Organ shortage has become one of the major challenges hindering the development of organ transplantation. Xenotransplantation is one of the most valuable methods to resolve global organ shortage. In recent years, the development of genetic engineering technique and research and development of new immunosuppressant have provided novel theoretical basis for xenotransplantation. International scholars have successively carried out researches on xenotransplantation in genetically modified pigs to non-human primates or brain death recipients, making certain substantial progresses. However, most of the researches are still in the preclinical stage, far from clinical application. Therefore, according to the latest preclinical experimental research progress at home and abroad, the history of xenotransplantation, the development of gene modification technology, xenotransplantation rejection and immunosuppression regimens were reviewed, aiming to provide reference for subsequent research of xenotransplantation, promote clinical application of xenotransplantation and bring benefits to more patients with end-stage diseases.

Subclinical research of xenotransplantation involves xenotransplantation trial using brain death donors,which is an important intermediate step from basic research and animal experiments to the clinical application of xenotransplantation.It provides necessary data support for the safety and efficacy of xenotransplantation.In order to promote the safe,orderly,scientific and standardized development of subclinical research on xenotransplantation,the Xenotransplantation Group of Branch of Organ Transplantation of Chinese Medical Association formulated the"Expert Consensus on Subclinical Research of Xenotransplantation(2024 Edition)"based on relevant laws and regulations.The consensus includes aspects such as the selection of donor pigs,recipient selection criteria,legal and ethical requirements,determination of trial termination time,family informed consent system,and brain death determination standards.

With the vigorous promotion of organ donation after citizen death in China, increased utilization of marginal livers, and continuous expansion of hepatocellular carcinoma indications for liver transplantation, innovations in techniques such as auxiliary liver transplantation, pediatric liver transplantation, laparoscopic liver transplantation, magnetic liver transplantation,and non-ischemic liver transplantation have significantly improved the number of liver transplantation surgery performed, patient survival rates, and graft survival rates in China, while complication rates have gradually decreased. As such,liver transplantation in China has reached leading or advanced levels internationally. In the new development context,Chinese liver transplantation faces new opportunities and challenges for development. Evolutions in basic diseases of transplant recipients and tumor classifications of will further broaden the population eligible for transplantation and introduce new demands for liver transplantation procedures. Emerging technologies including artificial organs, xenotransplantation,and artificial intelligence are bringing prospects for advancing liver transplantation. Looking ahead, the progression of liver transplantation will go beyond prioritizing patient survival rates and graft survival rates alone, instead emphasizing improved quality of life for transplant recipients post-surgery to an even greater extent.

With the vigorous promotion of organ donation after citizen death in China, increased utilization of marginal livers, and continuous expansion of hepatocellular carcinoma indications for liver transplantation, innovations in techniques such as auxiliary liver transplantation, pediatric liver transplantation, laparoscopic liver transplantation, magnetic liver transplantation,and non-ischemic liver transplantation have significantly improved the number of liver transplantation surgery performed, patient survival rates, and graft survival rates in China, while complication rates have gradually decreased. As such,liver transplantation in China has reached leading or advanced levels internationally. In the new development context,Chinese liver transplantation faces new opportunities and challenges for development. Evolutions in basic diseases of transplant recipients and tumor classifications of will further broaden the population eligible for transplantation and introduce new demands for liver transplantation procedures. Emerging technologies including artificial organs, xenotransplantation,and artificial intelligence are bringing prospects for advancing liver transplantation. Looking ahead, the progression of liver transplantation will go beyond prioritizing patient survival rates and graft survival rates alone, instead emphasizing improved quality of life for transplant recipients post-surgery to an even greater extent.

