Cold ischemia-warm reperfusion (CI-WR) injury of the liver is characterized by marked alterations of sinusoidal endothelial cells (SECs), whereas hepatocytes appear to be relatively unscathed. However, the time course and mechanism of cell death remain controversial: early versus late phenomenon, necrosis versus apoptosis? We describe the occurrence and nature of cell death after different periods of CI with University of Wisconsin (UW) solution and after different periods of WR in the isolated perfused rat liver model. After 24-and 42-hour CI (viable and nonviable livers, respectively), similar patterns of liver cell death were seen: SEC necrosis appeared early after WR (10 minutes) and remained stable for up to 120 minutes. After 30 minutes of WR, apoptosis increased progressively with WR length. Based on morphological criteria, apoptotic cells were mainly hepatocytes within liver plates or extruded in the sinusoidal lumen. In addition, only after 42-hour CI were large clusters of necrotic hepatocytes found in areas of congested sinusoids. In these same livers, the hepatic microcirculation, evaluated by means of the multiple-indicator dilution technique, revealed extracellular matrix disappearance with no-flow areas. In conclusion, different time courses and mechanisms of cell death occur in rat livers after CI-WR, with early SEC necrosis followed by delayed hepatocyte apoptosis. These processes do not appear to be of major importance in the mechanism of graft failure because they are similar under both nonlethal and lethal conditions; this is not the case for the loss of the extracellular matrix found only under lethal conditions and associated with hepatocyte necrosis. L iver transplantation is the most effective treatment for end-stage liver disease. However, poor initial graft function, with prolonged cholestasis, coagulopathy, and increased bacterial infection, remains a major clinical problem. 1-3 Its incidence (15% to 25% of transplantation patients) appears to depend on the length of cold storage 4 and has thus been ascribed to injury from harvesting, cold storage, and warm reperfusion after blood vessel reconnection; i.e., cold ischemia-warm reperfusion (CI-WR) injury.The underlying mechanism of CI-WR injury has been extensively studied over the last decade, but it remains poorly understood. Numerous investigations have shown that sinusoidal endothelial cells (SECs) are the targets of prolonged CI, while hepatocytes appear to be relatively unscathed. [5][6][7][8][9][10][11][12][13] Morphological studies have characterized the SEC alterations observed after CI as retraction and detachment of cell bodies progressing to almost complete denudation of the SEC lining during WR. 8,9,14 It was first generally accepted that SECs die early during WR secondary to a necrotic process. 6,10 However, recent studies have indicated that apoptosis might be the mechanism of SEC death after WR of rat livers following CI. [15][16][17] Unfortunately, cell damage was not evaluated during the early reperfusion phase, prevent...
