Hepatocyte transplantation using porous matrices is under investigation as an alternative therapy for certain liver diseases. For this purpose, long-term function of transplanted hepatocytes is mandatory. This problem has not been sufficiently investigated yet. In this study Lewis rats were used as donors and recipients. Stimulated (group A, portocaval shunt) or unstimulated (group B) hepatocytes were transplanted into prevascularized polyvinyl-alcohol matrices. Cell-free matrices served as controls (group C). Matrices were harvested between 1 h and 1 year after implantation and analyzed by morphometry; albumin RNA in situ hybridization; and cytokeratin-, actin-, desmin-, and macrophage-specific antigen immunohistology. The hepatocyte number significantly decreased within the first week following implantation. Between 1 month and 1 year after transplantation a significant increase in hepatocyte number was noted in groups A and B. Albumin transcripts of transplanted hepatocytes were at normal levels at all times except for group B after 1 year. The immunohistology suggested engraftment of nonparenchymal liver cells. We conclude that 3-dimensional matrices provide a sufficient environment for long-term engraftment of transplanted liver cells. The hepatocytes are able, despite suboptimal initial engraftment, to repopulate the scaffold for at least half of the recipient's life span and maintain cell-specific function after sufficient stimulation.
