Morphogenesis of primary human biliary epithelial cells: Induction in high-density culture or by coculture with autologous human hepatocytes

Although the control of biliary ductular morphogenesis has received some at tention particularly using isolated rat biliary epithelial cell models, the regulation of human bile duct formation is not well defined. In the presen t study, using a 3-dimensional culture model comprising primary human bilia ry epithelial cells (BECs) and coculture with primary human hepatocytes, we have sought to define the factors involved. We have shown that primary hum an BECs can be expanded on collagen gels in the absence of growth factors o r serum. When plated in high density in double collagen gels, BECs establis hed 3-dimensional structures that subsequently developed into well differen tiated polarized luminal ducts. This morphogenic response occurred in the a bsence of hepatocyte growth factor (HGF) and epidermal growth factor. Strik ingly, the addition of growth factors (in the presence of serum) resulted i n loss of polarity although the cells retained growth responses to both fac tors. Coculture of BECs with autologous human hepatocytes enhanced the abil ity of low-density BECs to undergo ductulo-genesis. This effect was mimicke d by addition of conditioned medium from previous hepatocyte-BEC cocultures , These findings indicate that for human biliary ductular morphogenesis, ep ithelial cell-cell interactions are required but that mesenchymally derived factors such as HGF may not be important.