Adhesion and growth of rat liver epithelial cells on an extracellular matrix with proteins from fibroblast conditioned medium.

We previously reported that proteins from serum-free conditioned medium (PCM) of rat embryo fibroblasts promote the adhesion of nonmalignant rat liver epithelial cells (RL34) seeded on a collagen substratum (Yamada, M. and Okigaki, T., Cell Biol. Int. Rep. 7, 1115(1983)). We now have compared the adhesion and growth of RL34 cells seeded on an extracellular matrix (RLECM), a product of RL34 cells, or on a collagen (type I) substratum with or without PCM in the medium. The adhesion rate for RL34 cells on RLECM was higher than on collagen, and once RL34 cells adhered to the collagen substratum they showed no growth, whether or not PCM was present. Cells that adhered to RLECM grew, and the growth rate was markedly higher in medium containing PCM than in medium without it. Immunological, enzymatic and chemical analyses revealed that the adhesion- and growth-promoting activities of RLECM involved trypsin-sensitive proteins other than collagens, fibronectin (FN) or laminin (LN), and that heparan sulfate proteoglycan may be a major component of RLECM.