No abstract

Although University of Wisconsin (UW) solution aims at the prevention of cold-induced cell injury, it failed to protect against cold-induced apoptosis of hepatocytes and liver endothelial cells: when incubated in UW solution at 4°C for 24 hours and subsequently rewarmed at 37°C, 72% ؎ 8% of rat hepatocytes and 81% ؎ 5% of liver endothelial cells lost viability. In both cell types, the observed cell damage occurred under an apoptotic morphology; it appeared to be mediated by a rapid increase in the cellular chelatable iron pool by a factor >2 (as determined in hepatocytes) and subsequent formation of reactive oxygen species (ROS). Consequently, this cell injury was decreased by iron chelators to 6 to 25% (hepatocytes) and 4% ؎ 2% (liver endothelial cells). Deferoxamine nearly completely inhibited the occurrence of apoptotic morphology in both cell types. In liver endothelial cells, cold-induced apoptosis occurring during rewarming after 24 hours of cold incubation in UW solution was far more pronounced than in cell culture medium (loss of viability: 81% ؎ 5% vs. 28% ؎ 13%), but viability could even be maintained for 2 weeks of cold incubation by use of deferoxamine. In conclusion, this pathological mechanism might be an explanation for the strong endothelial cell injury known to occur after cold preservation. With regard to the extent of this ironmediated injury, addition of a suitable iron chelator to UW solution might markedly improve the outcome of liver preservation. (HEPATOLOGY 2002;35:560-567.) T o protect organs from injury provoked by cold storage for transplantation, special storage solutions have been introduced into clinical use. The most widely used preservation solution, University of Wisconsin (UW) solution, aims to prevent cold-induced necrotic cell injury that was attributed to disturbances of the cellular ion homeostasis by the use of an intracellular ion composition and impermeable and/or osmotically active substances. 1 In contrast to the often-cited putative cell swelling-dependent hypothermia injury, 1-4 we recently described the occurrence of cold-induced apoptosis in cultured hepatocytes and liver endothelial cells after cold incubation and rewarming of the cells in cellculture medium. 5 This injury was closely related to an increase in the intracellular concentration of chelatable, redox-active iron and subsequent formation of reactive oxygen species (ROS), presumably by the Fenton reaction. 6 This iron-dependent mechanism strongly accounts for the injurious process in cultured liver endothelial cells, whereas in hepatocytes, an additional, iron-independent component contributes to hypothermia-induced cell injury. 5 In the present study, we demonstrate that cold-induced apoptosis also takes place in UW solution despite its completely different composition as compared with cell-culture medium. Even more so, this clinically used preservation solution can enhance coldinduced apoptosis. Different from the mechanism of hypothermia-induced cell death in cell-culture medium, iron-dependent pro...

No abstract

Two apparently independent mitochondrial alterations take place during cold incubation and subsequent rewarming of liver endothelial cells. Cold-induced mitochondrial shortening represents a reversible process, whereas iron-mediated mitochondrial permeability transition and ultracondensation during rewarming are irreversible and constitute an important mediator of cold-induced apoptosis.

Cultured porcine corneal endothelial cells incur a strong iron-dependent injury elicited by hypothermia. This cold-induced injury might provide an explanation for the known corneal endothelial susceptibility to hypothermic preservation injury, which thus might be amenable to therapeutic interventions (ie, by iron chelators).