The Effect of Liver Movement During Normothermic Machine Perfusion on Function and Tissue Integrity

Abstract

Liver transplantation remains the only definite cure for end-stage liver disease, yet the demand for donor livers far surpasses their supply, resulting in substantial wait-list mortality rates. This has led to the exploration of extended criteria donor (ECD) livers, which often exhibit compromised function and susceptibility to post-transplantation complications. Ex vivo normothermic machine perfusion (NMP), emerges as a promising approach to assess liver quality, extend preservation duration, and therefore reduce the supply-and-demand imbalance and post-transplantation complications. Moreover, long-term (> 24 hours) NMP could enable treatment, repair, and regeneration of liver grafts and serve as a valuable platform for drug testing and disease modeling. To achieve long-term NMP, it is crucial to recreate the in vivo physical conditions during ex vivo perfusion. The aim of this thesis was to incorporate liver movement during porcine liver NMP and assess the effect of liver movement on liver function and tissue integrity.

Therefore, a new liver reservoir including liver movement was developed and subsequently used to perform porcine liver NMP experiments. Slaughterhouse procured porcine livers (n = 4), were perfused via the hepatic artery (HA) and portal vein (PV) under the established movement condition for 360 minutes. After 120 and 300 minutes of perfusion, indocyanine green (ICG), a fluorescent dye, was dosed, and samples were taken from the arterial circulation and bile to study the clearance capacity of the liver. Hourly samples of the perfusate and bile were taken for blood gas analysis and measurement of injury markers, to assess the general viability and functionality of the liver. And tissue samples were taken at the end of perfusion to study tissue integrity.

Liver movement was established by alternatively inflating and deflating two balloons underneath the liver, with both inflation and deflation lasting 8 seconds. The 6-hour porcine liver NMP experiments under the established movement condition showed liver viability and functionality in terms of glucose metabolism, lactate and bilirubin clearance, stable levels of injury markers, and continuous bile production. The ICG clearance capacity of the liver showed to be improved, although not significantly, under the movement condition, with a mean perfusate disappearance rate (PDR$_\text{ICG}$) of 30.6 $\pm$ 11.7 \% per minute, compared to the static condition (11.0 $\pm$ 3.3 (Zeist) and 21.8 $\pm$ 13.8 (Leiden) \% per minute), after 300 minutes of NMP. The macroscopic appearance and histological analysis of the liver revealed some non-perfused areas on the bottom of the liver, but overall, the liver tissue was intact, and no major hepatocellular damage occurred after 5$-$7 hours of NMP under the movement condition.

A novel liver reservoir including liver movement was established to study the sole effect of movement during NMP. During the 6-hour porcine liver NMP experiments under the established movement condition, the livers showed proper clearance capacity and tissue integrity. Although inclusion of movement did not result in a significant improvement with respect to liver function, it is hypothesized that movement will prolong the viability and functionality of livers when performing NMP for more than 24 hours.