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Background: Normothermic machine perfusion (NMP) is used for the viability assessment of high-risk donor livers before transplantation. The production of hemostatic proteins is one of the major synthetic functions of the liver. The objective of this study was to measure the concentration and functionality of hemostatic proteins concentration in the NMP perfusate of human donor livers., Methods: Thirty-six livers that underwent NMP for viability assessment were included in this study. Perfusate samples taken during NMP (start, 150 min, and 300 min) were used for the measurement of antigen and activity levels of hemostatic proteins (factors II, VII, and X; fibrinogen; plasminogen; antithrombin; tissue plasminogen activator; von Willebrand factor; and proteins induced by vitamin K absence). The antigen levels were correlated with hepatocellular function according to previously proposed individual hepatocellular viability criteria: lactate clearance and perfusate pH., Results: Antigen levels of hemostatic proteins reached subphysiological levels in the NMP perfusate. Hemostatic proteins that were produced during NMP were at least partially active. All livers produced all hemostatic proteins tested within 150 min of NMP. Hemostatic protein concentrations did not significantly correlate with perfusate lactate and perfusate pH after 150 min of NMP., Conclusions: All livers produce functional hemostatic proteins during NMP. The generation of a functional hemostatic system in NMP perfusate confirms the need for adequate anticoagulation of the perfusate to avoid generation of (micro)thrombi that may harm the graft., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Nowadays, the main cause for early graft loss is renal graft thrombosis because kidney transplant outcomes have improved drastically owing to advances in immunological techniques and immunosuppression. However, data regarding the efficacy of antithrombotic therapy in the prevention of renal graft thrombosis are scarce. Adequate antithrombotic management requires a good understanding of the pathophysiological changes in the hemostatic system in patients with end-stage kidney disease (ESKD). Specifically, ESKD and dialysis disrupt the fine balance between pro- and anticoagulation in the body, and further changes in the hemostatic system occur during kidney transplantation. Consequently, kidney transplant recipients paradoxically are at risk for both thrombosis and bleeding. This overview focuses on the pathophysiological changes in hemostasis in ESKD and kidney transplantation and provides a comprehensive summary of the current evidence for antithrombotic management in (adult) kidney transplant recipients., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 The Author(s). Published by Wolters Kluwer Health, Inc.)

Objectives: The Hepatology Committee of the European Society for Pediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) aims to educate pediatric gastroenterologists, members of ESPGHAN and professionals from other specialties promoting an exchange of clinical expertise in the field of pediatric hepatology., Methods: The 2020 single topic ESPGHAN monothematic 3-day conference on pediatric liver disease, was organized in Athens, Greece and was entitled " Acute Liver Failure" (ALF). ALF is a devastating disease with high mortality and in a considerable fraction of patients, the cause remains unresolved. As knowledge in diagnosis and treatment of ALF in infants and children has increased in the past decades, the objective was to update physicians in the field with developments in medical therapy and indications for liver transplantation (LT) and to identify areas for future research in clinical and neurocognitive outcomes in ALF., Results: We recently reported the epidemiology, diagnosis, and initial intensive care management issues in separate manuscript. Herewith we report on the medical treatment, clinical lessons arising from pediatric studies, nutritional and renal replacement therapy (RRT), indications and contraindications for LT, neurocognitive outcomes, new techniques used as bridging to LT, and areas for future research. Oral presentations by experts in various fields are summarized highlighting key learning points., Conclusions: The current report summarizes the current insights in medical treatment of pediatric ALF and the directions for future research., Competing Interests: The authors report no conflicts of interest., (Copyright © 2021 by European Society for Pediatric Gastroenterology, Hepatology, and Nutrition and North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition.)

