Oxygenation during hypothermic rat liver preservation: An in vitro slice study to demonstrate beneficial or toxic oxygenation effects

Abstract

Hypothermic machine perfusion (HMP) of abdominal organs is shown to be superior compared to cold storage. However, the question remains if oxygenation is required during preservation as oxygen is essential for energy resynthesis but also generates toxic reactive oxygen species (ROS). To determine if oxygenation should be used during HMP, urea-synthesis rate, adenosine triphosphate (ATP), and generation of ROS were studied in an in vitro model, modeling ischemia-reperfusion injury. Furthermore, expression of uncoupling protein-2 (UCP-2) mRNA was assessed since UCP-2 is a potentially protective protein against ROS. Rat liver slices were preserved for 0, 24, and 48 hr in University of Wisconsin machine perfusion solution (UW-MP) with 0%, 21%, or 95% oxygen at 0 -4°C and reperfused for 24 hours. In the 0% and 95% groups, an increase of ROS was found after cold storage in UW-MP. After slice reperfusion, only the 0% oxygen group showed higher levels. The 0% group showed a lower urea-synthesis rate as well as lower ATP levels. mRNA upregulation of UCP-2 was, in contrast to kidney mRNA studies, not observed. In conclusion, oxygenation of UW-MP gave better results. This study also shows that ROS formation occurs during hypothermic preservation and the liver is not protected by UCP-2. We conclude that saturation of UW-MP with 21% oxygen allows optimal preservation results. (Liver Transpl 2005; 11:1403-1411.)

The Groningen Hypothermic Liver Perfusion Pump: Functional Evaluation of a New Machine Perfusion System

“…After 8 h reservoir saturation was reached and oxygen uptake by the liver remained constant but still considerable (35 kPa). This finding is in accordance with other authors, 9,10,13 who showed an improved liver viability after oxygenated versus nonoxygenated HMP indicating that the liver, even under hypothermic conditions, has a considerable oxygen demand.…”

“…Previously, many authors have pointed at the potential importance of additional oxygenation during liver HMP. 9,10,13,25,31 Based on the data of Fuija et al 10 as well as our experiments 13 the required partial oxygen pressure was determined at 55 kPa 31 to comply with total liver oxygen demand during HMP. In addition to an adequate perfusion, we concluded that the hypothermic liver uses oxygen and thus oxygenation of the perfusate, even at low temperatures, remains necessary.…”

Perspectives in Organ Preservation

“…To further improve organ viability, a more dynamic preservation method is needed to better fulfil the metabolic demands of damaged organs. Therefore, many groups have recently switched gears and are revisiting the possibilities of hypothermic machine perfusion (HMP) (103)(104)(105).…”

Ex vivo evaluation of porcine livers post-hypothermic machine perfusion at 4-6ºC and 12-14ºC

“…Several studies demonstrated that perfusion with oxygenated solutions prevented ATP loss and avoided the injurious ischemic cascades that are set into motion after ATP depletion [7,8,9,10]. The role of oxygenation has also been supported by other studies [11,12,13,14]. More recently, Figure. 1: Prototype liver device during HMP.…”