Cell choice for bioartificial livers.

It is unlikely that human hepatocytes can be isolated on a scale sufficient to treat more than a fraction of the patients who need bioartificial liver (BAL) treatment. The use of animal cells results in the concerns related to the transmission of infectious pathogens and immunologic and physiologic incompatibilities between the donor and humans. Human embryonic stem cells and bone marrow multipotent adult progenitor cells have received great attention as a possible source for BALs. The use of tightly regulated clonal hepatocyte cell lines would be attractive. Such cell lines grow economically in tissue culture and provide the advantage of uniformity, sterility, and freedom of pathogens. In this paper, the authors review the choice of cells for BALs and discuss our reversible immortalization system of human liver cells using a retroviral transfer of immortalizing genes and subsequent Cre/loxP-mediated site-specific recombination.