CULTURE MATRIX CONFIGURATION AND COMPOSITION IN THE MAINTENANCE OF HEPATOCYTE POLARITY AND FUNCTION

Several extracellular matrix (ECM) configurations involving type I col lagen and Matrigel were examined for their ability to support differen tiated function and polarity of cultured adult rat hepatocytes. Collag en sandwich- and Matrigel-based cultures yielded superior and comparab le albumin secretion for at least 2 weeks. In collagen sandwich, hepat ocytes were polygonal, and formed multicellular arrays. Collagen sandw ich was also found to promote in vivo-like polarization of F-actin, ce ll adhesion molecules (E-cadherin), and lateral (Na+, K+-ATPase, gluco se transporter) and apical (dipeptidyl peptidase, aminopeptidase) memb rane polarity markers, but not the expression of the gap junction prot ein connexin 32 and the epidermal growth factor (EGF) receptor. In con trast, hepatocytes cultured in or on Matrigel were more rounded and fo rmed aggregates. Matrigel-based cultures also elicited detectable leve ls of connexin and EGF receptor and an altered distribution of F-actin , E-cadherin, and apical and lateral membrane proteins. Composite sand wich configurations containing collagen I and Matrigel restored marker s lacking in the collagen sandwich, and showed a variable morphology a nd membrane polarity. Hepatocyte polarity could thus be manipulated by the overall ECM composition. Furthermore, in composite sandwich cultu res, these manipulations can be effected largely independent of change s in hepatocyte morphology and albumin secretion.