The release of microRNA‐122 during liver preservation is associated with early allograft dysfunction and graft survival after transplantation

Abstract

Early allograft dysfunction (EAD) after liver transplantation (LT) is associated with inferior graft survival. EAD is more prevalent in grafts from donation after circulatory death (DCD). However, accurate prediction of liver function remains difficult because of the lack of specific biomarkers. Recent experimental and clinical studies highlight the potential of hepatocyte-derived microRNAs (miRNAs) as sensitive, stable, and specific biomarkers of liver injury. The aim of this study was to determine whether miRNAs in graft preservation fluid are predictive for EAD after clinical LT and in an experimental DCD model. Graft preservation solutions of 83 liver grafts at the end of cold ischemia were analyzed for miRNAs by reverse transcription polymerase chain reaction. Of these grafts, 42% developed EAD after transplantation. Results were verified in pig livers (n = 36) exposed to different lengths of warm ischemia time (WIT). The absolute miR-122 levels and miR-122/miR-222 ratios in preservation fluids were significantly higher in DCD grafts (P = 0.001) and grafts developing EAD (P = 0.004). In concordance, the miR-122/miR-222 ratios in perfusion fluid correlate with serum transaminase levels within the first 24 hours after transplantation. Longterm graft survival was significantly diminished in grafts with high miR-122/miR-222 ratios (P = 0.02). In the porcine DCD model, increased WIT lead to higher absolute miR-122 levels and relative miR-122/miR-222 ratios in graft perfusion fluid (P = 0.01 and P = 0.02, respectively). High miR-122/miR-222 ratios in pig livers were also associated with high aspartate aminotransferase levels after warm oxygenated reperfusion. In conclusion, both absolute and relative miR-122 levels in graft preservation solution are associated with DCD, EAD, and early graft loss after LT. As shown in a porcine DCD model, miRNA release correlated with the length of WITs. Liver Transplantation 23 946-956 2017 AASLD.

Cell‐free microRNAs as early predictors of graft viability during ex vivo normothermic machine perfusion of human donor livers

“…Studies have shown that HDmiR‐122 levels in graft preservation fluid are higher in DCD grafts and in livers that went on to develop EAD and NAS . Higher HDmiR‐122 levels in perfusate were also measured in a porcine DCD NMP model with increasing warm ischemia times .…”

“…In the early detection of hepatic injury during machine perfusion, miRs in perfusate offer several advantages. miRs can withstand harsh environmental conditions, and because the perfusate circulates through the entire liver during machine perfusion, miR levels in perfusate provide a better and non‐invasive representation of the entire liver compared to miR levels measured in total RNA samples from biopsies . Furthermore, miRs have been shown to be earlier and more sensitive markers of liver damage than more conventional markers such as AST or ALT, and machine perfusion potentially allows for an even more representative and dynamic evaluation of the liver graft .…”

“…The relative ratio of hepatocyte‐derived and cholangiocyte‐derived miRs represents a relative degree of hepatocellular injury using an internal stabilization factor. Elevated HDmiR‐122/CDmiR‐222 ratios in the flushing solution of liver grafts, obtained prior to implantation, have previously been associated with NAS, EAD, graft loss, and DCD livers in humans, and was, in a porcine DCD model, directly correlated with increasing WIT . Future research is necessary to determine whether miR levels in bile and perfusate during NMP (but also at other temperatures) can be used to predict clinical outcomes, such as NAS or EAD.…”

“…They can down‐regulate certain processes by preventing translation of messenger RNA (mRNA) into functional proteins whereas others upregulate other cellular functions . Several studies have recently investigated the release of miRs in relation to cellular injury resulting from liver transplantation . It was shown that not only levels of released miRs differ between damaged and normal functioning hepatocytes and cholangiocytes but also that, during impaired excretory function and injury of hepatocytes, the liver shows polarized release of extracellular hepatocyte‐derived miRs (HDmiRs) and cholangiocyte‐derived miRs (CDmiRs) into both bile and serum, suggesting active rather than passive underlying release mechanisms …”

Circulating miRNA or circulating DNA—Potential biomarkers for organ transplant rejection

“…However, accurate prediction of liver function is still difficult due to the lack of specific biomarkers. Recent experimental and clinical studies have emphasized the potential of hepatocyte‐derived miRNAs as a sensitive, stable, and specific biomarker for liver injury . Moreover, in pancreatic islets undergoing autologous transplantation, high‐quality islets are essential for better post‐transplantation endocrine function; however, pressure during the separation affects quality and yield.…”