Improvement of Normothermic Ex Vivo Machine Perfusion of Rat Liver Grafts by Dialysis and Kupffer Cell Inhibition With Glycine

Normothermic ex vivo liver machine perfusion might be a superior preservation strategy for liver grafts from extended criteria donors. However, standardized small animal models are not available for basic research on machine perfusion of liver grafts. A laboratory-scaled perfusion system was developed consisting of a custom-made perfusion chamber, a pressure-controlled roller pump, and an oxygenator. Male Wistar rat livers were perfused via the portal vein for 6 hours using oxygenated culture medium supplemented with rat erythrocytes. A separate circuit was connected via a dialysis membrane to the main circuit for plasma volume expansion. Glycine was added to the flush solution, the perfusate, and the perfusion circuit. Portal pressure and transaminase release were stable over the perfusion period. Dialysis significantly decreased the potassium concentration of the perfusate and led to significantly higher bile and total urea production. Hematoxylin-eosin staining and immunostaining for single-stranded DNA and activated caspase 3 showed less sinusoidal dilatation and tissue damage in livers treated with dialysis and glycine. Although Kupffer cells were preserved, tumor necrosis factor α messenger RNA levels were significantly decreased by both treatments. For proof of concept, the optimized perfusion protocol was tested with donation after circulatory death (DCD) grafts, resulting in significantly lower transaminase release into the perfusate and preserved liver architecture compared with baseline perfusion. In conclusion, our laboratory-scaled normothermic portovenous ex vivo liver perfusion system enables rat liver preservation for 6 hours. Both dialysis and glycine treatment were shown to be synergistic for preservation of the integrity of normal and DCD liver grafts.

Co-culture system of hepatocytes and endothelial cells: two in vitro approaches for enhancing liver-specific functions of hepatocytes

Although hepatocyte transplantation and bioartificial liver support system provide new promising opportunities for those patients waiting for liver transplantation, hepatocytes are easily losing liver-specific functions by using the common in vitro cultured methods. The co-culture strategies with mimicking the in vivo microenvironment would facilitate the maintenance of liver-specific functions of hepatocytes. Considering that hepatocytes and endothelial cells (ECs) account for 80-90% of total cell populations in the liver, hepatocytes and ECs were directly co-cultured with hepatic stellate cells (HSCs) or adipose tissue-derived stem cells (ADSCs) at a ratio of 700:150:3 or 14:3:3 in the present study, and the liver-specific functions were carefully analyzed. Our results showed that the two co-culture systems presented the enhanced liver-specific functions through promoting secretion of urea and ALB and increasing the expressions of ALB, CYP3A4 and HNF4α, and the vessel-like structure in the co-culture system consisted of hepatocytes, ECs and ADSCs. Hence, our results suggested that the directly co-culture of hepatocytes and ECs with HSCs or ADSCs could significantly improve liver-specific functions of hepatocytes, and the co-culture system could further promote angiogenesis of ECs at a later stage. Therefore, this study provides potential interesting in vitro strategies for enhancing liver-specific functions of hepatocytes.

Isolation, characterization and cold storage of cells isolated from diseased explanted livers

INTRODUCTION

Livers discarded after standard organ retrieval are commonly used as a cell source for hepatocyte transplantation. Due to the scarcity of organ donors, this leads to a shortage of suitable cells for transplantation. Here, the isolation of liver cells from diseased livers removed during liver transplantation is studied and compared to the isolation of cells from liver specimens obtained during partial liver resection.

METHODS

Hepatocytes from 20 diseased explanted livers (Ex-group) were isolated, cultured and stored at 4°C for up to 48 hours, and compared to hepatocytes isolated from the normal liver tissue of 14 liver lobe resections (Rx-group). The nonparenchymal cell fraction (NPC) was analyzed by flow cytometry to identify potential liver progenitor cells, and OptiPrep™ (Sigma-Aldrich) density gradient centrifugation was used to enrich the progenitor cells for immediate transplantation.

RESULTS

There were no differences in viability, cell integrity and metabolic activity in cell culture and survival after cold storage when comparing the hepatocytes from the Rx-group and the Ex-group. In some cases, the latter group showed tendencies of increased resistance to isolation and storage procedures. The NPC of the Ex-group livers contained considerably more EpCAM+ and significantly more CD90+ cells than the Rx-group. Progenitor cell enrichment was not sufficient for clinical application.

CONCLUSIONS

Hepatocytes isolated from diseased explanted livers showed the essential characteristics of being adequate for cell transplantation. Increased numbers of liver progenitor cells can be isolated from diseased explanted livers. These results support the feasibility of using diseased explanted livers as a cell source for liver cell transplantation.