Effects of Platelet Mimicking Nanoparticles in Patients With Cirrhosis

Hepatic cirrhosis is accompanied by an alteration of the haemostatic balance (primary haemostasis, coagulation, fibrinolysis). With regard to primary haemostasis, thrombocytopenia is usually moderate, due to splenic or hepatic sequestration associated with portal hypertension. Platelet synthesis is also reduced. There are also autoimmune thrombocytopenia due to the presence of anti-platelet autoantibodies. In addition, there is a thrombopathy with functional alterations in platelet adhesion and aggregation. In parallel with these abnormalities in platelet adhesion and aggregation, the quantitative increase in the level of Von Willebrand factor (VWF) preserves the capacity for platelet aggregation, even under conditions of circulating flow, despite the reduction in the intrinsic functional capacity of VWF. This increase can be explained by increased hepatic synthesis, a larger endothelial surface area in the presence of collateral circulation and repeated endothelial aggression by endotoximia during infections, as well as a decrease in clearance due to a decrease in the synthesis of ADAMTS13.

Routine investigation of abnormalities in primary haemostasis is based almost exclusively on platelet counts, as well as plasma VWF and ADAMTS13 assays. Functional platelet tests (PFA®, impedance aggregometry, light transmission aggregation) are more difficult to perform, particularly in the case of thrombocytopenia, and are not performed under circulating flow conditions. The Total Thrombus Formation Analysis System (T-TAS®01) allows analysis of haemostatic capacity in whole blood and flow conditions. Whole blood is deposited in a reservoir and then perfused onto a type I collagen-coated chip (PL chip) at a shear rate of 1500 s-1, mimicking blood flow in small arteries. As the clot forms, the pressure in the perfusion chamber increases until total occlusion occurs. The parameters measured are :

• the time required to achieve a pressure within the perfusion chamber equal to 10 kilopascal (kPa) above the baseline pressure,
• the time required to reach a pressure of 60 kPa above the base pressure in the infusion chamber (occlusion time)
• the area under the curve at 10 min. The perioperative management of cirrhotic patients leads the clinician to ask the question of prophylactic platelet transfusion in the event of thrombocytopenia of less than 30 to 50 G/L. While this threshold value is based on a low level of evidence, platelet transfusion has a poor performance in cirrhotic patients and is not without side effects. Thus, preventive platelet transfusion is not recommended. In the event of bleeding, management should consist of platelet transfusion, combined with fibrinogen and antifibrinolytic administration. Synthetic platelet mimicking particles (SPs) are made of a liposomal membrane, and "decorated" with 3 different peptides: collagen binding peptide (CBP), which binds to fibrillar collagen exposed at the subendothelium, fibrinogen mimetic peptide (FMP), which can bind to the active form of platelet integrin αIIbβ3, and VWF binding peptide (VBP), which is derived from the C2 domain of factor VIII and can bind to the D'-D3 domain of VWF.

Ex vivo, in the absence of endothelial injury, these SPs do not induce platelet aggregation in the absence of agonist but enhance aggregation in the presence of agonist. These SPs do not trigger thrombin formation on their own but in the presence of tissue factor SPs increase thrombin generation and fibrin formation. In perfusion chambers, these nanoparticles allow platelets to adhere to a collagen-coated surface and to aggregate with each other. In vivo, SPs collaborate with platelets to restore effective haemostasis in thrombocytopenic mice undergoing tail-clipping. Their haemostatic efficacy has also been demonstrated in various animal models of traumatic injury, including a mouse model of liver laceration, a porcine model of traumatic arterial haemorrhage, and a rodent model of liver resection.

The assumption of this study is that the characteristics of infusions with the T-TAS®01 system will be altered in cirrhotic patients, reflecting impairment of primary haemostasis, compared to control patients and that platelet-mimicking nanoparticles (PMNs) will correct these alterations.