Slow cooling rate with a shock cooling program can effectively cryopreserve pig hepatocytes.

Hepatocyte transplantation is a potential alternative to whole organ liver transplantation. To realize this procedure, a hepatocyte bank system capable of supplying large numbers of hepatocytes must be established. The aim of this study was to develop a cryopreservation protocol using controlled rate freezers (CRF) for the application of a bioartificial system of porcine hepatocytes. Hepatocytes were harvested from 3- to 4-week-old male pigs weighing 11-14 kg. Liver cell preparations were prepared and the spheroid hepatocytes were cryopreserved using University of Wisconsin (UW) solution in controlled freezing. After thawing, viability, plating efficiency, urea synthesis, and ammonia removal were measured to assess the effects of freezing methods. Freezing methods had effects on the viability and specific functions of hepatocytes after thawing. About 80% of the cell viability could be obtained with an optimal computer programming method (-1°C slow cooling rate with shock cooling, using UW solution with 15% dimethyl sulfoxide [DMSO]). The cryopreservation method for hepatocytes was significantly improved by using the above cryopreservation conditions. However, research on application to large-scale cryopreservation is needed for practical use.