Objectives: The Hepatology Committee of the European Society for Pediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) aims to educate pediatric gastroenterologists, members of ESPGHAN and professionals from other specialties promoting an exchange of clinical expertise in the field of pediatric hepatology. Herewith we have concentrated on detailing the recent advances in acute liver failure in infants and children., Methods: The 2020 ESPGHAN monothematic three-day conference on pediatric hepatology disease, entitled "acute liver failure" (ALF), was organized in Athens, Greece. ALF is a devastating disease with high mortality and most cases remain undiagnosed. As knowledge in diagnosis and treatment of ALF in infants and children has increased in the past decades, the objective was to update physicians in the field with the latest research and developments in early recognition, curative therapies and intensive care management, imaging techniques and treatment paradigms in these age groups., Results: In the first session, the definition, epidemiology, various causes of ALF, in neonates and older children and recurrent ALF (RALF) were discussed. The second session was dedicated to new aspects of ALF management including hepatic encephalopathy (HE), coagulopathy, intensive care interventions, acute on chronic liver failure, and the role of imaging in treatment and prognosis. Oral presentations by experts in various fields are summarized highlighting key learning points., Conclusions: The current report summarizes the major learning points from this meeting. It also identifies areas where there is gap of knowledge, thereby identifying the research agenda for the near future., Competing Interests: The authors report no conflicts of interest., (Copyright © 2021 by European Society for Pediatric Gastroenterology, Hepatology, and Nutrition and North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition.)

Background: The specific effect of donation after circulatory death (DCD) liver grafts on fibrinolysis, blood loss, and transfusion requirements after graft reperfusion is not well known. The aim of this study was to determine whether transplantation of controlled DCD livers is associated with an elevated risk of hyperfibrinolysis, increased blood loss, and higher transfusion requirements upon graft reperfusion, compared with livers donated after brain death (DBD)., Methods: A retrospective single-center analysis of all adult recipients of primary liver transplantation between 2000 and 2019 was performed (total cohort n = 628). Propensity score matching was used to balance baseline characteristics for DCD and DBD liver recipients (propensity score matching cohort n = 218). Intraoperative and postoperative hemostatic variables between DCD and DBD liver recipients were subsequently compared. Additionally, in vitro plasma analyses were performed to compare the intraoperative fibrinolytic state upon reperfusion., Results: No significant differences in median (interquartile range) postreperfusion blood loss (1.2 L [0.5-2.2] versus 1.3 L [0.6-2.2]; P = 0.62), red blood cell transfusion (2 units [0-4] versus 1.1 units [0-3]; P = 0.21), or fresh frozen plasma transfusion requirements (0 unit [0-2.2] versus 0 unit [0-0.9]; P = 0.11) were seen in DCD compared with DBD recipients, respectively. Furthermore, plasma fibrinolytic potential was similar in both groups., Conclusions: Transplantation of controlled DCD liver grafts does not result in higher intraoperative blood loss or more transfusion requirements, compared with DBD liver transplantation. In accordance with this, no evidence for increased hyperfibrinolysis upon reperfusion in DCD compared with DBD liver grafts was found., Competing Interests: The authors declare no funding or conflicts of interest., (Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc.)

Competing Interests: F.S. received fees from speaker’s bureau of CSL Behring and Werfen but no funding for the article. The other authors declare no funding and conflict of interests.

Objective: The full spectrum of coronavirus disease 2019 (COVID-19) infection ranges from asymptomatic to acute respiratory distress syndrome, characterized by hyperinflammation and thrombotic microangiopathy. The pathogenic mechanisms are poorly understood, but emerging evidence suggest that excessive neutrophil extracellular trap (NET) formation plays a key role in COVID-19 disease progression. Here, we evaluate if circulating markers of NETs are associated with COVID-19 disease severity and clinical outcome, as well as to markers of inflammation and in vivo coagulation and fibrinolysis. Approach and Results: One hundred six patients with COVID-19 with moderate to severe disease were enrolled shortly after hospital admission and followed for 4 months. Acute and convalescent plasma samples as well as plasma samples from 30 healthy individuals were assessed for markers of NET formation: citrullinated histone H3, cell-free DNA, NE (neutrophil elastase). We found that all plasma levels of NET markers were elevated in patients with COVID-19 relative to healthy controls, that they were associated with respiratory support requirement and short-term mortality, and declined to those found in healthy individuals 4 months post-infection. The levels of the NET markers also correlated with white blood cells, neutrophils, inflammatory cytokines, and C-reactive protein, as well as to markers of in vivo coagulation, fibrinolysis, and endothelial damage., Conclusions: Our findings suggest a role of NETs in COVID-19 disease progression, implicating their contribution to an immunothrombotic state. Further, we observed an association between circulating markers of NET formation and clinical outcome, demonstrating a potential role of NET markers in clinical decision-making, as well as for NETs as targets for novel therapeutic interventions in COVID-19.

