Functional engineering of hepatocytes via heterocellular presentation of a homoadhesive molecule, E-cadherin

Abstract

Engineering functional activity of liver cell cultures requires the modulation of specific cell–cell interactions. We have investigated the quantitative role of systematically varied presentation of the cell–cell adhesion molecule, E-cadherin, on the differentiated function of cocultured parenchymal liver cells, hepatocytes. Specifically, we incorporated different proportions of E-cadherin transfected L-929 chaperone cells and untransfected chaperone cells, within cultures of primary rat hepatocytes on a collagen substrate. By using a strongly adhesive substrate that restricted cadherin-induced variations in cell spreading and growth-arresting chaperone cells, we could carefully isolate the potential role of cell–cell adhesion on cell differentiation. Using immunofluorescence microscopy, we confirmed that cadherins expressed at hepatocyte–hepatocyte contacts as well as hepatocyte–chaperone contacts were crossreactive. However, hepatocytes cocultured with cadherin-presenting chaperone cells had a 55–65% increase in longterm function over hepatocytes cocultured with control, nonpresenting chaperone cells. Notably, the cadherin-induced increase in function occurred over and above the basal, coculture-induced functional elevation. Further, we quantified the stoichiometric importance of cadherin contacts by comparing established markers of hepatocyte functional activity across a graded range of E-cadherin presentation. At low levels of cadherin-mediated contacts, the induction of differentiated function was weak, while high levels of contacts elicited a marked increase in function. Thus, hepatocyte biochemical functions (albumin and urea secretion) were biphasically governed by the degree of cadherin-based contacts presented during culture. Overall, our results demonstrate the unequivocal role of cell–cell adhesion molecules in hepatocyte functional engineering, through the graded use of cadherin presentation from functionally incompetent, heterotypic chaperone cells. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 76: 295–302, 2001.