Establishment of a hepatocytic epithelial cell line from the murine fetal liver capable of promoting hemopoietic cell proliferation.

Although the fetal liver has been thought to be the main hemopoietic organ in the embryonal period, whether or not hepatocytes play a major role in hemopoiesis remains obscure. We have established an epithelial cell line from the murine fetal liver, which can support hemopoiesis in vitro. The proliferation of the epithelial cells was promoted synergistically by both epidermal growth factor (EGF) and insulin. The cells were identified as epithelial cells by the presence of desmosomes and tight junctions. Cytoplasmic organelles including small mitochondria and dilated Golgi apparati as well as intercellular canalicular structures similar to bile canaliculus also helped in confirming the hepatic origin of the cell line (designated as FHC). The cells in the primary culture were positive for both alpha-fetoprotein and albumin, indicating the hepatocytic nature of the cell line. Cloned FHC cells were demonstrated to have the ability to maintain hemopoietic progenitors in fetal liver and adult bone marrow in the coculture, and among them, FHC-4D2 clone displayed the greatest activity. Hemopoiesis-supporting function could also be seen even when bone marrow cells were separated from FHC-4D2 cells by nitrocellulose membrane. Column chromatography revealed three distinct peaks of hemopoietic activities with different molecular sizes in the supernatant of FHC-4D2. Neutralization test with antibodies and proliferative response to interleukin-3 (IL-3)/granulocyte-macrophage colony stimulating factor (GM-CSF)-responding IC2 cells demonstrated that the hemopoietic activities were attributed to GM-CSF and macrophage colony stimulating factor (M-CSF). Transcripts of GM-CSF and M-CSF were readily detectable in Northern blot analysis, whereas no messages for IL-3, IL-6, CSF for granulocytes (G-CSF) or erythropoietin (EPO) were identified. Therefore, this is the first report on the fetal hepatocyte cell line capable of supporting hemopoiesis.