Objective: Patients with coronavirus disease 2019 (COVID-19) have a high rate of thrombosis. We hypothesized that severe acute respiratory syndrome coronavirus 2 infection leads to induction of TF (tissue factor) expression and increased levels of circulating TF-positive extracellular vesicles (EV) that may drive thrombosis. Approach and Results: We measured levels of plasma EV TF activity in 100 patients with COVID-19 with moderate and severe disease and 28 healthy controls. Levels of EV TF activity were significantly higher in patients with COVID-19 compared with controls. In addition, levels of EV TF activity were associated with disease severity and mortality. Finally, levels of EV TF activity correlated with several plasma markers, including D-dimer, which has been shown to be associated with thrombosis in patients with COVID-19., Conclusions: Our results indicate that severe acute respiratory syndrome coronavirus 2 infection induces the release of TF-positive EVs into the circulation that are likely to contribute to thrombosis in patients with COVID-19. EV TF activity was also associated with severity and mortality.

Background: Preconditioning of donor livers before organ retrieval may improve organ quality after transplantation. We investigated whether preconditioning with metformin reduces preservation injury and improves hepatobiliary function in rat donor livers during ex situ normothermic machine perfusion (NMP) and after orthotopic liver transplantation., Methods: Lewis rats were administered metformin via oral gavage, after which a donor hepatectomy was performed followed by a standardized cold storage period of 4 hours. Graft assessment was performed using NMP via double perfusion of the hepatic artery and portal vein. In an additional experiment, rat donor livers preconditioned with metformin were stored on ice for 4 hours and transplanted to confirm postoperative liver function and survival. Data were analyzed and compared with sham-fed controls., Results: Graft assessment using NMP confirmed that preconditioning significantly improved ATP production, markers for hepatobiliary function (total bile production, biliary bilirubin, and bicarbonate), and significantly lowered levels of lactate, glucose, and apoptosis. After orthotopic liver transplantation, metformin preconditioning significantly reduced transaminase levels., Conclusions: Preconditioning with metformin lowers hepatobiliary injury and improves hepatobiliary function in an in situ and ex situ model of rat donor liver transplantation.

Objective: The aim of this study was to evaluate sequential hypothermic and normothermic machine perfusion (NMP) as a tool to resuscitate and assess viability of initially declined donor livers to enable safe transplantation., Summary Background Data: Machine perfusion is increasingly used to resuscitate and test the function of donor livers. Although (dual) hypothermic oxygenated machine perfusion ([D]HOPE) resuscitates livers after cold storage, NMP enables assessment of hepatobiliary function., Methods: In a prospective clinical trial, nationwide declined livers were subjected to ex situ NMP (viability assessment phase), preceded by 1-hour DHOPE (resuscitation phase) and 1 hour of controlled oxygenated rewarming (COR), using a perfusion fluid containing an hemoglobin-based oxygen carrier. During the first 2.5 hours of NMP, hepatobiliary viability was assessed, using predefined criteria: perfusate lactate <1.7 mmol/L, pH 7.35 to 7.45, bile production >10 mL, and bile pH >7.45. Livers meeting all criteria were accepted for transplantation. Primary endpoint was 3-month graft survival., Results: Sixteen livers underwent DHOPE-COR-NMP. All livers were from donors after circulatory death, with median age of 63 (range 42-82) years and median Eurotransplant donor risk index of 2.82. During NMP, all livers cleared lactate and produced sufficient bile volume, but in 5 livers bile pH remained <7.45. The 11 (69%) livers that met all viability criteria were successfully transplanted, with 100% patient and graft survival at 3 and 6 months. Introduction of DHOPE-COR-NMP increased the number of deceased donor liver transplants by 20%., Conclusions: Sequential DHOPE-COR-NMP enabled resuscitation and safe selection of initially declined high-risk donor livers, thereby increasing the number of transplantable livers by 20%., Trial Registration: www.trialregister.nl; NTR5972.

