Fig. 1.

Establishment of a tight, mature cobblestone monolayer assessed by phase contrast microscopy. HUVECs (passage 1, p1) were seeded at 20,000 cells/cm² on ordinary polystyrene culture vessels coated with Matrigel, left to grow and differentiate for several days and regularly monitored by phase-contrast microscopy. At “subconfluent” state cells are spread and divide actively. When the monolayers get confluent, cells are more compact and stop proliferating by contact inhibition. In unripe cobblestone cultures (“2-days cobblestone”) cell limits are bright. As cobblestone cells mature (“4-days cobblestone”), cell limits get dark until they become distinct lines (“7-days cobblestone”). Arrows point out cell peripheries. Scale bar (applicable to all the panels): 50 μm