EXTRA-CORPOREAL PERFUSION OF NORMAL AND hDAF TRANSGENIC LIVERS WITH HUMAN BLOOD

Abstract

212 The development of pigs transgenic for human decay accelerating factor (hDAF) has led to a resurgence of interest in extra-corporeal liver perfusion in the treatment of acute liver failure. We have developed an isolated perfusion system which incorporates oxygenation, temperature regulation and independent perfusion of the artery and portal vein. When pig livers were perfused with pig blood (n=5), reliable synthetic function and metabolic function were maintained for at least 3 days, at which stage essentially normal histological appearances were seen. Synthetic function was demonstrated by CH50 analysis (complement levels increased four-fold), urea production (increased 15 fold with unchanged creatinine levels) and factor V synthesis (stable factor V levels, whereas anhepatic perfusions showed no factor V activity after 36 hours). Metabolic function was demonstrated by acid base and potassium maintenance within the normal physiologic range. When connected to an anaesthetised pig in acute liver failure, stabilisation of metabolic (pH) and cardiovascular (arterial pressure, peripheral vascular resistance, inotrope requirement) parameters were maintained for the duration of perfusion. Unsupported control animals died with a mean survival of 17 hours (n=5). When normal (n=5) and hDAF transgenic (n=5) pig livers were perfused with fresh human blood, synthetic and metabolic function was demonstrated in both groups. Transgenic livers produced significantly more complement and urea (p<0.01) while factor V production was similar. Factor V levels stabilised at porcine rather than at human levels (400% vs. 100%). Metabolic function was significantly better (p <0.01) in transgenic livers than in nontransgenic livers as assessed by acid-base and potassium homeostasis. There was no evidence of hyperacute rejection. However, in both groups of xenoperfusions the duration of function was limited by progressive loss of red cells. The red cell loss appears to be of immunological origin and due to phagocytosis rather than haemolysis. The rate of red cell consumption, however, is compatible with a modest transfusion requirement and may not, therefore, restrict clinical application.