The clonal characteristics of human aortic intima. Comparison with fatty streaks and normal media.

The clonal characteristics of normal-appearing but thickened aortic intima were studied by the use of the isoenzymes of glucose-6-phosphate dehydrogenase (G-6-PD) as cellular markers in females heterozygous for this X-linked enzyme. Isoenzyme patterns of 133 samples of intima were compared with those of 237 samples of underlying media and with those of 58 fatty streaks dissected from the same aortas. The proportion of samples of intima and fatty streaks with monoclonal or intermediate characteristics was the same, but both had more monoclonal or intermediate samples than underlying media (P less than 0.05). However, samples of intima showed a central clustering tendency of isoenzyme values similar to that of underlying media, while values from fatty streaks showed a bimodal distribution suggesting the presence of cell populations in the process of becoming monoclonal. The data suggest that clonal proliferation may begin in normal-appearing intima but that it progresses through a fatty streak stage before proceeding to the monoclonal fibrous plaque.