Chondroitin sulfate immobilized onto culture substrates modulates DNA synthesis, tyrosine aminotransferase induction, and intercellular communication in primary rat hepatocytes.
Newly prepared phosphatidylethanolamine (PE) conjugates of glycosaminoglycans (GAGs) enabled us to immobilize GAGs to solid phase through hydrophobic interaction. Using these compounds, called GAG-PEs, we studied the effects of GAGs immobilized to culture plates coated with various extracellular matrix (ECM) proteins in terms of cell-substrate adhesion, DNA synthesis, tyrosine aminotransferase (TAT) induction, and intercellular communication in primary rat hepatocytes. Treatment with chondroitin sulfate (CS)-PE at 10 micrograms/ml made laminin, fibronectin, vitronectin, and collagens type I-V less adhesive as substrates for cell attachment and inhibited cell spreading on these substrates. The effect on cell attachment was lost after long incubations over 2 h. Dermatan sulfate (DS)-PE was also inhibitory, but less effective. The conjugates of heparan sulfate (HS), heparin, and hyaluronan were much less effective. DNA synthesis initiated by EGF in the culture on laminin substrates was inhibited most strongly by CS-PE, as well as by DS-PE and hyaluronan-PE, but not by either HS-PE or heparin-PE. With type I collagen substrates, GAG-PEs had similar effects but to lesser extent. TAT induction in the culture on laminin substrates but not on type I collagen substrates was significantly enhanced by CS-PE. In terms of DNA synthesis and TAT induction, the culture on laminin substrates treated with CS-PE was comparable to that at higher cell density on the non-treated laminin substrates. Intercellular communication assessed by dye coupling was maintained longer on the substrates treated with CS-PE. Taken together, our results demonstrate that CS immobilized especially onto laminin substrates inhibits the growth of hepatocytes and enhances their differentiated functions by modulating cell-ECM protein interactions.