Background: Ex situ normothermic machine perfusion (NMP) can be used to assess viability of suboptimal donor livers before implantation. Our aim was to assess the diagnostic accuracy of bile biochemistry for the assessment of bile duct injury (BDI)., Methods: In a preclinical study, 23 human donor livers underwent 6 hours of end-ischemic NMP to determine biomarkers of BDI. Livers were divided into groups with low or high BDI, based on a clinically relevant histological grading system. During NMP, bile was analyzed biochemically and potential biomarkers were correlated with the degree of BDI. Receiver operating characteristics curves were generated to determine optimal cutoff values. For clinical validation, identified biomarkers were subsequently included as viability criteria in a clinical trial (n = 6) to identify transplantable liver grafts with low BDI., Results: Biliary bicarbonate and pH were significantly higher and biliary glucose was significantly lower in livers with low BDI, compared with high BDI. The following cutoff values were associated with low BDI: biliary bicarbonate greater than 18 mmol/L (P = 0.002), biliary pH greater than 7.48 (P = 0.019), biliary glucose less than 16 mmol/L (P = 0.013), and bile/perfusate glucose ratio less than 0.67 (P = 0.013). In the clinical trial, 4 of 6 livers met these criteria and were transplanted, and none developed clinical evidence of posttransplant cholangiopathy., Conclusions: Biliary bicarbonate, pH, and glucose during ex situ NMP of liver grafts are accurate biomarkers of BDI and can be easily determined point of care, making them suitable for the pretransplant assessment of bile duct viability. This may improve graft selection and decrease the risk of posttransplant cholangiopathy.

Background: Ex situ normothermic machine perfusion (NMP) can be performed after traditional static cold preservation to assess graft function and viability before transplantation. It is unknown whether this results in activation of coagulation and fibrinolysis, as may occur upon graft reperfusion in vivo., Methods: Twelve donor livers declined for transplantation underwent 6 hours of end-ischemic NMP using a heparinized plasma-based perfusion fluid. Concentration of prothrombin fragment F1 + 2 (marker of coagulation activation), D-dimer, plasmin-antiplasmin complex, tissue plasminogen activator and plasminogen activator inhibitor-1 (markers for fibrinolysis) and alanine aminotransferase (ALT) (marker of ischemia-reperfusion [I/R] injury) were measured in perfusion fluid at regular intervals. Liver biopsies were examined for the presence of fibrin, using light microscopy after Maurits, Scarlet and Blue staining., Results: No significant increase in prothrombin F1 + 2 was noted during NMP. D-dimer and plasmin-antiplasmin complex levels increased soon after start of NMP and D-dimer concentrations correlated significantly with levels of tissue plasminogen activator. In livers displaying good function during NMP, perfusate levels of ALT and D-dimers were low (≤3500 ng/mL), whereas significantly higher D-dimer levels (>3500 ng/mL) were in found in livers with poor graft function. Activation of fibrinolysis correlated significantly with the degree of I/R injury, as reflected by ALT levels., Conclusions: End-ischemic ex situ NMP results in activation of fibrinolysis, but not of coagulation. Markers of fibrinolysis activation correlate significantly with markers of I/R injury. High concentrations of D-dimer early after start of NMP can be considered a marker of severe I/R injury and a predictor of poor liver graft function.

