Consideration of a Safe Protocol for Hepatocyte Transplantation Using Infantile Pigs

Hepatocyte transplantation is hoped to be an alternative treatment to certain cases of liver transplantation. The most promising indication is for congenital metabolic diseases, especially in infants. To establish a safe protocol for hepatocyte transplantation into infants, we examined physiological changes during treatment using infantile pigs. Recipient pigs (domestic, crossbred with Large-Yorkshire, Landrace, and Duroc; 2.5 kg; 7-14 days old) were anesthetized with isoflurane; a midline incision of minimum length provided access to the superior mesenteric vein. A double lumen catheter was inserted through the vein to within 1 cm of the hepatic portal region. Physiological parameters such as heart rate, systemic blood pressure, and portal pressure were monitored. Cryopreserved porcine hepatocytes isolated from the same strain were suspended in physiological saline and transfused through the catheter. In experiments requiring tracing, cells were stained with fluorescent dye prior to transfusion. Recipient pigs were kept for 1 day and sacrificed for histological liver examination. After preliminary experiments, the optimized number and concentration for hepatocyte transplantation were determined to be 1 × 10⁸ cells/kg and 1 × 10⁷ cells/ml. The cell suspension was transfused at a rate of 0.67 ml/min. No marked anomaly of physiological parameters was observed, whereas light tachycardia occurred in preliminary trials when the transfusion rate was faster than our standard protocol. All five pigs transfused with the established method recovered from anesthesia and survived with good vital signs. Histology revealed that the transfused hepatocytes were integrated in the hepatic tissue.