Smooth muscle phenotypic expression in human carotid arteries. II. Atherosclerosis-free diffuse intimal thickenings compared with the media.

The volume fraction of synthetic organelles in smooth muscle cells from areas of atherosclerosis-free, diffuse intimal thickenings (DIT) and media of human carotid artery has been determined morphometrically. Tissue was obtained at autopsy from men and women aged 35 to 80 years, at 6 to 12 hours after death. With both sexes, the volume fraction of synthetic organelles in smooth muscle cells from the DIT was not significantly different from the volume fraction of synthetic organelles in cells of the subjacent media (0.25 and 0.21, respectively). This is in marked contrast to our earlier study in which the volume fraction of synthetic organelles in smooth muscle cells of DIT from a similar region of artery, but adjacent to atheromatous plaques, was highly significantly different from cells of the subjacent media (0.48 and 0.23, respectively). Only in regions near atherosclerotic plaques do the majority of smooth muscle cells of DIT express a different phenotype from cells of the media.