Studies on the Safety of Intrasplenic Hepatocyte Transplantation: Relevance toEx VivoGene Therapy and Liver Repopulation in Acute Hepatic Failure

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Abstract
Hepatocytes transplanted into the host liver engraft promptly, retain normal function, and survive indefinitely. Although intrasplenic transplantation is effective in delivering hepatocytes to the liver, to define potentially limiting complications, we studied its safety in normal, cirrhotic, and partial portal vein-ligated rats. In normal rats, portal pressures increased severalfold after hepatocyte transplantation but returned to normal within 3 weeks. In contrast, in portal hypertensive rats with partial portal vein ligation or cirrhosis, portal pressures were either unchanged or increased less after hepatocyte transplantation. However, more transplanted cells migrated to the lungs along with a rise in right atrial pressures in portal hypertensive rats. Further quantitative studies using 111Indium-labeled hepatocytes showed that intrasplenic retention of transplanted hepatocytes was similar in all animal groups. Intrahepatic cell translocation was comparable in normal and cirrhotic rats, whereas fewer cells migrated to the liver in partial portal vein-ligated rats. The most remarkable difference, however, was significantly greater intrapulmonary translocation of hepatocytes in portal hypertensive rats, which was presumably related to portosystemic shunting. These results indicate that because intrasplenic hepatocyte transplantation induces only temporary portal hypertension in normal subjects, potential strategies to augment liver repopulation could include repeated cell transplantation. This should be useful for optimizing the results of ex vivo gene therapy, or other hepatocyte-based therapies. However, the hepatic and portal hemodynamic status requires careful evaluation in portal hypertensive or cirrhotic subjects if serious complications are to be avoided.