| The liver is one of the earliest organ selected for transplantation. In recent years human hepatocytes transplantation has been emphasized very much on the domain of medicine. Liver cell transplantation is not olny as a effective therapy technique, but also useful to establish animal model with allogeneic hepatocytes in understanding liver disease with virus infection.Transplantation of allogeneic hepatocytes into immunocompetent rodents has been shown to result in rejection of donor cells by host immune system, with T- cell activation and a delayed type hypersensitivity reaction. This can been overcome by generalized immunosuppression or through the use of genetically immunodeficient animals. Another strategy to avoid rejection is by inducing immunological tolerance specifically to the transplanted cells. It has been demonstrated that the ability of the immune system to distinguish between endogenous and exogenous antigens develops shortly before birth. Tolerance to endogenous tissue or cell and exclude exogenous material through immune rejection after effective recognition. Studies have shown that if foreign antigens are introduced during this formative period, when the animals mature, they will be tolerant to those antigens, permitting the survival of allogeneic transplants in rats.Tolerance to human hepatocytes was established by injection of human fetal hepatocytes into the peritoneal cavities of fetal rats. Corresponding cells were subsequently transplanted into newborn rats via intrasplenic injection within 24 hours after birth to establish tolerized rats with chimeric human liver. After that, rats were inoculated with hepatitis B virus (HBV), characterize the host response to HBV infection in human hepatocytes transplanted into immunocompetent rodent rats tolerized by, and transplanted with human fetal hepatocytes(HFH). Following is methods and result:The first study were performed to establish an animal model of tolerized rats with chimeric human liver. Rats were rendered tolerant to HFH by intrafetal injection of those cells. In brief, at 14 to 18 days of gestation, groups of pregnant rats were anesthetized. Laparatomies were performed under sterile conditions; gravid uteri were exposed, HFH were injected through the uterine wall into the peritoneal cavities of rat fetuses using a sterile syringe and sew up. Within 24 hours of birth, HFH were injected into the spleen by sterile syringe in newborn rats. Transplanted human hepatocytes in rat livers were visualized at different time with different assays after birth. Human albumin protein was detectable in rat serum by Western blot from 4 to 8 weeks. Human albumin mRNA was detected in rat livers by RT-PCR from 4 to 10 weeks, and cell keratin from human hepatocyte of Cytokeratin 18 was also detected in rat livers by immunohistochemical staining from 4 to 12 weeks. The second studies were performed to evaluate the effects of HBV infection on tolerized rats with chimeric human liver. This was accomplished by rendering normal rats tolerant to human hepatocytes by intrafetal injection of HFH. The rats were then transplanted with the same batches of cells within 24 hours of birth, and one week following human hepatocytes transplantation tolerized rats were inoculated with 7.154×107 HBV particle in 100(l human HBV infective serum with normal liver functional examine (surface antigen, e antigen and anti center antibody of HBV were all positive). HBV infected rats with transplanted HFH causes a biochemical and histological changes , that were visioned at different time with different assays. HBsAg were detected for 4~12 week-age in rat serum, and HBsAg positive rate were each 61.9%,53.8%,42.1%,40.6% and 23.3% at 4,6,8,10,12 week in rat serum. Based on if detectable HBsAg positive in rat serum, we collected experimental rats with HBsAg positive in serum united into a group, named HBV infection group, the negative were non-HBV infection group. Though serum Alanine aminotransferase(ALT) levels rose in experimental rats from 4 to 12 week-age, ALT of HB...
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