Role of extracellular vesicles as markers of inflammation and adverse clinical outcomes in orthotopic liver transplantation

Extracellular vesicles (EVs) are present throughout the organism and are intracellular transmitters of biological signals under physiological and pathological conditions. Its pathogenic actions occur mainly in inflammatory processes, degenerative diseases and cancer. In orthotopic liver transplantation (OLT) there is a persistent inflammatory state, which determines the prognosis of the procedure, in which EVs may participate. In this context, the aim of this study was to evaluate the release of EVs during OLT and the association between EVs and adverse transplant outcomes. To this end, 90 patients were included and their blood samples were collected pre-transplant (T1), in the reperfusion phase (T2) and at the end of hospitalization (T3) for the quantification of the following EVs markers by flow cytometry: CD14 (monocytes); CD41 (platelets); CD62P (P-selectin); CD162 (PSGL-1); CD31 (endothelium-platelet adhesion); CD9 and CD81 (cell surface). Statistical tests of frequency, ANOVA with repeated measures, Mann-Whitney and regression methods were used. The population studied was predominantly male, white, with a median age of 60 years, and a resident of the State of São Paulo. The following EVs were increased at T2 compared to T1: EVs-CD162+ (P<0.0001), EVs-CD31+ (P<0.0001), EVs-CD41A+ (P<0.0001), EVs-CD9+ (P <0.0001), and EVs-CD81+ (P<0.0001). At T1, patient age was associated with EVs-CD162+ (P=0.02), EVs-CD31+ (P=0.02), EVs-CD41A+ (P=<0.0001), and EVs-CD9+ (P=0.02), and also association of female sex with EVs-CD162+ (P=0.02), EVs-CD31+ (P=0.005), EVs-CD41A+ (P=0.01), EVs-CD9+ (P=0.002) and EVs-CD81+ (P=0.04). Fulminant hepatitis, primary biliary cirrhosis, autoimmune hepatitis, and sclerosing cholangitis were associated with increased levels of EVs-CD162+ (P=0.04), EVs-CD31+ (P=0.006), EVs-CD41A+ (P=0.005), and EVs-CD9+ (P=0.002) in T1. There was also a correlation between INR values and EVs-CD162+ (P=0.001), EVs-CD31+ (P=<0.0001), EVs-CD41A+ (P=<0.0001) and EVs-CD9+ (P=0.005), and between lactate and EVs-CD162+ (P=<0.0001), EVs-CD31+ (P=0.007), EVs-CD41A+ (P=0.02), EVs-CD9+ (P=0.02) and EVs-CD81+ (P=0.002). In T2, increased levels of EVs-CD162+ (P=0.003), EVs-CD31+ (P=0.01) and EVs-CD9+ (P=0.05) were associated with a higher risk of death, and increased levels of EVs-CD162+ to the highest risk of infection (P=0.01). There was a weak correlation between EVs-CD162+ (P=0.03) and INR, and EVs-CD41A+ (P=0.04) and EVs-CD81+ (P=0.002) with lactate. In conclusion, EVs that express platelet-endothelium and leukocyte-platelet adhesion antigens are released after liver reperfusion and are associated with adverse OLT outcomes. These findings contribute to the pathophysiological understanding of OLT complications (AU)