title: Repopulation of the immunosuppressed retrorsine-treated infant rat liver with human hepatocytes.
abstract: BACKGROUND
  We previously generated humanized chimeric mice by transplanting h-hepatocytes into the livers of the diseased-liver transgenic mouse model with immunodeficient background. These mice with livers mostly replaced by human (h) hepatocytes have been proved to be useful for research on drug metabolism and toxicity and on intrahepatic pathogens such as hepatitis. However, their small body size prohibited collecting sufficient biological samples and made surgical manipulation difficult, which motivated us to produce humanized larger animal(s) bearing h-hepatocytes.
  
  
  METHODS
  Fischer 344 (F344) rats at 2 weeks of age were administrated with hepatotoxin retrorsine (RS) and then transplanted with syngeneic F344 rat (r)- or h-hepatocytes via the portal vein. The hosts were injected daily with FK506 immunosuppressant. The livers were harvested periodically for determining donor-cell replacement ratios and compared with those of the humanized chimeric mice, and liver-specific mRNA and protein expressions by immunohistochemistry and reverse-transcription PCR.
  
  
  RESULTS
  RS treatment of infant rats inhibited hepatocyte proliferation, resulting in decreased liver weight and megalocytic changes in hepatocytes. R-hepatocytes transplanted into RS-treated rats engrafted into and repopulated the liver at ratios of 16.4 ± 6.7% and 48.3 ± 29.3% at 3 and 6 weeks after transplantation, respectively. H-hepatocytes also engrafted into the rat liver and showed a repopulation ratio of 2.5 ± 1.5% at 3 weeks post-transplantation, which was comparable to the ratio in the humanized chimeric mouse model at least until 3 weeks. Propagated h-hepatocytes in the rat liver expressed hepatocyte-specific mRNA and proteins at least 3 weeks after transplantation.
  
  
  CONCLUSIONS
  Xenogeneic hepatocytes were able to engraft rat liver and grow well therein for at least 3 weeks post-transplantation in rats when immunosuppression was combined appropriately with liver injury at comparable levels to the well-characterized humanized chimeric mouse model.
authors.affiliation: Yoshizato Project, Cooperative Link of Unique Science and Technology for Economy Revitalization (CLUSTER), Hiroshima Prefectural Institute of Industrial Science and Technology, Higashihiroshima, Hiroshima, Japan.
authors.forename: Asato
authors.initials: A
authors.lastname: Tachibana
authors.forename: Chise
authors.initials: C
authors.lastname: Tateno
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Yoshizato
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D017690:Cell Transplantation / Q000379:methods*; D005260:Female; D022781:Hepatocytes / Q000166:cytology*; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007275:Injections, Intravenous; D008099:Liver / Q000166:cytology* / Q000187:drug effects; D008297:Male; D023421:Models, Animal; D011763:Pyrrolizidine Alkaloids / Q000494:pharmacology*; D051381:Rats; D011916:Rats, Inbred F344; D016559:Tacrolimus / Q000494:pharmacology; D018183:Transplantation Chimera; D014183:Transplantation, Heterologous / Q000379:methods*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D007166:Immunosuppressive Agents; D011763:Pyrrolizidine Alkaloids; D016559:Tacrolimus; C003300:retrorsine
keywords: human hepatocytes; retrorsine; xenotransplantation