The influence of storage temperature during machine perfusion on preservation quality of marginal donor livers.

BACKGROUND: Although non-heart-beating donors have the potential to increase the number of available organs, the livers are used very seldom because of the risk of primary non-function. There is evidence that machine perfusion is able to improve the preservation of marginal organs, and therefore we evaluated in our study the influence of the perfusate temperature during oxygenated machine perfusion on the graft quality. METHODS: Livers from male Wistar rats were harvested after 60-min warm ischemia induced by cardiac arrest. The portal vein was cannulated and the liver flushed with Lifor (Lifeblood Medical, Inc.) organ preservation solution for oxygenated machine perfusion (MP) at 4, 12 or 21 degrees C. Other livers were flushed with HTK and stored at 4 degrees C by conventional cold storage (4 degrees C-CS). Furthermore two groups with either warm ischemic damage only or without any ischemic damage serve as control groups. After 6h of either machine perfusion or cold storage all livers were normothermic reperfused with Krebs-Henseleit buffer, and functional as well as structural data were analyzed. RESULTS: Contrary to livers stored by static cold storage, machine perfused livers showed independently of the perfusate temperature a significantly decreased enzyme release of hepatic transaminases (ALT) during isolated reperfusion. Increasing the machine perfusion temperature to 21 degrees C resulted in a marked reduction of portal venous resistance and an increased bile production. CONCLUSIONS: Oxygenated machine perfusion improves viability of livers after prolonged warm ischemic damage. Elevated perfusion temperature of 21 degrees C reconstitutes the hepatic functional capacity better than perfusion at 4 or 12 degrees C.

Biphasic onset of splenic apoptosis following hemorrhagic shock: critical implications for Bax, Bcl-2, and Mcl-1 proteins.

INTRODUCTION: The innate immune response to trauma hemorrhage involves inflammatory mediators, thus promoting cellular dysfunction as well as cell death in diverse tissues. These effects ultimately bear the risk of post-traumatic complications such as organ dysfunction, multiple organ failure, or adult respiratory distress syndrome. In this study, a murine model of resuscitated hemorrhagic shock (HS) was used to determine the apoptosis in spleen as a marker of cellular injury and reduced immune functions. METHODS: Male C57BL-6 mice were subjected to sham operation or resuscitated HS. At t = 0 hours, t = 24 hours, and t = 72 hours, mice were euthanized and the spleens were removed and evaluated for apoptotic changes via DNA fragmentation, caspase activities, and activation of both extrinsic and intrinsic apoptotic pathways. Spleens from untreated mice were used as control samples. RESULTS: HS was associated with distinct lymphocytopenia as early as t = 0 hours after hemorrhage without regaining baseline levels within the consecutive 72 hours when compared with sham and control groups. A rapid activation of splenic apoptosis in HS mice was observed at t = 0 hours and t = 72 hours after hemorrhage and predominantly confirmed by increased DNA fragmentation, elevated caspase-3/7, caspase-8, and caspase-9 activities, and enhanced expression of intrinsic mitochondrial proteins. Accordingly, mitochondrial pro-apoptotic Bax and anti-apoptotic Bcl-2 proteins were inversely expressed within the 72-hour observation period, thereby supporting significant pro-apoptotic changes. Solely at t = 24 hours, expression of the anti-apoptotic Mcl-1 protein shows a significant increase when compared with sham-operated and control animals. Furthermore, expression of extrinsic death receptors were only slightly increased. CONCLUSION: Our data suggest that HS induces apoptotic changes in spleen through a biphasic caspase-dependent mechanism and imply a detrimental imbalance of pro- and anti-apoptotic mitochondrial proteins Bax, Bcl-2, and Mcl-1, thereby promoting post-traumatic immunosuppression.