Morphological aspects of hepatocytes transplanted into the spleen

The morphology of intrasplenic hepatocytes was investigated in the rat from one to twenty months after transplantation. Routine light and electron microscopy confirmed that the appearance of most hepatocytes was normal throughout all the experiments and that at no time were the hepatocytes organized in a structure comparable to the hepatic lobule, with recognizable periportal and perivenous zones. Enzyme histochemical techniques demonstrated that lactate dehydrogenase, a marker of the periportal hepatic zone, was coexpressed in the intrasplenic hepatocytes with NADH dehydrogenase, a marker of the perivenous zone. This finding suggests that, in the spleen, hepatocytes may express new phenotypes, perhaps related to microenvironmental changes. However, immunocytochemical analysis of several components of the extracellular matrix surrounding the intrasplenic hepatocytes did not differ with respect to the normal liver. This suggests that if microenvironmental changes are found to play a role in gene expression by transplanted cells, further investigations will be necessary to analyze this role.