Structural alterations in vascular endothelial tight junctions in the course of their gradual degradation in vitro

Rabbit aorta explants in organ culture maintained their endothelium as a confluent cell layer for 1-6 days. Depending on culture time, interendothelial tight junctions underwent gradual morphological changes in their substructure, as seen in freeze-fracture replicas. The formation of a P-face associated groove and concurrent confluence of tight junction particles on E-faces after 24 hr in vitro was followed by a rarefaction of particles and shortening of tight junctional strands. By day 6 in vitro, almost all tight junctions have disappeared. We interpret these findings as signs of a degradation of tight junctions in vitro, involving three different substructural components: a component facing the protoplasm, tight junction particles and a component facing the extracellular space. The degradation was inhibited by culturing under increased ambient pressure (910 mmHg).