Enhanced proliferation and differentiation of rat hepatocytes cultured with bone marrow stromal cells

Liver transplantation is the only clinically effective method of treating a cute liver failure. However, wider application of this therapeutic modality is restricted primarily by shortage of donor organs. in the search for alt ernative methods of liver replacement therapy, investigators have focused o n transplantation of normal allogeneic hepatocytes and on the development o f liver support systems utilizing isolated hepatocytes. Since all human liv ers suitable for cell harvest are being used for transplantation, hepatocyt e therapy using human tissue would require growing of cells in vitro. Unfor tunately, although hepatocytes have tremendous capacity to proliferate in v ivo, their ability to grow in culture is severely limited. Stromal cells fr om bone marrow and other blood-forming organs have been found to support he matopoiesis. In this paper, we show that bone marrow-derived stromal cells (BMSCs) enhance proliferation and support differentiation of rat hepatocyte s in culture. Further, we demonstrate that in hepatocyte/BMSC co-cultures, clonal expansion of small hepatocytes (SH) is increased. Using semipermeabl e membrane cultures, we established that direct cell-cell contact is necess ary for stimulation of cell proliferation. We also show that BMSCs which ar e in direct contact with hepatocytes and SH colonies express Jagged1. This suggests a potential role for Notch signaling in the observed effects. Fina lly, we present evidence that the expression and activity of liver specific transcirption factors, CCAAT/enhancer binding proteins and liver specific key enzymes Such as tryptophan 2,3-dioxygenase, are improved in hepatocyte/ BMSC co-cultures. In conclusion, results of this study indicate that BMSCs could facilitate proliferation and differentiation of primary rat hepatocyt es and their progenitors (SH) in vitro. J. Cell. Physiol. 189: 106-119, 200 1. (C) 2001 Wiley-Liss, Inc.