A Review of Machine Perfusion Strategies in Liver Transplantation

An innovative model of en bloc liver-pancreas-kidney preservation via ex vivo hypothermic acellular machine perfusion

BACKGROUND

Liver machine perfusion (MP) has emerged as a promising organ preservation modality. Recent studies have shown that the addition of the kidneys to the circuit improves the biochemical environment and could benefit liver preservation. The aim of this study was to explore the technical and anatomical feasibility of en bloc liver-pancreas-kidney MP. We also examined the safety of ex vivo perfusion with a nonoxygen carrier solution and its effects on acid-base and metabolic parameters using this novel multivisceral perfusion platform.

METHODS

Five multivisceral allografts, including liver, pancreas, duodenum, and kidney, were perfused for 4 h with acellular perfusate. Hemodynamic and laboratory data were evaluated throughout the experiment.

RESULTS

No system failure was reported. There were minimal changes in the acid-base parameters during the experiment. Lactate and glucose levels were stable throughout hypothermic perfusion. There was a mild increase in liver function parameters in the last hour of hypothermic perfusion. No changes in creatinine levels were observed throughout the study. The urine output increased steadily during the experiment, with an average of 155.6 mL/h.

CONCLUSION

We described an innovative multivisceral MP technique that could be further used as a platform for physiological studies and targeted therapeutic interventions. Further investigations are necessary to evaluate this ex vivo perfusion technique and provide insights into the feasibility of hypothermic acellular multivisceral MP in clinical scenarios.

Equal performance of HTK-based and UW-based perfusion solutions in sub-normothermic liver machine perfusion

Machine perfusion (MP) is gaining importance in liver transplantation, the only cure for many end-stage liver diseases. Varieties of different MP protocols are available. Currently, various MP protocols are available, differing not only in perfusion temperature but also in the specific perfusion solution required. We aimed to investigate the performance of an HTK-based perfusate during sub-normothermic MP (SNMP) of discarded human liver grafts compared to that of a UW-based solution. Twenty discarded livers (rejected for transplantation by all centers) were subjected to ex-vivo SNMP at 21°C with either HTK- or UW-based solution for 12 h. Perfusate and tissue samples collected before the start, after 6 h, and at the end of SNMP were analyzed for liver enzymes, along with mRNA expression of perfusate and tissue markers associated with organ damage. Hepatocellular viability was assessed by measuring bile production, monitoring pH stability, and analyzing histological changes in HE stained tissue sections. After propensity score matching 16 livers were analyzed. Overall, no differences between HTK- and UW-based solution were detected, except for an increased MLKL mRNA expression and impaired pH stability during SNMP with HTK-based perfusate. No other investigated parameters of cell injury, inflammation or hepatocellular viability supported this finding. Bile production was higher in the 6 HTK-perfused livers compared to the three UW-perfused livers that produced bile. Overall, these findings suggest that HTK performs comparably to a UW-based solution during 12 h of liver SNMP.

MicroRNA-21 (miR-21) in breast cancer: From apoptosis dysregulation to therapeutic opportunities

Breast cancer, a pervasive and complex disease, continues to pose significant challenges in the field of oncology. Its heterogeneous nature and diverse molecular profiles necessitate a nuanced understanding of the underlying mechanisms driving tumorigenesis and progression. MicroRNA-21 (miR-21) has emerged as a crucial player in breast cancer development and progression by modulating apoptosis, a programmed cell death mechanism that eliminates aberrant cells. MiR-21 overexpression is a hallmark of breast cancer, and it is associated with poor prognosis and resistance to conventional therapies. This miRNA exerts its oncogenic effects by targeting various pro-apoptotic genes, including Fas ligand (FasL), programmed cell death protein 4 (PDCD4), and phosphatase and tensin homolog (PTEN). By suppressing these genes, miR-21 promotes breast cancer cell survival, proliferation, invasion, and metastasis. The identification of miR-21 as a critical regulator of apoptosis in breast cancer has opened new avenues for therapeutic intervention. This review investigates the intricate mechanisms through which miR-21 influences apoptosis, offering insights into the molecular pathways and signaling cascades involved. The dysregulation of apoptosis is a hallmark of cancer, and understanding the role of miR-21 in this context holds immense therapeutic potential. Additionally, the review highlights the clinical significance of miR-21 as a diagnostic and prognostic biomarker in breast cancer, underscoring its potential as a therapeutic target.

