Intimal cells and atherosclerosis. Relationship between the number of intimal cells and major manifestations of atherosclerosis in the human aorta.

The subendothelial intima of human aorta is populated by cells of various shapes. Round and ovoid cells which are lymphocyte- and monocyte-like hematogenous cells account for less than 5% of the cell population. The bulk of the intimal population (over 95%) is made up of cells that can be described as elongated, stellate, elongated with side processes, and irregularly shaped. To identify these morphologic forms, the authors have used target electron microscopy. It has been established that elongated cells devoid of side processes possess all the ultrastructural features of differentiated smooth muscle cells: a developed contractile apparatus in the form of microfilament bundles with dense bodies occupying most of the cytoplasm, basal membrane surrounding the whole of the cell, and micropinocytotic vesicles along the plasma membrane. The other morphologic forms have an ultra-structure that allows us to identify them as so-called modified smooth muscle cells. They differ from the typical smooth muscle cells in that they have fewer contractile structures and a more developed biosynthetic apparatus. Some of stellate and irregular shaped cells are utterly devoid of contractile structures. To quantitate the number of cells of different morphologic forms, the authors used alcoholic-alkaline dissociation of prefixed intima. It was established that the intimal population is multiplied at the site of an atherosclerotic lesion, the number of stellate cells being increased much more substantially, compared with other morphologic cell forms. It was found that an increase in the number of stellate cells is related to such sequelae of atherosclerosis in aorta as intimal thickening, deposition of lipids, and an increased amount of collagen. There was a high positive correlation between the alteration in the stellate cell number occurring in the intima and the above-mentioned parameters (correlation coefficients were 0.732, 0.800 and 0.953, respectively). The correlations between these indexes and the total number of intimal cells or the number of cells belonging to each of the other morphologic forms were not so high. A multivariate analysis gave similar results. Thus, it may be suggested that stellate cells are the principal cell type involved in the disease. This report discusses the origin of stellate and other intimal cells and their role in atherogenesis.