Ultrastructural variability of macrophages in the wall of selected aorto-coronary bypass grafts

Macrophages, detected as CD68+ cells, are considered to have marked contribution to aorto-coronary grafts disease. The purpose of this study was to find any ultrastructural differences in CD68+ cells between arterial and venous aorto-coronary grafts.

The surplus segments of radial artery (RA) and saphenous vein (SV) were obtained from 50 patients with the mean age of 63.4±9.2 years who undergo elective coronary artery bypass grafting (CABG). The vascular segments were analyzed by means of both light (to assess number and distribution of macrophages within their walls) and transmission electron microscopy (to evaluate ultrastructure of CD68+ cells in the vessel layers).

Histological analysis revealed that not only more macrophages (median (25th; 75th percentile)) were found on the transverse sections of veins (95 (67; 135)) than arteries (66 (43; 108)) (p<0.05) but also at least of 50% of them were found in the tunica intima and tunica media in SV while only 30% in RA. TEM studies showed that biological activity of macrophages depended on CD68+ location and was irrespective of the vessel type. Those found in the tunica intima and tunica media presented ultrastructure typical for active cells rich in numerous lysosomes, well developed rough endoplasmic reticulum and Golgi apparatus whereas adventitial macrophages for unreactive residual cells.

Ultrastructural characteristics of both forms of macrophages infiltrating wall of aorto-coronary grafts is similar irrespective of the vessel type. More active cells in the inner layers of the venous conduits may contribute to their inferior outcomes compared to the arteries.

Running title: Macrophages and aorto-coronary grafts