The fate of fragments of liver implanted in ectopic sites

Whole fetal liver transplantation--a new approach to cell therapy

We recently developed a novel rat model for liver repopulation, heterografting of microliver slices, aimed at overcoming the limitations inherent in both whole liver and hepatocyte transplantations. The aim of the present study was to evaluate the potential of whole fetal liver transplantations to survive and differentiate within the adult liver, using the adult liver slice transplantation model. Embryonic day 14 whole fetal livers from dipeptidyl peptidase IV+/+ wild-type Fischer 344 rats were transplanted into the livers of dipeptidyl peptidase IV-/- mutant rats. Adult hepatic markers, dipeptidyl peptidase IV, albumin, glycogen, and proliferation cell nuclear antigen- proliferation cell nuclear antigen (PCNA) were assessed in the transplanted liver tissue by immunohistochemistry. Two groups of 9 rats each were transplanted with 3 fetal livers per recipient. Two months later the rats were sacrificed and the markers were detected in the transplanted tissues. In conclusion, the results of this study raise the possibility that fetal liver transplantation could serve as a model for genetic metabolic liver diseases.

A study of liver regeneration using fetal rat liver tissue transplanted into the spleen

The liver morphology of fetal hepatic tissue transplanted into an ectopic location was investigated over one year period. Fetal liver fragments prepared from a maternal rat on the 18th or 19th day of pregnancy were injected into the splenic parenchyma of syngeneic rats using a 21 gauge needle. Histologically, the fetal liver did not essentially show any apparent lobular architecture or cord structure. The transplanted fetal hepatic tissues survived and formed hepatic cords in the spleen instead of undergoing degeneration and necrosis. Three characteristic features became complete during the 4 weeks following transplantation, namely; clumps of hepatocytes with obvious hepatic cords and sinusoids, markedly proliferating bile ducts and proliferating individual hepatocytes. Macroscopic nodules of the hepatocytes on the spleen were seen at about 6 months after transplantation. When the differentiation of the transplanted fetal hepatic tissue was compared with the development of a normal neonatal liver after birth, it was delayed by only about one week, while there was no proliferation of bile ducts in the normal neonatal liver. This experimental model provides a useful system for investigating liver regeneration and the mechanism of cell growth.

Promoting effect of estrogen on regeneration of the liver transplanted to an ectopic site in mice

A single oral administration of a pharmacological dose of estriol (E3) immediately after transplantation of small liver fragments of mice under the kidney capsule induced a remarkable growth of regenerating liver tissue. The hepatocytes were successfully arranged in cords with well developed sinusoids between them. The cytoplasm of the hepatocytes showed prominent basophilia. In mice injected with carbon intravenously, large numbers of carbon-laden endothelial lining cells and Kupffer cells appeared in the newly building sinusoids. E3 raised the mitotic activity of the regenerating hepatocytes markedly and for a long period. The act of E3 on mitosis was much more effective on the regenerating hepatocytes than on the recipient's own hepatocytes.

The origin of hemopoietic cells in ectopic implants of spleen and marrow

Spleen and marrow tissues were cross-transplanted between CBA and CBA/HT6 mice. The majority of karyotypes in the regenerated implants were of recipient origin indicating that these implants are chimeric structures with the stroma of donor origin providing a framework for the proliferation of the recipient's hemopoietic stem cell.

Differences in susceptibility of tissues to revascularization studied in ectopic implants

The survival rate of implanted marrow is reduced when the tissue is transferred from one site to another within the first 24 hours but not more than 48 hours after the initial implantation. Splenic implants can be transferred at any time after implantation without affecting the survival rate. The observation suggests a difference in the sensitivity of the two tissues to the avascular period that they experience prior to initiation of angiogenesis.