EXPERIMENTAL HYPERCHOLESTEROLEMIA INDUCES ULTRASTRUCTURAL-CHANGES IN THE INTERNAL ELASTIC LAMINA OF PORCINE CORONARY-ARTERIES

The internal elastic lamina (IEL) serves as a barrier for cells and ma cromolecules migration between the intima and the media in the vascula r wall. Several investigators have reported internal elastic lamina ul trastructural changes in elastic arteries with atherosclerosis. Howeve r, no quantitative and qualitative assessment of the internal elastic lamina architecture in muscular arteries such as the coronary circulat ion during early atherosclerosis have been performed yet. In this stud y, we therefore evaluated the ultrastructural morphological changes of the IEL in the coronary circulation of pigs fed with high cholesterol diet. Animals were sacrificed after being fed either a high cholester ol diet for 10-12 weeks (n = 5, 12 coronary segments) or a control die t (n = 4, 15 coronary segments). Coronary arteries were analyzed by tr ansmission and scanning electron microscopy. In addition, computerized digital analysis of the images obtained by confocal scanning microsco py was performed for the quantitation of the morphologic changes in th e internal elastic lamina. Confocal microscopy and scanning electron m icroscopy revealed an altered pattern characterized by large oval fene stration formation in the internal elastic lamina of hypercholesterole mic animals. Computerized morphometric analysis of confocal microscopy images demonstrated that compared to controls, the IEL of cholesterol -fed animals was characterized by an increase in the minor diameter of the fenestrae (2.16 +/- 0.04 mu m versus 3.32 +/- 0.06 mu m, P = 0.00 3) and a decrease in the fenestrae density (22333 +/- 1334/mm(2) versu s 17552 +/- 931/mm(2), P = 0.015) of the internal elastic lamina. The percentage of the IEL area covered by the fenestrae correlated with th e intimal thickness (r = 0.79, P = 0.004). This study demonstrates tha t experimental hypercholesterolemia is characterized by ultrastructura l changes of the internal elastic lamina in the coronary circulation. This study suggests that the IEL may play an important role in the dev elopment of structural changes which characterize the early phase of c oronary atherosclerosis. (C) 1998 Elsevier Science Ireland Ltd. All ri ghts reserved.