Smooth muscle phenotypic expression in human carotid arteries. I. Comparison of cells from diffuse intimal thickenings adjacent to atheromatous plaques with those of the media.

The volume fraction of synthetic organelles in smooth muscle cells from diffuse intimal thickenings (DIT) and media of human carotid arteries has been determined morphometrically. Fresh tissue from surgical endarterectomy was obtained from both male and female patients between 50 and 80 years of age. The results show that 87% of cells within the DIT can be readily identified as smooth muscle. The volume fraction of synthetic organelles in smooth muscle cells from the DIT of both males and females is of a highly significant difference from the volume fraction of synthetic organelles in cells of the subjacent media. This represents a 2-fold increase in the content of synthetic organelles in the cells of the DIT. The results also show greater phenotypic variability among cells of the DIT than among cells of the media. The results are discussed in the context of smooth muscle cell phenotypic changes in cell culture and the implications of such changes in phenotypic expression in the initiation of atherogenesis.