DEDIFFERENTIATION OF HUMAN HEPATOCYTES BY EXTRACELLULAR-MATRIX PROTEINS IN-VITRO - QUANTITATIVE AND QUALITATIVE INVESTIGATION OF CYTOKERATIN-7, CYTOKERATIN-8, CYTOKERATIN-18, CYTOKERATIN-19 AND VIMENTIN FILAMENTS

Background/Aims: Liver cirrhosis and carcinogenesis are accompanied by an alteration in extracellular matrix material. Histological studies reveal upregulation of the intermediate filaments cytokeratins 8 and 1 8 and de novo synthesis of vimentin, and cytokeratin 7 or 19 in hepato cytes. The aim of this study was to investigate how these two processe s are linked, Methods: Human hepatocytes were seeded: (i) on the matri x components collagen I, IV: laminin, or fibronectin; (ii) on stoichio metrically different complete matrices, derived from human placenta (m atrix I) or the Englebreth-Holm-Swarm tumor (matrix II), and (iii) ins ide a three-dimensional collagen I sandwich. Filament expression and a ssembly were measured by cytofluor analysis or confocal laserscan micr oscopy. Results: The matrix components or complete matrices triggered enhancement of cytokeratins 8 and 18 and de novo synthesis of cytokera tins 7, 19 and vimentin in a characteristic way Confocal images demons trated a dense and uniform network of cytokeratin 18 in freshly isolat ed cells, which was ''replaced'' by a few, thick protein bundles withi n 20 days. Interestingly, newly synthesized cytokeratin 19 structurall y resembled the cytokeratin 19 organization in biliary epithelial cell s, Marked cytokeratin alterations could be partially prevented when he patocytes were grown in a three-dimensional collagen sandwich. Conclus ions: Pathological alterations to the chemical composition, molecular structure, or spatial arrangement of the liver matrix lead to specific changes in the intermediate filament pattern in human hepatocytes. We assume that degradation of the matrix results in pathological alterat ions to the hepatocyte-receptor matrix-ligand ratio, followed by a sni tch from physiological to pathological cell-activation.