Scanning electron microscopy of endothelium around an experimental stenosis in the rabbit aorta using a new casting material

Abstract

Four New Zealand White rabbits had bands fitted to their thoracic aorta causing a 73 ± 2 (SD) % reduction in cross-sectional area. The resulting stenosis produced a slight pressure drop and a post-stenotic dilatation that was evident at the time of preparation for microscopy 47 ± 2 days after fitting the band. Four other rabbits served as unoperated controls In all animals a portion of the thoracic aorta was glutaraldehyde-fixed and the lumenal surface cast by injecting a silicone rubber impression material. Casts were photographed and measured before being viewed under the scanning electron microscope. Micrographs were taken from predetermined areas and nuclear numerical density measured. No significant dorso-ventral differences in nuclear numerical density appeared in any aorta and no significant differences existed between sites in the 4-cm region of thoracic aorta sampled from control animals. Endothelial cells upstream to stenoses appeared identical to those from control arteries, although there was a greater incidence of spindle cells and cellular adherence than elsewhere. Nuclear density here was significantly higher than in control arteries but not different to any other region in the stenosed aorta. However, cells from within the stenosis and from just downstream were noticeably altered. Within the stenosis the cast reproduced longitudinal folds and the cells were strictly oriented with the long axis of the vessel. Nuclear density here was higher than any other region except just distal to the stenosis where there was a marked loss of normal longitudinal orientation and a change in the shape of some cells from elongated to polygonal. Swirling patterns and other zones of disorientation were evident up to 2 diameters distal to the stenosis, while within 2–4 diameters distal the cells appeared somewhat rounder and less strictly oriented than in control vessels. Beyond 4 diameters downstream, the cells appeared identical with those of control arteries and were of the same density as in mid-dilatation or in controls. These observations relate to expected local flow patterns, and are relevant to the role of haemodynamic factors in atherosclerosis.