Previous work has demonstrated that aortic endothelial cells (EC) produce a heparin-like inhibitor of smooth muscle cell (SMC) growth when both cell types were cultured on plastic. We have now tested the influence of the extracellular matrix on this EC-SMC interaction. Specifically, we examined: 1) the role of different substrates (plastic, fibronectin, monomeric, and fibrillar collagens I and Ill, and EC-derived matrices) on the growth rate and population density of SMC; 2) the heparin-sensitivity of SMC on these diverse substrates; and 3) the effect of these same substrates on EC ability to secrete heparin-like and polypeptide inhibitors of SMC growth. SMC demonstrated a sixfold difference in sensitivity to heparin when grown on different substrates, with the following rank order: EGTA matrix > collagens = plastic = fibronectin > deoxycholic acid (DOC) matrix. Maximally, we found a 10-fold difference in the potency of the inhibitory activity secreted by EC grown on different substrates, with the following order: plastic = EGTA matrix > fibronectin > collagens = DOC matrix. Treatment of the conditioned mediums with heparinase and trypsin indicated that 58% to 76% of the inhibitory activity was due to heparin-like species, and 24% to 42% was due to protein@). When EC cultured on EGTA matrix are compared to those plated on DOC matrix, the potency of the heparin-like and peptide inhibitory activities increased 8and 17-fold, respectively. Hypothetically, one would predict a 60-fold change in the potency of the antiproliferative effect if the contributions of substrate to EC production of inhibitors and SMC sensitivity were additive. In practice, we obtained 30to 40fold changes In potency between the different substrate combinations. These results indicate that EC-derived matrices strongly influence both the EC production of heparin-like and polypeptide inhibitory activity and the SMC response to the growth regulators.
Arteriosclerosis – Wolters Kluwer Health
Published: Sep 1, 1987