Reversible microcarrier-mediated junctional communication between endothelial and smooth muscle cell monolayers: an in vitro model of vascular cell interactions.

Junctional communication between cultured monolayers of aortic endothelial and smooth muscle cells was established as an in vitro model of vessel wall cell interactions. Confluent monolayers of endothelial cells on microcarriers placed on the surface of a smooth muscle cell monolayer became attached within 1 hour. After 3 hours of contact co-culture, approximately 4% of each monolayer was involved in heterocellular attachment (range 2% to 6%; 4 to 12 cells per microcarrier). Endothelial-smooth muscle cell junctions formed between the two cell populations at the sites of attachment on the lower surface of each microcarrier. When either endothelial cells or smooth muscle cells were prelabeled with [3H]uridine, intracellular nucleotide was rapidly transferred across the region of heterocellular attachment to the complementary cell population. Heterocellular gap junctional transfer was inhibited when endothelial-smooth muscle attachment was prevented by slowly rocking the culture vessel. No evidence of nucleotide transfer was obtained when endothelial cells were co-cultured with MDCK cells incapable of forming gap junctions. Contact co-culture of endothelium and smooth muscle cells were reversed by gentle agitation of the cultures; the microcarriers detached allowing the recovery of pure cell populations. The contact co-culture technique is well suited to studies of vascular cell interactions and is of general applicability to anchorage dependent cells.