Abstract
Extracorporeal liver support has been used to bridge patients with acute liver failure to orthotopic liver transplantation. However, the limited functional sustainability of adult hepatocytes in bioreactors mandates the investigation of alternate cell sources. Owing to their plasticity, fetal hepatocytes are an attractive source for use in bioartificial liver devices. Establishing a renewable in vitro source of fetal hepatocytes would also be of interest with regard to possible hepatic cell transplantation studies. Herein, we discuss the use of single-cell suspensions of murine and human fetal liver cells in a dynamic 3D perfusion bioreactor based on artificial capillary beds which form four interwoven compartments. Histology showed neo-tissue formation in between the artificial capillaries. Further immunohistochemical characterization using proliferating cell nuclear antigen and Ki-67 demonstrated ongoing cell proliferation and survival. These tissues were comprised of albumin-positive hepatocytes, while fewer cells were positive for α-fetoprotein, CK-19, and c-kit, indicating a progenitor compartment. Cells expressing mesenchymal markers, including endothelial and stellate cells, were also observed. While the results of human and murine studies were comparable there were still some dissimilarities which support species differences and perhaps initial viability issues with human fetal hepatocytes. Thus, our preliminary results on human fetal liver cells, supported by experimental data using murine fetal liver cells, suggest that the former have distinct advantages over adult hepatocytes for possible studies in regenerative medicine and can be maintained in vitro over prolonged periods, due to maintenance of the tissue-replenishing progenitor pool.