The Rationale for Combining Normothermic Liver Machine Perfusion with Continuous Renal Replacement Therapy to Maintain Physiological Perfusate during Ex Vivo Organ Perfusion

Background: The possibility of keeping liver grafts viable and functioning until transplantation has been explored since the 1950s. However, the current modalities of Normothermic Machine Perfusion (NMP) have shown several limitations, such as the inability to correct electrolytes and pH derangements efficiently. Combining NMP with continuous kidney replacement therapy (CKRT) might provide a promising new model to overcome these issues. Methods: An NMP that covers the organ perfusion, oxygenation, carbon dioxide removal, and thermal balance was connected to a CKRT circuit to ensure physiological hydro-electrolytes, acid-base balance, and catabolite removal from the perfusate. Results: The integration of NMP and CKRT maintains a neoplastic liver in a perfusion system with physiological perfusate for 100 h. CKRT re-established and maintained the hydro-electrolyte and acid-base status throughout the 100 h of perfusion. Significant limitations were the need for frequent monitoring of electrolytes and acid-base disorders and the loss of low molecular weight nutrients, which have to be replenished by manual infusion into the system. Conclusions: This novel CKRT-NMP integrated system may represent a practical and versatile model to support organs' perfusion and extend preservation times. Further experiments are needed to fix monitoring and adjusting processes.

Association of donor hepatectomy time with liver transplantation outcomes: A multicenter retrospective study

BACKGROUND

Prolonged donor hepatectomy time may be implicated in early and late complications of liver transplantation.

AIM

To evaluate the impact of donor hepatectomy time on outcomes of liver transplant recipients, mainly early allograft dysfunction.

METHODS

This multicenter retrospective study included brain-dead donors and adult liver graft recipients. Donor-recipient matching was obtained through a crossover list. Clinical and laboratory data were recorded for both donors and recipients. Donor hepatectomy, cold ischemia, and warm ischemia times were recorded. Primary outcome was early allograft dysfunction. Secondary outcomes included need for retransplantation, length of intensive care unit and hospital stay, and patient and graft survival at 12 months.

RESULTS

From January 2019 to December 2021, a total of 243 patients underwent a liver transplant from a brain-dead donor. Of these, 57 (25%) developed early allograft dysfunction. The median donor hepatectomy time was 29 (23-40) min. Patients with early allograft dysfunction had a median hepatectomy time of 25 (22-38) min, whereas those without it had a median time of 30 (24-40) min (P = 0.126).

CONCLUSION

Donor hepatectomy time was not associated with early allograft dysfunction, graft survival, or patient survival following liver transplantation.

Therapeutic potentials of mesenchymal stromal cells-derived extracellular vesicles in liver failure and marginal liver graft rehabilitation: a scoping review

