Abstract
The protective mechanisms for liver preservation associated with hypothermic machine perfusion (HMP) remain unclear. However, the lack of a common and portable HMP system for rat livers limits the study of HMP. The present study aimed to develop a novel, modified HMP system using a LifePort Kidney Transporter for preserving rat livers. A simple 'Y' shunt combined with a pressoreceptor for flow and pressure regulation was adapted to perfuse rat livers via the portal vein continuously using a LifePort Kidney Transporter under its 'prime mode' setting. An electronic scale was installed under the liver container to calculate the portal inflow according to the association with weight, density and volume of the perfusate. A total of 10 rat livers underwent 6 h of HMP using histidine-tryptophan-ketoglutarate solution enriched with acridine orange (AO) and propidium iodide (PI). The perfusion status of HMP was assessed by comparison of AO+PI-positive cell count in core region (CR) and peripheral region (PR) of rat liver under fluorescence microscopy. The dynamics (inflow, pressure and intrahepatic resistance of perfusion) were assessed to identify whether this system met the demands for HMP of rat livers. Biochemical [alanine transaminase (ALT), lactate dehydrogenase (LDH) and endothelin levels] and histological parameters (sinusoidal dilatation, endothelial cell detachment and vacuolization) were measured to determine cellular damage associated with HMP. No significant difference was observed between the CR and PR according to the comparison of the AO+PI-positive cell count, which indicated that complete perfusion was achieved. Intrahepatic resistance significantly decreased during the initial 3 h of HMP (P<0.01), but remained stable during the final 3 h. ALT and LDH levels significantly increased over the 6 h HMP duration: ALT (0 h, 42.67±5.81 U/l; 3 h, 90.67±6.74 U/l; 6 h, 164.33±7.31 U/l; P<0.01) and LDH (0 h, 492.90±90.20 U/l; 3 h, 973.53±97.4; 6 h, 1,843.40±85.78 U/l; P<0.01) However, the levels of endothelin and oxygen consumption were constant throughout HMP. Furthermore, histological analysis indicated sinusoidal dilation was significantly increased in the post-HMP group compared with the pre-HMP group (P<0.01); however, no other significant differences were observed. Combined with the results of ATP test (640.64±29.46 nmol/l) and bile production (4.88±0.69 µl/h/g of liver) at the end of HMP, the present results demonstrated minimal cellular injury associated with HMP while retaining the dependability and portability of the LifePort Kidney Transporter, which suggests the modified HMP system met the demands required and may be suitable for rat liver preservation.