean pulmonary artery pressure doubled, intrapulmonary shunt fraction (Qs/Qt) increased, PaO2 decreased, and extravascular lung water doubled in 4 hours. In Group III, the pulmonary hypertension, hypoxemia, increase in Qs/Qt, and increase in EVLW were all significantly less than in Group II. Neutropenia occurred with the Pseudomonas infusion in Groups II and III.     

Pig to canine auxiliary hepatic xenotransplantation model: prevention of hyperacute rejection via Kupffer cell blockade and complement regulation

Objectives

Large animal experiment models are a critical prerequisite to preclinical trials. However, the pig-to-primate model is expensive and proper experimental conditions are difficult to establish. Several pig-to-canine lung xenotransplantation experiments have shown hyperacute rejection. Therefore, we designed a pig-to-canine liver xenotransplantation model to study the diverse immunologic and hemodynamic consequences after xenotransplantation and hyperacute rejection.

Methods

Animals were divided into two groups of 3 each: a cobra venom factor plus gadolinium trichloride (GdCl₃) treatment group (CVF+Gd group) and a control group. Whole livers from 15-kg donor pigs were harvested and perfused with histidine-tryptophan-ketoglutarate solution. Seventy percent of the left lobe of the livers of 17-kg recipient dogs was resected. The harvested pig whole liver was transplanted using the canine left hepatic vein, left portal vein, and common hepatic artery. After graft reperfusion, blood samples and aliquots of liver, lung, and kidney tissues were obtained at 1 hour after reperfusion.

Results

We successfully completed 6 pig-to-canine auxiliary hepatic xenotransplantations. In the control group, the grafts showed a patchy hypoperfused liver surface that was rubbery solid compared with the CVF+Gd group. Serum total protein, albumin, fibrinogen, and platelet counts decreased abruptly; however, there were no significant differences between the two groups. There were no identifiable changes in blood urea nitrogen and creatinine concentrations. Serum prothrombin time, partial thromboplastin time, and further degradation product were increased in both groups; however, in the CVF+Gd group, the slope was more obtuse than in the control group. At microscopy, the graft at 20, 40, and 60 minutes after reperfusion, no intravascular pathologic changes were noted. Only scant intravascular fibrin deposition was observed. Hepatocellular vacuolization and sinusoidal dilatation were seen. There was patch necrosis without a zonal distribution, and intrasinusoidal neutrophil sequestration and interstitial hemorrhage. These findings were milder in the CVF+Gd group.

Conclusion

A pig-to-canine partial auxiliary liver xenotransplantation model is feasible. In the CVF+Gd treatment group, pathologic findings of patch hepatocyte necrosis were less severe. Inasmuch there was no corresponding vascular pathologic finding, these abnormalities are not a direct effect of CVF+Gd treatment. Other factors such as ischemia-reperfusion injury should be considered.     

Characterization of a pig-to-goat orthotopic lung xenotransplantation model to study beyond hyperacute rejection.

BACKGROUND: A pig-to-goat orthotopic lung xenograft model was developed to test whether depletion of goat xenoreactive antibodies against pig red blood cells would prolong pig lung xenograft survival. METHODS: Adult goats with anti-pig xenoreactive antibodies underwent left pneumonectomy followed by orthotopic transplantation of pig left lung (group 1) or immunodepletion of their xenoreactive antibodies by extracorporeal right pig lung perfusion before transplantation without (group 2) or with (group 3) complete clampage of the right pulmonary artery. In group 4, goat left lungs were orthotopically transplanted into pigs and served as negative controls (pig serum does not have anti-goat xenoreactive antibodies). Each study group included 5 animals. Immunosuppression in surviving recipients included cyclosporine and azathioprine. RESULTS: Group 1 recipients died 7 +/- 3 hours after xenograft reimplantation of severe pulmonary hypertension and dysfunction and vasogenic shock, with little evidence of histologic xenograft injury. Group 2 xenografts had a stable circulatory and respiratory function on reperfusion and survived 9 +/- 4 days. Group 3 animals also tolerated complete occlusion of the right pulmonary artery, and xenografts assured the total respiratory support for 4 +/- 1 days. After immunodepletion, goat serum showed no detectable titers of xenoreactive antibodies, which began to reappear by postoperative day 2, where xenografts showed histologic stigmata of acute (humoral and cellular-mediated) rejection that evolved to a complete xenograft necrose at death. Group 4 xenografts showed scattered features of acute rejection 5 +/- 1 days after the operation. CONCLUSIONS: Pig left lung xenografts can provide prolonged and complete respiratory support after depletion of goat xenoreactive antibodies, but they ultimately necrose once recipient xenoreactive antibodies return to pretransplantation values.     

Complement depletion with cobra venom factor delays acute cell‐mediated rejection in pig‐to‐mouse corneal xenotransplantation

Oh JY, Kim MK, Lee HJ, Ko JH, Kim Y, Park CS, Kang HJ, Park CG, Kim SJ, Lee JH, Wee WR. Complement depletion with cobra venom factor delays acute cell‐mediated rejection in pig‐to‐mouse corneal xenotransplantation. Xenotransplantation 2010; 17: 140–146. © 2010 John Wiley & Sons A/S. Abstract: Background: We have demonstrated earlier that porcine corneal xenografts underwent an acute cell‐mediated rejection in mice despite the absence of T cells. In the present study, we investigated the effect of complement depletion by cobra venom factor (CVF) on the corneal xenograft rejection in a pig‐to‐mouse model. Methods: Porcine corneas were orthotopically transplanted into C57BL/6 (B6) and severe combined immunodeficiency (SCID) mice. For complement depletion, 25 μg of CVF (1 g/kg bodyweight) was injected intraperitoneally on the day before and 1, 3, 5, and 7 days after transplantation. Graft survival was clinically assessed by slit lamp biomicroscopy and the median survival time (MST) was calculated. The grafts were histologically evaluated serially after transplantation using antibodies against CD4, CD8, NK1.1, and F4/80. Results: The CVF treatment significantly prolonged the porcine corneal xenograft survival in both B6 (MST 9.4 vs. 15.5 days; P = 0.0011) and SCID mice (MST 16.4 vs. 20.5 days; P = 0.0474). Histologically, whereas macrophages and CD4⁺ T cells were progressively infiltrated into porcine corneal grafts in CVF‐untreated B6 mice, the infiltration by both cells was markedly delayed and decreased in the xenografts in CVF‐treated B6 mice. Likewise, macrophage infiltration, which was prominent in rejected porcine xenografts in SCID mice, was also reduced in CVF‐treated SCID mice. Conclusions: Our results suggest that complement depletion by CVF delayed, although did not prevent, an acute cell‐mediated rejection in a pig‐to‐mouse corneal xenotransplantation.