Molecular expression of acute phase mediators is attenuated by machine preservation in human liver transplantation: Preliminary analysis of effluent, serum, and liver biopsies

Abstract

Hypothermic machine perfusion (HMP) mitigates the effects of ischemia/reperfusion injury (IRI) in renal transplantation and preclinical work with livers. In liver transplantation, IRI increases the likelihood of primary graft dysfunction and is associated with significant morbidity. We recently completely the first phase 1 clinical trial of liver HMP at our center, and demonstrated improved clinical parameters and shorter duration of stay for patients who received grafts stored by HMP than patients who received grafts preserved in cold storage. Biomarker analysis of venous effluent collected from the hepatic veins during HMP may yield predictive information reflecting the condition of the donor liver, such as graft injury sustained during brain death and graft preservation. The aim of this study was to characterize biomarkers released into the effluent during HMP. Effluent was collected every 30 minutes during liver HMP during our phase 1 clinical trial. Serum was extracted from blood samples obtained at incision, before explantation, and at 1, 2, and 3 hours after reperfusion. The effluent and serum samples were assayed in multiplex to determine the concentration of inflammatory cytokines and growth factors. Tissue obtained from liver biopsies was processed for either downstream reverse transcription-polymerase chain reaction or immunofluorescence. Statistical significance was determined by a two-tailed t-test. Growth factors and most cytokines were not readily detectable in levels above baseline with this technique; however, interleukin-1 (IL-1) receptor antagonist and monocyte chemotactic protein-1 were present in significant concentrations in the effluent at all time points. This finding was confirmed with serum samples and mRNA expression obtained from liver biopsies. The concentrations of these proteins decreased from their initial values over the course of HMP, and mRNA expression levels were decreased by the use of HMP. IL-1β and tumor necrosis factor (TNF)-α are key mediators of inflammation in IRI. Although difficult to measure because of short half-lives, their downstream effectors indicate their levels of activity. IL-1 receptor antagonist is secreted in response to IL-1β, and monocyte chemotactic protein in response to TNF-α. Their decreased production over the course of HMP suggests that interruption of acute-phase inflammation in the graft may attenuate reperfusion-related graft injury. Further cDNA studies and effluent analyses are required to confirm this hypothesis.