Objective:To investigate the influencing of high sodium donor liver transplan-tation from the death of a citizen′s organ donation (DCD) on the prognosis of recipients.Methods:The retrospective cohort study was constructed. The clinicopathological data of 125 pairs of donors and recipients who underwent DCD liver transplantation in Xijing Hospital of Air Force Military Medical University from January 2015 to June 2021 were collected. Of the 125 donors, there were 93 males and 32 females. Of the 125 recipients, there were 92 males and 33 females, aged 48(41,55)years. According to the last time of serum sodium level of donor liver in the 125 recipients, 9 donor livers with serum sodium level ≥170 mmol/L were divided into group 1 (extremely high sodium), 33 donor livers with serum sodium level ≥150 mmol/L and <170 mmol/L were divided into group 2 (moderate high sodium), and 83 donor livers with serum sodium level <150 mmol/L were divided into group 3 (normal sodium), respectively. Observation indicators: (1) postoperative recover situations; (2) follow-up and survival analysis. Measurement data with normal distribution were represented as Mean± SD. Repeated measures were analyzed by repeated measures ANOVA. Measurement data with skewed distribution were represented as M( Q1, Q3), and comparison between groups was analyzed using the Kruskal-Wallis test. Count data were described as absolute numbers, and Pearson chi-square test or Fisher exact probability were used for data test. The Kaplan-Meier method was used to draw survival curves and Log-rank test was used for survival analysis. Results:(1) Postoperative recover situations. The changes of alanine transaminase (AlT), aspartate aminotransferases (AST), total bilirubin (TBil), alkaline phosphatase (ALP), prothrombin time (PT), international normalized ratio (INR), albumin (Alb) and creatinine (Cr) from the first day to the 14th day after operation were (736±972)IU/L to (75±46)IU/L, (1 290±1 651)IU/L to (38±20)IU/L, (102±98)μmol/L to (33±11)μmol/L, (66±34)IU/L to (104±54)IU/L, (19.9±3.3)seconds to (11.3±1.0)seconds, 1.76±0.31 to 1.00±0.08, (34±5)g/L to (38±3)g/L and (91±41)μmol/L to (76±19)μmol/L, respectively, in the recipients of group 1. The above indicators were (505±377)IU/L to (48±46)IU/L, (855±727)IU/L to (24±17)IU/L, (64±42)μmol/L to (32±22)μmol/L, (68±51)IU/L to (91±46)IU/L, (16.8±3.5)seconds to (11.9±1.2)seconds, 1.47±0.30 to 1.04±0.09, (33±4 g/L) to (40±5)g/L and (106±32)μmol/L to (97±27)μmol/L in the recipients of group 2 and (637±525)IU/L to (65±60)IU/L, (929±1 193)IU/L to (33±27)IU/L, (66±48)μmol/L to (33±36)μmol/L, (64±28)IU/L to (125±64)IU/L, (17.2±4.7)seconds to (13.3±12.8)seconds, 1.51±0.42 to 1.05±0.13, (35±6)g/L to (39±4)g/L, (105±44)μmol/L to (94±40)μmol/L in the recipients of groups. Results of overall effect showed there were significant differ-ences in the change trend of TBil (time effect, inter-group effect, interaction effect) in recipients among the three groups after liver transplantation ( Fgroup=5.42, Ftime=22.78, Finteraction=3.85, P<0.05). There were significant differences in the time effect of ALT, AST, ALP, PT, INR, Alb, Cr in recipients among the three groups after liver transplantation ( Ftime=50.17, 36.24, 19.24, 10.55, 59.61, 41.94, 10.82, P<0.05). (2) Follow-up and survival analysis. All recipients were followed up. Cases with early postoperative liver dysfunction, cases with donor liver failure 1 year after operation, cases with biliary complica-tions 1 year after operation, cases with vascular complications 1 year after operation, cases with rejection 1 year after operation were 2, 1, 0, 0, 0 in the recipients of group 1. The above indicators were 2, 1, 3, 0, 1 in the recipients of group 2 and 10, 8,20, 1, 6 in the recipients of group 3. There was no significant difference in the above indicators among the three groups ( χ2=1.58, 0.60, 5.19, 1.62, 0.97, P>0.05). The 1-year and 3-year cumulative survival rates of the donor liver were 100.00% and 100.00% in the recipients of group 1 after liver transplantation. The above indicators were 94.74% and 77.16% in the recipients of group 2 and 91.57% and 89.30% in the recipients of group 3. There was no significant difference in the cumulative survival rate of donor liver among the three groups ( χ2=2.69, P>0.05). The 1-year and 3-year cumulative survival rates were 100.00% and 100.00% in the recipients of group 1 after liver transplantation. The above indicators were 93.74% and 77.16% in the recipients of group 2 and 89.40% and 86.00% in the recipients of group 3. There was no significant difference in the cumulative survival rate among the three groups ( χ2=1.94, P>0.05). Conclusion:Donor livers with high serum sodium level can be used in the DCD liver transplantation.

The donor liver shortage is the bottles-neck limitation for clinical liver transplantation to save patients' life. Liver transplantation is a treatment option for end-stage liver diseases, like Cirrhosis and hepatocellular carcinoma, and acute liver failure; however, due to availability of donor liver, lots of patients never received such treatment option and passed way. Most recently, non-human primates after a liver transplantation with GTKO pigs survived for nearly 1 month indicates a promise of clinical use of liver xenotransplantation and could offer "a bridge transplantation" for fulminant liver failure patients. This review discussed and summarized the advancement and progress in the field, i.e., history of liver xenotransplantation research, model animals, clinical selection criteria, and future research directions and clinical trials.

