Erythrocytophagocytosis by arterial smooth muscle cells in experimental atherosclerosis.

The morphological examination of advanced atherosclerosis caused by atherogenic diet in the coronary arteries and in the aorta abdominalis (trifurcation) of pigs showed plaque hemorrhage and signs of vascularisation. In these areas phagocytosis of erythrocytes could be observed. The cells involved in the phagocytic process vary considerably in size and shape but show common features of arterial smooth muscle cells. The modulation of smooth muscle cells is evident and progresses as the process of phagocytosis progresses. In early stages of erythrocyte engulfment the morphological characteristics which identify these cells as of smooth muscle origin are parts of surrounding basement membrane, caveolae intracellulares and myofilaments. The authors suggest, that under certain conditions arterial smooth muscle cells participate in phagocytic processes in the injured vessel wall as potential macrophages with lysosomal enzyme adaptation. Changes in extracellular surroundings and the actual situation of the vessel wall condition seem to play an important role in the induction of phagocytosis. Relations to vascularisation processes of the arterial plaques are evident.