Role of fibronectin and sulfated proteoglycans in endothelial cell migration on a cultured smooth muscle layer.

Endothelial cell (EC) migration is essential for the healing of denudation injuries to the vessel wall. This event occurs in vivo in a pericellular environment and should be regulated in part by juxtacrine and paracrine interactions with underlying smooth muscle cells (SMCs). To investigate the EC migration behavior over SMCs under direct cell-cell contact conditions, we have utilized human umbilical vein endothelial cells (HUVECs) grown to confluence on microcarrier beads and radiolabeled with chromium-51. The EC carrying beads were spread over a confluent human aortic SMC monolayer and cocultured for 48 hr, allowing the EC to migrate from beads onto the underlying SMC monolayer in the presence of sodium chlorate, cycloheximide (CHM), or anti-fibronectin monoclonal antibody (anti-FN mAb). The level of EC migration was quantified by counting the amount of radioactivity on the SMC layer after the removal of the beads. The presence of a SMC layer enhanced EC migration more than threefold (P < 0.05). Furthermore, EC migration was inhibited from 30 to 80% (P < 0.05) by sodium chlorate, CHM, and anti-FN mAb in a dose-dependent fashion. This model has shown that smooth muscle cells augment endothelial motility. Both fibronectin and sulfated proteoglycans released by ECs and SMCs likely play an important role in the regulation of EC migration behavior over SMCs. The method described of using radiolabeled ECs on microcarrier beads should prove to be a useful tool in the study of cell migration in a heterotypic cellular environment.