The shortage of donors restricts the development of organ transplantation. Xenotransplantation might act as an effective approach to resolve this problem. With the advancement of genome editing technologies as well as research and development of novel immunosuppressant, lots of breakthroughs have been achieved in the field of xenotransplantation. Nevertheless, a majority of researches are still in the preclinical stage. Recently, the success of the world's first genetically engineered pig-to-human heart transplantation has greatly inspired researchers. However, clinical xenotransplantation still faces an array of problems, including counteracting rejection, controlling inflammation, regulating coagulation disorder, improving physiological compatibility of xenografts, paying attention to the risk of interspecific infection, optimizing immunosuppressive regimen, screening donor genome editing types, selecting suitable recipients, modifying xenotransplantation guidelines, and awareness of public recognition, etc. In this article, these 10 problems were summarized, aiming to provide reference for promoting the clinical application of xenotransplantation.

Objective To establish Cdh5-Cre ERT /Acta2-tdTomato-STOP floxed -eGFP knockin genetic tracing mice, and to investigate its application in studies on vascular endothelial cell transition in liver fibrosis. Methods Cdh5-Cre ERT mice were mated with Acta2-KI mice, and the Cdh5-Cre ERT /Acta2-KI genetic tracing mice were obtained and identified by PCR genotyping. Primary liver sinusoid endothelial cells (LSECs) were isolated and cultured, and a model of CCl 4 -induced liver fibrosis was established. LSECs and liver tissue were collected for immunofluorescent staining to observe the expression of the fluorescent proteins tdTomato and eGFP. Results After being induced by tamoxifen, LSECs and liver tissue of Cdh5-Cre ERT /Acta2-KI genetic tracing mice expressed eGFP under the conditions for epithelial-mesenchymal transdifferentiation established in vivo and in vitro, while the control group without induction expressed tdTomato alone. Conclusion The successfully established Cdh5-Cre ERT /Acta2-KI genetic tracing mice can realize the effective labeling of epithelial-mesenchymal transdifferentiation, which provides a genetic tracing basis for the diverse sources of mesenchymal myofibroblasts in liver fibrosis.

Objective To investigate the application prospect of the most extensive genome engineering pig internationally in preclinical xenotransplantation. Methods Porcine endogenous retrovirus (PERV) knockout combined with 3 major heterologous antigen gene knockouts and 9 humanized genes for inhibition of complement activation, regulation of coagulation disorders, anti-inflammatory and anti-phagocytosis were transferred into a pig (PERV-KO/3-KO/9-TG) as a donor, and the heart, liver and kidney were obtained and transplanted to 3 Rhesus macaque recipients respectively to establish a preclinical research model of pig-to-Rhesus macaque xenotransplantation. The functional status of xenografts after blood flow reconstruction was observed and the survival of recipients was summarized. The hemodynamics of xenografts were monitored. The change of hematological indexes of each recipient was compared. The histopathological manifestation of xenografts was observed. Results After the blood flow was reconstructed, all xenografts showed ruddy color, soft texture and good perfusion. The transplant heart, liver and kidney showed full arterial and venous blood flow and good perfusion at 1 d after operation. The postoperative survival time of heart, liver, and kidney transplant recipients was 7, 26, and 1 d, respectively. The levels of creatine kinase, creatine kinase isoenzyme, and lactate dehydrogenase increased in heart transplant recipient at 1 d after operation, and gradually recovered to near normal levels at 6 d after operation. All indexes increased sharply at 7 d after operation. The level of aspartate aminotransferase increased in liver transplant recipients at 2 d after operation, and the alanine aminotransferase basically returned to normal at 10 d after operation, but the total bilirubin continued to increase. Both aspartate aminotransferase and alanine aminotransferase increased at 12 d after operation, and reached a peak at 15 d after operation. The kidney transplant recipient developed mild proteinuria at 1 d after operation, and died of sudden severe arrhythmia. Histopathology showed that the tissue structure of cardiac and renal xenografts was close to normal, and liver xenografts presented with patchy necrosis, the liver tissue structure was disordered, accompanied by inflammatory damage, interstitial hemorrhage and thrombotic microangiopathy. Conclusions PERV-KO/3-KO/9-TG pig shows advantages in overcoming hyperacute rejection, mitigating humoral rejection and coagulation dysregulation. However, whether it can be used as potential donor for clinical xenotransplantation needs further evaluation.

Non-alcoholic fatty liver disease (NAFLD) is characterized by increased fat depositions in the liver while the patients do not have drinking history.NAFLD has a prevalence of 10％ ～40％ in global,25％ ～26％ in Western populations.From 2004 to 2013,the numbers of new patients on the waitlist who had NASH increased by 170％ in America.The prevalence of NAFLD in China is 20％.With the decrease of HBV and HCV and the increase of diabetes mellitus type 2 and obesity,NAFLD will become the most common chronic liver disease in China over the next 20 years.NAFLD related end-stage liver disease will become the most common indication of liver transplantation.In this paper,the epidemiological features,pathogenesis,indication and prognosis of liver transplantation are reviewed.