Background: The mechanism through which oxygenated hypothermic machine perfusion (HMP) improves viability of human extended criteria donor (ECD) livers is not well known. Aim of this study was to examine the benefits of oxygenated HMP after static cold storage (SCS)., Methods: Eighteen ECD livers that were declined for transplantation underwent ex situ viability testing using normothermic (37 °C) machine perfusion (NMP) after traditional SCS (0 °C-4 °C) for 7 to 9 hours. In the intervention group (n = 6), livers underwent 2 hours of oxygenated HMP (at 12 °C) after SCS and before NMP. Twelve control livers underwent NMP without oxygenated HMP after SCS., Results: During HMP, hepatic ATP content increased greater than 15-fold, and levels remained significantly higher during the first 4 hours of NMP in the HMP group, compared with controls. Cumulative bile production and biliary secretion of bilirubin and bicarbonate were significantly higher after HMP, compared with controls. In addition, the levels of lactate and glucose were less elevated after HMP compared with SCS preservation alone. In contrast, there were no differences in levels of hepatobiliary injury markers AST, ALT, LDH, and gamma-GT after 6 hours of NMP. Hepatic histology at baseline and after 6 hours of NMP revealed no differences in the amount of ischemic necrosis between both groups., Conclusions: Two hours of oxygenated HMP after traditional SCS restores hepatic ATP levels and improves hepatobiliary function but does not reduce (preexisting) hepatobiliary injury in ECD livers.

Objective: We investigated the effect of human bile on the stability of plasma clots and of fibrin sealants., Background: Fibrin sealants are extensively used in liver surgery, for example, during liver resections. Although these sealants have been developed to induce hemostasis, in practice these products are actually mainly used to seal dissected bile ducts to prevent postsurgical bile leakage., Methods: We performed in vitro assays in which clotting and lysis of human plasma clots or fibrin sealants was studied in presence or absence of human bile., Results: Addition of bile to human plasma resulted in a dose-dependent increase in clotting time, and a dose-dependent decrease in clot lysis time. Bile also accelerated lysis of in vitro clotted fibrin sealants. Immunodepletion of tissue-type plasminogen activator (tPA) resulted in partial depletion of the lysis promoting activity of bile. Immunodepletion of both tPA and lysine-binding proteins from bile fully abolished the lytic activity, suggesting that tPA and plasminogen present in human bile are responsible for the lysis-promoting effect. Surprisingly, addition of high dose plasminogen activator inhibitor type 1 (PAI-1) to bile did not attenuate the lytic activity toward fibrin sealants, which suggested that tPA in a biliary environment may be unsusceptible to PAI-1 inhibition. Indeed, bile acids were shown to prevent tPA from interacting with PAI-1, although preformed complexes were not destabilized upon addition of bile acids., Conclusions: These combined results suggest that the presence of tPA and other fibrinolytic proteins in human bile results in lysis of plasma clots or fibrin sealants, which potentially could affect the efficacy of the latter products.

Background: Gene polymorphisms involved in hemostasis have been associated with an increased risk of thromboembolic events. The aim of this study was to assess whether prothrombotic gene polymorphism is a risk factor for hepatic vascular thrombosis after orthotopic liver transplantation (OLT)., Methods: In a series of 421 transplant procedures, genomic DNA was available for genotyping in 381 donors (91%) and 382 recipients (91%). In donors and recipients, the presence of factor V Leiden mutation, the prothrombin G20210A, and the factor XIII G100T polymorphisms were identified. In recipients, the C677T methylenetetrahydrofolate reductase (MTHFR), the platelet glycoprotein integrin α2 C807T, the integrin β3 C1565T, and the thrombospondin 4 A387P polymorphisms were identified. Clinical data were obtained from a prospectively maintained database and medical records. All recipients underwent screening for hepatic vascular thrombosis using Doppler ultrasonography, followed by catheter or computed tomography angiography if indicated., Results: In an overall analysis, none of the polymorphisms were associated with hepatic vascular thrombosis. When thrombosis in the first 7 days after OLT was excluded, we found a 3- to 7-fold increased risk for hepatic artery thrombosis (HAT) in association with factor V Leiden or factor XIII G100T (donor), and MTHFR C677T (recipient)., Conclusions: The presence of factor V Leiden or factor XIII G100T in the donor liver or MTHFR C677T in the recipient is associated with an increased risk of HAT after OLT. However, because the prevalence of these polymorphisms is low and the overall impact on the incidence of HAT is minimal, routine screening for these genotypes seems not justified.

