Published online Oct 28, 2017. doi: 10.3748/wjg.v23.i40.7221
Peer-review started: August 19, 2017
First decision: August 29, 2017
Revised: September 10, 2017
Accepted: September 20, 2017
Article in press: September 19, 2017
Published online: October 28, 2017
Liver transplantation is the only effective therapy for end-stage liver disease. At present, due to the shortage of liver donation, marginal donation, which includes aged donation, adipo-hepatic donation, and donation after cardiac death, increases the risk for more severe ischemic reperfusion injury (IRI) because of suboptimal function and long-term warm and cold ischemia. Therefore, there is a current pressing need to explore and improve methods of organ preservation and minimize IRI of donor livers during transplantation.
According to the latest research, machine perfusion has been meaningful for the preservation and repair of marginal liver donation. Another important direction of research on donor liver cold preservation is the auxiliary protective intervention of donor livers against IRI factors of microcirculation and hepatocyte metabolism through drugs. Activation of adenosine 5’-monophosphate-activated protein kinase (AMPK) signaling pathways increases eNOS activity to generate nitric oxide (NO), which plays an important role in the protection of liver sinusoidal endothelial cells. Metformin is an agonist of AMPK. Hence, we assumed that liver sinusoidal endothelial cells can be protected from injury by activating AMPK signaling pathways with the addition of metformin perfused in vitro, which could ultimately cause an improvement of liver donor organ preservation.
In this study, we added metformin to University of Wisconsin (UW) solution, to compare the effect of UW solution with or without metformin, an AMPK activator, for preserving standard and marginal criteria liver grafts of young and aged rats ex vivo by hypothermic machine perfusion (HMP).
Eighteen young (4-mo-old) and 18 aged (17-mo-old) healthy male SD rats were selected and randomly divided into three groups: control group, UW solution perfusion group (UWP), and UW solution with metformin perfusion group (MUWP). Aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), interleukin-18 (IL-18), and tumor necrosis factor-alpha (TNF-α) in the perfused liquid were tested. The expression levels of AMPK and eNOS in liver sinusoidal endothelial cells were also examined. Additionally, microscopic evaluation of the harvested perfused liver tissue samples was done.
AST, ALT, LDH, IL-18 and TNF-α levels in the young and aged liver-perfused liquid in the MUWP group were, respectively, significantly lower than those in the UWP group (P < 0.05), but no significant differences between the young and aged MUWP groups were found. Metformin increased the expression of AMPK and eNOS protein levels, and promoted the extracellular release of nitric oxide through activation of the AMPK-eNOS mediated pathway. Histological examination revealed that in the MUWP group, the extent of liver cells and tissue damage was significantly reduced compared with the UWP group.
This experiment confirmed that the addition of metformin to organ preservation solution can activate AMPK/eNOS pathway, which can not only reduce injury to ex vivo rat livers during cold ischemia, but can reduce the difference between aged and young livers after HMP, with especially significant effects of protecting livers of aged rats, which should probably improve the utilization of marginal liver donor tissues. However, whether metformin can sequentially improve hepatic injury during reperfusion-ischemia requires further investigation. But at least, we provided a novel idea, which is also a simple procedure for drug auxiliary intervention with HMP in ex vivo rat donor livers and deserves further research with a promising prospect.