Histological identification of purified and cryopreserved allogeneic hepatocytes following transplantation in a murine model without host immunosuppression.

Hepatocyte transplantation is a conceptually attractive alternative to whole organ grafting for some inborn metabolic errors and for fulminant liver failure. However, studies of the immunogenicity of transplanted allogeneic hepatocytes have yielded contradictory results. In these experiments, the effect of purification and cryopreservation of the hepatocytes on the ability of these cells to engraft in the mouse allogeneic recipients without immunosuppression was studied. BALB/cByJ mouse crude (unpurified), modified (purified or cryopreserved), or dead (irradiated) hepatocyte preparations labeled with fluorescein dye CFSE were infused either into the portal vein or into the spleen parenchyma of the recipient CBA mice. A histological examination revealed normal appearance of engrafted modified hepatocytes with no signs of acute rejection up to 21 days posttransplant. Many of the intrasplenically implanted hepatocytes migrated into the hepatic sinusoids. The modified hepatocytes showed intact ultrastructural appearance 7 days after transplantation. The numbers of inoculated crude hepatocytes rapidly declined with signs of dense infiltration of mononuclear cells in the graft indicating destructive response. The fluorescence of dead hepatocytes was undetectable. These results suggest that reduced immunogenicity may be responsible for the longer survival time of inoculated, purified or cryopreserved hepatocytes with no adverse morphological effects.