Immunohistochemical and Ultrastructural Examination of Smooth Muscle Cells in Aortocoronary Saphenous Vein Grafts

Abstract

In this study, phenotypic modulation and remodulation of smooth muscle cells and associated intermediate filament expression were demonstrated by means of immunohistochemistry and ultrastructure to understand the development of intimal hyperplasia in aortocoronary saphenous vein grafts. In nongrafted saphenous veins, all smooth muscle cells expressed vimentin and desmin and were of a contractile form. In saphenous vein grafts showing stenotic intimal hyperplasia (luminal stenosis < 75%), expression of desmin was notably lower, whereas that of vimentin was higher. The cells were shown to be of a synthetic phenotype, suggesting modulation from the original contractile form. In saphenous vein grafts showing occlusive intimal hyperplasia (luminal stenosis >76%), desmin expression in smooth muscle cells was increased again, and such cells were of a contractile form, suggesting remodulation from the synthetic phenotype. Some of the smooth muscle cells of the synthetic phenotype were positive for an antibody against proliferation cell nuclear antigen. Smooth muscle cells of the contractile form were negative for this antibody. The study suggests that smooth muscle cells of synthetic phenotype are highly respon sible for "growing" intimal hyperplasia of aortocoronary saphenous vein grafts.