Cell proliferation and collagen synthesis are two independent events in human atherosclerotic plaques.

We have used a double-immunolabelling technique on human carotid atherosclerotic plaques to measure cell proliferation and type-I collagen gene expression, using antibodies to proliferating cell nuclear antigen (PCNA) and type-I procollagen protein, respectively. Although cell proliferative activity and type-I collagen gene expression can occur simultaneously in the same cell, this is a rare event, and the vast majority of collagen-producing cells do not show proliferative activity. These two processes also tend to occur in separate locations, although they can coexist in certain regions of the plaque. This disparate location of these two important modes of plaque growth suggests that cell proliferation and collagen gene expression may be under separate biological controls during the development and evolution of human atherosclerosis.