Isolation, characterization, and transplantation of bone marrow-derived hepatocyte stem cells

Recently it was shown that a population of cells in the bone marrow-express ing hematopoietic stem cell antigens could differentiate into hepatocytes. However, explicitly committed hepatocyte progenitors, which exhibit highly differentiated liver functions, immediately upon isolation, have not yet be en isolated from bone marrow. After studying common antigens on blast-like cells in fetal and adult regenerating cholestatic rat livers and human rege nerating and malignant livers, we hypothesized that beta-2-microglobulin-ne gative (beta (2)m(-)) cells might represent dedifferentiated hepatocytes an d/or their progenitors. Utilizing a two-step magnetic bead cell-sorting pro cedure, we show that in bone marrow from rat and human, beta (2)m(-)/Thy-1( +) cells consistently express liver-specific genes and functions. After int raportal infusion into rat livers, bone marrow-derived hepatocyte stem cell s (BDHSC) integrated with hepatic cell plates and differentiated into matur e hepatocytes. In a culture system simulating liver regeneration and contai ning cholestatic serum, these cells differentiated into mature hepatocytes and metabolized ammonia into urea. This differentiation was dependent on a yet nondescript humoral signal existing in the cholestatic serum. Transmiss ion electron microscopy and three-dimensional digital reconstruction confir med hepatocyte ultrastructure of cultured BDHSC. (C) 2001 Academic Press.