IntroductionEx vivo machine perfusion describes the technique where organs are continuously perfused and oxygenated extracorporeally (at physiological conditions) to maintain the organs' viability. To our knowledge, there are currently no reported studies describing ex vivo perfusion of a single hepatic segment. Here, we describe the development of a porcine ex vivo hepatic segmental perfusion model to demonstrate proof of concept and support further research into the ex vivo perfusion of the human liver using discarded tissue. MethodsWhole livers were retrieved from abattoir-derived pigs and connected to a normothermic extracorporeal perfusion circuit. Constant segmental perfusion via the common or segmental hepatic artery and portal vein with heparinised autologous blood was established. The viability of the perfused organ was assessed by monitoring perfusion pressures, flow rates and histology samples. ResultsFollowing perfusion and optimisation of the model for three hepatic segments, the third perfusion demonstrated viable hepatocytes centrally after 4 h of segmental perfusion. ConclusionEx vivo hepatic segmental perfusion is technically challenging but its success in a porcine model and the principles learned should facilitate the development of an analogous human model using discarded tissue following formal liver resections. The model would use a healthy liver segment following a major formal resection such as a hemi-hepatectomy and ex vivo perfusion performed via a segmental hepatic artery and portal vein. If successful this model would represent a significant development and enable ethical translation research to assess the response of human livers to a variety of stressors, including toxicity and infection.

Background The human immune response to bacterial and viral pathogens has been the focus of intense research, but details on the earliest phases of infection remain unclear. Better knowledge regarding the response of immune cells in the liver is important for the treatment of severe bacterial disease. Ex vivo perfusion which mimics physiological conditions of the liver may provide useful models for this research.  An ex vivo model which perfuses hepatic segments would allow translational research on a physiological and reliable model in the scarce resource of human organs. Here we describe the extra-corporeal perfusion of a porcine hepatic segment. Methods Whole porcine livers were retrieved from animals slaughtered according to UK laws for food production and connected to a normothermic extracorporeal perfusion circuit. Constant perfusion via the hepatic artery and portal vein with heparinized autologous blood was established. Sodium bicarbonate, epoprostanol sodium and calcium chloride were also added to the perfusate to regulate acid-base status and reduce vasospasm. Functionality was assessed by monitoring blood-gases, perfusion pressures and flow rate. A segmental ex-vivo liver resection was performed to leave hepatic segment IV in circuit and isolated segment IV perfusion was maintained for one hour. Results Portal venous pressure was maintained between 8-16mmHg and hepatic arterial pressure between 80-90mmHg. Metabolic acidosis resolved with addition of sodium bicarbonate to the circuit with a pH of 7.42 after segmental perfusion for 1 hour. The lactate increased over the course of the perfusion to 20mmol/L after 1 hour of perfusion, however glucose levels were found to improve with the addition of sodium bicarbonate to the circuit.   Conclusions Isolated segmental perfusion via ex-vivo resection of porcine hepatic segments is technically challenging. Ischaemic-reperfusion injury coupled with progressive metabolic acidosis may limit model viability. However, addition of sodium bicarbonate to the perfusate aids reduction of glucose levels and improves acidosis. Successful perfusion of a porcine hepatic segment provides the potential for segmental perfusion of human hepatic segments such as those resected during hemi-hepatectomies (HRA approved; REC 21/PR/0287). This is an important milestone leading to the creation of a model to study the early changes in human liver tissue for example during infection.