PB0565 - Long-term ex-situ normothermic machine perfusion of human livers provides a platform to study (patho)physiology and production of hemostatic proteins

Background: Normothermic machine perfusion (NMP) is an ex-situ method for preservation and/or testing of (extended) criteria donor livers prior to transplantation. During NMP, the liver is metabolically active which allows to study the physiology of an isolated liver, including the production of hemostatic proteins.

Aims: To investigate the production and activity of hemostatic proteins during long-term NMP of human livers.

Methods: Three discarded human donor livers underwent NMP with a perfusate based on red blood cells, albumin, colloids and parenteral nutrition, using a modified Liver Assist device (XVIVO, Groningen, Netherlands) for up to 7 days. Heparin was added to the perfusion fluid continuously. Perfusate samples were collected before the start of perfusion and daily thereafter. After heparin neutralization, international normalized ratios (INR) were analyzed. In addition, we measured antigen and activity levels of factor II and V, antithrombin, and fibrinogen, as well as levels of protein induced by vitamin K absence (PIVKA-II).

Results: Perfusate INR values declined over time, which was accompanied by detection of substantial quantities of all analyzed coagulation proteins (Figure 1). Antigen and activity levels of factor V and antithrombin increased to a similar extent resulting in a specific activity comparable to pooled normal plasma (PNP). The specific activity of factor II and fibrinogen was substantially decreased compared to PNP. The lower specific activity of factor II was accompanied by elevated levels of PIVKA-II.

Conclusion(s): During ex-situ NMP of human donor livers, hemostatic proteins are produced in substantial quantities, resulting in stable perfusate protein levels after a few days of perfusion. This may indicate establishment of an equilibrium between the production and clearance of these proteins. We propose that NMP of human livers may be used as a platform to test efficacy of drugs that stimulate or inhibit the production of coagulation factors, or to test liver-mediated clearance of prohemostatic protein therapeutics.