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 glycosamino glycans (GAGs) enabled us to immobilize GAGs to solid phase through hy drophobic interaction. Using these compounds, called GAG-PEs, we studi ed the effects of GAGs immobilized to culture plates coated with vario us extracellular matrix (ECM) proteins in terms of cell-substrate adhe sion, DNA synthesis, tyrosine aminotransferase (TAT) induction, and in tercellular communication in primary rat hepatocytes. Treatment with c hondroitin sulfate (CS)-PE at 10 mu g/ml made laminin, fibronectin, vi tronectin, and collagens type I-V less adhesive as substrates for cell attachment and inhibited cell spreading on these substrates. The effe ct on cell attachment was lost after long incubations over 2 h. Dermat an sulfate (DS)-PE was also inhibitory, but less effective. The conjug ates of heparan sulfate (HS), heparin, and hyaluronan were much less e ffective. DNA synthesis initiated by EGF in the culture on laminin sub strates 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 coll agen substrates, GAG-PEs had similar effects but to lesser extent. TAT induction in the culture on laminin substrates but not on type I coll agen substrates was significantly enhanced by CS-PE. In terms of DNA s ynthesis and TAT induction, the culture on laminin substrates treated with CS-PE was comparable to that at higher cell density on the non-tr eated laminin substrates. Intercellular communication assessed by dye coupling was maintained longer on the substrates treated with CS-PE. T aken together, our results demonstrate that CS immobilized especially onto laminin substrates inhibits the growth of hepatocytes and enhance s their differentiated functions by modulating cell-ECM protein intera ctions.