Liver transplantation is an effective treatment of end-stage liver diseases. However, liver ischemia-reperfusion injury (IRI) and rejection significantly cause the decrease of survival rate of liver graft. Therefore, it is urgent to explore a novel method, which can not only alleviate liver IRI, but also promote immune tolerance of allograft, thereby improving the survival rate of liver graft. Extracellular vesicle (EV) is nanoparticle released from cells into the extracellular microenvironment, which may alleviate graft injury by repairing autophagy, immunosuppression and accelerating tissue regeneration. Hence, EV becomes a research hot spot in the field of liver transplantation. Nevertheless, the clinical application of EV encounters multiple challenges, such as separation, purification, identification, storage of EV and how to deliver EV to the target cells. In this article, the mechanism of EV in liver IRI, the challenges in clinical application of EV and the potential application of EV were reviewed, aiming to provide reference for the clinical application of EV in liver transplantation.

Objective To evaluate the effect and mechanism of nicotinamide mononucleotide (NMN) on ischemia-reperfusion injury (IRI) induced by donor liver after cardiac death in rat models. Methods Rat models of orthotopic liver transplantation were established by "magnetic ring + double cuff" method. SD rats were randomly divided into the sham operation group (Sham group), orthotopic liver transplantation group (OLT group), NMN treatment + orthotopic liver transplantation group (NMN group), NMN+sirtuin-3 (Sirt3) inhibitor (3-TYP) + orthotopic liver transplantation group (NMN+3-TYP group), respectively. Pathological changes and hepatocyte apoptosis of the rats were observed in each group. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were determined. Superoxide dismutase (SOD) and malondialdehyde (MDA) contents in liver tissues were detected. The expression levels of Sirt3, microtubule-associated protein 1 light chain 3 (LC3)Ⅱ, PTEN-induced putative kinase 1 (PINK1), Parkin and translocase of the outer mitochondrial membrane 20 (TOMM20) in liver tissues were measured. Postoperative survival of the rats in each group was analyzed. Results Compared with the Sham group, serum ALT and AST levels were higher in the OLT group. Compared with the OLT group, the levels of ALT and AST were decreased in the NMN group. Compared with the NMN group, the levels of ALT and AST were increased in the NMN +3-TYP group (all P < 0.05). The liver tissue structure of rats in the Sham group was basically normal. In the OLT group, pathological changes, such as evident congestion, vacuolar degeneration and hepatocyte necrosis, were observed in the liver tissues. Compared with the Sham group, Suzuki score and apoptosis rate were higher in the OLT group. Suzuki score and apoptosis rate in the NMN group were lower than those in the OLT group. Suzuki score and apoptosis rate in the NMN+3-TYP group were higher compared with those in the NMN group (all P < 0.05). Compared with the Sham group, the SOD content was decreased, whereas the MDA content was increased in the OLT group. Compared with the OLT group, the SOD content was increased, whereas the MDA content was decreased in the NMN group. Compared with the NMN group, the SOD content was decreased, whereas the MDA content was increased in the NMN+3-TYP group (all P < 0.05). Compared with the Sham group, the relative expression levels of Sirt3 and TOMM20 proteins were down-regulated, whereas those of PINK1, Parkin and LC3Ⅱproteins were up-regulated in the OLT group. Compared with the OLT group, the relative expression levels of Sirt3, PINK1, Parkin and LC3Ⅱproteins were up-regulated, whereas that of TOMM20 protein was down-regulated in the NMN group. Compared with the NMN group, the relative expression levels of PINK1, Parkin and LC3Ⅱproteins were down-regulated, whereas that of TOMM20 protein was up-regulated in the NMN+3-TYP group (all P < 0.05). In the Sham group, the 7 d survival rate of rats was 100%, 50% in the OLT group, 75% in the NMN group and 58% in the NMN+3-TYP group, respectively. Conclusions NMN may enhance the antioxidative capacity of the liver, induce PINK1/Parkin-mediated mitochondrial autophagy, and alleviate IRI of the liver by up-regulating Sirt3, thereby playing a protective role in the donor liver after cardiac death.

Objective To analyze the difference and influential factors of clinical prognosis between liver transplantation with autoimmune liver disease (AILD) and viral hepatitis cirrhosis. Methods Clinical data of 75 recipients undergoing liver transplantation from January 2002 to January 2017 were retrospectively analyzed. All recipients were divided into the AILD group (n=25) and viral hepatitis cirrhosis group (n=50). The intraoperative conditions of the recipients were observed including warm ischemia time, cold ischemia time, operation time, anhepatic phase and blood transfusion volume. Postoperative complications were observed including severe acute kidney injury (AKI), infection, acute rejection, biliary tract-related complications, vascular-related complications and post transplantation diabetes mellitus (PTDM). The follow-up status were monitored after discharge. The prognostic factors of liver transplant recipients were analyzed. Results The warm ischemia time, cold ischemia time, operation time and anhepatic phase did not significantly differ between two groups (all P > 0.05). In the AILD group, the incidence of postoperative acute rejection was remarkably higher, whereas the incidence of postoperative severe AKI was significantly lower than those in the viral hepatitis cirrhosis group (both P < 0.05). The postoperative 1-, 3- and 5-year survival rates in the AILD group was 92%, 87%, and 87%, which did not significantly differ from 88%, 88% and 88% in the viral hepatitis cirrhosis group (all P > 0.05). Univariate analysis showed that age, model for end-stage liver disease (MELD) score, severe AKI, infection and biliary tract-related complications were the influencing factors of clinical prognosis of the recipients (all P < 0.05). Conclusions The overall survival prognosis does not significantly differ between the AILD and viral hepatitis cirrhosis groups. Age, MELD score, severe AKI, infection and biliary tract-related complications are the risk factors affecting the clinical prognosis of liver transplantation recipients.