Biliary complications, especially nonanastomotic biliary strictures (NAS), are a major cause of morbidity after orthotopic liver transplantation. Of all donor and recipient characteristics known to increase the risk of developing NAS, the role of prolonged ischemia times is most extensively described in the literature. However, there is increasing evidence that several other, non-ischemia-related factors play a critical role in the pathogenesis of NAS as well. The clinical presentation of NAS may vary considerably among liver transplant recipients, including large variations in time of occurrence, and in location and severity of the strictures. Additional underlying causes such as bile salt toxicity and immune-mediated injury are believed to explain the wide spectrum of biliary strictures after orthotopic liver transplantation. Current and emerging insight in the pathogenesis of NAS and potential targets to reduce biliary injury and preserve bile ducts are discussed in this overview.

Objective: To evaluate whether a low postoperative platelet count is associated with a poor recovery of liver function in patients after partial liver resection., Background: Experimental studies in rodents have recently suggested that blood platelets play a critical role in the initiation of liver regeneration. It remains unclear whether platelets are also involved in liver regeneration in humans., Methods: In a series of 216 consecutive patients who underwent partial liver resection for colorectal liver metastases, we studied postoperative mortality and liver dysfunction in relation to the immediate postoperative platelet count. All patients had normal preoperative liver function and none of them had liver fibrosis or cirrhosis. Delayed postoperative recovery of liver function was defined as serum bilirubin >50 micromol/L or prothrombin time >20 seconds at any time point between postoperative day 1 and 5., Results: Patients with a low (<100 x10(9)/L) immediate postoperative platelet count had worse postoperative liver function, higher serum markers of liver injury, and increased mortality compared with patients with normal platelet counts (>100/L). A low immediate postoperative platelet count was identified as an independent risk factor of delayed postoperative recovery of liver function (OR, 11.5; 95% CI, 1.1-122.4; P = 0.04 in multivariate analysis)., Conclusion: After partial liver resection, a low platelet count is an independent predictor of delayed postoperative liver function recovery and is associated with increased risk of postoperative mortality. These clinical findings are in accordance with the accumulating evidence from experimental studies, indicating that platelets play a critical role in liver regeneration.

Background: Platelet transfusions have been identified as an independent risk factor for survival after orthotopic liver transplantation (OLT). In this study, we analyzed the specific causes of mortality and graft loss in relation to platelet transfusions during OLT., Methods: In a series of 449 consecutive adult patients undergoing a first OLT, the causes of patient death and graft failure were studied in patients who did or did not receive perioperative platelet transfusions., Results: Patient and graft survival were significantly reduced in patients who received platelet transfusions, compared with those who did not (74% vs 92%, and 69% vs 85%, respectively at 1 yr; P < 0.001). Lower survival rates in patients who received platelets were attributed to a significantly higher rate of early mortality because of acute lung injury (4.4% vs 0.4%; P = 0.004). There were no significant differences in other causes of mortality between the two groups. The main cause of graft loss in patients receiving platelets was patient death with a functioning graft., Conclusions: These findings suggest that platelet transfusions are an important risk factor for mortality after OLT. The current study extends previous observations by identifying acute lung injury as the main determinant of increased mortality. The higher rate of graft loss in patients receiving platelets is related to the higher overall mortality rate and does not result from specific adverse effects of transfused platelets on the grafted liver.

Objective: Carriers of the factor V Leiden mutation (FVL-carriers) have a substantially increased risk of deep venous thrombosis (DVT), whereas the risk of pulmonary embolism (PE) is only mildly increased compared with noncarriers. So far few studies have investigated possible mechanisms for this so-called FVL paradox., Methods and Results: Consecutive patients with a first DVT or PE were included in a large population-based case-control study (MEGA study). Patients, aged 18 to 70 years, provided a questionnaire, DNA (n=3313), or plasma (n=1474). Surgery, injury, and travel were considered thrombosis-provocative. Of 2063 patients with isolated DVT, 20% were FVL-carrier, as were 8% of the 885 patients with isolated PE. Among DVT patients, FVL-carriers had their thrombi more often proximal and a higher number of affected veins than noncarriers. No differences were observed between FVL-carriers and noncarriers in time between provocation and diagnosis, in vitro coagulation time, and thrombus density. Compared with patients with both DVT and PE, isolated DVT patients more often had thrombi located distally and had a similar number of affected veins. Compared with isolated PE patients, isolated DVT patients had a similar time between provocation and diagnosis, and similar in vitro coagulation time and thrombus density., Conclusions: Although some effects were differential for FVL-carriers and noncarriers, and some were differential for PE and DVT patients, none of the potential mechanisms offered a clear explanation.

