Myoendothelial contacts in the human fetal aorta.

Intracellular communication is an essential process in both embryological development and for the maintenance of normal tissue physiology. We have established the presence of this type of communication between endothelial cells and vascular smooth muscle cells in man and have here investigated the close contacts between endothelial and smooth muscle cells in the aorta of the 10-week-old human fetus. Transmission electron microscopy revealed myoendothelial contacts in the form of cytoplasmic projections, usually originating from the muscle cells. The nature of the cell-cell contacts was via simple appositions with an intercellular space of 6-15 nm. Myoendothelial contacts are sites for communication between elements of the intima and media, ensuring that paracrine secretion can occur and that the vessel wall, during growth and development, works as a unit.