Multi-modal assessment of liver grafts undergoing normothermic machine perfusion to stratify quality and deliver therapy

Liver transplantation is a curative treatment for patients with end stage liver disease but a global shortage of donor organs means that many patients die waiting for suitable liver. To address this, livers from older donors with increasing comorbidity and livers donated after circulatory death areroutinely considered. Many of these livers are turned down for transplantation due to concerns about function and appearance. The critical decisions are based on scarce functional data available
at the time of donation and subjective appearance as judged by the retrieving surgeons.

Normothermic perfusion technology is now increasingly used in clinical practice and appears to improve the utilisation of organs for transplantation and provide better clinical outcomes. Normothermic perfusion of the liver maintains the organ in a functional state outside the body and delivers oxygen and nutrients at normal body temperature for up to a week. This allows a dynamic assessment of the function of the organ increasing surgeons' confidence to use the organ. At present this assessment is based on limited biochemical parameters.

Normothermic perfusion of the organs offer several additional opportunities which are yet to be developed in the clinical setting, which include an in-depth assessment of liver quality and function, delivery of new therapies directly into the liver and evaluation of how these therapies affect the quality and function of the organ. We want to explore some of these opportunities by perfusing human organs retrieved for the purpose of transplantation from consenting donors.
In the first instance, we want to assess the liver in real time combining imaging modalities (such as Raman spectroscopy or multiplex multi-sensing fiber optics) with analysis of the metabolic function of the liver using technologies such as proteinomics, cell free DNA, single cell sequencing. This will allow us to understand the difference in how brain death (DBD) and circulatory death (DCD) affect the livers and its various cells and develop potential therapies to target and repair these negative effects.
Secondly, we want to deliver cell therapies directly into the liver whilst kept alive on the machine. We will focus on therapies directed at improving the quality of the liver as identified in the first part of the project and isolate the cells for these therapies from livers that are unsuitable for human transplantation to maximise organ utilisation.
Using the multi-modal assessment strategies developed in the first stage of the project we will evaluate how effective these therapies are in improving the quality of the liver.

If the organs are transplanted, we will use machine learning and informatics to analyse data generated from these assays and correlate with the clinical outcome post transplant. If the organs are found unsuitable by clinicians and there is the next of kin has consented to use these organs for research, we will isolate the cells from these liver to use as therapies.

This proposed research will generate novel clinically relevant biomarkers and develop new real time technology to assess in depth the quality of the liver grafts and the effect of any interventional therapy. This will have a significant clinical impact allowing an increase in organ utilisation and minimise organ discard. Secondly, establishing the concept of liver derived cell therapies and delivery of therapies targeted to the organ during machine perfusion, will allow the utilisation of all donated organs and enable the development of organ repair centres where such therapies can be delivered in appropriate environments and their effects assessed using the multi-modal assessment tools developed.

The perfusion programme has three key linked aims and is a preclinical, experimental study whereby human organs will be normothermically perfused. Up to 40 livers will undergo normothermic perfusion during the three year period of the study. Access to human organs discarded from transplantation is already in place through national approval from NHSBT and ethical committees. In addition access to the national organ donation biobank (QUOD) will provide control tissue samples from organs that are transplanted and linked clinical data to establish correlation of the biomarkers with clinical outcomes.
We will analyse whole organs and cell subsets looking for injury, senescence and cell death using an array of cutting edge technologies (e.g. proteinomics, cell free DNA, Raman spectroscopy, multiplex multi-sensing fiber optics) together with point of care biochemical analysis. Perfusate, tissue, bile and urine samples will be taken for analysis across the course of the perfusion up to 48-72 hours (or longer if perfusion technology allows it). Using MR spectroscopy and Raman spectroscopy we will assess changes in the liver structure during machine perfusion. The biliary cellular compartment will be assessed in real time continuously using in vivo multicore fibre based multiparametric multiplexed sensing which will be confirmed with traditional biochemical parameters to determine accuracy.
We will use machine learning and informatics to analyse data generated and if organs are used clinically, we will link the experimental data with the clinical outcomes using the QUOD and NHSBT If organs are not used clinically, cell populations will be rested in vivo/vitro and additional data generated as feedback on the predictive ability of the assays used. These cell populations will then be infused in the liver during normothermic machine perfusion and effects assessed using the above assays.