Transplantation of human hepatocytes into tolerized genetically immunocompetent rats

AIM To determine whether normal geneticallyirnmunocornpetent rodent hosts could bemanipulated to accept human hepatocytetransplants with long term survival withoutirnrnunosuppression.METHODS Tolerance towards humanhepatocytes was established by injection ofprimary human hepatocytes or Huh7 humanhepatoma cells into the peritoneal cavities offetal rats. Corresponding cells weresubsequently transplanted into newborn rats viaintrasplenic injection within 24 h after birth.RESULTS Mixed lymphocyte assays showedthat spleen cells from non-tolerized rats werestimulated to proliferate when exposed to humanhepatocytes, while cells from tolerized ratswere not. Injections made between 15 d and 17 dof gestation produced optimal tolerizaton.Transplanted human hepatocytes in rat liverswere visualized by immunohistochemicalstaining of human albumin. By dot blotting ofgenomic DNA in livers of tolerized rats 16 weeksafter hepatocyte transplantation, it was foundthat approximately 2.5 × 105 human hepatocytessurvived per rat liver. Human albumin mRNA wasdetected in rat livers by RT-PCR for 15 wk, andhuman albumin protein was also detectable in ratserum.CONCLUSION Tolerization of an immuno-competent rat can permit transplantation, andsurvival of functional human hepatocytes.

AIM: To determine whether normal genetically immunocompetent rodent hosts could be manipulated to accept human hepatocyte transplants with long term survival without immunosuppression. METHODS: Tolerance towards human hepatocytes was established by injection of primary human hepatocytes or Huh7 human hepatoma cells into the peritoneal cavities of fetal rats. Corresponding cells were subsequently transplanted into newborn rats via intrasplenic injection within 24h after birth. RESULTS: Mixed lymphocyte assays showed that spleen cells from non-tolerized rats were stimulated to proliferate when exposed to human hepatocytes, while cells from tolerized rats were not. Injections made between 15 d and 17 d of gestation produced optimal tolerization. Transplanted human hepatocytes in rat livers were visualized by immunohistochemical staining of human albumin. By dot blotting of genomic DNA in livers of tolerized rats 16 weeks after hepatocyte transplantation, it was found that approximately 2.5 X 10(5) human hepatocytes survived per rat liver. Human albumin mRNA was detected in rat livers by RT-PCR for 15 wk, and human albumin protein was also detectable in rat serum. CONCLUSION: Tolerization of an immuno-competent rat can permit transplantation, and survival of functional human hepatocytes.