The early phase of liver regeneration after 70% partial hepatectomy is enhanced in Kupffer cell depleted rats

Transplantation of isolated primary hepatocytes is effective in amelioration of inherited metabolic deficiencies.But survival of allografted hepatocytes (HC) in immunocompetent recipients is limited by immune rejection.We hypothesized that intrathymic injection of cells of the donor strain in the recipient, along with ablation of peripheral lymphocytes should result in the deletion or down-regulation of the newly formed host lymphocytes that recognize the alloantigen.To test this hypothesis, we transplanted allogeneic normal brown Norway rat (BN) hepatocytes into 200 g Gunn rats.All recipients received anti-rat lymphocyte serum (I ml i.p.) 14 days and 7 days before HC transplantation.Splenocytes (5x107) from donor BN rats were injected into both lobes of the thymus of recipient Gunn rats (n =6).Forteen days later, HCs (107) were transplanted by intrasplenic injection.Transplanted hepatocytes were identified in the spleen by in siru hybridization for albumin mRNA.Survival of the transplanted hepatocytes migrating to the liver was determined by amplification of a segment of the 3' domain of bilirubin-UDP-glucuronosyltransferase (B-UGT) mRNA by RT-PCR and digestion with Bat N1 (this restriction site is absent in Gunn rat B-UGT mRNA).Function of the transplanted cells was determined by serial determination of serum bilirubin levels.Transplanted HCs were found to survive in the host liver and spleen throughout the duration of the experiment (154 days).Serum bilirubin concentrations decreased in this group to 40 -50% of the pretransplantation levels in 3 weeks and remained at that level throughout the study period.Analysis of the bile at the end of the experimental period showed the presence of bilirubin mono-and diglucuronides.Two control groups were studied.One group received splenocytes from BN and HC from Gunn rats (n =4), and the other group was injected with splenocytes from Sprague-Dawley rats followed by HC from BN (n=5).In these groups, serum bilirubin levels did not decrease and bilirubin glucuronides were absent in the bile (examined 145 days after transplantation.Conclusion: The results indicate that intrathymic injection of donor splenocytes along with the ablation of host peripheral Jymphocytes results in strain-specific tolerization to allografted HCs.This method may facilitate the treatment of inherited metabolic disorders of the liver by liver cell trans01antation or by hepatocyte-directed ex vivo gene therapy.