MYOENDOTHELIAL CONTACTS IN ARTERIOSCLEROSIS

Human renal biopsies were examined electron microscopically to investigate close contacts between endothelial and smooth muscle cells in small arterioles. These myoendothelial contacts were seen in the form of cytoplasmic projections passing through fenestrae in the basal lamina. Most of these cell processes seem to arise from the endothelial cells. In the control vessels, the separation between the endothelial cells and smooth muscle cells of the tunica media is 0.090.27-mu-m. With arteriolosclerosis there is an increasing separation between the elements of the intima and the media, from 1.0 to 2.42-mu-m. In spite of this increasing separation, myoendothelial contacts maintain an intercellular space of 10-15 nm, as observed in the control vessels. At 2.42-mu-m of separation, the amount of extracellular material accumulated is such that the cells can no longer keep in contact. Break up of the myoendothelial contacts may be responsible for impairment of communication between the tunica intima and media in the vessel wall in arteriolosclerosis.