SUBENDOTHELIAL SMOOTH-MUSCLE CELLS OF HUMAN AORTA EXPRESS MACROPHAGE ANTIGEN IN-SITU AND IN-VITRO

Cells bearing a smooth muscle cell marker-alpha-actin and a macrophage marker-CD68 antigen were immunocytochemically identified on 'en face' preparations of human aortic intima. Cells, expressing smooth muscle alpha-actin, macrophage CD68 antigen and both markers, i.e. smooth mus cle cells possessing the macrophage antigen, were identified both in g rossly normal aortic areas and in atherosclerotic lesions (fatty strea ks and atherosclerotic plaques). CD68-positive smooth muscle cells wer e most common in the lipid-rich areas: fatty streaks and atherosclerot ic plaque shoulders. Cells expressing smooth muscle cc-actin and CD68 were also revealed in primary cultures prepared from grossly normal an d atherosclerotic intima. Cells expressing both antigens were found in all examined cultures. The proportion of these cells in cultures from grossly normal areas and atherosclerotic plaques was similar: 14.5 +/ - 4.1 and 14.6 +/- 4.8%, respectively. Cultures from fatty streaks had a higher content of cells expressing both antigens: 25.1 +/- 7.0%. Mo dified low density lipoprotein-induced intracellular lipid accumulatio n in cells cultured from grossly normal intima led to a three-fold inc rease in the number of cells sharing cc-actin and CD68 antigen. Accumu lation of latex beads by phagocytosis had a similar effect. It was sug gested that in atherosclerotic lesions intracellular lipid accumulatio n and other stimulators of phagocytosis may provoke the expression of macrophage-associated antigen CD68 in settled cells of the subendothel ial intima of human aorta. (C) 1997 Elsevier Science Ireland Ltd.