Purpose of Review: Hemostatic alterations in cirrhosis involve molecular pathways that both promote and stabilize blood clotting and pathways that mediate clot dissolution. Orthotopic liver transplantation for end-stage liver disease historically was a long and risky procedure, accompanied by substantial blood loss. The aim of this review paper is to provide an overview of recent studies and developments that have gradually changed our understanding about the hemostatic system and changes that may occur in patients undergoing liver transplantation., Recent Findings: Patients with severe liver disease not only have a deficiency of procoagulant and antifibrinolytic factors, but also have a deficiency of naturally occurring anticoagulants and profibrinolytics. Studies using modern laboratory technology have shown that thrombin generation in these patients is less abnormal than traditionally believed based on standard coagulation tests. In addition, clinical observations indicated that patients with cirrhosis are not protected against thromboembolic complications., Summary: Hemostatic alterations in cirrhosis concern both pro- and antihemostatic pathways and the net result is a rebalancing of the hemostatic system, albeit with narrower margins. This delicate balance will become precarious when the system is heavily challenged such as during liver transplantation. The balance may than be turned to either hypocoagulation or hypercoagulation, making patients with cirrhosis both prone to bleeding as well as thromboembolic complications.

Objective: The interaction of platelets with low density lipoprotein (LDL) contributes to the development of cardiovascular disease. Platelets are activated by native LDL (nLDL) through apoE Receptor 2' (apoER2')-mediated signaling to p38(MAPK) and by oxidized LDL (oxLDL) through lysophosphatidic acid (LPA) signaling to Rho A and Ca2+. Here we report a new mechanism for platelet activation by oxLDL., Methods and Results: Oxidation of nLDL increases p38(MAPK) activation through a mechanism that is (1) independent of LPA, and (2) unlike nLDL-signaling not desensitized by prolonged platelet-LDL contact or inhibited by receptor-associated protein or chondroitinase ABC. Antibodies against scavenger receptors CD36 and SR-A alone fail to block p38(MAPK) activation by oxLDL but combined blockade inhibits p38(MAPK) by >40% and platelet adhesion to fibrinogen under flow by >60%. Mouse platelets deficient in either CD36 or SR-A show normal p38(MAPK) activation by oxLDL but combined deficiency of CD36 and SR-A disrupts oxLDL-induced activation of p38(MAPK) by >70%., Conclusion: These findings reveal a novel platelet-activating pathway stimulated by oxLDL that is initiated by the combined action of CD36 and SR-A.

Objective: Thrombin interacts with platelets via the protease-activated receptors (PARs) 1 and 4, and via glycoprotein Ibalpha (GPIbalpha). Recently, it was shown that platelets are able to adhere to immobilized thrombin under static conditions via GPIbalpha., Methods and Results: Here, we show that platelets are also able to adhere to and form stable aggregates on immobilized thrombin under conditions of flow. Adhesion and aggregation to thrombin was dependent on the interaction with GPIbalpha, as addition of glycocalicin or an antibody blocking the interaction between thrombin and GPIbalpha inhibited platelet adhesion. Additionally, platelet adhesion to recombinant thrombin mutants, which are unable to bind GPIbalpha, was severely suppressed. Furthermore, platelet adhesion to thrombin was dependent on activation of PARs, and partly on granule secretion and thromboxane-A2 synthesis. Immobilization of thrombin on a fibrin network resulted in substantially increased adhesion compared with fibrin alone. The adhesion to fibrin alone was completely abolished by addition of dRGDW, whereas fibrin-bound thrombin still showed substantial platelet adhesion in the presence of dRGDW, indicating that fibrin-bound thrombin is able to directly capture platelets under flow., Conclusions: These results indicate that platelets are able to adhere to thrombin under flow conditions, which is dependent on the interaction with GPIbalpha.