Revolutionizing liver transplants in pigs with magnetic anastomosis technology

In a recent study published in Scientific Reports, a group of researchers evaluated the effectiveness of magnetic anastomosis technology (MAT) in reducing the duration of vascular anastomosis and improving outcomes in pig orthotopic liver transplantation (OLT).

Study: Liver transplantation using magnetic anastomosis in pigs. Image Credit: mi_viri/Shutterstock.com

Background

Liver transplantation is a crucial treatment for end-stage liver diseases, with the duration of the anhepatic phase being a significant factor affecting the prognosis of recipients.

A prolonged anhepatic period, associated with longer warm ischemia times and blood flow disturbances, increases the risk of several complications, such as allograft dysfunction and renal insufficiency. While effective, traditional hand-sewn vascular anastomosis techniques are time-consuming and contribute to the length of the anhepatic phase.

MAT presents a convenient, time-saving method for revascularization, potentially reducing these risks. Despite its promising applications in animal models, further research is needed to refine this technology for clinical use in human liver transplantations, particularly in understanding its long-term effects and biocompatibility.

About the Study

The study utilized a novel magnetic device for MAT to perform liver transplantations in pigs for which twenty healthy adult Bama pigs, randomly divided into donors and recipients, were used.

The donor livers were harvested, cold-flushed with University of Wisconsin solution, and preserved in the same solution at 4°C. During transplantation, the magnetic rings were applied to both donor and recipient livers’ stumps of the portal vein and inferior vena cava (suprahepatic and infrahepatic). 

Anastomosis was achieved by bringing the magnetic rings of corresponding vessels into proximity, allowing for rapid magnetic attachment and vascular connection. The hepatic artery and biliary anastomosis were completed manually.

Postoperative management included antibiotics and analgesics but excluded immunosuppressants. Liver and kidney functions were monitored pre-surgery and at various intervals post-surgery. Imaging studies, including abdominal vascular ultrasound and venography, were conducted to assess the patency of vascular anastomoses. 

Tissues were sampled for histopathological analysis after euthanasia. Data were presented as either counts (percentages) or median values with interquartile ranges (IQR).

The paired t-test or the Wilcoxon signed rank test was employed to assess differences between means, depending on the suitability of the data set. A p-value less than 0.05 was regarded as indicative of statistical significance.

Study results

In the present study involving liver transplants using MAT in pigs, all surgeries performed on the recipients were successful. The average duration of the operation was recorded as 225 minutes, with the cold ischemia time for donor livers being around 59 minutes.

The anhepatic phase, crucial in liver transplantation, was relatively short, with a duration of 13 minutes. During this phase, the suprahepatic and infrahepatic inferior vena cava were connected along with the vein, taking 4, 3, and 3 minutes, respectively. Additionally, recipients had a ischemia time of just 4 minutes. On the other hand, suturing techniques for connecting the artery and bile ducts manually took more time.

After the surgery, there was an increase in serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, which are indicators of liver injury. Still, these levels began to decrease within 24 hours.

Serum total bilirubin also showed a considerable increase postoperatively but declined after 24 hours. Kidney function remained stable throughout both surgery periods, as assessed by blood urea nitrogen (BUN) and serum creatinine (CRE) levels.

The median survival time for recipients following transplantation was 115 days. The main reasons for death included liver failure, rejection by the system, and infections. Other contributing factors were edema and bleeding from the artery anastomosis. Fortunately, during the recovery period after surgery, there were no complications, like blockages or leaks, in the liver’s blood vessels.

A detailed examination of the vascular anastomoses performed with MAT revealed positive outcomes. In one instance, a recipient who survived for 13 days post-operation showed well-healed vascular anastomosis.

The magnetic devices used for the anastomosis were perfectly aligned, with no signs of stenosis or angulation, and the anastomotic stoma surface was smooth. The histological analysis supported these findings, showing a neat alignment of the intima and regular arrangement of endothelial cells and collagen fibers at the anastomotic site.

These results demonstrate the potential of MAT in liver transplantation for effectively reducing critical operation times while ensuring the integrity and functionality of vascular anastomoses.

Conclusions 

To summarize, in the study, MAT was successfully used for rapid donor liver implantation in pig liver transplantations without any postoperative complications related to the technology. Traditional hand-sewn vascular anastomosis methods in liver transplantation are complex and time-consuming, often leading to longer anhepatic phases.

The newly designed MAT, employing Ti-NdFeB composite magnetic rings suitable for permanent implantation, demonstrated excellent biocompatibility and significantly reduced the anhepatic duration to 13 minutes.

This innovation not only simplifies vascular anastomosis but also minimizes the renal and intestinal damage typically associated with prolonged anhepatic phases.

The study also addressed potential concerns regarding anastomotic angulation or distortion due to magnetic forces. It confirmed the safety and effectiveness of the magnetic rings, underscoring their potential to enhance liver transplantation outcomes by reducing ischemia-reperfusion injury.