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Comparison of thrombin generation in transplanted primates recipients of pig hDaf or hDaf-GalT-KO kidney

Claudia Maria Radu¹, Sabrina Gavasso¹, Massimo Boldrin³, Cristiana Bulato¹, Luca Spiezia¹, Andrea Perota⁴, Cesare Galli⁴, Emanuele Cozzi^2,3, Paolo Simioni¹

¹Cardiologic, Thoracic and Vascular Sciences, University of Padua, Padua; ²Surgical and Gastrointestinal Sciences, University of Padua, Padua; ³Consortium for Research in Organ Transplantation (CORIT), Padua; ⁴Istituto Sperimentale Italiano L. Spallanzani, AVANTEA srl, Cremona; Italy

Introduction: Transgenic pigs expressing human complement regulator proteins (hDAF) or lacking expression of α1,3-galactosyltransferase gene (GalT-KO), have been considerated a strategy in preventing hyperacute rejection in xenotransplantation. Vascular injury and microvascular thrombosis are key features of the rejection process. Thrombin plays a central role in haemostasis through both procoagulant and anticoagulant functions. The measure in vitro of thrombin generation has been proposed as a potential relevant marker of in vivo haemostasis.

Aim of the study: To evaluate Thrombin Generation (TG) parameters in kidney transplanted primates who received kidney from hDaf or hDaf-Galt-KO transgenic pigs.

Methods: We studied TG profiles in the two groups of transplanted monkeys before transplantation and at euthanasia. TG assay was performed in poor platelet plasma by Calibrated Automated Thrombogram (Thrombinoscope). TG was triggered using 5pM Tissue Factor and 4µM phospholipids. The parameters detected was Endogenous Thrombin Potential, nM*min (ETP), maximum thrombin Concentration, nM (Cmax) and Lag Time, min (time to clot).

Results: We evaluated TG (mean ±SD) in 10 hDAF and in 8 hDAF-GalT-KO transplanted monkeys (hDAF-M and hDAF-GalT-KO-M). Before transplantation the ETP measured in the two groups was 1971.79±276.79 and 2092.50±693.90 nmol*min (p=ns), respectively; Cmax was 560.12±48 and 474±40 nM (p=ns) and Lag Time was 1.35±0.19 and 2.15±0.33 min (p=0.01), respectively. At euthanasia ETP was 892±260 and 296.48±90.14 nmol*min (p=0.008); Cmax was 240±43.14 nM and 43.50±23.48 (p=0.007) and Lag Time was 2.64±1.6 and 2.15±0.33 min (p=ns), respectively.

Conclusions: Before transplantation there is not significant different in TG in the two groups of transplanted monkeys. At euthanasia, in hDaf-GalT-KO-M we showed a significant decreased in thrombin formation, maybe due to a major consumption of the coagulation factors in comparison to hDAF-M. Data obtained could explain the consumptive coagulopathy observed in these animals, following a massive activation of clotting cascade.