Thromboinflammation in a Model of Hepatocyte Transplantation

Sammanfattning: Hepatocyte transplantation is an attractive method for the treatment of metabolic liver disease and acute liver failure. The clinical application of this method has been hampered by a large initial loss of transplanted cells.This thesis has identified and characterized an instant blood-mediated inflammatory reaction (IBMIR), which is a thromboinflammatory response from the innate immunity that may partly explain the observed loss of cells. In vitro perifusion experiments were performed and established that hepatocytes in contact with blood activate the complement and coagulation systems and induce clot formation in conjunction with the recruitment of neutrophils.  Within an hour, the hepatocytes were surrounded by platelets and entrapped in a clot infiltrated by neutrophils. Furthermore, hepatocytes expressed tissue factor (TF), and the reactions were shown to be initiated through the TF pathway. Monitoring of hepatocyte transplantation in vivo revealed activation of the same parameters as were noted in vitro.For the first time, von Willebrand factor (vWF) was identified on the hepatocyte surface, being demonstrated by flow cytometry and confocal microscopy. mRNA for vWF was also confirmed in hepatocytes. Complex formation between platelets and hepatocytes was also identified. Addition of antibodies targeting the binding site for vWF on the platelets reduced the complex formation.Two different strategies, systemic and local intervention, were applied to diminish the thromboinflammation elicited from the hepatocytes in contact with ABO-matched blood. Systemic inhibition with LMW-DS, in a clinically applicable dose, was found to be superior in controlling the IBMIR in vitro when compared to heparin. Cryopreserved hepatocytes elicited the IBMIR to the same extent as did fresh hepatocytes, and the IBMIR was equally well controlled with LMW-DS in both cryopreserved and fresh cells.Hepatocytes were coated with two layers of immobilized heparin in an attempt to protect the cells from the IBMIR. In vitro perifusion experiments showed heparinized hepatocytes triggered a significantly lower degree of IBMIR.