Liver failure includes distinct subgroups of diseases: Acute liver failure (ALF) without preexisting cirrhosis, acute-on-chronic liver failure (ACLF) (severe form of cirrhosis associated with organ failures and excess mortality), and liver fibrosis (LF). Inflammation plays a key role in ALF, LF, and more specifically in ACLF for which we have currently no treatment other than liver transplantation (LT). The increasing incidence of marginal liver grafts and the shortage of liver grafts require us to consider strategies to increase the quantity and quality of available liver grafts. Mesenchymal stromal cells (MSCs) have shown beneficial pleiotropic properties with limited translational potential due to the pitfalls associated with their cellular nature. MSC-derived extracellular vesicles (MSC-EVs) are innovative cell-free therapeutics for immunomodulation and regenerative purposes. MSC-EVs encompass further advantages: pleiotropic effects, low immunogenicity, storage stability, good safety profile, and possibility of bioengineering. Currently, no human studies explored the impact of MSC-EVs on liver disease, but several preclinical studies highlighted their beneficial effects. In ALF and ACLF, data showed that MSC-EVs attenuate hepatic stellate cells activation, exert antioxidant, anti-inflammatory, anti-apoptosis, anti-ferroptosis properties, and promote regeneration of the liver, autophagy, and improve metabolism through mitochondrial function recovery. In LF, MSC-EVs demonstrated anti-fibrotic properties associated with liver tissue regeneration. Normothermic-machine perfusion (NMP) combined with MSC-EVs represents an attractive therapy to improve liver regeneration before LT. Our review suggests a growing interest in MSC-EVs in liver failure and gives an appealing insight into their development to rehabilitate marginal liver grafts through NMP.

Characteristics of Gram-positive cocci infection and the therapeutic effect after liver transplantation

OBJECTIVES

Gram-positive cocci is the main pathogen responsible for early infection after liver transplantation (LT), posing a huge threat to the prognosis of liver transplant recipients. This study aims to analyze the distribution and drug resistance of Gram-positive cocci, the risk factors for infections and efficacy of antibiotics within 2 months after LT, and to guide the prevention and treatment of these infections.

METHODS

In this study, data of pathogenic bacteria distribution, drug resistance and therapeutic efficacy were collected from 39 Gram-positive cocci infections among 256 patients who received liver transplantation from donation after citizens' death in the Third Xiangya Hospital of Central South University from January 2019 to July 2022, and risk factors for Gram-positive cocci infection were analyzed.

RESULTS

Enterococcus faecium was the dominant pathogenic bacteria (33/51, 64.7%), followed by Enterococcus faecalis (11/51, 21.6%). The most common sites of infection were abdominal cavity/biliary tract (13/256, 5.1%) and urinary tract (10/256, 3.9%). Fifty (98%) of the 51 Gram-positive cocci infections occurred within 1 month after LT. The most sensitive drugs to Gram-positive cocci were teicoplanin, tigecycline, linezolid and vancomycin. Vancomycin was not used in all patients, considering its nephrotoxicity. Vancomycin was not administered to all patients in view of its nephrotoxicity.There was no significant difference between the efficacy of daptomycin and teicoplanin in the prevention of cocci infection (P>0.05). Univariate analysis indicated that preoperative Model for End-Stage Liver Disease (MELD) score >25 (P=0.005), intraoperative red blood cell infusion ≥12 U (P=0.013) and exposure to more than 2 intravenous antibiotics post-LT (P=0.003) were related to Gram-positive cocci infections. Multivariate logistic regression analysis revealed that preoperative MELD score >25 (OR=2.378, 95% CI 1.124 to 5.032, P=0.024) and intraoperative red blood cell transfusion ≥ 12 U (OR=2.757, 95% CI 1.227 to 6.195, P=0.014) were independent risk factors for Gram-positive cocci infections after LT. Postoperative Gram-positive cocci infections were reduced in LT recipients exposing to more than two intravenous antibiotics post-LT (OR=0.269, 95% CI 0.121 to 0.598, P=0.001).

CONCLUSIONS

Gram-positive cocci infections occurring early after liver transplantation were dominated by Enterococcus faecalis infections at the abdominal/biliary tract and urinary tract. Teicoplanin, tigecycline and linezolid were anti-cocci sensitive drugs. Daptomycin and teicoplanin were equally effective in preventing cocci infections due to Gram-positive cocci. Patients with high preoperative MELD score and massive intraoperative red blood cell transfusion were more likely to suffer Gram-positive cocci infection after surgery. Postoperative Gram-positive cocci infections were reduced in recipients exposing to more than two intravenous antibiotics post-LT.