Topographical and ultrastructural alterations of smooth muscle cells lining damaged rabbit aorta.

The notion that medial smooth muscle cells can be a source of neointima has been a subject of several recent publications. However, the morphological and topographical changes and the degree of thrombogenicity of these cells once they are lining the vessel wall have not been investigated. We were able to inflict a lesion on the rabbit abdominal aorta which resulted in the sloughing of the intima and several layers of the media. As a result, a layer of medial smooth muscle cells was exposed to the circulating blood. Each of these cells retained its characteristic myofilaments but underwent structural as well as topographical changes. The ribosomal elements were greatly increased and mitochondrial cristea obliterated. The cells were closely approximated, leaving no large gaps to permit escape of blood cells. The subjacent region of the lining cells was somewhat oedematous and the internal elastic lamina was absent. On the luminal surface of the lining cells, remnants of connective tissue fibres were not detected and the cell surface was free of platelets, fibrin strands or other formed elements of the blood.